Building Construction Terms      

Above-grade walls: Those walls on the exterior of the building and completely above grade (soil level), or the above-grade portion of a basement or first-story wall that is more than 15 percent above grade.

Absorptance: The ratio of the radiation absorbed by a surface to the total energy falling on that surface.

Absorption: Process whereby a porous material extracts one or more substances from the atmosphere, a mixture of gasses, or a mixture of liquids.

Abutment: A masonry mass (or the like) that receives the thrust of an arch, vault, or strut. Sometimes a wall buttress.

Accent lighting: Any directional lighting that emphasizes a particular object or draws attention to a particular area.

Acceptable indoor air quality: according to ASHRAE, air in an occupied space toward which a substantial majority of occupants express no dissatisfaction and in which there are not likely to be known contaminants at concentrations leading to exposures that pose a significant health risk.

Access door: A small door provided through finished construction providing access to a duct, through a ceiling, behind a wall, or into a large piece of mechanical equipment for inspection of equipment or services housed within.

Acid leachate: Water that has become acidic after seepage through landfills; potentially very damaging to fish habitats and drinking water supplies.

Acid rain: Precipitation that has a pH below 5.6. Main contributors are sulfur dioxide from industrial burning of fossil fuel, and nitrogen oxide from automobile emissions, which is transformed into nitrogen dioxide.

Acre-foot of water: The amount of water required to cover 1 acre of land 1 foot deep; equal to 325,851 gallons, or 43,560 cubic feet. A family of four uses ½ acre-foot of water per year.

Acrylic: A thermoplastic with good weather resistance, shatter resistance, and optical clarity, used often for glazing.

Acrylic impregnated flooring: Prefinished sheet flooring system that has had liquid acrylic forced under pressure into its structure. The acrylic hardens, forming an extremely abrasion-resistant finish throughout the entire thickness. Dyes and fire retardants may be added.

Active Noise Cancellation (ANC): The reduction of a sound field through the interaction of a primary sound source with an actively controlled identical secondary sound source that is 180 degrees out of phase.

Active solar energy system: A system using electrical or mechanical devices (pumps, fans, etc.) to assist in the collection, transport, and storage of solar energy for the purpose of heating or cooling or to make electricity.

Active solar water heater: See solar water heater.

Active system: Traditional heating, cooling and ventilating systems which use mechanical means to artificially condition (cool, heat, ventilate) the air supply in buildings, and draw power for these mechanical processes from electricity, gas, oil, or coal.

Adaptable buildings: Buildings that can be easily remarketed, retrofitted, or reconfigured to better meet the changing needs of occupants, maintenance crews, and the larger community.

Adaptation: In lighting design, the process by which the human visual system becomes accustomed to more or less light, resulting from a change in the sensitivity of the eye to light.

Adaptive controllers: Controls in which one or more features are sensed and used to adjust feedback control signals to satisfy performance criteria.

Addition: An extension or increase in the height, conditioned floor area, or conditioned volume of a building. The building codes apply to additions of existing buildings. Additions include new construction, such as a conditioned bedroom or sunspace. Additions also include existing spaces converted from unconditioned to conditioned spaces (converting an existing porch to a conditioned sunroom).

Additive: A substance added to facilitate processing, strengthen, stabilize, or otherwise improve the performance of a product. The most widely used additives to plastics are plasticizers, which both improve the processing of plastics and increase their flexibility; antioxidants; metal scavengers; light stabilizers; lubricants which expedite processing during manufacture; fillers, extenders, or reinforcements; and flame retardants. Also may include antistatic agents, pigments, whitening agents, blowing agents, accelerators, impact modifiers, antimicrobials, and biostabilizers (pesticides).

Adhered backing: A secondary carpet backing that is applied to the primary backing with adhesives (latex adhesives are the most common). Cushion backings usually fall into this category.

Adhesive: Material that bonds surfaces of different materials. Adhesives may be liquid or tacky semisolids, natural or synthetic, organic or inorganic, waterborne, solvent-borne, or solventless. Solvent-based adhesives can be sources of VOCs (see VOCs definition).

Admixture: A material, other than aggregate, cement, or water, added in small amounts to a cement base mixture (e.g., concrete or plaster) to change its properties, such as improved workability, faster setting time, increased strength, and greater water tightness.

Adobe Brick: Large, roughly molded, sun dried clay brick of varying sizes.

Advanced industrial societies: Nations such as Japan and those of Europe and North America whose economies are based on industrial manufacturing and the use of fossil fuels. While virtually all nations have developed an industrial base to some extent, the advanced nations dominate the world economy in both their use of resources and in the total value of their economic activity.

Aerobic digestion: Treatment of sludge or other thickened slurries that is typically used to decrease the solids content of the sludge or to remove pathogenic organisms. Examples include extended aeration and ATAD (auto thermal aerobic digestion). Composting can be thought of as an aerobic digestion process.

Aerobic treatment: Removal of organic pollutants in wastewater by bacteria that require oxygen. Water and carbon dioxide are the end results of this treatment process. Types include trickling filtration, activated sludge, and rotating biological contactors.

Aerogel: A microporous, transparent silicate foam used as a glazing cavity fill material, offering possible U-values below 0.10 BTU/(h-sq. ft.-deg. F).

Aerosol: A solid or liquid particle small enough to become suspended in the air. Aerosol cans use compressed gas to dispense a liquid product.

Aggregate: Natural sands, gravels, and crushed stone used for mixing with cementing materials in making mortars and concretes. Also can be added to paint for texture or nonslip flooring surface.

Agricultural by-products: Ancillary products of farming, several of which may be used as building materials, e.g. straw to make wall panels.

Agricultural fiber: Materials (like cotton, straw, and sunflower seeds) that are used as building materials.

Air barrier: A system of materials that enclose a volume of air with minimal air leakage between the enclosed air and the exterior. In construction, it is a flexible or rigid membrane designed to reduce the movement of air between the interior and exterior of a building. See also air retarder.

Air changes per Hour (ACH): The number of times in one hour the entire volume of air in a building is replaced with outdoor air.

Air cleaner: A device that removes contaminants from indoor air.

Air economizer: Ducting arrangements and automatic control systems that allow a cooling supply fan system to supply outside air to reduce or eliminate the need for mechanical refrigeration during mild or cold weather.

Air-entrained concrete: Concrete made with air-entraining cement, typically alumina; has increased workability and frost resistance and is lighter weight. See also concrete.

Air handler: The fan on a forced-air heating or cooling system.

Air infiltration: Uncontrolled inward air leakage through cracks in a building envelope.

Air infiltration barrier (AIB): One or more air-impermeable components, sealed at all seams and penetrations to form a continuous wrap around building walls. Such barriers can dramatically reduce the air infiltration rates through a building envelope.

Air leakage: The uncontrolled movement of air in or out through the building structure. Air leakage carries heat with it by convection. Also referred to as air infiltration.

Air leakage rating: A measure of the rate of infiltration around a window or skylight in the presence of a specific pressure difference. Expressed in units of cubic feet per minute per square foot of window area (cfm/sq. ft.).

Air retarder: A material installed around a building frame to prevent or reduce the infiltration of air into the interior. Installed as an energy-efficiency measure to keep out air, which may be too hot or too cold for comfort, or too moist. Not to be confused with a vapor retarder. See also air barrier.

Air-to-air heat exchanger: Also known as a heat recovery ventilator, the air-to-air exchanger transfers heat directly from one airstream to another through either side of a transfer surface.

Airway: In a vented roof, the passage for ventilation between thermal insulation and roof deck.

Albedo: Ratio of reflected light to the total amount of light falling on a surface. In hot climates, it is desirable to use roofing materials with a high albedo.

Allergen: A substance capable of causing an allergic reaction because of an individual’s sensitivity to that substance.

Alloyed metal: A metal consisting of a combination of two or more elements. Alloys have different properties than pure metals, e.g., strength, corrosion resistance, or hardness. Examples include brass, bronze, and steel.

Alteration: Any construction renovation, or change in a mechanical system that involves an extension, addition, or change to the arrangement, type, or purpose of the original installation.

Alternating current (AC): An electrical current flowing at varying voltage. Flow of electricity that constantly changes direction between positive and negating sides. Almost all power produced by electric utilities in the US is this type of current.

Altitude: The angle of the sun above the earth at a give latitude and time of year.

Ambient lighting: General lighting designed to provide uniform illumination in a given area.

Ambient temperature: Dry bulb temperature of the medium (air, water, or earth) surrounding people, objects, or equipment.

American Architectural Manufacturers Association (AAMA): A national trade association that establishes voluntary standards for the window, door and skylight industry.

Ammonia fumigation: A process using ammonia gas to neutralize formaldehyde emissions from such materials as particleboard and adhesives.

Ampere (Amp): The unit of measure that tells how much electricity flows through a conductor.

Angle of incidence: The angle that direct light (such as the sun’s rays) makes with a line perpendicular to a surface. The angle of incidence is a key determinant of the percentage of direct light intercepted by a surface. The sun’s rays that are perpendicular are said to be “normal” to that surface.

Annealed glass: Standard sheet of plate glass. See also float glass.

Annealing: Heating above the critical or recrystallization temperature, then controlled cooling of metal, glass, or other materials to eliminate the effects of cold-working, relieve internal stresses, or improve strength, ductility, or other properties.

Annual fuel utilization efficiency (AFUE): A measure of efficiency of a combustion heating appliance. AFUE differs from steady-state efficiency since it employs an empirical equation to deduct all operational losses, such as vent losses, cyclic effects, and part-load operation. New equipment typically ranges from about 78- to 96-percent AFUE. Higher AFUE ratings indicate more efficient equipment.

Antigen: Any substance that stimulates the production of antibody and/or activated immune cells.

Aperture: That part of the south facing glazing on a building that contributes to solar heating. An opening in the building façade, usually glazed to allow daylighting.

Aquifer: A porous underground formation that contains groundwater.

Artificial sky: An enclosure that simulates the luminance distribution of a real sky for the purpose of testing physical daylighting models (e.g., a hemispherical-dome or mirror-box artificial sky).

Asbestos: Describes six naturally occurring fibrous minerals and has been commonly used in many building construction materials for insulation and as a fire-retardant. It is heat-resistant and chemically inert and is also used as filler in tile, reinforced cement, gaskets, and brake linings. Invisible fibers of asbestos may be inhaled and result in a diffuse interstitial fibrosis of the lung tissue (asbestosis) or lung cancer.

Asphalt: Black, semi-soft mixture of hydrocarbons from animal origins. Also, residue left after removing tar tailings from petroleum distillation. Asphalt fumes are carcinogenic. Used in adhesives, coatings (roofs, floors, wood), sealants, rubber, and paint.

Asphalt treated paper: A paper that is coated or impregnated with a bituminous material known as asphalt. Used to provide a moisture barrier in exterior wall construction or as a facing on batt insulation.

Attic venting system: Venting devices installed in an attic structure, which allow fresh outside air to enter the attic and exhaust out of it, so the attic will be cooler and drier. The most effective attic venting system combines a continuous soffit vent with a continuous ridge vent. This system allows the most even flow of air over the underside of the roof, and the best position for the exhaust vent - at the highest point of the attic - where the air is hottest.

Autoclaved Aerated Concrete (AAC) or Autoclaved cellular concrete (ACC): Concrete made with an aluminum powder that causes the mass to foam and expand. It is then steam-cured in an autoclave oven, which renders it stable. The resulting material has many benefits (non-combustible, easily worked, R-value of 1.25 per inch, etc.)

Automatic time-switch controls: Controls that automatically switch lights or equipment on and off.

Automatically operated control damper: A damper, which automatically opens and closes.

Awning: A roof-like covering of canvas, or the like, often adjustable, over a window, door, etc., to provide protection against the sun, rain, and wind.

Awning Window: A window similar to a casement except the sash is hinged at the top and always swings out.

Azimuth: The angular distance between due South and the projection of the line of sight to the sun on the ground. A positive solar azimuth angle indicates a position East of South, and a negative azimuth angle indicates West of South.

Backdraft damper: A damper, installed near a fan, which allows air to flow in only one direction.

Backdrafting: The pressure-induced spillage of exhaust gases from combustion appliances into the living space. Also, reverse airflow down flues or chimneys that allows exhaust gases from combustion appliances to return indoors.

Backed vinyl: Vinyl product consisting of a surface wear layer of vinyl and a backing layer, usually of fabric, paper, or plastic foam. Also known as laminated vinyl.

Backing: Plastic coating for upholstery and wall fabric to ensure dimensional stability, or to resist slippage, unraveling, and fraying.

Bacteria sink: Porous material that allows the growth of biological contaminants within the material.

Bactericide: Any agent that will destroy bacteria, only safe in very low concentrations.

Baffle: A single opaque or translucent element used to diffuse or shield a surface from direct or unwanted light.

Bakeout: A process used to remove VOCs by elevating the temperature in an unoccupied, fully furnished, and ventilated building.

Balance: A mechanical device (normally spring-loaded) used in single- and double-hung windows as a means of counterbalancing the weight of the sash during opening and closing.

Balance point: The outdoor temperature at which a building’s heat loss to the environment is equal to internal heat gains from people, lights, and equipment. Surface load dominated buildings such as single family detached residences will have balance points in the 55-65 degree Fahrenheit range. Internally load dominated structures, like office buildings, may have balance points so low that the climate never overcomes their internal heat gain.

Ballast: A device used to operate fluorescent and HID lamps. The ballast provides the necessary starting voltage, while limiting and regulating the lamp current during operation.

Ballast factor (BF): The ratio of light output of fluorescent lamps operated on a ballast to the light output of lamps operated on a reference ballast.

Ballasted roofing membrane: A method by which roofing membranes are held in place by rounded gravel spread on the surface of the roofing material. Ballast protects the roofing material from wind uplift and excessive ultraviolet exposure. With this technique, materials are not glued or mechanically fastened and are easily separated at the end of their life for reuse, recycling, or disposal.

Bar joist: An open-web steel joist consisting of a single bar, bent in a zigzag pattern, and welded at its points of contact to upper and lower chords.

Barge rafter: A rafter in the projecting portion of a gabled roof (under the barge course, which projects beyond the wall face), which serve as grounds for the barge boards (or fascia) and carry the plastering or boarding of the soffits. Also called a fly rafter.

Barrier cloth: A special synthetic or cotton fabric that does not allow dust or plant roots, but does allow water, to penetrate. It has very high thread count (300 per inch) and is tightly woven.

Basement walls: Basement walls that enclose conditioned spaces are part of the building envelope. Basement wall refers to the opaque portion of the wall (excluding windows and doors). To be considered a basement wall, at least 50% of the wall's total wall area (including openings) must be below grade. Treat walls on each side of the basement individually when determining if they are above-grade or basement walls. For any individual wall less than 50% below grade, include the entire opaque wall area of that individual wall as part of the above-grade walls.

Batt insulation: Glass or mineral wool or cotton, which mayor may not be faced with paper, aluminum, or other vapor retarder. Used in walls and ceiling cavities.

Battery: A device that can store and release electrical energy.

Bay window: An arrangement of three or more individual window units, attached so as to project from the building façade at various angles.

Beam: A structural member transversely supporting a load.

Bearing wall: A wall that supports any vertical load in addition to its own weight.

Below-grade walls: Basement or first story walls associated with the exterior of the building that are at least 85 percent below-grade.

Biocide: Toxic chemical or physical agent capable of killing or inactivating one or more groups of microorganisms such as vegetative bacteria, mycobacteria, bacterial spores, fungi parasites, or viruses. Used in paint, preservatives, floor coverings, or fabrics. Biocides are safe only in low concentrations.

Biodegradable: Capable of decomposing into elements found in nature within a reasonable short period of time after customary disposal.

Biodegradation: Decomposition of material due to action of living organisms.

Biodiversity: According to the World Conservation Union (IUCN), biodiversity is "the variety of life in all its forms, levels and combinations. Includes ecosystem diversity, species diversity, and genetic diversity."

Bioengineering: The use of living plants, or a combination of living and non-living materials, to stabilize slopes and drainage ways.

Biogas: A combustible gas (composed primarily of methane) produced when sewage or manure is fermented in the absence of oxygen. The solid material that remains in the digester after fermentation can be used as an organic fertilizer.

Bio-indicators: Fish and other freshwater organisms from polluted waterways, for example, whose death or unusual behavior may indicate the presence of hazardous pollutants that have escaped other detection methods.

Biological oxygen demand: Amount of dissolved oxygen used by microorganisms in the biochemical oxidation process to break down organic matter.

Biological productivity: Nature's capability to reproduce and regenerate, thereby accumulating biomass. Biological productivity of a given land category is determined by dividing the total biological production by the total land area available in this category.

Biological wastewater management: Purifying wastewater in a natural or emulated wetland environment. Such systems are powered mainly by sunlight and achieve treatment through the combined action of living food chains, many of which are microscopic.

Biologically productive land: Land that is sufficiently fertile to accommodate forests or agriculture, i.e., there is significant net primary production.

Biomass: the amount of living organic matter of an ecosystem - usually measured in dry weight.

Biomass energy: The energy released from biomass when it is eaten, burned, or otherwise used as or converted into fuel.

Biophysical: The living and non-living components and processes of the ecosphere. Biophysical measurements of nature quantify the ecosphere in physical units such as cubic meters, kilograms or joules rather than in dollars.

Blackwater: Water from toilets, kitchen sink, or other sources, which may be contaminated with microorganisms or harmful bacteria and should not be reused until such sources of contamination are removed.

Blanket wrapped: A form of packaging for shipping furniture, using returnable blankets. This method leaves no packaging materials that require disposal.

Blended cement: A mixture of Portland cement and other material such as granulated blast furnace slag, pozzolan, hydrated lime, etc. combined either during or after the finish grinding of the cement.

Block filler: Surface coating used over concrete or CMU substrates that can be thickly applied to reduce or eliminate small holes or other surface imperfections. Block filler smoothes out the rough texture associated with CMUs, thus requiring less paint for the finish coat and increasing cleanability.

Blower door: A variable speed fan used to pressurize or depressurize a house to measure air leakage. It is mounted in an adjustable frame that fits snugly in the doorway.

Blowing agent: Also known as foaming agent, this chemical agent is added to plastics and rubbers. When heated, it generates inert gases to give resins in the materials cellular structure, thereby strengthening materials like carpet foam cushions. Traditionally, chlorofluorocarbons (CFCs) were used as blowing agents and contributed to the degradation of ozone. Although very few manufacturers use CFCs, some have substituted methylene chloride, a gas that also damages the upper ozone layer. Pantene may be substituted for as a non-CFC blowing agent.

Blown-in blanket (BIB): Loose insulation that is installed in wall cavities using a powerful blower and a fabric containment screen.

Blue Angel (Blaue Engel): The first environmental listing program, started in Germany in the late 1970s, identified by a blue angel symbol. Blue Angel currently lists hundreds of European consumer products.

Boiler: A pressurized system in which water is vaporized to steam by heat transferred from a source of higher temperature, usually the products of combustion from burning fuels. Steam thus generated may be used directly as a heating medium, or as the working fluid in a prime mover to convert thermal energy to mechanical work, which in turn may be converted to electrical energy. Not usually intended to heat domestic hot water (see combined/indirect water heater).

Bonded urethane cushion: Carpet cushion made predominantly from scrap polyurethane foam.

Bonding: A guarantee of completion or performance typically issued by an insurance company. For example, contractors are often bonded as assurance that they will complete the work.

Book-matched veneer: A method of matching veneer to produce symmetric patterns. Also called herringbone-matched veneer.

Borate-treated wood: Borate is a mineral product derived from borax. Wood treated with borates is resistant to termites and moisture.

Bottom ash: The divided residue resulting from the combustion of ground or powdered coal. Similar to fly ash, but not deposited within the flue. Bottom ash is used for fill material, soil stabilization and waste remediation.

Bottom plate: A horizontal timber that serves as a base for the studs in a stud partition. A plate riveted to the bottom flange of a plate girder to bear on the masonry plate. Also called a sole plate.

Bow window: A rounded bay window that projects from the wall in an arc. Also called a bay window.

Box beam: A hollow beam, usually rectangular in section; fabricated of wood, steel, or a combination of wood and steel. On exterior applications, the hollow portion of the box beam can contain insulation.

Branch duct: An air duct that branches from the main duct, at which point the main duct is reduced in cross-sectional area.

Branch system: The standard method of distributing hot water or air using a large main line with many small branches.

Breathability: Property indicating permeability to gas. Also, the ability of a finish to allow moisture to escape from behind the film without causing blistering or peeling.

Brick moulding: A standard milled wood trim piece that covers the gap between a window frame and masonry.

Brick veneer: A facing of brick laid against and fastened to sheathing of a frame wall or tile wall construction.

Bridging: A brace or system of braces placed between joists or the like to stiffen them, hold them in place, and help distribute loads.

Brightness: The subjective perception of relative luminance in a space or on a surface.

British thermal unit (BTU): The energy needed to raise the temperature of 1 pound (0.454 kg) of water 1°F (0.56°C). 1 Btu = 1,055 Joules (J).

Brise soleil: An exterior fixed or movable device, such as fins or louvers, designed to block the direct entrance of sun into a building.

Broad-spectrum biostat: A biocide effective on a wide range of microorganisms (including unintended targets).

Broadloom carpet: A tufted, woven, or knitted rug or carpet in continuous rolls in a variety of widths.

Brownfields: Abandoned, idled, or under-used industrial and commercial facilities where expansion or redevelopment is complicated by real or perceived environmental contamination.

Build to suit: Construction of land improvements and buildings to a tenant or buyer’s specifications.

Building codes: Municipal ordinances that regulate the construction and occupancy of buildings for health and safety reasons.

Building commissioning (Cx): The startup phase of a new or remodeled building. This phase includes testing and fine-tuning of the HVAC and other systems to assure proper functioning and adherence to design criteria. Commissioning also includes preparation of the system operation manuals and instruction of the building maintenance personnel. True whole building commissioning includes an independent authority involved in the project from early in design phases through the completion of the one-year warranty period.

Building ecology: Physical environment and systems found inside the building. Key issues include air quality, acoustics, and electromagnetic fields.

Building envelope: The shell of the building that separates what is inside from what is outside. Elements of the building envelope are the exterior walls (including windows and doors), the roof and the floor of the lowest level of the building. The building envelope has a number of functions: it holds the building up; it keeps the rain and ground water out; it keeps the wind out; it keeps water vapor out; and it controls the transfer of energy (heat) between the inside and the outside. One material may control only one of these functions or may control several functions at once. (Note: Although floors of conditioned basements and conditioned crawl spaces are technically part of the building envelope, the code does not specify insulation requirements for these components and they can be ignored.)

Building integrated photovoltaics (BIPV): Portions of a building envelope (walls, roof, and fenestration) that not only provide enclosure but also incorporate photovoltaic materials that generate electricity.

Building pressurization: The air pressure within a building relative to the air pressure outside. Slight positive building pressurization is usually desirable to avoid infiltration of unconditioned and unfiltered air. Positive pressurization is maintained by providing adequate outdoor makeup air to the HVAC system to compensate for exhaust and leakage.

Building-Related Illness (BRI): Clinically verifiable diseases, which are attributed to a specific source or pollutant within a building, and are more serious than Sick Building Syndrome (SBS) condition. The symptoms of the disease persist after the occupant leaves the building, unlike SBS in which the occupant experiences relief shortly after leaving the building.

Built environment: All human-built structures (as opposed to the natural environment).

Built-up roofing: Seamless, flexible, waterproofed roofing system, traditionally of plies of felt moped with asphalt or pitch.

Butterfly roof: A roof shape that has two surfaces that rise from the center to the eaves with a valley in the center; resembles the wings of a butterfly.

Buttress: A structure, usually brick or stone, built against a wall for support or reinforcement.

By-product: Anything produced in the course of making another product.

BX wiring: A type of wiring installed in a house. It is enclosed in a metallic sheathing and is more resistant to damage than Romex wiring. Also called armored cable.

Calcination: Prolonged heating at a high temperature to remove moisture and increase hardness, e.g., gypsum is calcinated to produce plaster.

Calendering: The process of passing hot, dough-like emulsions of vinyl or linseed oil through heated rollers, forming flat sheets for the manufacture of flooring.

Caliche: Calcium carbonate in earth. It makes a very hard brick/block without firing and is a common roadbed material. Also called hardpan.

Candela (cd): The SI unit of luminous intensity (formerly called the “candle”). One candela equals one lumen per steradian—a specific measure of luminous intensity, in a given direction.

Cantilever: A beam, girder, truss, or other structural member that projects beyond its supporting wall or column.

Capillary action: The movement of water in the interstices of a porous material as a result of surface tension.

Carcinogen: Cancer-causing agent, that may be physical, viral, or chemical. Cancers arise from aberrations in cellular DNA.

Carnauba: Hard natural wax, exuded from carnauba palm leaves. Sparingly soluble in fat solvents. Very low toxicity. Used in waxes and varnishes where a hard, high-polish finish is needed. Also called Brazil wax.

Carpet backing: The supportive structure for carpet, providing a durable surface to bond the face fibers to each other and to the flooring system. Backing enhances the dimensional stability, resilience, and comfort; however, it may also be a source of VOC emissions.

Carpet tile: Carpet made and laid out in small units (2 or 3 feet square), allowing for easy removal and replacement.

Carrying capacity: The amount of demand or usage for a particular resource that can be sustained without depletion or degradation of dependent life forms.

Case goods: Hard furniture storage components, such as cabinets and files.

Casement: A window sash that swings open on side hinges.

Cathedral ceiling: A sloped or vaulted ceiling, usually with the rafters serving as the ceiling joists. There is generally no attic above a cathedral ceiling, although some cathedral ceilings have a short truss attic.

Casing: Exposed moulding or framing around a window or door, on either the inside or outside, to cover the space between the window frame or jamb and the wall.

Caulking: A resilient mastic compound used to seal cracks, fill joints, prevent leakage, and/or provide waterproofing. Caulks fabricated with butyl rubber or polyurethane can be sources of VOC emissions indoors.

Cavity Insulation: Insulation installed between structural members.

Cavity wall: A wall often built of masonry cavity block to provide an airspace within the wall. Also double-framed wall with space between walls for plumbing, ducts, and soundproofing.

Ceiling: The ceiling requirements apply to portions of the roof and/or ceiling through which heat flows. Ceiling components include the interior surface of flat ceilings below attics, the interior surface of cathedral or vaulted ceilings, skylights, or vaulted ceilings, skylights and sloped building assemblies less than 60° from horizontal, but excluding skylight shafts.

Ceiling cavity: The cavity formed by the ceiling, the plane of the luminaires, and the wall surfaces between them.

Cellulose: The fibrous part of plants used in making paper and textiles, which may be made into building products, such as insulation.

Cellulose insulation: Thermal insulation manufactured from recycled newspaper, typically treated with natural borates to provide vermin and fire protection. More recently, fungicides and chemical fire retardants have been used and may prove problematic for sensitive individuals.

Cement: A material or mixture of materials without aggregate which, when in a plastic state, possesses adhesive and cohesive properties and hardens in place. Made by processing limestone, clay, cement rock, and other materials into a fine powder. It is the basic ingredient of concrete.

Cementitious: Having the properties of cement. Cement is the primary binding agent in concrete.

Cementitious foam insulation: A magnesium oxide-based material blown with air to create an inert, effective insulation. It is especially helpful for people with chemical sensitivities.

Certified sustainably managed forest: Some certifying organizations have been established that oversee the harvesting of wood for lumber. The underlying guideline is preservation of a diverse forest that exhibits the same ecological characteristics as a healthy natural forest.

Change order: A form used by an architect or contractor to specify changes from the approved original plan.

Charge controller: A device used to prevent over- or undercharging of a battery or bank of batteries.

Charrette: An intensive design process that involves the collaboration of all project stakeholders at the beginning of a project to develop a comprehensive plan or design. Although it may only take place over a few short days, it establishes project goals and groundwork for communication and a team-oriented approach to be carried throughout the building process.

Chase: A vertical or horizontal opening, through the building frame, skeleton, or structure, for ducts, plumbing, telephone, and electrical lines.

Check metering: Measurement instrumentation for the supplementary monitoring of energy consumption (electric, gas, oil, etc.) to isolate the various categories of energy use to permit conservation and control, in addition to the revenue metering furnished by the utility.

Check dam: Low dam of stone, wood, or other material used for holding and spreading runoff and sediment in a swale.

Chemical or environmental sensitivity: Chronic multisystem disorder, usually involving symptoms of the central nervous system and at least one other system. However, no objective test is available to diagnose this condition. Affected persons are frequently intolerant to some foods, and they react adversely to some chemical and environmental agents at levels tolerated by most people. Reactions may range from mild discomfort to total disability, and improvement may occur by avoiding suspected agents.

Chemical weld: A method of joining the surface of two substrates (e.g. edges of vinyl flooring) by applying a solvent or adhesive and joining them together with a chemical and/or physical reaction.

Chemically stable material: Material that will not readily break down, release chemicals, or change into other (potentially toxic) chemicals with age, heat, or light.

Chimney effect: Tendency of air or gas in vertical passage to rise when it is heated because it becomes lighter (less dense) than the surrounding air or gas. Useful in promoting cooling through enhanced natural ventilation.

Chipboard (or particleboard): A building panel consisting of wood chips and fibers pressed together, using a synthetic resin as a binding agent.

Circuit: One complete run of a set of electric conductors from a power source to various electrical devices and back to the same power source.

Circulation pumps: Pumps that are used to keep hot water circulating through the distribution system.

Cistern: A tank to hold a supply of fresh water. May be above or below ground.

Clear-cut: Harvesting all the trees in an area; can result in accelerated runoff, erosion, sedimentation of lakes and streams, flooding, and habitat destruction.

Clerestory: That part of a building rising above the roofs or other parts, whose walls contain windows specifically intended to provide lighting and/or ventilation to the interior.

Closed-loop control: A control system that utilizes measurement of a controlled variable for feedback. Based on the measured feedback, the control system alters its output in an attempt to force the controlled variable to reach a given set point.

Closed-loop recycling: Reclaiming or reusing wastewater or process chemicals in an enclosed process in manufacturing.

Cluster housing: Building of multi- or single-family housing close together to save land costs and provide for more common open spaces.

CO2-based high-limit ventilation control: A ventilation strategy that monitors the CO2 concentration in a building zone or in the return air duct from the zone. If the CO2 concentration approaches a predetermined high limit, the outdoor airflow controller is reset to provide additional ventilation. This process supplements standard ventilation-control strategies by providing additional ventilation for unexpected occupancy.

Cob: A mixture of straw, gravel, and clay, used to make thick earthen mass walls.

Code: A published body of rules and regulations for building practices, materials, and installations, designed to protect the health, welfare, and safety of the public.

Code of practice: A set of rules, criteria, values and/or beliefs by which an individual, business, agency, government department or organization chooses to live, work, and operate under.

Codes, Covenants and Restrictions (CC&Rs): A declaration filed by a developer to specify his intended restrictions on what one can or cannot build in the development.

Coefficient of performance (COP): The ratio of the rate of heat delivery or removal to the energy input of the machine in consistent units. COP = energy output / energy input.

Coefficient of utilization (CU): The ratio of light energy (lumens) from a source, calculated as received on the work plane, to the light energy emitted by the source alone.

Coffering: Ceiling with deeply recessed panels, often highly ornamental.

Cogeneration: A facility in which two or more forms of energy are generated simultaneously or interchangeably. Commonly, a cogeneration facility produces steam for an industrial or commercial process and uses some of the steam to turn a turbine that generates electricity. Another type of cogeneration arrangement combines several energy sources in a single facility to provide a mix of energy forms (heat, electricity, etc.) in varying proportions according to the needs of the energy users.

Co-housing: Housing that combines the privacy of single-family dwelling units with extensive common facilities, such as kitchens, dining rooms, children’s playrooms, and laundry facilities, thus enhancing a sense of community. Residents often join together early to identify a site and raise pre-development funds, making the development process much different than the usual development of communities.

Coir: Coarse, brown fiber from coconut husks; used in rope, matting, and carpet backing.

Cold Joint: A joint formed when a concrete surface hardens before the next batch of concrete is placed against it; characterized by a poor bond unless special procedures are observed.

Collector efficiency: A measure of the percentage of available solar energy that a solar hot water collector will transmit to the heat transport fluid.

Color Rendering Index (CRI): A value ranging from 0 to 100, where 100 represents light with qualities identical to sunlight.

Color temperature: In general terms, a means of defining the relative whiteness of a light source, specifically the absolute temperature (degrees Kelvin) of a blackbody radiator having a chromaticity equal to that of the light source. Used in measuring high quality in light bulbs.

Column: A relatively long, slender structural compression member such as a post, pillar, or strut; usually vertical, supporting a load that acts in the direction of its longitudinal axis.

Combustion by-products: Any gas that is produced by the burning of wood or fossil fuels.

Combustion gases: The gases, such as carbon monoxide, that result from the process of burning. In a building, these are produced by gas appliances, such as furnaces and water heaters. Proper venting must be assured.

Comfort zone: The effective temperature range over which the majority of adults feel comfortable.

Commissioning: The process of ensuring, verifying, and documenting that new equipment and systems are installed and able to operate according to the design intent.

Common Rafter: A rafter that is at right angles to the rafter plate (at the eaves) of a roof and extends from the plate to the ridge board or ridgepole.

Community (Biological definition): An association of organisms of different species living together in a defined habitat with some degree of mutual interdependence.

Compact fluorescent light: Small fluorescent lamps that are often used as a much more efficient alternative to incandescent lighting.

Comparable property (comps): Another property to which a subject property can be compared to reach an estimate of market value.

Composite construction: A type of construction made up of different materials or of members produced by different methods.

Composite material: A complex material made up of two or more complementary substances. They can be difficult to recycle. Plastic laminates are an example. Composite materials are best applied in situations where they can be removed for reuse (not requiring remanufacture).

Composite panel: Laminated panels made of different materials, such as foam core panels with Oriented Strand Board (OSB) or metal skin.

Compost: Relatively stable humus material produced for the biodegradation of organic refuse.

Composting: A waste management option involving the controlled biological decomposition of organic materials into a relatively stable humus-like product that can be handled, stored, and applied to the land with a positive affect on the soil.

Composting toilet: A toilet that uses little or no water and in which human waste composts to a material that can be safely used as a soil amendment.

Concentration: The amount of pollutant in a given volume of air or water.

Concrete: A composite material that consists essentially of a binding medium (typically Portland cement and often fly ash) within which are embedded particles or fragments of aggregate (typically sand and larger aggregate rock). (see also air-entrained concrete)

Concrete masonry unit (CMU): A block or brick cast of Portland cement and suitable aggregate with or without admixtures, and intended for laying up with other units as in normal stone masonry construction. Also called A-block or cinder block.

Condensation: The deposit of water vapor from the air on any surface whose temperature is below the dew point, as in the case of cold window glass or frame that is exposed to humid indoor air.

Condensation Resistance Factor (CRF): An indication of a window’s ability to resist condensation. The higher the CRF, the less likely condensation is to occur.

Conditioned air: Air treated to control its temperature, relative humidity, purity, pressure, movement, or other characteristics to obtain a desired environment.

Conditioned space: The area supplied with conditioned air from HVAC system to provide comfort for the occupants; ideally the boundary of the conditioned space is located at the pressure boundary, which is located with the thermal boundary.

Conduction: Process by which heat transfers through a solid material by direct molecular interaction. Heat always flows from a higher-temperature area to a lower-temperature one.

Conductivity (k): The quantity of heat (BTUs) that will flow through 1 square foot of material, 1 inch thick, in one hour, when there is a temperature difference of 1 degree F between its surfaces.

Conductor: A substance or body capable of transmitting electricity, heat, or sound.

Connected lighting load: The sum of all non-exempt interior lighting power, measured in watts. Also called connected lighting power (CLP).

Conservation (nature): Protection against irreversible destruction and other undesirable changes, including the management of human use of organisms or ecosystems to ensure such use is sustainable.

Constructed wetland: Any of a variety of designed systems that are modeled after natural wetlands, use aquatic plants, and can be used to treat wastewater or runoff.

Contaminant: Foreign and/or unwanted physical, chemical, biological, or radiological material in a product or in the environment, or any such substance that is present in a greater-than-normal amount.

Contrast sensitivity: The ability to detect the presence of luminance differences.

Convection: Process by which heat transfers by transportation in air or water.

Conversion: A form of recycling in which a waste material is turned into a useful material of substantially lower quality. An example is the use of crushed concrete and bricks as a granular base for roads and sidewalks. Also known as downcycling.

Conversion efficiency: The ratio of raw materials going into a process to the product coming out.

Cooling degree-day (CDD): A unit, based on temperature difference and time, used in estimating cooling energy consumption and specifying nominal cooling load of a building in summer. For any one day, when the mean temperature is more than a reference temperature (typically 65°F), there are as many degree-days cooling as degrees Fahrenheit difference in temperature between the mean temperature for the day and the reference temperature. Annual cooling degree-days (CDD) are the sum of all degree-days over a calendar year.

Cooling/heating load: A building’s demand for heat/cool to offset a deficit/overage of the opposite.

Coolness index: The visible light transmittance of a glazing divided by its shading coefficient. Glazings with high coolness indices let more light and less heat into a building.

Co-products: Materials that are incidentally or intentionally produced when making another material.

Cordwood construction: A building technique that involves piling cords (short, cut logs) of wood, usually of relatively small diameter, into a wall structure or enclosed building. Typically the long dimension of the small wood members is perpendicular to the length of the wall.

Cornice: An ornamental molding, usually of wood or plaster, running round the walls of a room just below the ceiling.

Covenants: Promises written into deeds and other instruments agreeing to performance or nonperformance of certain acts, or requiring or preventing certain uses of the property.

Cradle-to-grave analysis: Analysis of the impact of a product from the beginning of its source gathering processes, through the end of its useful life, to disposal of all waste products. Cradle-to-cradle is a related term signifying the recycling or reuse of materials at the end of their first useful life.

Crawl space: In a building without a basement, an unfinished accessible space below the first floor which is usually less than a full story in height; normally enclosed by the foundation wall or skirting.

Creative feasibility: Used during market research, this process involves using market indicators such as the growing demand for green consumer products and extrapolating to trends in demand in real estate markets. It can be used to identify markets for ecologically-sensitive developments and convince financiers of their feasibility by combining primary market research, focus groups, and traditional supply (comparatives) and blending this information with analysis of the best practices used in a variety of environmentally responsible projects.

Cripple Stud: In a building frame, a structural element that is shorter than usual, as a stud above a door opening or above or below a window opening.

Critical zone: Any location in a building with contaminant sources sufficiently strong enough that proper control of ventilation, with no margin for error, is crucial for maintaining the immediate comfort of occupants. Critical zones may include conference rooms, smoking rooms, cafeterias, washrooms, auditoriums, or anywhere occupancy can rapidly change.

Cross ventilation: Passive building strategy which aids in cooling a building using outdoor breezes which enter the building by passing through an opening, then exit the building through another opening, extracting some of the heat from inside the building as it leaves.

Crumb rubber: Rubber fragments ground to the size of sand or silt, used in rubber or plastic products or processed further for use in paving and other asphalt applications. Workers applying crumb rubber modified asphalt paving have experienced acute eye, nose, throat, and skin irritation.

Cullet: Crushed, waste glass that is returned for recycling.

Culvert: A sewer or drain running under a road or embankment.

Curing: Conversion of raw products to finished material. In rubber technology, vulcanization. In thermosetting resins, the final cross-linking procedure. In concrete, the process of bringing freshly placed concrete to required strength and quality by maintaining humidity and temperature at specified levels for a given length of time. In textile manufacture, heat treatment with chemicals or resins to impart water or increase resistance.

Current: The flow of electrons through a conductor.

Curtain wall: A nonbearing exterior building wall, between piers or columns that is not supported by the beams or girders of a skeleton frame.

Custom builder: One who builds to a specific buyer’s order, as opposed to a speculative, or ‘spec’ builder.

Cut-off angle: The critical viewing angle beyond which a source can no longer be seen because of an obstruction (such as a baffle or overhang).

Dado: The middle portion of a protective, ornamental paneling applied to the lower walls of a room above the baseboard. Or, a rectangular groove cut across the full width of a piece of wood to receive the end of another piece.

Damper: A device in a duct or vent that restricts airflow.

Damp-proofing: A treatment, such as a sealer or asphalt coating, that inhibits the transfer of moisture. Used in locations where higher-quality waterproofing is not needed.

Dander: Tiny scales from human or animal hair, skin, or feathers.

Daylight factor (DF): The ratio of daylight illumination at a given point on a given plane, from an obstructed sky of assumed or known illuminance distribution, to the light received on a horizontal plane from an unobstructed hemisphere of this sky, expressed as a percentage. Direct sunlight is excluded for both values of illumination. The daylight factor is the sum of the sky component, the external reflected component, and the internal reflected component. The interior plane is usually a horizontal work plane. If the sky condition is the CIE standard overcast condition, then the DF will remain constant regardless of absolute exterior illuminance.

Daylight sensing control (DS): A device that automatically regulates the power input to electric lighting near fenestration to maintain the desired workplace illumination, taking into account available natural light.

Daylighted zone: The area adjacent to vertical glazing that receives daylighting. The daylighting zone is assumed to extend into the space 15 feet or to the nearest opaque barrier, whichever is less. The zone’s width is assumed to be the width of the window plus two feet on either side, or one-half the distance to the adjacent vertical glazing, whichever is the least. The daylighting zone can be increased by using high glazing strategies or light shelves.

Daylighting: The use natural light to minimize the need for artificial lighting during the day. Common daylighting strategies include the proper orientation and placement of windows, use of light wells, light shafts or tubes, skylights, clerestory windows, light shelves, reflective surfaces, and shading, and the use of interior glazing to allow light into adjacent spaces.

Dead air space: A confined space of air with no airflow. Dead air space tends to reduce both conduction and convection of heat. This attribute is utilized in virtually all insulating materials and systems, such as double-glazed windows, fiberglass batt insulation, rigid foam panels, and loose-fill insulations.

Deadband: The temperature range in which no heating or cooling is used.

Decay: Disintegration of wood or other substance through the action of fungi.

Decibel (dB): Unit of sound level or sound-pressure level. It is ten times the logarithm of the square of the sound pressure divided by the square of reference pressure, 20 micropascals.

Deciduous: Trees that lose their leaves seasonally differing from coniferous.

Deflection: Amount of bending of a truss or beam under a load.

Defoliant: Toxic chemical sprayed on plants that causes their leaves to fall off prematurely.

Degree-days: The difference between the average daily temperature and a building’s balance point, usually assumed to be 65 degrees Fahrenheit. This measure is used to estimate building energy needs. It is also a quick way to compare the severity and character of a climate. Heating degree-days (HDDs): areas with more than 5500 HDDs per year are characterized by long cold winters. Areas with less than 2000 HDDs per year are characterized by very mild winters. Areas with more than 1500 Cooling Degree-Days (CDDs) are characterized by long hot summers and substantial cooling requirements. Areas with less than 500 CDDs per year are characterized by mild summers and little need for mechanical cooling.

Delamination: A failure in a laminated structure, characterized by the separation or loss of adhesion between plies, as in built-up roofing, plywood, or glue-laminated timber.

Demand-controlled ventilation (DCV) CO2-based: A ventilation-control strategy in which the concentration of CO2 is the measured variable that is controlled to a set point by modulating outdoor airflow. With this strategy, only human source contaminants are considered. CO2DCV will not comply with either procedure of ASHRAE Standard 62-1989.

Demand-side management: A program consisting of the planning, implementing, and monitoring activities of electric utilities that are designed to encourage consumers to modify their level and pattern of electricity usage.

Dematerialization: Shifting from selling products with intense use of resources to selling 'value-added' services.

Densitometer: A photometer for measuring the optical density (the opposite of transmittance) of materials.

Desiccant: A drying agent such as silica gel, which can be used to reduce latent cooling loads. Also used to absorb moisture from within the sealed airspace of an insulating glass unit.

Design conditions: The exterior and interior environmental parameters specified for air conditioning (heating, cooling, ventilation) and electrical design for a building.

Design energy consumption (DECON): An ASHRAE term defined by the computed annual energy usage of a proposed building design.

Design energy cost (DECOS): The computed annual energy expenditure of a proposed building design.

Design temperatures: Temperatures used for modeling energy calculations. They are established for winter and summer for specific cities, representing the calculated low and high extremes.

Detention: In stormwater management, ponding of runoff in pools and basins for water-quality improvement and flood prevention.

Development: A process of economic and social transformation that defies simple definition. Though often viewed as a strictly economic process involving growth and diversification of a country's economy, development is a qualitative concept that entails complex social, cultural, and environmental changes. There are many models of what 'development' should look like and many different standards of what constitutes 'success'.

Dewpoint: The temperature at which water vapor in the air will condense at a given state of humidity and pressure.

Dielectric unions: Fittings made of corrosion-resistant metals.

Diffuse lighting: Illumination dispersed widely; produces less-distinct shadows than directional lighting.

Diffuse radiation: Radiation that has traveled an indirect path from the sun because it has been scattered by particles in the atmosphere such as dust and water vapor.

Diffusion: The movement of individual molecules through a material. The movement occurs because of the kinetic energy of the individual molecules, independent of airflow. Kinetic energy increases as the temperature increases.

Dimensional lumber: Conventional lumber, such as 2x4s and 2x6s, typically used for studs, joists and rafters.

Dimensional lumber: Lumber ranging only from 2x to 4x. Boards are 1x and timbers are 5x and greater.

Dimensional stability: The degree to which a material maintains its original dimensions when subjected to changes in temperature and humidity.

Dimming: System that automatically turns down the output of artificial lighting. Dimming is often used in areas of buildings that receive sunlight to save electricity and reduce the building’s cooling loads.

Direct cooling: A cooling strategy comprised of four main components: keeping the heat out by primarily avoiding direct solar gain, providing ventilation, underground construction, and evaporative cooling. Specific strategies include orienting a building away from intense solar exposure, using indirect daylighting instead of artificial lighting, shading roofs, walls, and windows, and adjusting surface-to-volume ratios.

Direct current: An electrical current flowing at constant voltage. Electricity that flows continuously in the same direction.

Direct expansion cooling: Mechanical cooling where the air of the space being cooled passes directly over the cooling coil (evaporator).

Direct gain systems: A widely used passive solar design approach that uses vertical and generally south-facing glazing in combination with materials inside the building envelope to absorb heat.

Direct glue-down: Method where flooring is glued directly to the substrate surface, rendering that material unusable upon removal.

Direct-indirect lighting: Lighting in which the luminaires are in the general diffuse category but they emit little or no light at angles near a horizontal plane drawn through them. They allow light to be directed in the vertical plane (both up and down).

Direct radiation: Light that has traveled a straight path from the sun, as opposed to diffuse radiation.

Direct solar gain: Heat that enters the building as solar radiation through windows.

Direct sunlight (beam sunlight): That portion of daylight arriving at a specified location directly from the sun, without diffusion.

Directional lighting: The distribution of all, or nearly all, of the light from a fixture in one direction.

Dirunal flux: The difference between daytime and nighttime temperatures. A diurnal flux of 25 degrees Fahrenheit or above indicates an arid climate suitable for mass building construction.

Distributed systems: An alternative to the traditional large remote power plant that uses smaller power plants distributed throughout a service area. Transmission lines can be smaller because distances are smaller, and high voltage transmission over long distances becomes unnecessary.

Distribution system: A system of pipes or ducts used to distribute energy.

Disuse: The complete sequence and series of activities and actions that eliminate the “Building” in its present form. There are basically two options: (1) demolition and return of the “Building,” “Site,” and all of its components to the natural environment; and (2) renovation. The renovation option essentially leads back to the beginning of the building life cycle model or to some intermediate stage within that model.

DOE-2.1E: A building-simulation computer program used to calculate total annual energy use.

Domestic hardwood: Deciduous trees that grow in the United States. This is the only type of wood in the United States where the regeneration (production of new trees) exceeds the removal rate.

Domestic hot water: The water that comes out of the taps or appliances, as distinguished from the hot water circulated through the radiators and pipes of a hydronic heating system for the house.

Dormer: A structure projecting from a sloping roof, usually housing a window or ventilating louver.

Double-glazing: Two thicknesses of glass separated by an airspace. This arrangement improves the insulative quality of a window unit.

Double-hung window: A window consisting of two sashes of glass operating in a rectangular frame, in which both the upper and lower halves can be slid up and down. A counterbalance mechanism usually holds the sash in place.

Double-strength glass: Sheet glass between 0.115” and 0.133” (3-3.38 mm) thick.

Downstream impact: Impact to the environment from an upstream activity.

Drip irrigation: Aboveground, low-pressure watering system with flexible tubing that releases small, steady amounts of water through emitters placed near individual plants.

Dry bulb temperature: The temperature of air indicated by an ordinary thermometer.

Dry construction: Use of dry materials such as wallboard, plywood, etc. without the use of plaster or mortar.

Dry joint: A joint without mortar between stones or tiles.

Dry-pressed: A method of forming individual tiles by compressing dry clay under pressure, then firing it.

Drying oil: Linseed, cottonseed, or soybean oil that is highly unsaturated and is readily oxidized and polymerized to form a hard, dry film upon exposure to air, in paints and varnishes.

Drywall: Also called gypsum board or Sheetrock. The most common interior wall and ceiling finish material. Can be part of the building’s air barrier if it is sealed to make the barrier continuous.

Duct: Usually round or rectangular pipe for the distribution of conditioned air from an air handling unit to a supply air vent.

Duct leakage tester: A device with a fan and instruments used to find leaks in heating and cooling ducts. Also called a duct pressure test or dust blaster.

Duct system: A continuous passageway for the transmission of air that, in addition to ducts, includes duct fittings, registers, dampers, plenums, fans, and accessory air-handling equipment and appliances.

Due diligence: During the assessment phase, investigation of all reasonable considerations and factors ﷓ financial, legal, environmental, or other related to a project or property to prevent unpleasant future surprises.

Dust: Bits of solid matter that have been broken into tiny pieces.

Dynamic energy models: Simulated energy models that take into account the ability of thermal mass to modify and delay heating and cooling loads.

Earth berm: A bank of earth placed up against the exterior of a building to provide thermal stability.

Earth’s thermal energy: A short distance below the surface, the earth maintains a mostly constant temperature reasonably close to the human comfort range. This can be used advantageously by certain heating and cooling systems.

Earth sheltering (also earth berming): Building partially or fully below ground level. Soil temperature varies less than air temperature [deeper soil = more constant temperature]; an earth-sheltered structure provides an interior climate, which is generally closer to comfort level than a conventional interior space. Savings on heating and cooling bills are often in the range of 40-60%.

Earthship: A structure that has been designed to reduce or minimize the impact of the building on the planet and increase resident’s connection to it by utilizing recycling and low embodied energy materials, passive solar heating and cooling, photovoltaic power systems, rainwater harvesting, solar hot water, and gray water and black water treatment systems.

Eave: The lower edge of a sloping roof or that part of a roof of a building that projects beyond the wall. See also soffit.

Eco-efficiency: The ability of an economic entity to generate great economic value from fewer resources.

Ecological cost: The total impact of an activity on the environment including source depletion, pollution and degradation of habitats.

Ecological integrity: A characteristic of a natural system in which it possesses a self-correcting ability to recover to an end state that is normal to that system, when subjected to a disturbance.

Ecology: In biology, it is the study of the relationship between living organisms and their environment. In sociology, it is the study of the relationship between the distribution of human groups with reference to material resources and the consequent social and cultural patterns.

Economically sustainable: The characteristic of prolonged, careful, efficient, and prudent (wise and judicious) use of resources (natural, fiscal, human), products, facilities, and services. It is based on thorough knowledge and involves operating with little waste and accounting for all costs and benefits, including those that are not marketable and can result in savings.

Economizer controls: HVAC system controls that operate mixed air dampers to mix return and outdoor air to obtain air of a temperature appropriate for “free cooling.” Economizer controls are used during periods when outdoor air requires less cooling energy input than return air.

Ecosystem: A complex set of natural interconnected elements on which a habitat’s survival depends directly or indirectly.

Eco-tourism: Partnerships between the tourism industry and conservation efforts to preserve natural and cultural resources in resort destinations.

Edible landscaping: Landscaping containing vegetation which is cultivated for its ability to be eaten and digested by humans, for example, fruit trees or grape arbors.

Efficacy: In lighting design, a measure of the luminous efficiency of a specified light source, expressed in lumens per watt. For daylighting, this is the quotient of visible light incident on a surface to the total light energy on that surface. For electric sources, this is the quotient of the total luminous flux emitted by the total lamp power input.

Efficiency: A conservation strategy which seeks through application of better technology or social organization to provide the same or better level of service or performance while using fewer resources. Also, a measure of the proportion of energy that is converted into useful work, such as electricity.

Effluent: Treated water that is returned to lakes, streams, and aquifers from municipal sewage plants, industrial operations, and household septic systems.

Electrical grid: The network of privately and publicly owned transmission and distribution facilities from which most homes and businesses get their electricity.

Electricity: A form of energy generated by friction, induction, or chemical change that is caused by the presence and motion of elementary charged particles of which matter consists.

Electrochromic: A material’s ability to change its optical properties due to the action of an electric field, and to change back upon field reversal. Electrochromic windows transition from transparent to fully darkened and heat absorbing, and can be maintained at any grade of tint in between.

Electrode: A conductor used to establish electrical contact with a nonmetallic part of a circuit.

Electromagnetic fields (EMF): Electric and magnetic fields are common in nature and in all living things. Electric power produces fields that have a possible association with health risks.

Electromagnetic interference (EMI): Interference in a piece of electronic equipment or bioelectrical function caused by a piece of electronic or other equipment. Also known as Radio Frequency Interference (RFI).

Electromagnetic radiation: A series of electromagnetic waves.

Electromagnetic spectrum: The entire range of wavelengths or frequencies of electromagnetic radiation extending from gamma rays to the longest radio waves and including visible light.

Electron: A subatomic particle with a negative electric charge equal in magnitude to the positive charge of the proton but with a much smaller mass. Electrons orbit the atom's positively charged nucleus and determine its chemical properties.

Electronic ballast: Type of ballast for a fluorescent light, which increases efficiency and reduces flicker and noise.

Electronic High-Frequency Ballasts: Electronic ballasts improve fluorescent system efficacy by converting the standard 60 Hz input frequency to a higher frequency, usually 25,000 to 40,000 Hz. Lights operating on these frequencies produce about the same amount of light, while consuming up to 30% less power than a standard magnetic ballast.

Electrostatic painting: A process in which the substrate is electrostatically charged, causing sprayed paint to cling directly to the surface, reducing waste and worker exposure.

Embodied energy: The total energy required to grow, harvest, extract, manufacture, refine, process, package, transport, install and dispose of a particular product or building material.

Emission: A substance (gas, particle, or liquid) released from a material into the environment.

Emissivity (or emittance): The property of radiating heat. Values range from 0.05 for brightly polished metals to 0.96 for flat black surfaces. Most non-metals have high values of emittance.

Emulsion: Dispersion of one liquid phase in another. Paints are emulsions.

End-of-pipe: A description of technologies that reduce pollutant emissions after they have been formed. Examples include scrubbers on smokestacks and catalytic converters on automobile tailpipes.

End-use/Least-cost: A decision-making tool that keeps the planning team focused on the end users’ needs. It is a key component of green design and development because it identifies how to achieve the greatest benefits at the least cost in financial, social, and environmental terms.

Energy: The capacity for doing work. Energy exists in several forms, which may be transformed from one to another, such as thermal, mechanical, electrical or chemical. English units express energy in BTUs or kilowatt-hours (kWh).

Energy budget: An accounting of the flow of energy through a system. Originally applied by ecologists to ecosystems, the approach is also useful in industry to check the energy efficiency of industrial processes.

Energy conservation: Efficiency of energy use, production, transmission, or distribution that yields a decrease in energy consumption while providing the same, or higher, levels of service.

Energy cost budget: ASHRAE term for the maximum allowable computed annual energy expenditure for a proposed building.

Energy efficiency ratio (EER): The ratio of cooling capacity in BTU per hour divided by the electrical power input in watts under designated operating conditions.

Energy intensity: The energy required to make a material, including that used in extracting raw materials and production processes.

Energy management system: A control system capable of monitoring environmental and system loads to adjust HVAC output in order to conserve energy while maintaining comfort.

Energy modeling: A computer model that analyzes the building’s energy-related features in order to project energy consumption of a given design.

Energy or water efficiency: Using less energy or water to perform the same tasks. A device is energy-efficient if it provides comparable or better quality of service while using less energy than a conventional technology. Building weatherization or high-efficiency showerheads are efficiency technologies.

Energy recovery ventilator (ERV): A ventilator that draws heated but stale air out of a building and transfers heat from it to fresh incoming air (so the heat is not wasted). This can help reduce energy costs while improving indoor air quality. In hot humid areas, ERVs should be selected that dehumidify the incoming air.

Engineered wood: Reconstituted wood products that result in appropriate-to-use strength and consistent quality with less material. Engineered products use less wood or wood from smaller trees and are generally stronger, straighter, and of more consistent quality than dimensional lumber. Examples are engineered I-beams, laminated veneer lumber, laminated strand lumber, parallel strand lumber, and finger-jointed studs.

Enthalpy: The total heat (both sensible and latent) present in an air-moisture mixture.

Environment: A combination of the various physical and biological elements that affect the life of an organism. Although it is common to refer to ‘the’ environment, there are in fact many environments, i.e., aquatic or terrestrial, microscopic to global, all capable of change in time and place, but all intimately linked and in combination constituting the whole earth/atmosphere system.

Environment Canada: Canada’s national agency responsible for air and water quality standards and programs, industry regulations, and statistics.

Environmental audit: A study of the environmental impact of a product or process.

Environmental choice/Ecologo: The environmental listing program of Environment Canada.

Environmental equity/impact: Equal protection from environmental hazards regardless of race, ethnicity, or economic status.

Environmental impact: The net change (positive or negative) in human health and the condition of the environment that results from human actions, activities, or development.

Environmental impact assessment: A process that predicts the magnitude and importance of effects of a proposed activity on the environment, and on human health, and establishes conditions under which the activity may be undertaken. The result of the process may prevent the activity from proceeding if the potential effects are unacceptable.

Environmental restoration: The act of repairing damage to a site caused by human activity, industry, or natural disaster. Examples are replanting forests, stabilizing soils, and filling in and replanting mine pits.

Environmental sustainability: Cross-generational maintenance of ecosystem components and functions.

Environmentally preferable: Products or services that have a lesser or reduced effect on human health and the environment when compared with competing products or services that serve the same purpose. The comparison may consider raw material acquisition, production, manufacturing, packaging, distribution, reuse, operation, maintenance, or disposal of the product or service.

Environmentally sound: The maintenance of a healthy environment and the protection of life-sustaining ecological processes. It is based on thorough knowledge and requires or will result in products, manufacturing processes, developments, etc. which are in harmony with essential ecological processes and human health.

Epoxy adhesive: Glue made of epoxy resin.

Epoxy paint: Pigments held by epoxy binders that can be oil-modified to dry by oxidation, or epoxy resin that is mixed with amine or polyamide to harden and cure. Used in outdoor environments due to abrasion and corrosion resistance, adhesion, and flexibility.

Equivalent leakage area of a building (EqLA or ELA): A field-determined, quantitative expression of the air tightness of a building envelope. EqLA is the method set by the Canadian General Standards Board in which a blower door depressurizes the building envelope to 10 Pascals and the leakiness of the envelope is expressed as a summary hole in square inches. ELA is set by the ASTM equivalent procedure with the pressure differential of 4 Pascals.

Ergonomics: The study of the fit between people and machines or furniture.

Eutetic salt: Salt used for storing heat.

Eutrophication: A process through which a body of water becomes richer in nutrients and lower in dissolved oxygen content, thus reducing the waterway’s ability to support fish and other inhabitants.

Evacuated glazing: Insulating glazing composed of two glass layers, hermetically sealed at the edges, with a vacuum between to reduce convection. A spacer system is needed to keep the panes from touching and reduce conduction.

Evaporative cooling: Passive building strategy employing the evaporation of water directly into hot, dry airstreams to produce cooling; limited to arid climates.

Exfiltration: The passage of interior air from a building through cracks and holes in its envelope to the outdoors.

Exhaust air: Stale interior air that flows out of a building by means of natural or forced ventilation.

Expandable spray foam: Generic term for a product used to seal small cracks and voids in the building envelope and around door and window openings.

Expanded polystyrene (EPS): A rigid insulation material (also called bead board) made by heating pentane-saturated polystyrene pellets. (Pentane is used instead of the CFC’s or HCFC’s used to make extruded polystyrene. CFC’s and HCFC’s cause damage to the ozone layer.) Can have recycled content. Comes in various densities for different purposes.

Exposed aggregate: A mixture of a variety of small stones that is poured or pressed onto a surface with a cement paste. When the concrete is partially hardened, the surface is washed or brushed, exposing the aggregate.

Extruding: A method of forming a liquid or solid material into a long thin piece, usually under high pressure.

Eyebrow dormer: A low dormer on the slope of a roof that has no sides. The roof is carried over it in a wavy line. It is a low-curving dormer.

Eyebrow window: Low, inward-opening window with a bottom-hinged sash, used typically as attic windows. It is the window in an eyebrow dormer.

Façade: The exterior face of a building that is the architectural front.

Face fiber: The fiber that is exposed on the surface face of carpeting. Typically it is stitched into a backing material.

Faced plywood: Plywood faced with any sheet material other than wood.

Fascia: A flat board, band or face, used sometimes by itself but usually in combination with mouldings, often located at the outer face of the cornice.

Faucet aerator: Device that can be installed on a sink faucet to reduce water use.

Feasibility study: A combination of a market study and an economic analysis that provides the investor with knowledge of both the environment where the project exists and the expected returns on investment from it.

Feedstocks: The raw material used in manufacturing a product, such as the oil or gas used to make a plastic.

Fenestration: The terms "fenestration", "window", and "glazing" are often used interchangeably. However, fenestration refers to the design and position of windows, doors and other structural openings in a building.

Fenestration Cooling Rating (FCR): A rating number developed by the National Fenestration Rating Council to indicate relative window performance during the cooling season. A higher FCR indicates better performance.

Fenestration Heating Rating (FHR): A rating number developed by the National Fenestration Rating Council to indicate relative window performance during the heating season. A higher FHR indicates better performance.

Fetotoxin: A toxin with the potential to harm a fetus.

Fiberboard: Rigid or semi rigid sheet material made from wood or other vegetal fibers. Made from compressed fibers, including wood, paper, straw, or other cellulose fibers.

Fiberization: The process of reducing a material, such as newspaper or cotton, into a loose fiber.

Filament: A continuous strand of natural or synthetic fiber. Silk is a natural filament.

Fill insulation: Any thermal insulation placed in cavities of an assemblage.

Filler: Inert material added to paper, resin, or bituminous material, or used to fill holes in wood, plaster, or other surfaces.

Finger joint: A joint having interlaced, finger-like projections on the ends of the joined members.

Finger-jointed: High-quality lumber formed by joining small pieces of wood glued end to end, so named because the joint looks like interlocked fingers.

Fire retardant: Material that reduces or eliminates the tendency of flammable or combustible materials to burn. Fire retardants may be applied to the surface, impregnated, or incorporated during polymerization of plastics and rubbers.

Fittings: The parts of a plumbing or other utility distribution system that screw together.

Flagstone: Thin slabs of stone used for paving walks, driveways, and patios.

Flame spread: The speed at which fire will move through a material; determined using laboratory testing methods.

Flange: A projecting collar, edge, rib, rim on a pipe, shaft, or the like; also one of the principal longitudinal outer components of a beam or girder that resists tension or compression.

Flashing: Sheet metal or other material applied to seal and protect the joints formed by different materials or surfaces. It prevents water penetration and/or provides water drainage, especially between a roof and wall, and over exterior door openings and windows.

Flat plate collector: An assembly containing a panel of metal or other suitable material that absorbs sunlight and converts it into heat. In the collector, the heat transfers to a circulating liquid or gas and is either utilized immediately or stored for later use.

Float charge: A low rate of charge that will maintain a battery at a full state of charge without overcharging.

Float glass: Glass formed by a process of floating the material on a bed of molten metal. This produces a high-optical-quality glass with parallel surfaces without polishing and grinding.

Floor Area Ratio (FAR): Typically used as a formula to regulate building volume. The ratio of floor area to land area, expressed as a percent or decimal, that is determined by dividing the total floor area of the building by the area of the lot. A low maximum FAR of 0.3 results in a low-density building pattern.

Floor cavity ratio: A number indicating floor cavity proportions calculated from length, width, and height. The floor cavity is formed by the work plane, the floor, and the wall surfaces between them.

Floor panel: A prefabricated unit consisting of flooring, subflooring, and reinforcing joists; supported by columns, walls, or beams.

Floor slab (slab): A structural slab serving as a floor; usually of reinforced concrete.

Flow: The volume of a substance passing a point per unit time (e.g., meters per second, gallons per hour, etc.)

Flow form features: Water features of a building that are not only viewed as artistic decorations, but also maintain a pleasant level of humidity and acoustics as part of the building ecology.

Flow hood: A device that measures the amount of air flowing through a HVAC register.

Flue: An incombustible and heat-resistant enclosed passage to control and carry away combustion products from a fireplace, furnace, or boiler to the outside air.

Fluorescent lamp: A lamp that produces visible light by emitting electromagnetic radiation. Commonly they consist of a glass tube filled with argon, along with krypton or other inert gas. When electrical current is applied, the resulting arc emits ultraviolet radiation that excites the phosphors inside the lamp wall, causing them to radiate visible light. Fluorescent lighting is significantly more efficient than incandescent, requiring only 25-35% of the energy to produce an equivalent amount of light. See also compact fluorescent

Flush out: A process used to remove VOCs from a building by operating the building’s HVAC system at 100 percent outside air for a specific period of time.

Fly ash: Fine, non-combustible particulate suspended in flue gases during coal combustion, from which it is collected. Most commonly used to replace a portion of Portland cement. Fly ash is also used for fill material, soil stabilization and waste remediation. Similar to bottom ash.

Fly rafter: A rafter in the projecting portion of a gabled roof (under the barge course, which projects beyond the wall face), which serve as grounds for the barge boards (or fascia) and carry the plastering or boarding of the soffits. Also called a barge rafter.

Footcandle: A unit of illumination equal to one lumen per square foot.

Footing: A masonry section, usually concrete, in a rectangular form that supports a foundation wall or pier.

Foundation: The supporting portion of a structure below the first-floor construction, or below grade, that transfers all loads from the building to the ground.

Foamed-in-place insulation: An insulating material containing cements or plastics that is installed wet using foaming equipment, and cures in place.

Focusing collector: A solar hot water collector that has a parabolic or other reflector that focuses sunlight onto a small area for collection. A reflector of this type greatly intensifies the heat at the point of collection, allowing the heat collection fluid to achieve higher temperatures. This type of collector will work only with direct beam sunlight.

Footcandle (fc): A unit of illumination equal to 1 lumen per square foot.

Force: Force is expressed in newtons (N). A force of 1 Newton accelerates a mass of 1 kilogram to a speed of 1 meter per second in 1 second. (A small, 100-gram apple on a tree experiences a gravitational force of about 1 Newton).

Forced air heating system: A heating system in which air, circulated mechanically by either blower or fan, is the transfer medium for heat.

Fossil fuels: Nonrenewable, naturally occurring fuels from organic material deposited in the earth. The altered remains of once-living organisms that are burned to release energy. Examples are coal, oil, and natural gas. It takes millions of years to form fossil fuels.

Foundation, water-managed: Systems for at- or below-grade envelope sections in which a system of techniques is used to move liquid water away from the structure, relieving both capillary and hydrostatic water forces. Unlike a barrier foundation, a water-managed foundation assumes the inevitable-holes, cracks, and unusual rain events will require a system of drainage from around and under any foundation.

Frame construction: Building homes or other structures with dimension lumber framework.

French drain: A drain consisting of a trench filled with loose stones and covered with earth.

Frit: Small friable particles produced by quenching a molten glassy material.

Frost line: Depth of frost penetration into soil. Footings should be placed below this depth to prevent movement by ‘frost heave.’

Fuel cells: Fuel cells are electrochemical devices that convert a fuel’s energy directly to electrical energy through a chemical reaction instead of combustion. Fuel cells operate much like continuous batteries when supplied with fuel to the anode (negative electrode). Fuel cells forego the traditional extraction of energy in the form of combustion heat, conversion of heat energy to mechanical energy (as with a turbine), and finally turning mechanical energy into electricity (e.g. using a dynamo). Instead, fuel cells chemically combine the molecules of a fuel and oxidizer without burning, dispensing with the inefficiencies and pollution of traditional combustion.

Full spectrum lights: Lights that come closer to the natural light spectrum and are considered healthier.

Fully adhered roofing: A membrane bonding technique for roofing that requires the use of an adhesive material to be distributed evenly between the membrane and the substrate over the entire surface. This technique has excellent long-term strength and wind uplift resistance qualities; however, it is very difficult to remove at the end of its useful life.

Fumes: Smoke, vapor, or gas formed during the combustion process.

Fungicide: An agent that destroys molds, mildews, yeasts. The destruction of fungi does not necessarily destroy its toxic or allergenic properties.

Fungus (pl. fungi): Parasitic lower plants (including molds and mildew) lacking chlorophyll and needing organic material and moisture to germinate and grow. All fungi are allergenic.

Furnishing and outfitting: The complete sequence or series of activities and actions that begins with the “Structure” and results in the completed “Building.”

Fusion bonding: Carpet manufacturing process in which yarn is embedded between two parallel sheets of adhesive-coated backing. The sheets are slit, forming 2 pieces of cut-pile carpet.

Gable roof: In house construction, the portion of the roof above the eave line of a double-sloped roof. Also the triangular end of an exterior wall above the top wall plate that encloses a pitched (gabled) roof.

Gambrel roof: A roof that has two pitches on each side, also known as a mansard roof.

Gamma ray: A high-energy photon emitted spontaneously by a radioactive substance. A form of radiation that can go through almost anything, and which is best stopped by a very dense substance such as lead.

Gas: A formless liquid that expands to occupy a space or enclosure completely and uniformly. Its molecules are less than 0.0001 micron in size.

Gas-filled window: Double- or multiple-glazed window systems where the air space(s) is (are) filled with a low-conducting gas, like argon or krypton. The fill reduces the heat exchange rate associated with windows. Gas-filled windows provide the greatest benefit when used in conjunction with low-emissivity coatings.

Gasket: Any ring or strip of resilient material, used at a joint to prevent leakage.

Gauge: The thickness of sheet material or metal tubing, usually designated by a number.

General contractor: The prime contractor who is responsible for most of the work at a construction site, including that performed by subcontractors.

Generally regarded as safe (GRAS): A designation given to products (originally foods) that have been in use for many generations without apparent toxic effects.

Geographical Information System (GIS): Detailed information on the soils, hydrology, land use patterns, and plant and animal habitats of sites, plotted on maps or entered in databases and employed to evaluate appropriate location of buildings and infrastructure, and to plan landscaping and other land use considerations.

Geotextiles: Synthetic fabric sometimes made from recycled materials, which is intended for use in the soil, usually for filtering, stabilizing, or containing soil water. Some types are used to prevent or control erosion.

Geothermal heat exchange technology: In winter, geothermal heat exchange technology utilizes heat from subsurface water and soils to heat buildings; in summer, this technology extracts heat from the building into subsurface water and soils for cooling.

Glue-laminated timber: A manufactured product consisting of four or more wood layers, none of which exceeds 2 inches in thickness, bonded together with adhesive; comprised either of pieces that are end-joined to form any desired length or of pieces glued edge-to-edge to give greater width. Also called glulam.

Glare: The effect produced by luminance within one's field of vision that is sufficiently greater than the luminance to which one's eyes are adapted; it can cause annoyance, discomfort, or loss in visual performance and visibility.

Glare index: A value for predicting the presence of glare as a result of daylight entering an area. The glare index is affected by the size and relative position of fenestration, orientation to the sun, sky luminance, and interior luminances. The glare index is similar to the index of sensation and the discomfort glare rating, which are used for electric lighting applications.

Glazing: Any translucent or transparent material in exterior openings of buildings, including windows, skylights, sliding doors, the glass area of opaque doors, and glass block.

Glazing U-Factor: Based on the interior-surface area of the entire assembly, including glazing, sash, curbing, and other framing elements. Center-of-glass U-factors should not be used.

Global warming: The process of the Earth's atmosphere warming to temperatures above normal due to high levels of gases, such as carbon dioxide, which trap radiation leaving the earth and prevent the Earth from cooling.

Global warming potential (GWP): The ratio of the warming caused by a given material to the warming caused by carbon dioxide (e.g. CFC-12 has a GWP of 8500).

Grade beam: That part of a foundation system poured at or just below the grade of the earth (usually in a building without a basement) that supports the exterior wall of the superstructure; commonly designed as a beam that bears directly on the column footings but can also be self-supporting.

Graywater: Water that has been used for showering, clothes washing, and faucet uses. Kitchen sink and toilet water is excluded. This water can be reused in subsurface irrigation for landscaping. Also spelled greywater.

Green Cross: An American environmental listing program.

Green development: A development approach that goes beyond conventional development practice, by integrating the following elements: Environmental responsiveness—Benefiting the surrounding environment; Resource efficiency—Using resources in the construction, development, and operations of buildings and/or communities in ways that are not wasteful; and Sensitivity to existing culture and community—Fostering community in design, construction, and operations. Bringing these elements together through the green development approach provides numerous environmental and economic benefits by capitalizing on the interconnections.

Green power: Term for electricity generated from renewable energy sources, such as sun, wind, biomass, geothermal, tidal, and small hydroelectric.

Green roof: Vegetation cover on roof surfaces.

Green wash (also faux green): To falsely claim a product is environmentally sound.

Greenfield: Undeveloped land.

Greenhouse effect: The cause of global warming. Incoming solar radiation is transmitted by the atmosphere to the Earth’s surface, which it warms. The energy is retransmitted as thermal radiation, but some of it is absorbed by molecules of greenhouse gases instead of being retransmitted out to space, causing the temperature of the atmosphere to rise. The name comes from the ability of greenhouse glass to transmit incoming solar radiation but retain some of the outgoing thermal radiation to warm the interior of the greenhouse. The ‘natural’ greenhouse effect is due to the greenhouse gases present for natural reasons. The ‘enhanced’ greenhouse effect is the added effect caused by the greenhouse gases present in the atmosphere due to human activities, such as burning of fossil fuels and deforestation.

Greenhouse gas: Any of several dozen heat-trapping (radiatively active) trace gases in the earth's atmosphere that absorb infrared radiation. The two major greenhouse gases are water vapor and carbon dioxide; lesser greenhouse gases include methane, ozone, CFCs, and nitrogen oxides.

Grid-connected: Attached to the utility electric service, or grid. Also called grid-tied.

Grommet: A metal or plastic eyelet that provides a reinforced hole for attachment or passage.

Gross wall area: The gross wall area includes the opaque area of above-grade walls, the opaque area of any individual wall of a conditioned basement less than 50% below grade (including the below-grade portions), all windows and doors (including windows and doors of conditioned basements), and the peripheral edges of floors.

Gross window area: Includes the rough-opening area of the window, not just the transparent-glass area.

Ground fault circuit interrupter: A device that detects leakage of electrical current to the ground and prevent accidental shock.

Ground light: Visible radiation from the sun and sky, reflected by exterior surfaces below the plane of the horizon.

Groundwater: Rainwater that collects in an aquifer. Groundwater supplies 50 percent of the drinking water in the US.

Groundwater recharge: The use of reclaimed wastewater, by surface spreading or direct injection, to prevent saltwater intrusion into freshwater aquifers, to store the reclaimed water for future use, to control or prevent ground subsidence, and to augment non-potable or potable ground water aquifers.

Grout: Fluid mixture of cement, water, and possibly sand.

Gusset: A plate, usually triangular in shape, used to connect two or more members, or to add strength to a framework.

Habitat: The environment in which an organism or biological population usually lives or grows.

Hardwood: Deciduous trees with broader leaves and slower growth rates compared to conifers, or softwoods. Examples of hardwoods include oak, maple, cherry, walnut, beech, birch, cypress, elm, and hickory. Used in furniture and flooring, for appearance, excellent durability, and resistance to wear.

Harvested rainwater: The rain that falls on a roof or other hard surface and is channeled to a storage tank (cistern) or pond. The first wash of water on a roof is usually discarded and the subsequent rainfall is captured for use if the system is being used for potable water. Good quality water is available by this method in most areas.

Hazardous air pollutant: Air contaminant not included in the ambient air quality standards of the Clean Air Act but which may present a threat of adverse human health or environmental effects. Also known as air toxics or toxic air pollutants.

Hazardous chemical: Any hazardous material requiring a Material Safety Data Sheet under the Occupational Safety and Health Administration’s hazard communication standard. Includes those associated with physical hazards such as fire and explosion, or health hazards such as cancer and dermatitis.

Hazardous waste: A class of waste materials that poses immediate or long-term risks to human health or the environment and requires special handling for detoxification or safe disposal. Both industrial and household wastes include hazardous materials.

Header: The upper horizontal member of a window or door frame that supports loads above. Also called ‘head.’

Healthy home: A term for a home built with least-toxic materials and designed to support and contribute to a better indoor environment.

Heartwood: Wood at the core of an exogenous tree; normally darker, denser, and much more durable than sapwood.

Heat capacity: The number of BTUs a cubic foot of a material can store with a 1°F increase in its temperature.

Heat gain: The transfer of heat from outside to inside by means of conduction, convection, and radiation through all surfaces of a building.

Heat island effect: The rise in ambient temperature that occurs over large paved areas. Strategic placement of trees and reflective surfaces can reduce this effect and reduce energy consumption for cooling by 15-30%.

Heat loss: The transfer of heat from inside to outside by means of conduction, convection, and radiation through all surfaces of a building.

Heat pump: A mechanical device that removes heat from one medium, concentrates it, and distributes it in another. This device can be used to heat or cool indoor space. The heat source can be air, water, or soil.

Heat recovery systems: Building mechanical systems that capture waste heat from another system and use it to replace heat that would otherwise come from a primary energy source.

Heat recovery ventilator (or air-to-air heat exchangers) (HRV): Exhaust fans that warm the incoming air with the heat from the outgoing air, recovering about 50-70% of the energy. In hot climates, the function is reversed so that the cooler inside air passes by the incoming hot air and reduces its temperature.

Heat sink: A body that is capable or accepting or storing heat and therefore, may act as a heat source.

Heat-strengthened glass: Glass that is reheated, after forming, to just below melting point, then cooled, forming a compressed surface that increases its strength beyond that of typical annealed glass.

Heat welding: A process of joining two sheets of resilient flooring by heating and inserting a color-matched welding thread of PVC along the length of the seam.

Heating degree-day (HDD): A unit, based on temperature difference and time, used in estimating heating energy consumption. For any one day, when the mean temperature is less than a reference temperature (typically 65°F), there are as many degree-days heating as degrees Fahrenheit difference in temperature between the mean temperature for the day and the reference temperature. Annual heating degree-days (AHDD) are determined by the sum of all degree-days over a calendar year.

Heating ventilating and air-conditioning (HVAC) system: The equipment, distribution network, and terminals that provide either collectively or individually the processes of heating, ventilating, or air conditioning to a building.

Heavy-timber construction: Construction in which fire resistance is obtained by using wood structural members of specified minimum size and wood floors and roofs of specified minimum thickness and composition; by using bearing walls and nonbearing exterior walls of noncombustible construction; by avoiding concealed spaces under floors and roofs; and by using approved fastenings, construction details, and adhesives for structural members.

Heliodon: A device used to orient a light source (representing the sun) with respect to an architectural model; calibrated in terms of latitude, time of day, and season of the year; used to study daylighting techniques and to illustrate the shadows cast by direct sun.

High-density fiberboard (HDF): A fiberboard with density greater than 50 pounds per cubic foot or 800 kilograms per cubic meter.

High-efficiency particulate air (HEPA) filter: A designation for very fine air filters (usually exceeding 98 percent atmospheric efficiency) typically used only in surgeries, clean rooms, or other specialized applications.

High intensity discharge (HID): Generic term describing mercury vapor, metal halide, high-pressure sodium, and low-pressure sodium light sources and luminaires.

High-mass construction: Passive building strategy of constructing building envelopes of massive, heat-retaining materials (such as masonry, adobe) to moderate diurnal temperature swings of arid climates. (See thermal storage capacity)

High-performance coating: An architectural coating formulated to withstand exposure to harsh environmental conditions, solvents, harsh detergents, abrasives or scouring agents, or corrosive atmosphere or fluids.

High-pressure sodium (HPS) lamp: A sodium-vapor lamp in which the partial pressure of the vapor during operation is about 0.1 atmosphere; produces a yellowish light having a wide spectrum, in contrast to the light produced at low pressures, which is characterized by sodium emission lines.

High quality duct system: This option avoids the potential of significant heating and cooling losses, as well as the potential health threats caused by leaky ducts that can depressurize or pressurize a building. All ducts are sealed using a fibrated latex mastic and fiberglass tape. Inner and outer linings of the duct are both sealed. The air handler, support platform and return plenum are sealed airtight at the joints. Duct tape is not used in any part of the system. The system can be performance tested to ensure proper ventilation.

Highest and best use: The conventional definition is the property use that, at a given time, is deemed likely to produce the greatest net return in the foreseeable future, whether or not such use is the current use of the property. Green development defines it as not just in terms of maximum return on investment, but also as that use which best reflects long-term social, cultural, and financial values held by a community.

Hip: The external angle at the junction of two sloping roofs or sides of a roof.

Hip roof: A roof that slopes upward from all four sides of a building requiring a hip rafter at each corner.

Home run: A length of pipe or wire that runs from the point of use (outlet) straight backwards without intersection to the originating utility panel or manifold for the structure.

Hopper: Window with sash hinged at the bottom.

Horizontal axis clothes washer: A washing machine designed to clean via tumble action of the drum rather than with a central agitator. It uses less than half of the water of vertical-axis models, reduces wear and tear on clothes, and result in drier clothes.

Horizontal slider: A window with a movable panel that slides horizontally.

Horsepower: A unit of power equal to 33,000 foot-pounds per minute, 550 foot-pounds per second, or 746 watts.

Housewrap: Any of several spun-fiber polyolefin rolled sheet goods for wrapping the exterior of the building envelope. Touted as an air barrier that can "breathe," with respect to water vapor, but repel water in the liquid state, its properties do NOT include uni-directional vapor permeability, and its properties in comparison to traditional asphalt-impregnated building paper must be carefully considered when designing exterior wall profiles.

Human comfort zone: A band of dry bulb temperatures from 67.5 degrees Fahrenheit to about 78 degrees Fahrenheit and 20% to 80% relative humidity. Within that zone on the Psychrometric Chart, all weather conditions that occur are said to be conducive to thermal comfort, assuming occupants are in full shade, lightly clothed and only moderately active. All climate data that are plotted at lower dry bulb temperatures (to the left of the comfort zone) are indicative of time when solar radiation (passive heating) could be utilized to restore comfort. All hours above 67.5 F require shading. (See Psychrometric Chart)

Humus: Decomposed organic material that is an essential component of fertile soil; produced through composting.

Humidifier fever: A respiratory disease that results in influenza-like symptoms. Also called air conditioner or ventilation fever, it is caused by exposure to toxins emitted by microorganisms that become established in air conditioners or humidifiers.

Humidistat: Device for measuring and controlling relative humidity. Also called a hygrometer.

HVAC system: The centralized heating, ventilation, and air-conditioning system used in a building to regulate temperature, humidity, and air quality.

HVAC system efficiency: The ratio of the useful energy output (at the point of use) to the energy input in consistent units for a designated time period, expressed in percent.

Hybrid solar system: A system that combines passive solar collection with active transport of heat to an isolated storage system.

Hydroelectric power: Energy generated by the weight of water flowing downhill. While large hydroelectric projects that utilize dams cause harm to ecosystems, small hydroelectric projects that preserve rivers and streams are sustainable.

Hydronic heating system: A heating system using hot water or steam as the heat-transfer fluid; a hot water heating system (common usage).

Hydropulp: A mechanical method of breaking down wood fiber into pulp using water pressure instead of caustic chemicals. A very low-emissions pulping method.

Hypersensitivity: Extremely high sensitivity of an individual to certain substances.

Hypersensitivity pneumonitis: A group of respiratory diseases that involve inflammation of the lungs and are caused by exposure to a biological agent.

I joist: A manufactured wood product so named because its section looks like an upper case ‘I.’ The top and bottom chord are lumber or laminated wood, and the vertical web is plywood or oriented strand board.

Igneous rock: The oldest type of stone, cooled from melted rock. Contains the hardest stones, such as granite, porphyry, gabbro, etc.

Illuminance: The density of the luminous flux incident on a surface, expressed in footcandles or lux. This term should not be confused with illumination (i.e., the act of illuminating or state of being illuminated).

Impact isolation class (IIC): A single-number rating system designed to provide a comparison between different floor/ceiling constructions for structure-borne impact transmission between vertically adjoining spaces. The IIC is calibrated so that comparable ratings for sound transmission class (STC) give equivalent degrees of protection. The IIC is measured with a standardized tapping machine to generate impact noise, measuring it in the space below at the one-third octave bands between 100 and 3150 hertz. The IIC is calculated using the ASTM E989-84 "Standard Classification for Determination of impact isolation Class."

Impervious cover: A ground cover or surface that does not allow water to pass through it to the soil below. Many jurisdictions have restrictions on the amount of impervious cover allowed on a building site, in order to reduce storm water runoff and resulting non-point source pollution.

Incandescent bulb: An incandescent bulb is the most common and least energy-efficient lamp. Electricity runs through a tungsten filament that glows and produces a soft, warm light. Because so much of the energy used is lost as heat, these are highly inefficient sources of light. Halogen lamps are a special, more energy-efficient type of incandescent lamps containing halogen gas to produce a brighter, whiter light than incandescent lamps.

Indigenous: Existing, growing, or produced naturally in a region. Native to a region.

Indirect gain system: A passive heating system in which sunlight strikes a thermal mass located between the sun and the conditioned space. The sunlight is absorbed by the mass, converted into thermal energy, and transferred into the conditioned spaces. In this way, indirect gain systems offer greater control over temperature swings and overheating. The two basic types of indirect gain systems are thermal storage walls and roof ponds.

Indirect lighting: Lighting from luminaires that distribute 90% - 100% of the emitted light upward so that illumination is provided primarily by reflected light rather than by direct light.

Indoor air quality (IAQ): ASHRAE defines acceptable indoor air quality as air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80 percent or more) of the people exposed do not express dissatisfaction. IAQ is heavily influenced by both choice of building materials (and cleaning procedures) and ventilation rates.

Indoor air quality procedure: One of two procedures listed in ASHRAE Standard 62-1989 to determine appropriate ventilation rates for buildings. The IAQ Procedure provides a method of measuring and controlling outdoor airflow in order to keep harmful substances diluted to acceptable levels. It is inherently a more rigorous strategy than the Ventilation Rate Procedure because it considers all contaminants. Implementation of this procedure is difficult because of monitoring costs and insufficient knowledge about acceptable concentration levels for the thousands of combinations of potential indoor contaminants.

Indoor environmental quality: The quality of facets of the environment that affect the health of the occupants of a building or interior space, including indoor air quality (IAQ), thermal comfort, and light quality.

Industrial hygiene: The science devoted to the recognition, evaluation, and control of those environmental factors or stresses arising in or from work situations that may cause sickness, impaired health and well-being, or significant discomfort and inefficiency among workers or the public.

Industrial waste: Materials remaining from industrial operations. Includes liquid, sludge, solid, or hazardous waste.

Industrialization: A development path based on expanding a country's capacity to process raw materials and manufacture products for consumers, businesses, and export. This approach to development, first seen in northern Europe in the Industrial Revolution typically entails heavy financial investment in factories and power plants and a rapidly growing demand for energy, particularly fossil fuels.

Industry standards: Standards imposed on an industry, either by that industry of by a regulatory agency, to control product quality, manufacturing processes, plant emissions, etc.

Infill: Developing on empty lots of land within an urban area rather than on new undeveloped land outside the city. Infill development helps prevent urban sprawl and can help with economic revitalization.

Infiltration: The uncontrolled inward air leakage through cracks and interstices in any building element and around windows and doors of a building caused by the pressure effects of wind, HVAC systems, or the effect of differences in the indoor and outdoor air density or both. In stormwater management, entry of runoff into the soil.

Infiltration barrier: A material placed on the outside or inside of exterior wall framing to restrict inward air leakage while permitting the outward escape of water vapor from the wall cavity.

Infrared emittance: The ability of a roofing material to reradiate absorbed solar heat back to the sky.

Infrared radiation: Electromagnetic radiation, whether from the sun or a warm body, that has wavelengths longer than the red end of the visible spectrum (greater than 0.75 microns). We experience infrared radiation as heat. Of the radiation emitted by the sun, 49 percent is in the infrared band.

Infrastructure: Services and facilities provided by a municipality or privately provided, including roads, highways, water, sewage, emergency services, parks and recreation, and so on.

Innovation: The use of a new idea, material, or technology to change an activity, development, good, or service or the way goods and services are produced, distributed, or disposed of.

Insecticide: a chemical agent that destroys insects. These toxins act on the reproductive or nervous system of larval or adult insects.

Insolation: Amount of solar energy reaching a surface per unit of time. Measured in BTU per square foot per hour.

Insulated concrete form (ICF): Lightweight blocks, commonly made of expanded polystyrene or extruded polystyrene that are filled with concrete and remain in place to provide thermal insulation for concrete walls.

Insulating Sheathing: Non-structural insulating board products that are most often cited for their varying R-values. Equally, if not more important, is the wide variation in other properties-vapor permeability, bonding qualities of surfaces to various other construction materials, and how well they are configured to act as a drainage plane. Materials include expanded polystyrene (EPS), extruded polystyrene (XPS), polyisocyanurate (most often foil-faced), rigid fiberglass, and mineral wool.

Insulating concrete: Concrete having low thermal conductivity; used as a thermal insulation.

Insulating glass: Two or more pieces of glass spaced apart and hermetically sealed to form a single glazed unit with one or more airspaces between. Also called double-glazing and triple-glazing.

Insulating sheathing: An insulating board having a minimum thermal resistance of R-2 of the core material and applied on the exterior of a wall beneath the final siding material.

Insulation: Material that has a resistance to transfer of energy (e.g., acoustic, electric, thermal, vibrational, or chemical).

Insulation R-values: R-values are used to rate insulation and are a measurement of the insulation's resistance to heat flow. The higher the R-value, the better the insulation.

Integrated collector storage: A type of solar thermal collector where the fluid being heated is stored within the collector.

Integrated-control economizers: Allows the cooling load of a building or space to be partially met by supplying outside air, while the rest of the load is met by the refrigeration equipment within an HVAC system. Field- and factory-installed economizers supplied by major equipment manufacturers include integrated controls.

Integrated design: A holistic process that considers the many disparate parts of a building project, and examines the interaction between design, construction, and operations, to optimize the energy and environmental performance of the project. The strength of this process is that all relevant issues are considered simultaneously in order to “solve for pattern” or solve many problems with one solution. The goal of integrated design is developments that have the potential to heal damaged environments and become net producers of energy, healthy food, clean water and air, and healthy human and biological communities. Also called ‘whole system design.’

Integrated pest management (IPM): A coordinated approach to pest control that is intended to prevent unacceptable levels of pests by the most cost-effective means with the least possible hazard to building occupants, workers and the environment.

Integrated waste management: A strategy that employs several waste management methods, usually in the following order of preference: source reduction, recycling and reuse, incineration, and disposal in landfills.

Interior furnishings: Those temporary or semi-permanent systems and components, which are generally required for the normal utilization of the “Building” for its intended purpose.

Interior lighting controls: Offer the ability for systems to be turned on and off either manually or automatically and include switches, time clocks, occupancy sensors and other devices that regulate a lighting system.

Interior lighting power limits: The maximum total wattage for a building or space that can be installed to meet the provisions of the energy code.

Interior walls: Those walls not on the exterior of the building that separate conditioned and unconditioned spaces.

Invasive vegetation: An exotic plant adapted to very similar growing conditions as those found in the region to which it is imported. Because such a species usually has no natural enemies (pests, diseases, or grazers), it flourishes, disrupting the native ecosystem and forcing out native plant species, resulting in habitat loss, water-table modification, and other serious problems.

Inverse square law: In lighting design, the law that states that the illuminance at a point on a surface varies proportionately with the intensity of a point source, and inversely to the square of the distance between that source and that surface.

Inverter: A device used to change DC energy to AC energy.

Irradiance (E): The amount (or density) of light energy incident on a surface.

Irritant: A chemical that is not corrosive, but which causes a reversible inflammatory effect on living tissue by chemical action at the site of contact.

Isolated gain system: A thermal gain system in which the solar collection and storage elements are separate from the spaces they heat. Generally south-facing solariums, greenhouses, and atriums are common examples of isolated gain spaces.

Jack rafter: Any rafter that is shorter than the usual length of the rafters used in the same building; usually a roofing rafter reaching from a valley to a ridge or from a hip to a wall top plate.

Jack stud: Short stud, which does not reach from the floor to the ceiling, but only from the floor to a window, for example.

Jalousie window: A window made up of horizontally mounted louvered glass slats that abut each other tightly when closed and rotate outward when open.

Jamb: A vertical member at the side of a window or door frame.

Joists: The horizontal structural framing for floors and ceilings. The ceiling joists of the first story are also the floor joists of the second story, or of the attic.

Joist cavity: The space between joists.

Joule: The international unit of energy or work in the meter-kilogram-second (MKS) system. One joule is equal to one watt per second or 0.737 foot-pounds. Named after James Joule. It takes one million joules to make a pot of coffee.

Jump Duct: A flexible, short, U-shaped duct (typically 10-inch diameter) that connects a room to a common space as a pressure balancing mechanism. Jump ducts serve the same function as transfer grilles. Used when return ducts are not located in every room.

Kelvin (K): The standard unit of temperature that is used in the Systeme Internationale d’Unites (SI) system of measurements. The Kelvin temperature scale is used to describe the correlated color temperature of a light source.

Kerf: Saw-cut on the underside of lumber to permit bending.

Kiln-dried lumber: Any lumber placed in a heated chamber or "shed" to reduce its moisture content to a specified range or average under controlled conditions. For softwood framing lumber, the moisture content of KD lumber is somewhat based on regional conventions but is most often an average of 12% by weight. In comparison, the moisture content of thoroughly air-dried softwood framing lumber is 15% to 20%.

Kiln drying: A method of drying wood in an oven after sawing that results in 10% or less moisture content. This makes the wood more dimensionally stable and better able to resist decay, but results in higher embodied energy associated with production.

Kilovolt (kV): One thousand volts.

Kilowatt (kW): A unit of power equal to 1,000 watts. It is used as a measure of electrical power. On a hot summer afternoon a home with central air conditioning and other equipment in use might have a demand of 4 kW each hour.

Kilowatt-hour (kWh): A measure of energy usage equal to the amount of power multiplied by the amount of time the power is used. A 100-watt light bulb burning for 10 hours uses one kilowatt-hour of power.

Kitchen recycling center: A built-in section of the kitchen cabinetry that allows convenient separation of recyclable materials.

King post: The central or primary vertical post that supports the primary or hip rafters

King studs: The two studs that flank a door or window opening running without break from the sole plate to the top plate plate.

Knocked-down: Prefabricated but not assembled building components that are assembled on-site.

Kraft: A papermaking process using softwoods and sulfites, the largest volume paper production process in the U.S. and Canada.

Laminated glass: Two or more sheets of glass with an inner layer of transparent plastic to which the glass adheres if broken. Used for safety glazing and sound reduction.

Labeled: Devices, equipment, appliances, assemblies, or materials to which have been affixed a label, seal, symbol, or other identifying mark of a nationally recognized testing laboratory, inspection agency, or other organization concerned with product evaluation that maintains periodic inspection of the production of the above-labeled items and by whose label the manufacturer attests to compliance with applicable nationally recognized standards and/or regulations.

Lacquer: A glossy finish for woods or metals, traditionally prepared from plant resins.

Laminate: A thin layer of material (veneer) bonded to another surface. Wood and plastics are both commonly laminated.

Laminated strand lumber: A manufactured wood product similar to oriented strand board (OSB) but made in thick sections with all the grain oriented one way for the use as beams or columns.

Laminated veneer lumber: A manufactured wood product similar to plywood but made in thick sections with all the grain oriented one way for use as beams.

Land stewardship: The act of managing the land and its resources in a sustainable or restorative manner.

Landfill: A site designated for disposal of solid or chemical wastes by burial. It may be essentially an open pit or a highly engineered facility that includes special linings to prevent wastes from leaking into water supplies.

Lanolin: The natural oil that wool contains.

Latent heat: A change in the heat content that occurs without a corresponding change in temperature, usually accompanied by a phase change, as from liquid to vapor during evaporation.

Latent load: Cooling load resulting from thermal energy released when moisture in the air goes from a vapor to a liquid state. In hot humid climates, cooling equipment must have sufficient capacity to handle this load for occupants to be comfortable.

Latex: A naturally occurring, sticky resin from rubber tree sap used for rubber products, carpet backings, and paints.

Latitude: The angular distance north or south of the equator, measured in degrees of a circle.

Lead: Soft heavy metal. A harmful environmental pollutant that can be found in the home in lead-based paints and in lead solder used in plumbing before 1978. Lead is toxic to many organs an can cause serious damage to the brain, kidneys and nervous system.

Lead ventilation: Ventilation of an unoccupied building space immediately prior to its occupancy. Lead ventilation is performed to dilute contaminants from building and HVAC sources to acceptable levels by the time occupants arrive.

Lease: A contract that gives the tenant the right of possession for a period of time in return for paying rent to the landlord.

LEEDTM: Leadership in Energy and Environmental Design is a building rating and certification program developed and operated by the U.S. Green Building Council.

Leichtlehm: Straw/clay mixture, moistened and pressed between forms, which hardens into a strong wall. An old and durable wall technique (German for light loam).

Level spreaders: A stormwater management device installed parallel to a slope that changes concentrated flow to sheet flow.

Life cycle: The consecutive, interlinked stages of a product, beginning with raw materials acquisition and manufacture and continuing with its fabrication, manufacture, construction and use, and concluding with a variety of recovery, recycling, or waste management options.

Life cycle assessment (LCA): The comprehensive examination of a product’s environmental and economic aspects and potential impacts throughout its lifetime, including raw material extraction, transportation, manufacturing, distribution, use, reuse, maintenance, recycling, and disposal.

Life cycle cost (LCC) analysis: An objective assessment of the cost of a design feature that allows for production, sales, operation, maintenance, and demolition or recycling costs. The cost also encompasses all the environmental burdens of a product or process through its entire service life. This approach can often be used to justify more expensive and energy efficient systems, which save money over the life of the product.

Light adaptation: The process by which the retina becomes adapted to a luminance greater than about 1.0 foot Lambert.

Light construction: Method of constructing a building using materials that have low densities (like wood or aerated concrete). The lower densities of these materials reduce their capacity to store heat.

Light distribution: The pattern of light created in a room.

Light output: A measure of a light’s total integrated light output, measured in lumens.

Light shelf: Horizontal projections at the building interior that reflect direct sun rays onto the ceiling deep into a space and shield direct sunlight from the area immediately adjacent to the window. The upper surface of the shelf may be specular or nonspecular but should be highly reflective (that is, having 80 percent or greater reflectance). Light shelves work best on facades that are generally south facing.

Light-to-solar-gain (LSG) ratio: A measure of the ability of a glazing to provide light without excessive solar heat gain. The ratio between the visible transmittance and the solar heat gain coefficient.

Lighting power density: The installed lighting power in a building, typically measured in watts per square foot.

Linoleum: Natural linoleum is made from natural, minimally processed ingredients, including linseed oil, pine rosin, cork dust, wood flour, limestone, mineral pigments, and jute backing. Off-gassing will depend primarily on the adhesive used for installation. Some long-term off-gassing will occur with the linoleum due to oxidation of the linseed oil, resulting in emission of a mixture of aldehydes and carboxylic acids, which are not considered hazardous but may affect sensitive individuals.

Linseed oil: Derived from flaxseed by crushing and pressing. Used as a vehicle in oil paints and as a component of oil varnishes.

Lintel: A horizontal member above a window or door opening that supports the structure and/or veneer above.

Listed: Equipment, appliances, assemblies, or materials included in a list published by a nationally recognized testing laboratory, inspection agency, or other organization concerned with product evaluation that maintains periodic inspection of production of listed equipment, appliances, assemblies, or material, and whose listing states either that the equipment, appliances, assemblies, or material meets nationally recognized standards or has been tested and found suitable for use in a specified manner.

Load-bearing wall: A wall capable of supporting an imposed load in addition to its own weight.

Locally sourced materials: Materials obtained from a defined radius around a project site helping to support the local economy and reducing transportation costs and energy.

Long-wave infrared radiation: Invisible radiation, beyond red light on the electromagnetic spectrum, emitted by warm surfaces such as a body at room temperature.

Longitudinal seam: A duct seam that is parallel to the direction of the flow.

Loose-fill insulation: Insulation made from vermiculite, perlite, glass or mineral wool, shredded wood, cotton, or shredded paper, loosely packed to allow pockets of dead air space. For use in wall and ceiling cavities.

Louver: An opening with a series of horizontal slats so arranged as to permit ventilation but to exclude rain, sunlight, and/or vision.

Low-conductance spacers: An assembly of materials designed to reduce heat transfer at the edge of an insulating window. Typically placed between panes of glass in a double- or triple-glazed window.

Low-density fiberboard (LDF): See particleboard or chipboard.

Low density polyethylene (LDPE): Often refers to number 4 plastic.

Low-E: Most often used in reference to a coating for high-performance windows, the "e" stands for emissivity or re-radiated heat flow. The thin metallic oxide coating increases the U-value of the window by reducing heat flow from a warm(er) air space to a cold(er) glazing surface. The best location for the coating is based on whether the primary heat flow you want to control is from the inside out (heating climates) or the outside in (cooling climates).

Low-flow plumbing: Plumbing equipment that uses less water than was considered standard prior to January 1, 1994.

Low-impact development: New development that minimizes disturbance on-site due to construction and erosion. Low-impact developments are designed to blend well into their environmental setting to preserve natural features and the maximum amount of open space.

Low-pressure sodium (LPS) lamp: With efficiencies up to 200 lm/W, they are some of the most efficient lamps available. The light produced is a monochromatic yellow. Most commonly used in confined locations that do not demand color discrimination, such as road way applications.

Low-voltage Lighting: Lighting equipment that is powered through a transformer such as cable conductor, rail conductor, and track lighting.

Lumen (lm): A unit of measurement of the rate at which a point source produces light. A source’s light output rating expresses the total amount of light emitted in all directions per unit time.

Lumen method (daylighting): A method of estimating the interior illuminance from window daylighting at three locations within a room, based on empirical studies.

Luminaire: A complete lighting unit consisting of a lamp or lamps, along with the parts designed to distribute the light, hold the lamps, and connect the lamps to a power source. Also called a fixture.

Luminance: Luminous intensity of a surface in a given direction.

Luminous flux: The rate of flow of light, analogous to the rate of flow of a fluid.

Macroclimate: The climate of a defined region.

Makeup air: Outdoor air supplied to replace exhaust air and exfiltration.

Management: The effective and efficient integration and coordination of resources (natural, financial, human) in order to achieve desired goals, objectives, and mandates. The style, tenets, criteria, and techniques used will define the management philosophy.

Manometer: An instrument for the measurement of pressure; a U-shaped glass tube partially filled with water or mercury, one side of which is connected to the source of pressure. The amount of displacement of the liquid is a measure of the magnitude of the pressure.

Mansard roof: A roof that has two pitches on each side, also known as a gambrel roof.

Manufactured housing: Any type of structure or component that is produced in a factory to be transported to site for erection or placement.

Market niche: A particular subgroup within a market segment distinguishable from the rest of the segment by certain characteristics.

Mass transit: Conveyance of persons or goods from one place to another on a local public transportation system such as light rail, bus, or subway.

Mastic: Mixture of finely powdered rock and asphaltic material used in highway construction. Mastic gum is a natural solid resin used in adhesives and lacquers.

Material safety data sheets (MSDSs): OSHA-required documents supplied by manufacturers of potentially hazardous products. MSDSs contain information regarding potentially significant airborne contaminants, precautions, steps for inspection, health effects, odor description, volatility, expected contaminants from combustion, reactivity, and procedures for cleanup.

Matte surface: Surface from which the reflection is predominantly diffuse, with or without a negligible specular component.

Mechanical system: The system and equipment used to provide heating, ventilating, and air conditioning functions as well as additional functions not related to space conditioning, such as, but not limited to, freeze protection in fire protection systems and water heating.

Mechanical ventilation: Controlled, purposeful introduction of outside "fresh" air to the conditioned space. Building America performance targets and Energy & Environmental Building Association (EEBA) criteria call for a minimum base rate of 20 CFM per master bedroom and 10 CFM for each additional bedroom when the building is occupied (and spot ventilation for kitchen and baths and limits on room-to-room pressurization resulting from mechanical ventilation).

Mechanically adhered (roofing): A method of attaching a roofing material to its underlying substrate through the use of mechanical fasteners. This is a fast and easy method for installing modular roofing types; mechanical fasteners also allow for easy material recovery at the end of their useful life.

Medium Density Fiberboard (MDF): Composite panel product generally made from wood fibers combined with a synthetic resin or other bonding system and joined together under heat and pressure. Used in kitchen cabinets, paneling, doors, jambs and millwork, and laminate flooring.

Megawatt (MW): A million watts, or 1,000 kW.

Metamorphic rock: Formed from igneous or sedimentary deposits that have been subjected to intense stress, heat, or chemical effect, such as slate and marble.

Metal halide lamps: A type of high intensity discharge (HID) lamp in which most of the light is produced by radiation of metal halide and mercury vapors in the arc tube. Available in clear and phosphor coated lamps.

Meter: A device for measuring levels of a customer’s gas and electricity use.

Metering: Use of metering equipment that can provide essential data for charging fees based on actual consumer use.

Microbe: A microorganism, living or dead. Bacteria , viruses, mold, fungi, spores, and pollen are all microbes.

Microbial: Pertaining to microorganisms, such as bacteria, protozoans, yeasts, mold, viruses, and algae.

Microclimate: The small scale climate of a building site, affected by site geography, site topography, vegetation, and proximity to bodies of water, etc., which may very slightly from the prevalent regional climatic conditions.

Micron: One millionth of a meter.

Mil.: One thousandth of an inch (0.0254 mm).

Millwork: Generally, all building materials made of finished wood and manufactured in millwork plants and planing mills are included in this term.

Mineral fibers: Very fine insulation fibers made from glassy minerals that have been melted and are hazardous to inhale.

Mineral wool: A fibrous glass made from molten slag, rock, and/or glass, produced by blowing or drawing, used for insulation and fireproofing. Also known as rock wool.

Minimum efficiency rating value (MERV): A universal scale used to rate air filters. It is based on the efficiency of a filter to capture small particle sizes in the range of 0.20 to 10 microns – those particles that enter the lungs via the nose and mouth. The higher the filter efficiency, the higher the MERV value.

Mitigation: Techniques or requirements (e.g., conditions of development approval) aimed at reducing or neutralizing identified negative environmental, economic, or social effects of a proposed activity, policy, or development.

Mixed air: The mixture of outdoor air and return air in an HVAC system. When filtered and conditioned, mixed air becomes supply air.

Mixed-use: A development in one or several buildings that combines several revenue-producing uses that are integrated into a comprehensive plan—such as a project with a elements of housing, retail, and office space.

Model Energy Code (MEC): The MEC was first published in 1983, with subsequent full editions published in 1986, 1989, 1992, 1993, and 1995.

Modular housing: Refers to three dimensional sections of houses fabricated and assembled in a plant for shipment to the site, where they may be connected to similar units or to other systems for a complete structure.

Moisture barrier: A plastic film sheet material usually placed beneath interior wall finish to prevent moisture from penetrating into stud cavities or beneath the foundation to prevent moisture migration into the stud.

Monitor: A raised section of roof that includes a vertical (or nearly vertical) glazed aperture, for the purpose of daylight illumination.

Mortar: A cement-based mixture used to lay stone or ceramic tiles, or for use as a grout for these materials.

Mullion: A major structural vertical or horizontal member between window units.

Multifamily building: A residential building three stories or less in height that contains three or more attached dwelling units. Multifamily buildings include apartments, condominiums, townhouses, and row houses. Hotels and motels are considered commercial rather than residential buildings.

Multiple chemical sensitivity (MCS): A set of symptoms that follow exposure to an inciting agent or agents. Also known as idiopathic environmental intolerance.

Municipal electric utility: A power utility system owned and operated by a local jurisdiction.

Municipal utility district (MUD): An entity that typically engages in the supply of water, conservation, irrigation, drainage, fire fighting, emergency services, solid waste disposal, wastewater treatment, and recreational facilities.

Muntin: A secondary, non-structural framing member (horizontal, vertical, or diagonal) to hold window panes in a sash.

Mutagenic: A substance that is known to alter the DNA of cells, potentially causing changes in tissue growth.

Native vegetation: A plant whose presence and survival in a specific region is not due to human intervention or cultivation.

Natural: A substance or material that is taken from nature as directly as possible with minimal intervention of processing or chemical synthesis.

Natural air changes per hour (NACH): an estimate of building air tightness popular with builders, but not as quantitative or useful as air changes per hour at a blower door induced pressure of 50 Pascals (ACH50). The difficulty with NACH numbers is that they are derived by rule-of-thumb conversions from blower door measurements and leave the impression that a building has one "natural" air change rate, when in fact, the actual air change rate a building experiences is dependent on highly changeable factors such as wind speed, wind direction, and indoor/outdoor temperature differential. See Measured Air Change Rates and Distribution of Ventilation Air In A Single Family Home

Natural cooling: Use of environmental phenomena to cool buildings, e.g., natural ventilation, evaporative cooling, and radiative cooling.

Natural draft: A vent system that relies on the forces of gravity to draft exhaust gases out of the house.

Negative indoor pressure: When air is exhausted from a space faster than it is replaced.

Neo-traditional planning: Based on nineteenth-century American town prototypes, this type of planning minimizes automobile use and encourages a sense of community with a town center and open public areas.

Negawatts: A term coined by energy analyst Amory Lovins to signify that a unit of energy saved is exactly equivalent to an additional unit of energy supplied. If it is cheaper for a utility to save energy than to generate an equivalent amount of additional energy, the utility has more incentive to invest in negawatts than in megawatts.

Net metering: A program in which electric utilities buy power from customers with photovoltaics at the same rate as the utility charges the customer for electricity.

Net wall area: The net wall area includes the opaque wall area of all above-grade walls enclosing conditioned spaces, the opaque area of conditioned basement walls less than 50% below grade (including the below-grade portions), and peripheral edges of floors. The net wall area does not include windows, doors, or other such openings, as they are treated separately.

Neurotoxicity: Any toxic effect on any part of the central or peripheral nervous system.

New Urbanism: A city planning movement that focuses on revitalizing the inner city and reforming the American suburb within an integrated regional structure. New Urbanists strive for a built environment that must be diverse in use and population, must be scaled for pedestrian use without entirely eliminating automobile access, and must have a well-defined public realm supported by vernacular architecture.

Newton (N): The Newton is the basic metric unit of force, named in honor of Isaac Newton (1642-1727), who developed the laws of motion and gravitation. One Newton is a mass of 1 kilogram times an acceleration of 1 meter per second (sec) per second (1 N = 1 kg.m/sec2). One joule equals 1 meter-meter: (1 J = 1 Nm =1 kg.m2/sec2).

Nighttime ventilation: Passive building strategy of flushing building structures with cool, nighttime air to minimize the next day’s cooling load: work best in conjunction with massive building envelopes.

Nit (nt): Unit of luminance equal to one candela per square meter.

Noise criteria (NC): Series of curves of octave-band sound pressure levels from 63 to 8000 Hertz. They are commonly used in the United States to rate interior noise levels.

Noise reduction (NR): The simple loss of sound level that occurs in passing through a medium. Most often noise reduction refers to a single octave or one-third octave-band noise.

Noise reduction coefficient (NRC): Average of the sound absorption coefficient of the four octave bands 250, 500, 1,000, and 2,000 Hertz rounded to the nearest 0.05.

Nominal: The named thickness of a material, though not always its actual thickness. E.g. 2” nominal lumber is actually 1 ½” thick.

Non-point source pollution: Pollution, typically of water, that results from many difficult-to-pinpoint and control sources, rather than one specific source, such as a factory.

Nonrenewable energy: Sources of energy such as oil, coal, or natural gas that are not replaceable after they have been used.

Nonrenewable resource: A natural resource that cannot be replaced after it has been consumed. It applies particularly to fossil fuels, which can only be used once, but it also describes other mineral resources that are present in only fixed quantities in the earth’s crust, although metals can be reused through recycling. Central to the concept is human time frame. Oil and natural gas are being formed beneath the earth’s surface at present and new mineral ores are also being created. However, replacement may take millions of years, and society can consume them much more rapidly that they can be replaced. Thus in human terms they are effectively non-renewable.

Nontoxic: Not injurious to human health or the environment when used for its intended, normal use in specified concentrations.

Nuclear energy: Power obtained by splitting heavy atoms (fission) or by joining light atoms (fusion). These processes create heat, which in turn is used to make steam to run generators.

Obsolete building: A building that, for one reason or another, has reached the end of its useful life.

Occupancy type: The type of activity occurring within a building.

Occupant-sensing device: A device that detects the presence or absence of people within an area and causes any combination of lighting, equipment, or appliances to be adjusted accordingly. Also called an ‘occupancy sensor.’

Octave band: A group of frequencies whose lower boundary is one-half of the upper boundary. In acoustics, the first nine octave bands are identified by their center frequencies of 31.5, 63, 125, 250, 500, 1,000, 2,000, 4,000, and 8,000 Hertz. The 31.5 band is also referred to as the band number 0, and 63 Hertz is band number 1.

Off-gassing: The release of gaseous materials under atmospheric conditions.

Ohm: A unit of measure of electrical resistance.

Old growth: Wood from trees found in mature forests. In many cases, the trees have never been exposed to logging operations. In the northwest United States, only about 10 percent of these biologically rich areas are left.

On center: The distance from the center of one stud or joist to the center of the adjacent stud or joist. Most homes are built with studs and joists 16 inches on center.

Opaque areas: Opaque areas referenced in this guide include all areas of the building envelope except openings for windows, skylights, doors, and building service systems. For example, although solid wood and metal doors are opaque, they should not be included as part of the opaque wall area (also referred to as the net wall area).

Open office furniture system: A system using furniture screens (instead of drywall partitions) to provide acoustical and visual privacy.

Open-web wood joists: Wood joists built as flat trusses, using small-dimension lumber for web pieces. These are also available with stamped steel webs.

Operational energy: The energy used by a product to operate.

Optimal Value Engineering (OVE): A method of framing houses that minimizes the use of wood, while improving the builder’s ability to insulate effectively.

Organic matter: Materials of animal or vegetable origin.

Organic waste: Natural materials, such as food and yard waste, that decompose naturally.

Organically grown: Grown with minimal use of synthetic fertilizers or pesticides. There are various definitions concerning which products can be termed ‘organic.’

Orientation: The relation of a building and its associated fenestration and interior surfaces to compass direction and, therefore, to the location of the sun. It is usually given in terms of angular degrees away from south, i.e., a wall facing due southeast has an orientation of 45 degrees east of south.

Oriented strand board (OSB): A manufactured wood sheet product made from large flakes of wood pressed together with glue, usually a dry phenolic type. Neighboring layers of flakes are perpendicular in orientation. OSB is used for structural sheathing and sub-floors.

Outdoor air: Air taken from the outdoors and, therefore, not previously circulated through the system.

Out-gassing: The release of gaseous materials under sub-atmospheric conditions (e.g. in a vacuum).

Overhang: Any horizontal projection that serves as a shading element for a window or wall.

Ozone hole: A popular name given to a phenomenon discovered in 1987, when scientists measured unexpectedly low ozone concentrations in the stratosphere above the South Pole during the Antarctic spring. It is now generally accepted that the loss of stratospheric ozone is caused by chemical reactions initiated by chlorofluorocarbons.

Packaged boiler: A self-contained unit that generally requires little maintenance.

Packaged terminal air conditioner (PTAC): A factory-selected wall sleeve and separate unencased combination of heating and cooling components, assemblies, or sections (intended for mounting through the wall to serve a single room or zone). It includes heating capability by hot water, steam, or electricity.

Packaged terminal heat pump: A packaged terminal air conditioner capable of using the refrigeration system in a reverse cycle or heat pump mode to provide heat.

Panelized construction: Refers to either open or closed panel construction, where partly or fully finished walls, floor and roof trusses or panels are shipped to site, sometimes with cores and often with all other materials required to finish the building.

Paraffin wax: Solid, crystalline hydrocarbon mixture derived from the paraffin distillate portion of crude petroleum. Low toxicity. Used to waterproof wood and cork, and in the manufacture of varnishes.

Parallel Strand Lumber (PSL): A manufactured wood product which is composed of small, yet long, strips of wood glued together to form a thick section with all the strips oriented lengthwise for use in beams or columns.

Parquet: A small wooden tile made from interlocked strips of hardwood and used as a floor covering.

Particleboard (or chipboard): A building panel consisting of wood chips and fibers pressed together, using a synthetic resin as a binding agent.

Particulates: Fine solid particles of dust, spores, pollen, dander, skin flakes, allergens, cell debris, mold, mildew, mineral fibers, or solids escaping from combustion processes that are small enough to become suspended in air. Can cause health problems when inhaled.

Parts per million: A unit of measurement for very small concentrations of gases or liquids.

Passive building design strategy: Building configurations that take advantage of a natural, renewable resource (like sunlight, cooling breezes, etc.) Passive strategies typically do not involve any moving part or mechanical processes. Designing a building’s architectural elements to collect, store, and distribute solar resources for heating, cooling, and daylighting.

Passive solar cooling: Building design that avoids unneeded solar heat, utilizes natural ventilation, and employs thermal mass (especially in hot, dry climates) to retain coolness.

Passive solar heating: Building design that uses natural processes to collect, store, and distribute heat for a building. Most passively solar heated buildings require an auxiliary heating system for periods when solar heat is unavailable or insufficient.

Peak electrical demand: The maximum instantaneous load or the maximum average load over a designated interval of time, usually 15 to 30 minutes measured by the utility or power provider.

Peak load shedding: Deferring system loads from peak periods to periods of low demand. The result is a flattening of the system load schedule, thus decreasing demand charges from the electric utility.

Peak/off-peak rates: Energy rates charged in accordance with the most and least popular hours of water use during the day.

Pedestrian pocket: A simple cluster of housing, retail space, and offices within a quarter-mile radius of a transit system. Smaller scale than new towns or Planned Unit Developments (PUDs).

Pedestrian scale: An urban development pattern where walking is a safe, convenient, and interesting travel mode.

Penetrating/impregnating sealer: A finish that will penetrate the porous structure of wood, concrete, stone, or tile, thus protecting the entire upper layer of the material.

Performance approach: A performance approach (also known as a systems performance approach) allows you to compare your proposed design to a baseline or reference design and demonstrate that the proposed design is at least as efficient as the baseline in terms of annual energy use. This approach allows greater flexibility but requires considerably more effort. A performance approach is often necessary to obtain credit for special features, such as passive solar design, photovoltaic cells, thermal energy storage, fuel cells, and other nontraditional building components. This approach requires an annual energy analysis for the proposed design and the reference design.

Pergola: A garden structure with an open wooden-framed roof, often latticed, supported by regularly spaced posts or columns. The structure is often covered by climbing plants and shades a walk or passageway.

Perlite: An inert, natural volcanic glass that expands with heat and transforms into a fluffy form that can be used for insulation.

Perm rating: The amount of water vapor that passes through an area in a certain period of time.

Permaculture: A unique approach to the practice of sustainable farming, ranching, gardening and living, by designing constructed ecosystems that serve the needs of human populations without degrading the natural environment. Permaculture sites integrate plants, animals, landscapes, structures, and humans into symbiotic systems while requiring a minimum of materials, energy, and labor to maintain.

Permanently wired luminaires: Light fixtures physically attached to a surface (e.g. ceiling or wall) using a permanent mounting system and wired directly to a power source. Examples include fluorescent fixtures located in a ceiling grid and wall sconces.

Permeable: Open to passage of fluids/gases

Pervious paving: Paving material that allows water to penetrate to the soil below; this reduces the amount of water that needs to be treated by the stormwater system and increases water in the aquifer.

Pesticide: Lethal chemical that destroys pests, e.g., insects, rodents, nematodes, fungi, seeds, viruses, or bacteria. Term includes insecticides, herbicide, rodenticide, and fungicide. Also known as biocide. The EPA has identified many pesticides as persistent, bioaccumulative toxic pollutants. Alternative, safe forms of controlling pests include use of sticky or mechanical traps.

Petrochemical: Chemical derived from petroleum - a heavy, liquid oil consisting chiefly of carbon and hydrogen in the form of hydrocarbons; petroleum is stored under the surface of the earth and is formed as the byproduct of the action of bacteria on marine plants and animals.

Phenolic laminate: A high-pressure laminated sheet made from paper and phenol formaldehyde resin, commonly used for furniture and kitchen cabinet surfaces. Also called plastic laminate.

Photocell: A light sensing device used to control luminaires and dimmers in response to detected light levels.

Photochromic: Exhibiting reversible color change when exposed to visible or near-visible radiant energy. In glazing applications, this means the ability for glass to lower its transmissivity as outdoor light levels increase.

Photometer: An instrument for measuring photometric quantities, such as luminance, luminous intensity, luminous flux, and illuminance.

Photon: The elementary particle of electromagnetic energy; light. (From the Greek photos, meaning light).

Photosensor: A device that converts light to electrical current. A photosensor can switch a light on and off, or regulate its output to maintain a preset light level.

Photosynthesis: The utilization of light energy to create chemical bonds; the synthesis of organic compounds from carbon dioxide and water. (From the Greek photos, meaning light + syn, meaning together + tithemai, meaning to place).

Photovoltaic (PV) cells: Thin silicone wafers capable of generating a voltage as a result of exposure to visible or other radiation. Solid-state cells (typically made of silicon) directly convert sunlight to electricity. The electricity can be used immediately, stored in batteries, or sold to a utility. Costs continue to drop and efficiency is improving for this technology.

Pigment: Water-insoluble natural or synthetic coloring matter, used to impart color to other materials such as textiles, paints, stains, and plastics.

Pilaster: Column built within a wall, usually projecting beyond the face of the wall.

Pitch: The incline slope of a roof, or the ratio of the total rise to the total run of a roof slope.

Plain-sawn: Boards cut perpendicularly to the annual rings of a log, producing a wide grain with V-shapes that tend to wear unevenly.

Planned Unit Development (PUD): The PUD process addresses a wide range of development issues, including land use, site-planning, grading, traffic, noise, housing affordability, viewsheds, exterior architecture, colors, parking, illumination, landscaping, and open space.

Plant energy efficiency measures: Redesign of processes or equipment, or the addition of new equipment, which reduces energy requirements or recovers waste energy.

Plastic: Material that contains one or more organic polymeric substances of large molecular weight. It is capable of being shaped by flow at some stage in its manufacture or processing and is solid in its finished state. Many toxic chemicals are used in plastics manufacturing, including vinyl chloride.

Plasticizer: A nonvolatile organic liquid or low-melting-paint solid additive that gives an otherwise rigid plastic flexibility. Most plasticizers off-gas slowly and, in flooring, are a major source of VOC emissions.

Plate glass: A high-quality glass sheet similar to window glass, both faces are flat and parallel and then polished. See also annealed glass or float glass.

Plenum: The space between the ceiling of one floor and the surface of the floor above. HVAC ducts, variable air volume (VAV) boxes, pipes, lighting fixtures, and other building equipment are generally located in the plenum space. Can also refer to an enclosure that is part of the air-handling system and is distinguished by having a very low air velocity.

Plug loads: Electrical loads created by the use of devices that are plugged into wall sockets. This includes such items as: computers, printers, photocopiers, refrigerators, water coolers, fans, microwaves, heaters, and other pieces of equipment.

Plywood: Material composed of thin sheets of wood glued together, with the grains of adjacent sheets oriented at right angles to each other.

Point method: A method of estimating the illuminance at various locations in a building, using photometric data.

Pollutant: A contaminant found in concentrations high enough to adversely affect human health or the environment.

Pollution: An undesirable contaminant (gas, liquid, noise, solid), which has been released into, and is now a part of, the environment.

Porcelain: A glass-bodied, impervious, dense and homogenous tile with no surface porosity. It is unaffected by chemical and physical agents such as fire or frost.

Portland cement: A type of cement made by burning limestone and clay in a kiln. It is a basic ingredient in concrete and is used as the base for most grouts for ceramic mosaics, quarry, and paver tiles. Also known as hydraulic cement or cement.

Porte cochère: A carriage porch. A doorway large enough to let a vehicle pass from street to parking area.

Positive cooling supply: Mechanical cooling deliberately supplied to a space, such as through a supply register. Also, mechanical cooling indirectly supplied to a space through uninsulated surfaces of space-cooling components, such as evaporator coil cases and cooling distribution systems that continually maintain air temperatures within the space of 85°F (29°C) or lower during normal operation

Positive heat supply: Heat deliberately supplied to a space by design, such as a supply register, radiator or heating element. Also, heat indirectly supplied to a space through uninsulated surfaces of service water heaters and space-heating components, such as furnaces, boilers and heating and cooling distribution systems which continually maintain air temperature within the space of 50°F (10°C) or higher during normal operation.

Positive indoor pressure: When air is delivered to a space faster than it is exhausted.

Post-and-beam: Wood framing of buildings with load-bearing wood posts connected to horizontal wood beams. Also called ‘timber framing.’

Post-consumer recycled content: Material or finished product that has served its intended use and has been discarded for disposal or recovery by consumers, as opposed to by industry. Examples include newspaper, magazines, beverage containers, building materials, etc. To "close the recycling loop" we want to support products that make use of the highest post-consumer content.

Post-industrial recycled content (PIRC): Waste that is produced during the manufacturing process that is recycled back into the industrial process. In many cases, industry was already recycling this material back into the process and thus post-industrial recycled content is not as significant as post-consumer. Also known as post-commercial recycled content.

Post-commercial waste (industrial waste): Waste from industry processes or materials discarded from industrial plant renovations or maintenance.

Post-consumer waste: Goods or materials discarded by consumers after use.

Potable water: Water suitable for drinking.

Powder coating: A durable finishing method for metals using a dry, powdered plastic that is heat-fused onto the surface. No solvent is required and practically no waste produced.

Power: The rate at which energy is consumed or produced. It is expressed in watts (W). A 1-watt source supplies energy at the rate of 1 joule per second. (A 100-watt lamp consumes energy at the rate of 100 joules per second; the human body involved in normal activity is rated at about 100W, a significant proportion being used to drive the brain). The sun radiates energy at the rate of about 70 million watts per square meter of its surface; at the equator the Earth receives a mean annual solar energy flux of around 1,400 watts per square meter.

Pre-cast Autoclaved Aerated Concrete (PAAC): A lightweight artificial stone of uniform cellular structure. See also Autoclaved Aerated Concrete.

Pre-consumer recycled material: A material that is removed from source gathering or production processes (such as scrap, breakage, or returned inventory) and returned to the original manufacturing process or an alternative process. Pre-consumer recycled materials have not reached yet a consumer for the intended use. Usually referred to as post-industrial recycled material.

Pre-fab: (Short for prefabricated) Any building system where a portion of the assembly work is done in locations away from the final building site.

Prescriptive packages approach: A prescriptive packages approach lists the minimum R-value or maximum U-factor requirements for each building component such as windows, walls, and roofs. For lighting systems, a prescriptive approach would simply list the allowable watts per square foot for various building types. For mechanical systems and equipment, a prescriptive approach would list the minimum required equipment efficiencies. This approach is quick and easy to use, but you may find the approach somewhat restrictive because the requirements typically are based on worst-case assumptions and all requirements must be met exactly as specified. By locating the correct climate zone and looking up the appropriate table of packages, you can verify that your project meets one of the packages listed for that climate zone.

Pressure Boundary: This is the surface or plane that separates indoor air from outdoor air. The pressure boundary is defined by the air barrier, a continuous system of materials that blocks the flow of air between the inside and the outside. The pressure boundary is defined as the location where 50 percent or more of the air pressure drop across an assembly occurs. The pressure boundary is analogous to a balloon that encloses a volume of air and maintains that air at a pressure that is different from the pressure outside the balloon.

Pressure dose: A method of pumping wastewater to subsurface leaching fields in which soils or slopes are a limiting factor. Typical leach fields operate with gravity.

Pressure-sensitive adhesives: Dry adhesives that adhere with pressure but remain flexible.

Pressure-treated wood: Wood that is chemically preserved to prevent moisture decay, e.g., with chromated copper arsenate (CCA). Substitutes like ammonium copper quaternary (ACQ) and copper boron azole (CBA) have been developed because of concerns about leaching of chromium and arsenic into groundwater and soil over time, as well as concerns over skin contact during construction and inhalation of these metals during sawing. CCA is considered a suspected carcinogen and is classified as a hazardous waste. Pressure-treated wood products are currently not suitable for recycling. CCA treating of wood intended for residential use is prohibited as of January 1, 2004.

Pricing/rate structure: System used by utility managers to charge customers for usage.

Primary design consultant: Typically an architect or interior designer; the person responsible for hiring of subconsultants and communication with the client.

Primary input: A thing or things that represent the key or fundamental elements that are operated upon by the process and lead to the “Primary output” of the process. For a specific life cycle analysis, the “Primary inputs” of each process in the life cycle sequence need to be clearly defined in terms of what, when, and where. In general, the “Primary input” of one process will be the “Primary output” of the previous process.

Primary output: The thing, item, or article that represents the intended goal of the process. For a specific life cycle analysis, the “Primary outputs” of each process in the life cycle sequence need to be clearly defined in terms of what, when, and where.

Primary production: The process of extraction of raw materials.

Primary treatment: Basic wastewater treatment that only removes the bulk of solids but does not digest nutrients or render water safe for discharge.

Primer: First coat applied to a substrate, serving as a sealer and providing a base for finish coats.

Product differentiation: A function of advertising in which the aim is to convince the public that a particular brand of product is “different” from and “superior” to others.

Proffer: A developer’s promises that are approved by the local municipalities and tied to the land in the zoning process. They include any financial commitments made by the developer to offset costs the county would otherwise have to pay.

Programmable controller: A device that controls the operation of equipment (such as air conditioning units and lights) according to a pre-set time schedule.

Proper ventilation: Any ventilation arrangement where combustion gases are vented completely to the outdoors.

Psychrometric chart: An analytical tool combining temperature and humidity on which climatic data is plotted to reveal the potential effectiveness of passive strategies to maximize human comfort.

Purlin: A piece of timber laid horizontally on the principal rafters of a roof to support the common rafters on which the roof covering is laid or to directly support the roof covering.

Quality: In building science, quality is a three-legged stool of building design, integrity of building components and materials, and attention to detail during installation. In a systems thinking approach to building, ALL THREE are required for quality. And while the term quality control is used a lot more than the term quality assurance, the former is a largely reactive mechanism that, while important, means little without the latter . Quality assurance means planning and design, critical to a systems approach to building.

Quarter-sawn: Logs are quartered and boards are sawn toward the center, producing a narrow, parallel grain pattern. Boards sawn in this manner have less tendency to warp or shrink, though this technique wastes more wood.

Radiant barrier: A material (typically a metallic foil) that reflects thermal radiation without transferring heat to other materials. In a hot climate, it is often installed in attics under the roof decking to keep the attic cooler.

Radiant energy: Energy in the form of electromagnetic waves that travels outward in all directions from its source.

Radiant heating: Space heating by means of baseboard, wall, floor or ceiling panels with embedded electric conductors or hot water pipes that give off heat.

Radiation: Heat transfer in the form of electromagnetic waves from one surface to an unconnected colder surface. Examples are heat radiation from the sun to the earth, from a fireplace to people and objects in a room, or from a human body to a cool surface, such as a wall or window.

Radioactivity: The property possessed by some elements (as uranium) of spontaneously emitting alpha or beta rays and sometimes also gamma rays by the disintegration of the nuclei of atoms.

Radio frequency interference (RFI): See Electromagnetic interference (EMI).

Radon: A radioactive, colorless, odorless gas that occurs naturally in soil in many areas. When trapped in buildings, concentrations build up, and can cause health hazards. Radon and its decay products are carcinogens.

Rafter: One of a series of inclined members to which a roof covering is fixed.

Rain sensor: A device that measures rainfall and may be used to prevent unnecessary irrigation.

Rainscreen: A method of constructing walls in which the cladding is separated from a membrane by an airspace that allows pressure equalization to prevent rain from being forced in.

Raised Truss: Any roof/ceiling construction that allows the insulation to achieve its full thickness over the plate line of exterior walls. Several constructions allow for this, including elevating the heel (sometimes referred to as an energy truss, raised-heel truss, or Arkansas truss), use of cantilevered or oversized trusses, lowering the ceiling joists, or framing with a raised rafter plate.

Rammed earth: A wall-building technique, by which a certain mixture of earth, water, and usually a small amount of cement, is very forcibly tamped inside formwork. The resulting wall has high mass, so it works well in hot climates. It often needs no exterior or interior covering, thus saving materials.

Recirculated air: Indoor air that passes through an HVAC system to be heated or cooled then returned through the building. Generally, a small percentage of fresh outdoor air is mixed with recirculating indoor air.

Re-circulation system: A distribution system that keeps hot water running in the pipes to provide immediate hot water at the taps.

Reclaimed water: Wastewater that is treated and reused to supplement water supplies.

Recovered energy: Reused heat or energy that otherwise would be lost.

Recovered material: Waste materials and by-products that have been recovered or diverted from solid wastes.

Recycled material: Material that would otherwise be destined for disposal but is diverted or separated from the waste stream, reintroduced as material feedstock, and processed into marketed end products.

Recycled plastic lumber: Structural components fabricated from recycled plastic as a replacement for lumber. Insect, rot, and water-resistant.

Recycling: Series of activities, including collection, separation and processing, by which products or other materials are recovered from the solid waste stream for use in the form of raw materials in the manufacture of new products other than fuel for producing heat or power by combustion. True recycling is the conversion of a waste material back into its original form. An alternative is conversion into another material.

Redevelopment: The redesign or rehabilitation of existing properties.

Reflectance: The ratio of reflected light energy to incident light energy.

Reflected glare: Glare resulting from specular reflection of high luminances in polished, or glossy, surfaces in the field of view.

Reflection: The process by which incident light flux leaves a surface, or medium, from the incident side, without a change in frequency.

Reflective glass: Glass coated with metallic oxide or other material to increase the amount of solar energy reflected. The result is a reduction in the cooling load within the building.

Reflector: Highly reflective backing inserted behind a light fixture, used to reclaim lighting and improve efficiency.

Refraction: The deflection of a light ray from a straight path when it passes at an oblique angle from one medium to another.

Refrigerant: A volatile substance that can be used as a working fluid in a cooling system.

Regeneration: Restoration of harmed ecosystems such as logged forestlands and mined sites. Drainage, soil replacement, replanting, and fertilization are usually involved.

Register: A grille covering a duct outlet.

Relative humidity: The amount of water vapor in the air compared to the amount of water vapor the air can hold, which depends on the air’s temperature. It is expressed as a percentage. Hot air can hold more moisture than cold air before reaching its dew point and condensing.

Releasable adhesives / dry adhesives: A dry, tacky adhesive that holds a carpet or other finish in place but can be easily removed. After removal it leaves no residue and can be reattached.

Remanufacturing: Industrial process in which worn-out products are restored to “like new” condition.

Render: In construction, the application of stucco or cement mortar to the face of a wall to give a continuous surface finish. In architecture, to draw an image of a project.

Renewable energy: Energy produced from regenerative or virtually inexhaustible resources such as biomass, solar radiation, the wind, water (tides and waves), or heat from the Earth's interior.

Renewable resources: A resource that is replenished at a rate equal to or greater than its rate of depletion. If properly managed, renewable energy resources (e.g., solar, hydro, wind power, biomass, and geothermal) should last as long as the sun shines, rivers flow, wind blows, and plants grow. Renewable resources are sometimes referred to as regenerative, nondepletable, or current-income energy.

Renovation: The process of upgrading an existing building. Usually there is an attempt to keep the same general appearance of the building with new materials or to return the building to its original appearance.

Repair: A repair includes the reconstruction or renewal of any part of an existing building for maintenance purposes.

RESFEN: A computer program used to calculate energy use based on window selection in residential buildings.

Residential buildings: For the purposes of the code, Group R residential buildings include:

Type A-1 - Detached one- and two-family dwellings

Type A-2 - All other residential buildings, three stories or less in height

Resilient flooring: Resilience is the ability of a material to return to its original form after subjection to static or dynamic loads, or sudden impact. Resilient flooring may include rubber, vinyl, or linoleum floor coverings.

Resistance: The ability of all conductors of electricity to resist the flow of current, turning some of it into heat. Resistance depends on the cross section of the conductor (the smaller the cross section, the greater the resistance) and its temperature (the hotter the cross section, the greater the resistance).

Respirable suspended particulates: Bits of airborne matter small enough to be inhaled deep into the lungs yet large enough to become lodged there once they enter.

Restoration: The process of bringing back a structure or landscape to its original state.

Retaining wall: Wall that is subject to lateral pressures; typically retaining walls hold back earth.

Retrofit: The replacement, upgrade, or improvement of a piece of equipment or structure in an existing building or facility.

Return air: Air that has circulated through a building as supply air and has been returned to the HVAC system for additional conditioning or release from the building.

Return air ducts: Ducts through which air that has been supplied to conditioned space returns to the HVAC unit.

Reuse: The recovery of a material for additional use without reprocessing (e.g. glass bottles reused by a dairy).

Reverberation time (RT): The amount of time it takes for sound to decay 60 decibels in a given space. It is a function of room volume and amount of sound absorption provided by surface finishes in the room. Optimum levels are determined based on room volume and space usage.

Revitalize: To give new life or vigor to, for example, to revitalize inner-city neighborhoods.

Right-to-know laws: Regulations that require the disclosure of information about hazardous materials used, stored, emitted, or disposed of in a community, when requested by local authorities or citizens.

Ridge: The peak of the roof.

Ridge vent: A vent installed continuously along the ridge of the attic peak, to allow ventilation air from the soffit vents to flow out of the attic.

Rigid insulation: Insulation, such as foamed plastic, wood fibers, cork, glass or mineral fibers, pressed into standard-sized boards for easy handling. Used as a surface insulation.

Rock wool (mineral wool): Insulating material spun from heated slag from the metal smelting process, similar to glass fiber.

Romex wire: A type of wiring that is installed in a house. It is widely utilized but is less resistant to damage than BX wiring. Also called non-metallic sheathed wiring.

Roof Assembly: Considered to be all roof/ceiling components of the building envelope through which heat flows, thus creating a building transmission heat loss or gain, where such assembly is exposed to outdoor air and encloses conditioned space.

Roof pond: A body of water on the roof of a structure that is exposed to solar gain, which it absorbs and stores. The thermal energy is radiated into the building uniformly and at a moderated temperature, in both sunny and cloudy conditions.

Roof span: Distance between the supports for a roof.

Roof truss: A form of structural support of a building’s roof.

Room criteria (RC): Similar to Noise Criteria (NC) and Noise Reduction (NR), but from 16 to 8,000 Hertz and more recent. Room criteria also rates noise for rumble or hiss.

Room ratio (RR): A number indicating room proportions, or the ratio of room length to width. Room ratio is equal to 5.0/room cavity ratio.

Running bond: In masonry, a bond in which bricks or stones are laid lengthwise; all courses are laid as stretchers, with the vertical joints of one course falling midway between those of adjacent or superior courses.

Runoff: Water from rainfall or irrigation that flows off of land, instead of soaking in. It effectively becomes a lost resource, and contributes to non-point source pollution.

R-value: Quantitative measure of resistance to heat flow or conductivity, the reciprocal of U-factor. The units for R-value are ft2 °F hr/Btu (English) or m2 °K hr/W (SI or metric). While many in the building community consider R-value to be the primary or paramount indicator of energy efficiency, it only deals with conduction, one of three modes of heat flow, (the other two being convection and radiation). As an example of the context into which R-value should be placed, 25% to 40% of a typical home's energy use can be attributed to air infiltration.

Safety glass: A strengthened or reinforced glass that is less subject to breakage or splintering.

Salvage: Recovery and reclamation of damaged, discarded, or abandoned material, e.g., during demolition or renovation.

Sand barrier termite control: Use of sand of a specific type around and at penetrations of a building foundation as a means to prevent entry by termites. Termites cannot pass through this type of sand because their tunnels cave in.

Saturated air: Air whose vapor pressure is the saturation vapor pressure and whose relative humidity is 100.

Scheduled switching: The most basic type of automated lighting control. Lights are programmed to turn on or off (and brighten or dim) at prescribed times, according to occupancy patterns.

Screw lamp holders: A lamp base that requires a screw-in-type light such as an incandescent or tungsten-halogen bulb.

Sealant: A material with adhesive properties and the capability of expansion and contraction that is used primarily to fill, seal, waterproof, or weatherproof gaps or joints between two surfaces. VOC limits for sealants have been established by specific entities to protect against smog formation outdoors. See Caulking.

Seasonal Affective Disorder (SAD): Recurring winter depression characterized by oversleeping, overeating, and irritability, and relieved by the arrival of spring or by light therapy.

Seasonal Energy Efficiency Ratio (SEER): The total cooling output of an air conditioner during its normal annual usage period for cooling, in Btu/h (W), divided by the total electric energy input during the same period, in watt-hours, as determined by DOE 10 CFR Part 430, Subpart B, Test Procedures. New equipment ranges from 10 to about 16 SEER. Higher SEER ratings indicate more efficient equipment.

Seasonal rate structure: Rate structure that bills all water or electricity consumed during the summer or peak season at a higher rate than other seasons.

Secondary production: Refining, smelting, or processing raw materials into usable products.

Secondary treatment: Wastewater treatment that generally digests nutrients and collects fine solids so that wastewater is safe to discharge.

Sediment basin: A depression in the soil that is placed to retain sediment and debris on-site.

Sedimentary rock: Formed from ancient silt deposits subjected to great pressure, such as sandstone, limestone, and travertine.

Selective surface: A special surface material designed to have a high absorptivity and a low emissivity. Typically used to coat absorption surfaces in solar thermal collectors.

Semi-Permeable: The term vapor semi-permeable describes a material with a water vapor Permeance between 1 and 10 Perms. Water vapor can pass through a semi-permeable material but at a slow rate.

Sensible heat: Heat that results in a temperature change.

Sensible load: Heating or cooling load required to meet air temperature requirement for comfort.

Sensitivity: The degree to which a person is physiologically responsive to the presence of a substance.

Sensitization: The priming of the immune system following an initial exposure to an antigenic substance.

Sensitizer: A substance, exposure to which causes increased sensitivity or susceptibility to that substance on re-exposure.

Service penetration: A hole drilled for an electric line, television cable, plumbing, telephone, or other utility service.

Service water heating: The supply of hot water for purposes other than comfort heating and process requirements.

Setback thermostat: Combines a clock and a thermostat so that heating and cooling may be timed to keep the house or specific zones comfortable only when in use.

Shade screen: A specially fabricated screen of sheet material with small narrow louvers formed in place to intercept solar radiation from striking a window. Also, an awning with fixed louvers of metal or wood. Also called sun screen or solar screen.

Shading: The protection from heat gains due to direct solar radiation.

Shading coefficient (SC): The ratio of solar heat gain through a given window glazing material to that through 1/8 inch clear double strength glass. Used to express the effectiveness of glazing or a shading device.

Shallow trench system: A type of drain field used in conjunction with a graywater system that allows for shallow placement of distribution pipes and use of the greywater for irrigation.

Shear: A deformation (e.g. in a beam or flexural member) in which parallel planes slide relative to each other so as to remain parallel.

Shear braces: A bracing system, usually using metal brackets or straps, which eliminates most structural wall sheathing.

Sheathing: Exterior material used to cover roof and sidewall framing, for strengthening and/or insulation. Sometimes called sheeting. Also the structural covering, usually wood boards or plywood, used over studs or rafters of a structure.

Sheathing board: Composition board (e.g., fiber cement, OSB, plywood, etc.) that is used instead of wood sheathing. It can be used to cover the framework of buildings or cabinets.

Shed roof: A roof shape having only one sloping plane.

Sheen: Reflectivity of a surface.

Sheet glass: A soda-lime-silica glass, fabricated in continuous sheets up to 6 ft. wide, in thicknesses from 0.05 to 0.22 in.; graded AA, A, and B according to the quality, but actual quality depends on the manufacturer.

Shingles: Roof covering made of asphalt, asbestos, wood, tile, concrete, slate or other material cut to stock length, width and thickness, applied in consequent layers.

Short-wave infrared radiation: Invisible radiation, just beyond red light on the electromagnetic spectrum, emitted by hot surfaces.

Shutter: Usually lightweight louvered or flush wood or non-wood frames in the form of doors located at each side of a window, used to close over the window as a form of protection.

Sick building syndrome (SBS): A pattern of health complaints related to poor indoor air quality. According to the EPA and NIOSH, Sick Building Syndrome is defined as “situations in which building occupants experience acute health and/or comfort effects that appear to be linked to time spent in a particular building, but where no specific illness or cause can be identified. The complaints may be localized in a particular room or zone, or may be spread throughout the building.” Occupants experience relief of symptoms shortly after leaving the building. Less severe and more temporary than Building Related Illness (BRI).

Siding: Boards or other material used for final exterior wall finish of a house.

Siding shingles: Various kinds of shingles, such as wood shingles or shakes and non-wood shingles, which are used over sheathing for final exterior sidewall covering of a structure.

Sill: The lowest horizontal member in a door, window, or sash frame.

Sill plate/mudsill: The bottom horizontal member of the framing in a wood-framed house. The sill plate sits on the foundation.

Single family: A detached one- and two-family residential building, irrespective of height.

Single glazing: Single thickness of glass in a window or door.

Single-hung window: A window consisting of two sashes of glass, the top one stationary and the bottom movable.

Single-zone, Unitary HVAC Systems: Unitary HVAC systems that serve a single zone. Single zone systems can provide either heating or cooling, but provide supply air at the same volume and temperature to the entire zone that they serve.

Sink: Surfaces that tend to capture gases, vapors, or particles from air and release them at a later time. Carpets, gypsum board, ceiling tiles, and upholstery are all sinks.

Site: The natural location intended for the “Building,” altered, modified, and prepared to the point where “Construction” activities for the “Structure” can be initiated. (J.A. Tshudy, Part IV, Section C)

Site assessment: The thorough environmental analysis conducted as a stage in planning to assess a variety of measures from soils, topography, hydrology, environmental amenities such as wetlands, wind direction, solar orientation, animal and plant habitat, connections to community, etc. Geographical Information Systems (GIS) can facilitate this task.

Site built: Housing built at the site, usually with no factory-built components.

Site selection and preparation: That complete sequence or series of activities and actions that begins with the natural environment and results in some specific geographic location defined in terms of boundaries, and altered and modified to the point where it has become the building “Site” ready for “Construction” to begin.

Skylight: Glazing that is horizontal or sloped at an angle less than 60° (1.1 rad) from horizontal.

Slab: Concrete floor placed directly on earth or gravel base.

Slab Edge: Slab edge refers to the perimeter of a slab-on-grade floor, where the top edge of the slab floor is above the finished grade or 12 in. or less below the finished grade. The slab perimeter should include the length of all edges of a slab foundation that are part of the building envelope and are less than 12 in. below grade (i.e. all edges separating conditioned space from unconditioned space.

Slab-On-Grade Floor: A floor that is poured in direct contact with the earth.

Slab-On-Grade Floor Insulation: Insulation around the perimeter of the floor slab or its supporting foundation when the top edge of the floor perimeter slab is above the finished grade or 12 inches (305 mm) or less below the finished grade.

Slag: Nonmetallic by-product of smelting and refining of metals. Used in the manufacture of cement, lightweight concrete, and rock wool.

Slipforms: Concrete forms that are advanced for another pour after the concrete has set.

Slump: A measure of consistency of freshly mixed concrete, mortar, or stucco; equal to the decrease in height, measured to the nearest ¼ inch of the molded mass immediately after its removal from a slump cone.

Sludge: The sediment extracted from wastewater. Also mud, slime, and semisolid waste.

Sludge composting: Process of composting treated municipal sewage waste with organic matter for use as a soil amendment.

Slurry: Free-flowing, pumpable suspension of fine solid material in a liquid.

Smart building: Any building that makes use of programmable electronic controls and sensors that regulate heating, cooling, ventilation, lighting, appliance and equipment operation in an energy conserving and climatically responsive manner.

Smog: Originally a combination of smoke and fog, now used to describe other mixtures of air pollutants, especially ozone and other compounds formed when strong sunlight acts on a mixture of nitrogen oxides and volatile organic compounds from motor vehicle exhaust.

Soaker hose: Low-flow watering device; hose with numerous perforations, used to irrigate plant beds and gardens.

Soffit: The exposed underside of the part of a roof that extends out beyond the top of the wall, also called an “eave.”

Soffit vent: A screened vent located in the soffit of the roof overhang that allows air to flow through the eaves into the attic.

Softwood: Wood from a coniferous tree, such as pine, fir, hemlock, spruce, or cedar. Softwoods are fast growing and primarily used for construction.

Soil moisture sensor: A device that can be attached to any irrigation system that monitors the water available to plants and allows irrigation only when the soil moisture level drops below a desired point.

Solar access: Access to the sun’s rays by, for instance, restricting the location of shade trees or laying out the building so as to maximize the usefulness of solar energy.

Solar altitude: In solar analysis, the vertical angular distance of a point in the sky above the horizon. Altitude is measured positively from the horizon to the zenith, from 0 to 90 degrees.

Solar array: Any number of solar modules connected together to provide a single output of electricity.

Solar azimuth: In solar analysis, the horizontal angular distance between the vertical plane containing a point in the sky (usually the sun) and true south.

Solar cell: The most basic photovoltaic device. When exposed to sunlight, it generates electricity.

Solar collector: A device designed to gather and store energy from solar radiation, ranging from ordinary windows to complex mechanical devices. Photovoltaic panels (PV’s) that convert the sun’s energy directly into electricity, and solar hot water panels, which heat pre-heat water before sending it into a hot water heater are two examples.

Solar energy: Energy received from the sun in the form of electromagnetic radiation in the wavelength region from 0.3 to 2.7 microns. This includes all visible light as well as some ultraviolet and infrared radiation.

Solar module: A device designed to collect solar energy and output either a heated fluid or electricity. Modules may be connected together to form panels and arrays.

Solar panel: A group of modules, which are part of an array, wired or plumbed together in parallel or series to obtain a desired voltage, amperage, flow rate, temperature, or pressure drop.

Solar heat gain coefficient (SHGC): Indicates the glazing's effectiveness in rejecting solar heat gain. SHGC is part of a system for rating window performance used by the National Fenestration Rating Council (NFRC). SHGC is gradually replacing the older index, shading coefficient (SC), in product literature and design standards. If you are using glass whose performance is listed in terms of SC, you may convert to SHGC by multiplying the SC value by 0.87.

Solar radiation: Radiant energy received from the sun, from both direct exposure and diffuse or reflected sunlight. It includes ultraviolet, visible, and infrared wavelengths.

Solar reflectance: The percentage of the sun’s energy that is absorbed as heat by a roofing material.

Solar screen: A sun shading device, such as screens, panels, louvers, or blinds, installed to block solar radiation.

Solar thermal energy: Energy produced by using the sun's rays to heat a gas or liquid that then performs useful work, such as powering an electrical generator. Electricity from solar thermal power plants is now nearly competitive in cost with electricity from conventional fossil-fuel power plants.

Solar water heater: A water heating system in which heat from the sun is absorbed by collectors and transferred by pumps or natural convection to a storage unit. The water or heated fluid in the storage unit conveys its heat to the domestic hot water of the building directly or through a heat exchanger, respectively.

Sole plate: A horizontal timber that serves as a base for the studs in a stud partition. A plate riveted to the bottom flange of a plate girder to bear on the masonry plate. (also bottom plate).

Solid waste: Solid product or material disposed of in landfills, incinerators, or compost. Can be expressed in terms of weight or volume.

Solvent: Compound that is normally liquid, usually petroleum based, that can dissolve solids and keep them in solution. May contribute to pollution through evaporation.

Sone: A unit of loudness.

Sound: Minute changes in air pressure of 2 x 10- 1 0 to 2 x 10- 3 of an atmosphere at the rates of from 20 to 20,000 times per second.

Sound power level: Reported in decibels, it is 10 times the logarithm to the base of 10 of the ratio of the total sound power in watts to a reference power of 10-12 watts.

Sound pressure level (SPL): Reported in decibels, it is 20 times the logarithm to the base 10 of the ratio of sound pressure to a reference pressure of 20 micropascals.

Sound transmission class (STC): A single-number rating designed to provide a comparison between the noise losses of different structures for building-design purposes. The STC is calculated from the noise reduction at the 16 one-third octave bands between 125 and 4,000 Hertz. The American Society for Testing and Materials has published a standard, ASTM E413-73, "Standard Classification for Determination of Sound Transmission Class."

Source reduction: Elimination of waste at the beginning of a process. Sometimes called “pre-cycling”.

Source separation: Separating waste materials by type at the point of discard so they can be efficiently recycled.

Spec house: A single-family dwelling constructed in anticipation of finding a buyer.

Specifications (specs): Detailed instructions provided in conjunction with plans and blueprints for construction. Specifications may stipulate the type of materials to be used, special construction techniques, dimensions, and colors.

Spectrally selective glazing: Window glass that is coated or tinted in order to admit visible light while limiting heat radiation.

Spectrophotometer: An instrument for measuring the transmittance and reflectance of surfaces and media as a function of wavelength.

Split System HVAC: HVAC equipment that has the indoor and outdoor coils within separate cabinets. For a cooling only system, the outdoor cabinet would contain the condenser coil and the indoor cabinet would contain the evaporator coil.

Sprawl: An irregular, low-density spread of residential areas, shopping centers, and small industries outside of city boundaries.

Stack effect: The upward movement of air in a building or chimney, due to the buoyancy of warm air. It is responsible for pushing warm house air out though leaks in the upper floors and drawing air in on the lower levels.

Stakeholders: Individuals, groups, or businesses that are interested, involved, or affected by a particular action or activity.

Standard Truss: Any construction that does not permit the roof/ceiling insulation to achieve the required R-value over the exterior walls.

Standby loss: The energy lost through the walls and up the flue of a hot water tank.

Static pressure: In an air distribution system, the pressure that the fan must supply to overcome the resistance to airflow through the system ductwork and system components.

Stay-in-place insulating formwork: Concrete formwork made from expanded or extruded polystyrene foam units, which is permanent in the structure of the building. Such formwork serves as an insulator and can reduce the amount of concrete required. (sometimes called insulated concrete forms (ICFs)).

Steady-state combustion efficiency: The efficiency of a combustion-heating appliance, after an initial start-up period, that measures how much heat crosses the heat exchanger. A combustion analyzer measures the steady-state efficiency.

Stem wall: That part of the foundation wall that sits upon the pad footing and rising vertically.

Stressed skin panel: A structural panel with the sheathing permanently bonded to the frame or core to increase its strength.

Straw bale construction: Uses baled straw from wheat, oats, barley, rye, rice and other agriculture fiber in walls covered by stucco.

Straw-clay construction: A building technique including structural members and a light clay (compacted mixture of clay and straw) infill.

Strawboard: Straw mixed with a bonding ingredient and compressed into a board-type material. May be structural or non-structural.

Structural insulated panels (SIPs): A building component that combines exterior sheathing, structural support, and insulation, and interior sheathing into one modular factory-assembled unit, thus reducing the number of vertical joints, interior voids, and assembly time.

Structural masonry wall: A type of wall construction using masonry, precast or poured-in-place concrete, or concrete masonry units to bear building loads.

Structural: Term used to describe any supporting wall or member.

Structure: The completed building envelope on the “Site,” externally and internally complete, including all operating systems ready for its “Interior furnishings.”

Stucco: Most commonly refers to an exterior plaster made with Portland cement as its base.

Studs: Vertical framing, in slender wood or metal members, of the walls of the house.

Sub-flooring: Sheet material attached directly to floor joists or trusses as an underlayment for finished floor or finished floor substrates.

Submetering: Use of separate meters to indicate individual water use in apartments, condominiums, and trailer homes, while the entire complex of units continues to be metered by the main supplier.

Substrate: Basic surface on which a material, e.g., architectural coating or finish, is applied or installed.

Sun-bearing angle: The solar azimuth angle relative to the horizontal direction a building surface is facing. Often referred to as the “relative solar azimuth.”

Sun control film: A tinted or reflective film applied to a glazing surface to reduce visible, ultra-violet, or total transmission of solar radiation. Also reduces solar heat gain in summer and glare.

Sunscreen: A fixed exterior louver that reflects and/or absorbs solar radiation. A sunscreen’s effectiveness in shading a window depends on its light absorption properties and its geometry with respect to the window opening.

Sunspace: A well-glazed space, generally south facing, that collects heat and supplies some of it to another adjoining space. Temperatures within sunspaces are normally not controlled, but fluctuate daily and seasonally.

Superabsorbent materials: Various artificial materials capable of holding several times their own weight in water. Used in granular form, these are mixed with earth to increase the amount of water held in the soil, the length of time it is held before drying, and its availability to plants. Humus serves this purpose.

Superplasticizers: Chemical additives for concrete that increase the fluidity of the mix without excess water.

Superwindows: Double- or triple-glazed window sandwiches that contain a center sheet of coated Mylar “low-emissivity” film and are filled with argon or krypton gas. This construction and the coating on the film allow short-wave radiation (visible light) to pass through, but reflect long-wavelength radiation (infrared or heat) so heat cannot pass through. R-values of 4.5 or more are achieved.

Supply air: The total quantity of air supplied to a space of a building for thermal conditioning and ventilation. Typically, supply air consists of a mixture of return air and outdoor air that is appropriately filtered and conditioned.

Supply ducts: The ducts in a forced-air heating or cooling system that supply heated or cooled air from the furnace or air conditioner to the building.

Surface-area-to-volume ratios: A potential and often misleading indicator of building energy performance; the smallest (best) ratios apply to buildings that are most closely to square in shape, but overlook the fact that increased surface area may also mean increased potential for passive solar heating, natural ventilation, and/or daylighting.

Surface water: Water contained in lakes, rivers, streams, and reservoirs.

Sustainability: Meeting the needs of the present without compromising the ability of future generations to meet their own needs as defined by the Brundtland Commission, 1987.

Sustainable development: Sustainable development has as many definitions as subscribers. In essence, it refers to economic development that meets the needs of all without leaving future generations with fewer natural resources than those we enjoy today. It is widely accepted that achieving sustainable development requires balance between three dimensions of complementary change: economic (towards sustainable patterns of production and consumption), ecological (towards maintenance and restoration of healthy ecosystems), social (towards poverty eradication and sustainable livelihoods).

Sustainably sourced materials: Materials that are acquired in an environmentally sound manner emphasizing efficient and appropriate use of natural resources.

Swale: A hollow or depression on a wet, marshy ground through which water flows.

Switched receptacles: The ability to turn power on and off to an electrical outlet by using a control switch.

Synergy: Action of two or more substances to achieve an effect of which each is individually incapable. As applied to toxicology, two exposures together (for example, asbestos and smoking) are far more risky than the combined individual risks.

Synthetic: Produced by chemical methods.

Synthetic coal: A product that is made through the carbonization of shredded waste carpet; this product is then burned as an alternative fuel source that releases more energy per pound than coal and that burns more cleanly.

Systems (systemized) building: Any form of building that employs use of pre-made components and/or modular systems that are supplied and erected following an orderly plan to keep costs down and efficiency high.

Tack: The degree of stickiness or holding power of an adhesive.

Tandem wiring: A wiring option in which a ballast is shared by two or more luminaires. This reduces labor, materials, and energy costs.

Tankless / Instantaneous /Demand water heater: A water heater that heats water as needed with no storage tank, using large electric elements or gas burners.

Task lighting: Lighting to provide illumination for a specific activity in a specific place.

Temperature and pressure relief valve: A safety device on storage water heaters that relieves dangerously high temperatures or pressures if they build up inside the tank.

Temperature reset controls: Controls that automatically reset supply temperatures by representative building loads (including return water temperature) or by outside air temperature.

Tempered glass: Treated glass that is strengthened by reheating it to just below its melting point and then quickly cooling it. When shattered, it breaks into small pieces. Tempered glass is approximately five times stronger than standard annealed glass; it is required as safety glazing in patio doors, entrance doors, sidelights, and other hazardous locations. Cannot be re-cut after tempering.

Teratogenic: A substance that harms the developing fetus, thus causing birth defects.

Termite shield: A permanent physical barrier (i.e. mesh screen, solid metal, plastic) usually embedded into the foundation and around penetrations (e.g. piping) that prevents termites, and potentially other pests, from entering the building structure.

Terrazzo: Mosaic flooring surface made from marble, granite, other stone chips embedded in a binder, whose surface is ground and polished.

Tertiary treatment: Final wastewater treatment stage including destruction of active bacteria, rendering the water safe to drink.

Textile wall covering: Textile fibers laminated to a backing material that provides stability and adhering qualities. Examples include grass cloth, strings, woven wool, linen, jute, and sisal.

Thermal break: An element of low conductance placed between elements of higher conductance to reduce the flow of heat.

Thermal bridge: A component, or assembly of components, in a building envelope through which heat is transferred at a substantially higher rate than through the surrounding envelope area. Wall studs act as thermal bridges when insulation is installed only between them. Thermal bridging can be minimized by placing a layer of rigid insulation against the studs to break the un-insulated pathway.

Thermal chimney: A section of a building where solar heat or thermal currents are controlled and utilized to stimulate an updraft and exhaust hot air. This draws in fresh air through open windows or vents and is a passive cooling technique.

Thermal conductance: Time rate of heat flow through a body (frequently per unit area) from one of its bounding surfaces to the other for a unit temperature difference between the two surfaces, under steady conditions (Btu/h × ft²× °F) [W/(m² × K)].

Thermal conductivity (K): Measured amount of heat that will pass through a material or wall assembly in a given time.

Thermal envelope: The shell of a building that essentially creates a barrier from the elements and from fluctuations in outdoor temperature. This boundary or enclosure controls the transfer of energy (heat) between the interior and the exterior. It is a component of the building envelope and it may, but does not have to align with the pressure boundary. Also called thermal boundary.

Thermal expansion: The change in dimension of a material as a result of temperature change.

Thermal lag: The period of time between the absorption of solar radiation by a material and its release into a space. Thermal lag is an important consideration in sizing a thermal storage wall or Trombe wall.

Thermal mass: Material that have a high capacity for absorbing heat or coolness and releasing it slowly over a long period of time. These materials are commonly used to absorb and retain solar energy during the daytime for release at night. They include water, rocks, masonry, and earth.

Thermal pollution: Discharge of heated effluent into natural waters; this upsets the ecological balance of the waterway by changing its temperature.

Thermal resistance (R): The reciprocal of thermal conductance or thermal transmittance.

(h × ft² × °F/Btu) [(m² × K)/W].

Thermal storage capacity: The capacity for a building material to store heat internally from the sun, generally for later use or release.

Thermal storage wall: A masonry or water wall used to store heat from the sun. Typically, the south facing side is painted a dark color to improve absorption.

Thermal transmittance (U): The coefficient of heat transmission (air to air). It is the time rate of heat flow per unit area and unit temperature difference between the warm-side and cold-side air films (Btu/h × ft² × °F) [W/(m² × K)]. The U-factor applies to combinations of different materials used in series along the heat flowpath, single materials that comprise a building section, cavity airspaces and surface air films on both sides of a building element.

Thermochromic: Reversible change in color of a substance as its temperature changes.

Thermocirculation: The convective circulation of fluid that occurs when warm fluid rises and is displaced by denser, cooler liquid in the same system.

Thermodynamics: A study of the transformation of energy into other manifested forms and of their potential applications.

Thermogram: An image of an object taken with an infrared camera that shows surface temperature variations.

Thermostat: An automatic control device responsive to temperature.

Thermostat setback: Usually done at night to reduce the amount of conditioning provided at night by allowing the interior temperature to drift naturally to a marginal temperature during the night and then to recondition it to normal conditions in the morning.

Thermosiphon system: A flat-plate solar heating system that doesn’t require pumps. Considered a passive system.

Thickset method: A method for installing uneven masonry material, such as ungauged stone, where the mortar bed is ¾” to 1 ¼” thick.

Thinset method: A method for installing evenly gauged masonry material, such as ceramic or stone. A dry-set mortar as thin as 3/32” can be used, as can an adhesive. May contain an acrylic additive for strength.

Tidal/wave power: Power that can be generated in coastal locations from the twice-daily ebb and flow of the tides. As the tide rises, water is allowed to flow through gates in the dam to fill the basin behind it. At high tide the gates are closed and as the tide falls the water in the basin is retained behind the dam. Once a sufficient head of water is built up, the water behind the dam is released and the potential energy it possesses is converted into kinetic energy, which drives generators to produce electricity.

Tight buildings: Buildings that are designed to let in minimal infiltration air in order to reduce heating and cooling energy costs. In actuality, buildings typically exhibit leakage that is on the same order as required ventilation; however, this leakage is not well distributed and cannot serve as a substitute for proper ventilation.

Tint: A mineral coloring incorporated into the glass pane of a window to reduce solar heat gain. Tints also reduce visible transmittance through the window.

Tipping fees: Fees charged for dumping large quantities of trash into a landfill.

Title 24: California’s Energy Efficiency Standards for Residential and Nonresidential Buildings. The standards are for new construction (including requirements for entire new buildings, additions, alterations, and repairs in nonresidential buildings).

Ton: A common unit of measure for central air conditioning systems. (Before mechanical refrigeration, block ice was used for cooling. A ton of ice – 2,000 pounds—absorbs 12,000 Btu of heat per hour.) The actual capacity of the air conditioner will depend on the temperature and relative humidity in your area.

Tongue-and-groove (T&G): A type of joint formed by the insertion of the tongue of one member into the corresponding groove or another.

Top plate: A horizontal framing element use on top of a wall to which one must bond the vertical studs to prevent air leakage and flame spreading.

Topography: The physical features, including the configuration of a surface, of a place or region.

Topsoil: The uppermost soil horizon (layer), containing the highest amounts of organic material; depth varies greatly from region to region.

Torchiere: An indirect floor lamp sending all or nearly all of its light upward.

Toxic substance: In very general terms, any material considered to be hazardous to human health or the environment.

Toxicity: The nature and degree of a given substance’s adverse effects on living organisms.

Track lighting: A lighting system with an electrically fed linear track that accepts one or more track heads.

Tract house: A term for a house that is one of a number of speculative, suburban houses within a development area or tract.

Trade-off approach: A trade-off approach allows you to trade enhanced energy efficiency in one component against decreased energy efficiency in another component. These trade-offs typically occur within major building systems-envelope, lighting, or mechanical. You can, for example, trade decreased wall efficiency (lower R-value) for increased window efficiency (lower U-factor), or increase the roof insulation and reduce or eliminate slab-edge insulation. For lighting systems, the trade-off typically would occur between proposed lighting fixture wattages in various spaces within a building.

Traditional Neighborhood Development (TND): A basic unit of New Urbanism, which includes the following characteristics: a center that includes a public space and commercial enterprise; an identifiable edge, ideally a five-minute walk from the center; a mix of activities and variety of housing types; an interconnected network of streets and blocks usually laid out in a modified grid pattern; high priority given to public space with prominently located civic buildings and open space that includes squares, plazas, and parks.

Transit-oriented development: A mixed-use community within an average 2,000-foot walking distance of a transit stop and core commercial area that mixes residential, retail, office, open space, and public uses in a way that makes it convenient for residents and employees to travel by transit, foot, bike, etc.

Transmission: The process by which incident flux leaves a surface, or medium, on a side other than the incident side, without change in frequency.

Transmission loss (TL): Noise reduction corrected for wall area and room absorption.

Transmittance: The ratio of transmitted flux to incident flux; measured by a transmissometer.

Transom: A crosspiece separating a door or opening from a window or fanlight above it; also refers to a hinged ventilation window above a door or opening.

Transverse seam: All duct seams other than the longitudinal seam (which runs parallel to the direction of airflow).

Trellis: Lattice built as support for vines or other plants, or for shade.

Trim: The finish materials in a building, applied around openings (windows and doors) or at the meeting of two different materials or systems (baseboard, cornice).

Trimmer stud: A piece of timber inserted in a roof, floor, wooden partition or the like, to support a header which in turn supports the ends of the joists, rafters, studs, etc.

Trombe wall: A south-facing masonry wall that is covered with glass spaced a few inches away. Sunlight passing through the glass is transformed into heat at the wall’s surface, which either migrates into the building interior or is thermosyphoned to interior spaces through vents.

Tropical hardwood: Wood products harvested from tropical rainforests. Tropical rainforests are not being harvested in a well-managed manner except in a few isolated cases. Only wood certified from a sustainable source should be utilized.

Truss: A frame or jointed structure designed to act as a beam of long span. Uses triangulation to place each member in longitudinal stress only, either tension or compression.

Truth window (or wall): An exposed section of a wall or window that reveals the layered components within it.

Tubular skylight: New concept in channeling daylight into dimly lit areas for residential and commercial buildings. A prefabricated assembly of a clear dome attached to a reflective tube and a light diffuser at the level of the ceiling.

Turbine: Rotary engine that converts the energy of a moving stream of water, steam, or gas into mechanical energy. The basic element in a turbine is a wheel or rotor with paddles, propellers, blades, or buckets arranged on its circumference in such a fashion that the moving fluid exerts a tangential force that turns the wheel and imparts energy to it. This mechanical energy is then transferred through a drive shaft to operate a machine, compressor, electric generator, or propeller. Turbines are classified as hydraulic, or water, turbines, steam turbines, or gas turbines. Today turbine-powered generators produce most of the world's electrical energy. Windmills that generate electricity are known as wind turbines.

Ultraviolet (UV) radiation: Electromagnetic radiation, usually from the sun, that consists of wavelengths in the range of 4 to 400 nanometers; shorter than the violet end of the visible spectrum. UV radiation is a health hazard that can lead to skin cancer or cataracts.

Unconditioned space: An enclosed space within a building that is not heated or cooled.

Underlayment: A sheet material laid under finish flooring material to minimize irregularities in the subfloor or to add acoustic separation.

Underwriters Laboratories (UL): The U.S. testing agency responsible for verifying product electrical safety, fire ratings, etc.

Uninterruptible power supply (UPS): A system that provides continuous power regardless of what is happening to the grid.

Unitary cooling and heating equipment: One or more factory-made assemblies that include an evaporator or cooling coil, a compressor and condenser combination, and that shall be permitted to include a heating function as well. When heating and cooling equipment is provided in more than one assembly, the separate assemblies shall be designed to be used together.

Unitary heat pump: One or more factory-made assemblies that include an indoor conditioning coil, compressor(s) and outdoor coil or refrigerant-to-water heat exchanger, including means to provide both heating and cooling functions. When heat pump equipment is provided in more than one assembly, the separate assemblies shall be designed to be used together.

Unitary-packaged: Each package is a standalone system that provides all of the heating and cooling requirements for the area of the building that it serves.

Up-front planning: Comprehensive planning in advance of the development process.

Urban growth boundary: A boundary that identifies urban and urbanizable lands needed during a specified planning period to be planned and serviced to support urban development densities, and which separates these lands from rural lands.

U-factor: A quantitative measure of heat flow or conductivity, the reciprocal of R-value. While building scientists will use R-values for measures of the resistance to heat flow for individual building materials, U-factor is always used as a summary measure for the conductive energy measure of building envelopes. Lower values mean less heat flow. Also called U-value or thermal transmittance.

Valley: The trough or gutter formed by the intersection of two inclined planes of a roof.

Value-added: Secondary products with improved value over the raw materials.

Vapor: The gaseous phase of a substance which exists as a liquid or solid under normal conditions.

Vapor retarder / vapor barrier: A material that prevents or drastically reduces the passage of water in vapor form. Building materials are rated by permeance—their ability to let water vapor pass through them. Whether or not it is desirable to install a vapor retarder material on an exterior wall and where to place, depends on the climate where a building is located. In cold climates, vapor retarders are typically installed on the inside of the wall frame. In hot, humid climates, they are installed on the outside, or preferably omitted entirely. In hot, dry climates they are not needed.

Variable-Air Volume (VAV) system: HVAC system that controls the dry-bulb temperature within a space by varying the volume of heated or cooled supply air to the space.

Variable-frequency drive: Changes the speed of the motor by changing the voltage and frequency of the electricity supplied to the motor based upon system requirements.

Variance: A special permission to vary a physical structure or use a property in a way normally prohibited by existing zoning.

Varnish: Clear or pigmented surface coating that changes to a hard solid when dried from a liquid. All varnishes are solutions of resinous materials in a solvent.

Veneer: Thin ply of wood or other finish material that is usually laminated to a substrate of lower finish quality.

Vent: A pipe or duct that allows flow of air in or out.

Ventilated naturally: The process of supplying or removing air by natural means to or from any space.

Ventilated mechanically: The process of supplying or removing air by mechanical means to or from any space. Such air may or may not have been conditioned.

Ventilation: The process of supplying or removing air by natural or mechanical means to or from any space. Such air shall be permitted to be conditioned or unconditioned.

Ventilation air: That portion of supply air that comes from outside (outdoors) plus any recirculated air that has been treated to maintain the desired quality of air within a designated space (see ASHRAE 62 and definition of "Outdoor air").

Ventilation rate: The rate at which fresh outdoor air is introduced into a building to replace stale air. Commonly measured in air changes per hour (ACH) or cubic feet per minute (cfm).

Vernacular: In architecture, vernacular buildings are seen as the opposite of whatever is academic, or highstyle. The traditional architecture of a region. Often times, traditional architecture is a result of response to the regional climate and land conditions.

Visible light transmittance (VT): The fraction of solar radiation in the visible light spectrum that passes through the fenestration.

Visual Preference SurveysTM: Photographic images of various planning and design elements, accompanied by questionnaires and other analysis techniques. First developed by Anton Nelesson.

Vitrified: A clay fired to the point of melting into glass-like substance (glassification).

Volatile organic compound (VOC): Carbon based gases given off by polymers, solvents or plasticizers at room temperatures (called off-gassing). Of the VOCs, formaldehyde (a carcinogen) and acrolein (a suspected carcinogen) are known irritants at levels that may be encountered indoors. VOCs may also cause eye and upper respiratory irritation, nasal congestion, headache and dizziness. Examples of building materials that contain VOCs include, but are not limited to, solvents, paints, adhesives, carpeting, and particle board.

Volt: The meter-kilogram-second (MKS) unit of electromotive force, or potential difference. The potential difference between two points in an electric field such that one joule of work moves a charge of one coulomb between these points. The electrical force that, if steadily applied to a circuit with a resistance of one ohm, will produce a current of one ampere.

Voltage: The difference in electrical potential between any two conductors or between a conductor and ground. It is a measure of the electric energy per electron that electrons can acquire and/or give up as they move between the two conductors. Units of volts.

Vulcanize: Transformation of a soft or liquid rubber into a very tough, heat resistant rubber, usually by the application of heat and sometimes the addition of sulfur.

Waferboard: Panel board product made of hardwood (usually aspen) wafers or flakes, covered with adhesive resins, laid in random orientation, and hot pressed into panels.

Wall: Opaque portion of the building envelope.

Wall cavity: The space between the studs of a wall.

Wall washing: A lighting technique that illuminates a wall fairly evenly from top to bottom.

Wall sheathing: A structural component, such as plywood or OSB, installed as part of the wall assembly. Sometimes rigid insulation board is also called non-structural wall sheathing.

Waste heat: Heat escaping from combustion processes that can be captured and used for other processes.

Waste-to-energy incinerator: An incinerator that uses waste products as fuel, to provide energy for space or water heating or running a turbine. Various types or refuse are used, from simple paper products to plastic and scrap car tires. In many cases they are used as fuel supplements, since on their own they have an energy content that may be only 30 to 50 per cent that of solid fuels.

Waste-to-fuel process: Burning of industrial waste to provide steam, heat, and often electricity to operate a plant.

Wastewater: Water that is discharged from homes and businesses from sinks, toilets, washers, showers, etc. that contains dissolved or suspended matter.

Wastewater treatment plant: A facility with an engineered system designed to remove pollutants, such as phosphorous and nitrogen, from municipal and industrial wastewater for discharge into surface waters.

Water-based paint: Paint in which the vehicle or binder is dissolved in water or in which the vehicle or binder is dispersed as an emulsion. Latex paint is a water-based paint.

Water budget: An evaluation of the hydrologic balance in an area; or the calculated amount of water a household or business should use based on the type and number of fixtures, landscape requirements, and number of occupants.

Water conservation: Activities designed to reduce the demand for water, improve efficiency in use, and reduce losses and waste of water.

Water economizer: A system by which the supply air of a cooling system is cooled by evaporation of water or by other fluid, in order to reduce or eliminate the need for mechanical refrigeration.

Water heating: The process or system used to heat service water.

Water recycling: Reuse of water for the same application for which it was originally used.

Water repellant: A surface treatment that imparts resistance to water penetration.

Water reuse: Using wastewater or reclaimed water from one application for another application. The deliberate use of reclaimed water or wastewater must be in compliance with applicable rules for a beneficial purpose (landscape irrigation, agricultural irrigation, aesthetic uses, groundwater recharge, industrial uses, and fire protection).

Water temperature reset: Temperature shall be reset by at least 25% of the design supply-to-return water temperature difference.

Water use efficiency: Employing water-saving practices to reduce costs and to slow the depletion of the water supply to ensure future water availability.

Waterproofing: Make impervious to water, e.g., with a resin sealer or asphalt coating.

Watt (W): A unit of power, power being the rate at which energy is used to do work. The unit rate at which work is done in an electrical circuit. One watt equals one joule of work per second. Also equal to 3.4 BTUs per hour. Named after the Scottish inventor James Watt.

Wattle and daub: A very common form of primitive construction, consisting of a sort of coarse basketwork of twigs woven between upright poles, then plastered with mud; a substitute for brickwork in partitions.

Wavelength: The distance between two similar points of a given wave. Wavelengths of light are measured in nanometers (1 nm = 1 billionth of a meter).

Weather barrier: A flexible membrane installed on the exterior of a building to protect the building from wind, rain, and snow; it is permeable to allow the diffusion of vapor inside the wall.

Weatherstripping: Thin strips of metal, rubber, vinyl or foam around doors and windows that prevent infiltration of air or moisture.

Wet-bulb temperature: The temperature at which water, by evaporating into air, can bring the air to saturation at the same temperature.

Wetland: Land that is transitional between aquatic and terrestrial ecosystems and is covered with water for at least part of the year. These lands are important as buffer zones to help control flooding and also provide an ecosystem for many diverse species.

Wet spray: A method of applying insulation by adding water or an adhesive and spraying material into open cavities, such as walls.

Whole-house fan: A fan typically centrally located in the ceiling of a house that draws fresh outside air into the living space, flushes hot air up to the attic and exhausts it to the outside. Windows must be open and adequate venting area must be present in the attic. Inexpensive way to cool a house when outside air is cooler than inside air, and not excessively humid. Must be well sealed and insulated during cold weather.

Whole-systems thinking: A process through which the interconnections of systems are actively considered, and solutions are sought that address multiple problems at the same time.

Wind energy: Energy from moving air, which is converted to electricity, by using wind to turn electricity generators. Wind energy has a number of advantages over conventional forms of energy. It is pollution-free and renewable.

Wind farm: A cluster of wind turbines (up to several hundreds) for generating electrical energy, erected in areas where there is a nearly steady prevalent wind; such areas generally occur near mountain passes.

Wind load: A structural load representing pressure exerted on a structure by wind velocity.

Wind turbine: A machine that generates electricity from the wind by turning a generator-connected wind propeller.

Wind-Washing: The phenomenon of air movement due to increased pressure differences that occur at the outside corners and roof eaves of buildings. Wind-washing can have significant impact on thermal and moisture movement and hence thermal and moisture performance of exterior wall assemblies. This phenomenon reveals one advantage of an exterior air barrier.

Window: The terms fenestration, window, and glazing are often used interchangeably. However, window actually describes a system of several components: an entire assembly comprised of the sash, glazing, and frame.

Window projection factor: A measure of the portion of glazing that is shaded by an eave or overhang.

Window treatments: Curtains, blinds, shutters, etc.

Window-wall ratio: The gross window area divided by the gross wall area.

Wing wall: Outside walls attached perpendicularly to exterior walls properly placed near windows to direct air into the windows for ventilation purposes. A negative pressure zone is created by the wing wall, which stimulates air movement.

Wool: A natural fiber from the fur of sheep; characterized by absorbency, resiliency, fire resistance, and insulation. Wool is naturally resistant to fire, but prone to deterioration by moths and insects and so may contain chemical treatments.

Work: The application of a force through a distance. Energy is stored work. Power is the rate at which work is done, or the rate of flow of energy. The joule is exactly the amount of work done in exerting the basic metric unit of force. (1 Newton [N]) over the basic metric unit of distance (1 meter).

World Commission on Environment and Development: Established by the United Nations General Assembly in 1983 to examine international and global environmental problems and to propose strategies for sustainable development.

XeriscapeTM: It is derived from the Greek word "xeros", meaning "dry," and combined with "landscape," xeriscape means gardening with less than average water. The seven xeriscape principles for conserving water and protecting the environment are good planning and design; practical lawn areas; efficient irrigation; soil analysis improvement; use of mulches; use of well-adapted, low-water-demand plants; and good maintenance.

Zero-discharge technology: Technology that comprises of industrial processes designed to prevent the release of any pollutant harmful to the environment (e.g., recovery of solvents, cleaning rinses, and other chemicals used in manufacturing) by collecting them and removing dissolved and suspended materials so the liquids can be reused.

Zero Energy House: Any house that averages out to net zero energy consumption. A zero energy home can supply more than its needs during peak demand, typically using one or more solar energy strategies, energy storage and/or net metering. In a zero energy home, efficiencies in the building envelope and HVAC are great enough that plug loads can begin to dominate and so these homes must have the added focus of high efficiency appliances and lighting.

Zone: A space or group of spaces within a building with any combination of heating, cooling, or lighting requirements sufficiently similar so that desired conditions can be maintained throughout by a single controlling device.

Zoning: A legal mechanism for local governments to prevent conflicting land use and promote orderly development by regulating the use of privately owned land through enforcement.