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 restric