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Glossary of Energy Efficiency/Green Building Terms

At Bluegill Energy we believe in sharing our knowledge with others. With all the confusing technical terms and jargon associated with the energy efficiency and green building industry, our staff compiled a Glossary of Industry Terms (PDF) to help our clients better understand these terms.

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  – An abbreviation for air conditioner or air conditioning.
A/C Disconnect
  – The main electrical disconnection switch for the AC condenser, located near the near the unit on the exterior of the building.
  – The portion of a building that is above ground level.
Above-Grade Wall
  – A wall more than 50 percent above grade and enclosing conditioned space. This includes between-floor spandrels, peripheral edges of floors, roof and basement knee walls, dormer walls, gable end walls, walls enclosing a mansard roof and skylight shafts.
Absolute Humidity
  – Air moisture content expressed in grains (or pounds) of water vapor per pound of dry air.
  – The ratio of a solar energy absorbed to incident solar, also called absorptivity.
  – A solid material’s ability to draw in and hold liquid or gas.
Accent Lighting
  – Lighting that illuminates walls, reducing brightness contrast between walls and ceilings or windows.
Advanced Framing
  – A construction method (also known as "Optimum Value Engineering" or "OVE") that uses less material in the framing of a home and can reduce material costs and improve energy efficiency.
  – The round screened screw-on tip of a sink spout. It mixes water and air for a smooth flow.
  – Acronym for Annual Fuel Utilization Efficiency. It is a measure of the amount of heat actually delivered to your house compared to the amount of fuel that you must supply to the furnace.
  – Acronym for the Air Conditioning, Heating, and Refrigeration Institute (AHRI), formed in 2008 by a merger of the Air-Conditioning and Refrigeration Institute (ARI) and the Gas Appliance Manufacturers Association (GAMA). It is a North American trade association of manufacturers of air conditioning, heating, and commercial refrigeration equipment. The organization performs political advocacy on behalf of its member industries, maintains technical standards, certifies products, shares data, conducts research, and awards scholarships.
AHRI Matching
  – (a) The use by HVAC equipment manufacturers of the Air Conditioning, Heating, and Refrigeration Institute (AHRI) standards to certify that their equipment has been certified or “matched” to operate at an optimal efficiency when combined. (b) The use of the AHRI directory of certified equipment (air handler, evaporator and condensing coil) by design professionals to select “matched” equipment, which help to insure they perform optimally together.
Air Barrier
  – Material(s) assembled and joined together to provide a barrier to air leakage through the building envelope. An air barrier may be a single material or a combination of materials. It includes any part of the building shell that prevents infiltration of outdoor air into the conditioned space and exfiltration of indoor air to the outside. It may also be referred to as the “pressure boundary.” It should be continuous and aligned with the thermal boundary (the part of the home that physically separates the conditioned spaces from unconditioned spaces).
Air Changes at 50 Pascals (ACH50)
  – The number of times that the complete volume of a home is exchanged for outside air when a blower door depressurizes the home to 50 Pascals.
Air Conditioning
  – Cooling buildings with a refrigeration system. More generally means both heating and cooling. May be identified using the acronym HVAC.
Air Duct
  – A hollow conduit or tube (square or round) that circulates air from a forced-air heating and/or cooling system to a room (supply duct) or returns air back to the main system from a room (return duct). Ducts may be made of sheet metal, fiberglass board, or flexible plastic that carry conditioned air to all rooms.
Air Exchange
  – The total building air exchanged to the outdoors through air leakage and ventilation.
Air Exchange Rate
  – The measured value for total building air exchanged to the outdoors through air leakage and ventilation and usually referred to as Air Changes per Hour (ACH).
Air Filters
  – Adhesive filters made of metal or various fibers that are coated with adhesive liquid to which the particles of lint and dust adhere. These filters will remove as much as 90% of the dirt if they do not become clogged. The more common filters are of the throwaway or disposable type.
Air Handler
  – A steel cabinet containing a blower with cooling and/or heating coils connected to ducts.
Air Infiltration
  – This refers to the air leaking into a building through cracks in walls, windows and doors.
Air Leak
  – A hole, crack, or gap where air can leak in or out of a house. Air leaks can make a home feel drafty or uncomfortable and waste energy.
Air Sealing
  – This is the process of sealing bypass ducts in the pressure boundary to prevent air leakage. Air sealing reduces heat flow from air movement and prevents water vapor from entering the wall.
Air Space (Gap)
  – The area between insulation facing and interior of exterior wall coverings, normally a 1" air gap.
Air Transport Factor
  – The ratio of the rate of useful sensible heat removal from the conditioned space to the energy input to the supply and return fan motor(s), expressed in consistent units and under the designated operating conditions.
Ambient Lighting
  – Lighting spread throughout the lighted space for safety, security, and aesthetics.
  – Device to measure the current flowing in a circuit.
Ampere (AMPS)
  – Is the unit of measurement of electrical current flow, equals a coulomb per second. It is the rate at which electricity flows through a conductor.
Annual Fuel Utilization Efficiency (AFUE)
  – A laboratory-derived efficiency rating for heating appliances which accounts for chimney losses, jacket losses, and cycling losses. The ratio of annual output energy to annual input energy which includes any non-heating season pilot input loss, and for gas or oil-fired furnaces or boilers, does not include electrical energy.
Annual Return
  – The yearly savings divided by the initial cost needed to achieve the savings, expressed as a percent.
Approach Temperature
  – Is the difference in temperature between the fluid inside a heat exchanger and the fluid outside it.
  – A heating control that switches the burner or the circulator in a hydronic heating system.
  – A heat resistant material made of brittle mineral fibers that damage lungs and other bodily tissues. Previously in many building products; represents serious health hazard as an airborne particulate.
  – A dark brown to black, highly viscous, hydrocarbon produced from the residue left after the distillation of petroleum. Asphalt is used on roofs and highways as a waterproofing agent.
Atmospheric Venting System
  – A standard chimney system, used to remove combustion by-products from the home, relying on the atmospheric lift caused by the flue gas temperature, creating a negative pressure.
Attic Access
  – This is an opening that is placed in the ceiling or wall covering of a home providing access to the attic.
Attic Bypass
  – An air flow connection between the living space and attic.
Attic Ventilation
  – Intended to remove heat and moisture from attic areas to the outside
Attic Ventilators (Vents)
  – In houses, screened openings provided to ventilate an attic space.
  – The process of identifying energy conservation opportunities in buildings.
Back Draft(ing)
  – Is the continuous spillage of combustion by-products into the home (after running the appliance for one minute). Instead of venting out through the chimney or flue, the combustion by-products spill into the home.
Back Draft Damper
  – A damper, installed near a fan that allows air to flow in only one direction.
Backer Rod
  – Polyethylene foam rope used as a backer for caulking. Or in glazing, a polyethylene or polyurethane foam material installed under compression and used to control sealant joint depth, provide a surface for sealant tooling, serve as a bond breaker to prevent three-sided adhesion, and provide an hour-glass contour of the finished bead.
  – The flow of liquids through irrigation into the pipes of a potable or drinking water supply from any source which is opposite to the intended direction of flow.
Backflow Preventer
  – A device or means to prevent backflow into the potable water supply.
  – A plate or strip designed to retard or redirect the flow of flue gases or air when used for attic ventilation.
  – This is an instrument, a capture hood, that measures airflow.
Balance Point
  – This is the minimum outdoor temperature at which no heating is needed.
  – A coil of wire or electronic device that provides a high starting voltage for a lamp and limits the current from flowing through it. It used to “step up” the voltage in a florescent light.
  – Instrument for measuring atmospheric pressure.
  – The amount of energy (electric, natural gas, propane or oil if these are used for heating) used to operate lighting and appliances year round. The minimum energy you use.
Basement Wall
  – Is an opaque portion of a wall which encloses one or more sides of a basement and having an average below grade area greater than or equal to 50 percent of its total wall area, including openings (see “Gross area of exterior walls”).
  – A rectangular section of fiber-glass or rock-wool insulation measuring 14.5 or 22.5 inches wide, 4 to 8 feet in length and various thicknesses.  Sometimes "faced" (a paper covering on one side) or "un-faced" (without paper).
Batt Insulation
  – Strips of insulation, usually fiberglass that fit between studs or other framing.
  – An applied sealant in a joint irrespective of the method of application, such as caulking bead, glazing bead, etc. Also a molding or stop used to hold glass or panels in position.
Bed or Bedding
  – In glazing, the bead compound or sealant applied between a lite of glass or panel and the stationary stop or sight bar of the sash or frame. It is usually the first bead of compound or sealant to be applied when setting glass or panels.
  – The portion of a building that is below ground level.
Bimetal Element
  – A metal spring, lever, or disc made of two dissimilar metals that expand and contract at different rates as the temperature around them changes. This movement operates a switch in the control circuit of a heating or cooling device.
Blanket Insulation
  – Fiber-glass or rock-wool insulation that comes in long rolls 15 or 23 inches wide.
  – Draining water from a boiler to remove sediment and suspended particulates.
Blow(n) Insulation
  – Fiber insulation in loose form and used to insulate attics and existing walls where framing members are not exposed.
  – The squirrel-cage fan in a furnace or air handler.
Blower Door
  – A diagnostic device that consists of a fan, a removable panel, and gauges used to measure and locate air leaks.
Boot (Ducting)
  – A duct section that connects between a duct and a register.
Branch Circuit
  – An electrical circuit used to power outlets and lights within a home.
Breaker Panel
  – The electrical box that distributes electric power entering the home to each branch circuit (each plug and switch) and composed of circuit breakers.
  – The intensity of sensation resulting from viewing a lit surface measured in foot lamberts and referred to as luminance or luminous intensity.
British Thermal Unit (Btu)
  – The quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit.
British Thermal Unit / Hourly (Btu/h)
  – British thermal units per hour.
  – A former industrial site, particularly one compromised by hazardous contaminants; examples are former dry cleaning establishments and gas stations.
Building Cavities
  – The space(s) inside walls, floors, and ceilings between framing members and the interior and exterior sheeting.
Building Envelope
  – The elements of a building which enclose conditioned spaces through which thermal energy is capable of being transferred to or from the exterior or to or from spaces exempted by the provisions of Section 101.2.1.
Building Paper
  – A general term for papers, felts, and similar sheet materials used in buildings without reference to their properties or uses. Generally comes in long rolls.
Building Science
  – It is the collection of scientific knowledge and experience that focuses on the analysis and control of the physical phenomena affecting a building’s design. It traditionally includes the detailed analysis of building materials, building envelope, heating, ventilation and air conditioning systems, natural and electrical lighting, acoustic, indoor air quality, passive strategies, fire protection, and renewable energies in buildings.
Building Thermal Envelope
  – The basement walls, exterior walls, floor, roof, and any other building element that enclose conditioned space. This boundary also includes the boundary between conditioned space and any exempt or unconditioned space.
  – A device that facilitates the burning of a fossil fuel like gas or oil.
  – For window glazing, is an application of sealant or compound to the flat surface of some member before placing the member in position, such as the buttering of a removable stop before fastening the stop in place.
  – Type of non-curing and non-skinning sealant made from butylene. Usually used for internal applications.
  – An abbreviation for Combustion Appliance Zone.
CCA (Chromated Copper Arsenate)
  – A pesticide that is forced into wood under high pressure to protect it from termites, other wood boring insects, and decay caused by fungus.
  – 100 Cubic Foot is used as a measurement of natural gas usage and roughly equivalent to 1 Therm or 1020 BTUs.
C-Factor (Thermal Conductance)
  – The coefficient of heat transmission (surface to surface) through a building component or assembly, equal to the time rate of heat flow per unit area and the unit temperature difference between the warm side and cold side surfaces (Btu/h ft2°F) [W/(m2 K)].
  – Acronym used for Cubic Feet per Minute. This is a measurement of the flow of a gas or liquid that indicates how much volume in cubic feet pass by a stationary point in one minute. The higher the CFM value, the better the flow.
  – An abbreviation for Carbon Monoxide, the odorless, tasteless, poisonous combustion by-product lighter than air.
  – An abbreviation for Carbon Dioxide, a combustion by-product heavier than air.
  – A projecting beam or other structure supported only at one end or an overhang, where one floor extends beyond and over a foundation wall. For example; a fireplace or bay window is a cantilever. They typically do not extend over 2 feet.
Capillary Action
  – The ability of water to move through materials, even upward against gravity, through small tubes or spaces. Moisture transfer through which water is sucked into tiny spaces in and between building materials, caused by the attraction of water molecules to each other and to other substances.
Capillary Barrier
  – A material or air space designed to stop capillary action from carrying water into a building.
Carbon Dioxide (CO2)
  – One of two main products of complete combustion of a hydrocarbon (the other is water vapor).
Carbon Footprint
  – A calculation of the amount of greenhouse gases produced as a result of commercial, industrial, and individual activities.
Carbon Offset
  – A system intended to equalize carbon production around the globe by trading greenhouse gas emissions–typically produced through fossil fuel consumption–for environmentally friendly actions, such as planting trees and using clean energy sources.
Carbon Monoxide (CO)
  – An odorless and poisonous gas produced by incomplete combustion.
  – A compound used for sealing that has minimum joint movement capability; sometimes called low performance sealant.
  – A flexible material used to seal a gap between two surfaces e.g. between pieces of siding or the corners in tub walls or the act of filling a joint with mastic or asphalt plastic cement to prevent leaks.
Cellulose Insulation
  – Post Consumer Recycled Content - Plant fiber that is used in wall and roof cavities to separate the inside and outside of the building thermally and acoustically. Typical materials used to manufacture the product include old newspapers, and telephone directories and borates and ammonium sulfate are included to retard fire and pests. Four major types of loose-fill cellulose products have been developed under a variety of brand names and are generally characterized as dry cellulose, spray applied cellulose, stabilized cellulose and low dust cellulose.
  – Black fibrous board that is used as exterior sheathing.
  – A temperature scale on which water freezes at 0°C and boils at 100°C.
  – See Celsius
CFM (Cubic Feet per Minute)
  – Is the measure of a volume of air. When testing systems, you can determine the CFM by multiplying the face velocity times the free area in square feet. The face velocity is the speed of air passing through the face of an outlet or return. Free area is the total area of the openings in the outlet or inlet through which air can pass.
  – The number of cubic feet per minute of air flowing through the fan housing of a blower door when the house pressure is at 50 pascals (0.2 inches of water). This figure is the most common and accurate way of comparing the airtightness of buildings that are tested using a blower door.
  – The number of cubic feet of air flowing through a house from indoors to outdoors during typical, natural conditions. This figure can be roughly estimated using a blower door.
  – This is the process of installing (chinking) fiberglass insulation around the exterior door/ window frames, wall corners, and the small gaps of the exterior wall, in an effort to reduce air infiltration. This not considered an approved method for air sealing per the International Energy Conservation Code (IECC) or International Residential Code (IRC).
  – The path of electrical flow from a power source through an outlet and back to ground.
Circuit Breaker
  – Is a device that disconnects an electrical circuit from electricity when it senses excessive current.
Coefficient of Performance (COP)
  – A heat pump or air conditioner’s output in watt-hours of heat moved divided by watt-hours of electrical input.
Coefficient of Performance (COP) - COOLING
  – The ratio of the rate of heat removal to the rate of energy input in consistent units, for a complete cooling system or factory-assembled equipment, as tested under a nationally recognized standard or designated operating conditions.
Coefficient of Performance (COP) - HEATING
  – The ratio of the rate of heat delivered to the rate of energy input, in consistent units, for a complete heat pump system under designated operating conditions. Supplemental heat shall not be considered when checking compliance with the heat pump equipment
  – A snakelike piece of copper tubing surrounded by rows of aluminum fins that clamp tightly to the tubing in order to aid in heat transfer.
Cold Air Return
  – The ductwork (and related grills) that carries room air back to the furnace for re-heating.
Color Rendering Index (CRI)
  – A measurement of a light source’s ability to render colors the same as sunlight. CRI has a scale of 0 to 100.
Color Temperature
  – Is a measurement of the warmness or coolness of a light source in the Kelvin temperature scale.
  – The rating for building materials that will burn, although not readily.
Combustion Air
  – Air that provides oxygen for combustion.
Combustion Analyzer
  – A diagnostic device used to measure steady-state efficiency of combustion heating units.
Combustion Chamber
  – The area inside the heat exchanger where the flame burns.
Combustion Efficiency
  – Is synonymous with fuel burning efficiency or steady-state efficiency. Usually means the latter.
Comfort Envelope
  – The areas defined on a psychrometric chart and enclosing the range of operative temperature and humidity for both the winter and summer comfort zones as depicted in Figure 2 of ASHRAE 55.
  – (a) The process of testing and adjusting building mechanical systems after building construction or as a retrofit measure. (b) A quality assurance process intended to confirm that all systems of a building—heat, air conditioning, electrical, plumbing, safety, security—are operating as intended by the building owner and designed by the architect and engineer.
Compact Fluorescent Lamps (CFLs)
  – A re-designed fluorescent light for use in most conventional light fixtures. CFLs use about 75% less energy when compared to standard (incandescent) bulbs.
  – A mechanical device that pressurizes a gas in order to turn it into a liquid, thereby allowing heat to be removed or added. A compressor is the main component of conventional heat pumps and air conditioners. In an air conditioning system, the compressor normally sits outside and has a large fan (to remove heat).
  – Liquid formed by condensing vapor.
Condensate Receiver
  – Tank for catching returning condensate water from a steam heating system.
  – (a) The process by which moisture vapor changes to liquid form or appearance of moisture (water vapor) on the surface of an object caused by warm moist air coming into contact with a colder object. (b) Beads or drops of water (and frequently frost in extremely cold weather) that accumulate on the inside of the exterior covering of a building. Use of louvers or attic ventilators will reduce moisture condensation in attics.
  – When a gas turns into a liquid as it cools, we say it condenses. Condensation is the opposite of evaporation.
Condenser (HVAC)
  – The fan/compressor unit of the air conditioning system located on the outside of the home. It removes the heat and "condenses" the refrigerant gas coming from the evaporator coil, then turns the gas back into a liquid, pumping the liquid back to the evaporator coil in the air handler/furnace where it begins the process again. It consists of one or more power-driven compressors, condensers, liquid receivers (when required), and the regularly furnished accessories.
  – Intentionally heated or cooled areas of a building are conditioned.
Conditioned Floor Area
  – The horizontal projection of that portion of interior space which is contained within exterior walls and which is conditioned directly or indirectly by an energy-using system.
Conditioned Space
  – An area or room within a building being heated or cooled, containing uninsulated ducts, or with a fixed opening directly into an adjacent conditioned space. A heated or cooled space, or both, within a building and, where required, provided with humidification or dehumidification means so as to be capable of maintaining a space condition falling within the comfort envelope set forth in ANSI-Z765.
  – The property of a material to conduct some energy form like heat or electricity.
  – The direct transfer of heat energy through a material, molecule to molecule, through solid materials. A piece of iron with one end placed in a fire will soon become warm from end to end, from the transfer of heat by the actual collision of the air molecules.
  – The rate at which heat is transmitted through a material.
  – (a) Material that allows heat to flow unhindered. (b) In electrical contracting, a wire through which a current of electricity flows, better known as an electric wire. (c) In roofing, a pipe for conveying rain water from the roof gutter to a drain, or from a roof drain to the storm drain; also called a leader, downspout, or downpipe.
Consumption Analysis
  – The analysis of the energy consumption of a building or building system, used to determine efficiency improvements. This could be an in-depth review of month to month usage, or a comparative analysis before and after work is completed.
  – (a) Method of transferring heat by the actual movement of heated molecules, usually by a freestanding unit such as a furnace. Currents created by heating fluids (air/water/glycol), which then rises and pulls cooler air behind it.
Convective Loop
  – When air (or another medium) continuously circulates around in an enclosed space as it is heated and cooled.
Cooling Load
  – (a) The maximum rate of heat removal required of an air conditioner when the outdoor temperature and humidity are at the highest expected level. (b) The amount of cooling required in keeping a building at a specified temperature during the summer, usually 78° F, regardless of outside temperature. (c) The amount of energy consumed to provide seasonal cooling.
Cooling Tower
  – A large device mounted on roofs, consisting of many baffles over which water is pumped in order to reduce its temperature.
Cost Effective
  – Having an acceptable payback, return-on-investment, or savings-to-investment ratio. An indicator of how worthwhile an investment is.
Cubic Foot per Minute (cfm)
  – Is a measurement of air movement past a certain point or through a certain structure.
  – Acronym for Domestic Hot Water system
  – (a) Valve for controlling airflow. When ordering registers, make sure each supply outlet has a damper so the air flow can be adjusted and turned off. Dampers maybe either manually or automatically operated. Automatic dampers are required for exhaust air ducts. (b) A metal "door" placed within the fireplace chimney, normally closed when the fireplace is not in use.
Damp Proofing
  – (a) A process used on concrete, masonry or stone surfaces to repel water, the main purpose of which is to prevent the coated surface from absorbing rain water while still permitting moisture vapor to escape from the structure. (Moisture vapor readily penetrates coatings of this type.) "Damp-proofing" generally applies to surfaces above grade; "waterproofing" generally applies to surfaces below grade. (b) The black, tar like waterproofing material applied to the exterior of a foundation wall.
  – The use of natural lighting to reduce the need for electrical lighting sources.
Dead Band
  – The temperature range in which no heating or cooling is used.
Dedicated Circuit
  – Is an electrical circuit that serves only one appliance (i.e., dishwasher, refrigerator, etc.) or a series of electric heaters or smoke detectors.
Degree Day (Cooling)
  – 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 65°F (18°C), there are as many degree days as there are degrees Fahrenheit (Celsius) difference in temperature between the mean temperature for the day and 65°F (18°C). Annual cooling degree days (CDD) are the sum of the degree days over a calendar year.
Degree Day (Heating)
  – A unit, based on temperature difference and time, used in estimating heating energy consumption and specifying nominal heating load of a building in winter. For any one day, when the mean temperature is less than 65°F (18°C), there are as many degree days as there are degrees Fahrenheit (Celsius) difference in temperature between the mean temperature for the day and 65°F (18°C). Annual heating degree days (HDD) are the sum of the degree days over a calendar year.
  – Separation of the plies in a panel due to failure of the adhesive, usually caused by excessive moisture.
  – The peak need for electrical energy. Some utilities levy a monthly charge for demand.
  – The weight of a material divided by its volume, usually measured in pounds per cubic foot.
Demand Control Ventilation (DCV)
  – A ventilation system capability that provides for the automatic reduction of outdoor air intake below design rates when the actual occupancy of spaces served by the system is less than design occupancy.
  – Cause to have a lower pressure or vacuum with respect to a reference of a higher pressure.
  – A liquid or solid material used to absorb water or water vapor.
Design Pressure
  – Specified pressure a product is designed to withstand.
Design Temperature
  – A high or low outdoor temperature used for designing heating and cooling systems.
  – A heat exchanger that removes the superheat from a compressed refrigerant and transfers that heat to another fluid, usually water.
Dew Point
  – (a) The warmest temperature of an object in an environment where water condensation from the surrounding air would form on that object. (b)The critical temperature at which vapor condenses from the atmosphere and forms water.
  – A moisture transport mechanism; the way in which water vapor moves through materials such as sheetrock and plywood, working its way from high concentrations of moisture to low concentrations.
Dilution Air
  – Air that enters through the dilution device—an opening where the chimney joins to an atmospheric-draft appliance.
Dilution Device
  – A draft diverter or barometric draft control on a combustion appliance.
  – A large (generally 20 Amp) electrical ON-OFF switch.
Distribution System
  – (a) A system of pipes or ducts used to distribute energy. (b)The system through which heat/cooling is distributed throughout the house.
Double Glass
  – Window or door in which two panes of glass are used with a sealed air space between.  My also be referred to as insulating glass.
  – In general, any use of two panes of glass, separated by an air space, within an opening, to improve insulation against heat transfer and/or sound transmission. In insulating glass units the air between the glass sheets is thoroughly dried and the space is sealed, eliminating possible condensation and providing superior insulating properties.
  – The movement of combustion by-products through the flue and chimney and out of a building.
Draft Diverter
  – A device located in gas appliance chimneys that moderates draft and diverts down drafts that could extinguish the pilot or interfere with combustion.
Draft Inducer
  – A fan that depressurizes the venting system and exhausts combustion products.
Draft Test
  – A way to determine whether venting systems are effectively moving combustion gases out of the house, even under the worst-case conditions.
Drought Tolerant Plants
  – Species of plants, shrubs and vines which generally do not require additional watering in order to thrive in their native habitats. Landscapes with drought tolerant plants usually require little or no watering.
Dry-Bulb Temperature
  – Is the ambient air temperature measured by a thermometer.
Dual Flush Toilets
  – Toilets with two buttons for two flush options, one for liquid and another for solid waste. The button for liquid waste uses less water per flush.
  – A cylindrical or rectangular tube or conduit utilized for conveying air. The air passages of self-contained systems are not to be construed as air ducts. (See also Duct System)
Duct Blaster™
  – Duct leakage testing equipment, made by The Energy Conservatory.
Duct Blower
  – A device used for testing duct leakiness and air flow.
Duct System
  – A continuous passageway for the transmission of air that, in addition to ducts, includes duct fittings, dampers, plenums, fans and accessory air-handling equipment and appliances. It may also be referred to as duct work.
  – Acronym for “Energy Efficiency Ratio”. This is a measure of how efficiently a cooling system operates. The higher the EER value, the more efficient the air conditioner is.
  – Acronym for Environmental Protection Agency.
  – A ducting arrangement and automatic control system that allows a cooling supply fan system to supply outdoor air to reduce or eliminate the need for mechanical refrigeration during mild or cold weather.
Economizer (Water)
  – A system where the supply air of a cooling system is cooled indirectly with water that is itself cooled by heat or mass transfer to the environment without the use of mechanical cooling.
  – Acronym for Energy Efficiency Ratio; is figured by dividing BTU hours by watts.
  – The ratio of output divided by input.
  – (a) The number of lumens produced by a watt used for lighting a lamp. (b) The measure of lighting efficiency.
  – The process by which water leeches soluble salts out of concrete or mortar and deposits them on the surface. Also used as the name for these deposits.
  – An elastic rubber-like substance, such as natural or synthetic rubber.
  – Of or pertaining to any of the numerous flexible membranes that contain rubber or plastic.
Electric Resistance Coil
  – Metal wires that heat up when electric current passes through them and are used in electric heaters, furnaces and water heaters.
  – Describes controls where switching is performed by an automatic mechanical device like a bimetal or bulb-and-bellows.
  – Describes controls where switching is performed by transistors and other solid-state devices.
  – The measure of a surface’s ability to emit long-wave infrared radiation.
  – The ability of a material to emit radiant energy from its surface and is also referred to as emissivity.
  – (a) A quantity of heat or work. (b) The capacity for doing work (taking a number of forms) which is capable of being transformed from one into another, such as thermal (heat), mechanical (work), electrical and chemical in customary units, measured in joules (J), kilowatt- hours (kWh) or British thermal units (Btu).
Energy Analysis
  – A method for estimating the annual energy use of the proposed design and standard reference design based on estimates of energy use.
Energy Consumption
  – The conversion or transformation of potential energy into kinetic energy for heat, light, electricity, etc.
Energy Cost
  – The total estimated annual cost for purchased energy for the building functions regulated by this code, including applicable demand charges.
Energy Efficient Appliances
  – Products that use less energy than conventional models. The ENERGY STAR® label is a credible third-party certification of a product's energy efficiency. Consumers can also refer to the FTC's Energy Guide label, a yellow label affixed to most appliances today. Clothes washers, dishwashers, refrigerators, freezers, water heaters, window air conditioners, central air conditioners, furnaces, boilers, heat pumps, and pool heaters can get the label. Televisions, ranges, ovens, clothes dryers, humidifiers, and dehumidifiers do not receive such labels.
Energy Efficient Light Fixtures
  – The fixture or the type of bulbs used in a fixture. Compact fluorescent lights (CFLs) and light emitting diodes (LEDs) are becoming more common in homes and buildings and they are more efficient and last longer than incandescent bulbs.
Energy Efficient Mortgage (EEM)
  – Loan products that take a home's energy efficiency into account when determining the qualifying ratios for a buyer. The rationale is that an efficient home will result in lower monthly bills and potentially make buyers of such homes less risky borrowers than others. EEMs primarily apply to new construction. In some markets, an energy improvement mortgage (EIM) can be used to make energy improvements.
Energy Efficiency
  – Term used to describe how efficiently a building component uses energy.
Energy Efficiency Ratio (EER)
  – (a) A measurement of energy efficiency for air conditioners. The EER is computed by dividing cooling capacity, measured in British Thermal Units per hour (BTUh), by the watts of power. (b) The ratio of net equipment cooling capacity in British thermal units per hour (Btu/h) (W) to total rate of electric input in watts under designated operating conditions. When consistent units are used, this ratio becomes equal to COP (see also “Coefficient of performance”).
Energy Guide Label
  – An appliance label that provides an estimate of how much energy the appliance uses, compares energy use of similar products, and lists approximate annual operating costs. It is required by the U.S. Department of Energy to be placed on all major appliances mechanical equipment sold.
Energy Factor
  – The fraction of water heater input remaining in an assumed 64 gallons of hot water used by residents.
Energy Improvement Mortgage (EIM)
  – A mortgage intended for existing homes for the purpose of installing energy efficiency improvements.
Energy Rated
  – See "Energy Audit" above. An energy rating provides a score for home during energy audits. Energy ratings usually have to be used to determine the ratios for an energy efficient mortgage.
Energy Recovery Ventilator (ERV)
  – (a) A device used in a ventilation system that recovers latent and sensible energy from the exhaust airstream and imparts it to the incoming airstream. (b) A type of ventilation system wherein the heated (or cooled) air being vented out of the home is used to heat (or cool) the supply air being pulled in from outdoors. The approach decreases the amount of energy needed to heat or cool the supply air.
Energy Recovery Ventilation System
  – Systems that employ air-to-air heat exchangers to recover energy from exhaust air for the purpose of preheating, pre-cooling, humidifying or dehumidifying outdoor ventilation air prior to supplying the air to a space, either directly or as part of an HVAC system.
Energy Simulation Tool
  – An approved software program or calculation-based methodology that projects the annual energy use of a building.
Enhanced Air Filtration
  – An enhanced media filter, such as high level HEPA or high MERV (>11) filters on HVAC equipment.
  – The internal heat of a material measured in BTU’s per pound.
  – The building shell, made up of the exterior walls, floor, and roof assembly of a building.
Environmentally Sensitive
  – A person who is highly sensitive to pollutants, often because of overexposure, is said to be environmentally sensitive.
  – The change that occurs when a liquid becomes a gas. Evaporation is the key process in the operation of air conditioners and evaporative coolers.
Evaporative Cooler
  – A device for cooling homes in dry climates, which cools the incoming air by humidifying it. This device may also be referred to as a swamp cooler.
  – (a) The heat transfer coil of an air conditioner or heat pump that cools the surrounding air as the refrigerant inside the coil evaporates and absorbs heat. (b) That part of the system in which liquid refrigerant is vaporized to produce refrigeration.
  – The natural atmospheric process of water entering the atmosphere after plants and soil have soaked up the moisture.
  – Air leakage or air flowing out of a structures conditioned space through the building shell caused by pressurization with reference to outside.
  – A temperature scale used in the United States and a few other countries. On the Fahrenheit scale water boils at 212°F and freezes at 32°F.
Fan Brake Horsepower (BHP)
  – The horsepower delivered to the fan’s shaft. Brake horsepower does not include the mechanical drive losses (belts, gears, etc.).
Fan Control
  – Is a bimetal thermostat that turns the furnace blower on and off as it senses the presence of heat.
Fan System BHP
  – The sum of the fan brake horsepower of all fans that are required to operate at fan system design conditions to supply air from the heating or cooling source to the conditioned space(s) and return it to the source or exhaust it to the outdoors.
Fan System Design Conditions
  – Operating conditions that can be expected to occur during normal system operation that result in the highest supply fan airflow rate to conditioned spaces served by the system.
Fan System Motor Nameplate HP
  – The sum of the motor nameplate horsepower of all fans that are required to operate at design conditions to supply air from the heating or cooling source to the conditioned space(s) and return it to the source or exhaust it to the outdoors.
  – Skylights, roof windows, vertical windows (fixed or moveable), opaque doors, glazed doors, glazed block and combination opaque/glazed doors. Fenestration includes products with glass and non-glass glazing materials.
F - Factor
  – The perimeter heat loss factor for slab-on-grade floors (Btu/hft °F) [W/(m K)].
  – A fibrous material made by spinning molten glass, commonly used for insulation material.
Field Measure
  – To take measurements (cabinets, countertops, stairs, shower doors, etc.) in the home itself instead of using the blueprints.
Fill Tube
  – A plastic or metal tube used for its stiffness to blow insulation inside a building cavity.
Flame Impingement
  – Flame interference or obstruction.
Flame Rectification
  – A modern method of flame sensing, which uses the flame itself as a conductor in the flame-safety circuit.
Flame Retention Burner
  – An oil burner, designed to hold the flame near the nozzle surface. This is generally the most efficient type for residential use.
Flame Safety Control
  – A control for avoiding fuel delivery in the event of no ignition.
Fleet Averaging
  – By using a point system, builders can show compliance with energy building requirements by using average figures for all air conditioning units in the same sub division.
  – A channel within an appliance or chimney for combustion gases.
Fluorescent Lighting
  – A fluorescent lamp is a gas-filled glass tube with a phosphor coating on the inside.  Gas inside the tube is ionized by electricity which causes the phosphor coating to glow. Normally with two pins that extend from each end.
  – Large pipe through which fumes escape from a gas water heater, furnace, or fireplace. Normally these flue pipes are double walled, galvanized sheet metal pipe and sometimes referred to as a "B Vent". Fireplace flue pipes are normally triple walled. In addition, nothing combustible shall be within one inch from the flue pipe.
Flue Collar
  – Round metal ring which fits around the heat flue pipe after the pipe passes out of the roof.
Flue Damper
  – An automatic door located in the flue that closes it off when the burner turns off; purpose is to reduce heat loss up the flue from the still-warm furnace or boiler.
Flue Lining
  – 2-foot lengths, fire clay or terra-cotta pipe (round or square) and usually made in all ordinary flue sizes. Used for the inner lining of chimneys with the brick or masonry work done around the outside. Flue linings in chimneys run from one foot below the flue connection to the top of the chimney.
Foam Board
  – Plastic foam insulation manufactured most commonly in 4'x8' sheets in thicknesses of 1/4” to 3".
Foot Candle
  – The unit of measure, used to describe light striking a surface.
Foot Print
  – A description of the exact size, shape, and location of a building's foundation as the foundation has been installed on a specific site, also known as building footprint.
Forced Air Distribution System
  – A pressurized, air system that uses a blower and ductwork to distribute conditioned air from a source (furnace or air handler) to each room.
Forced Air Heating
  – This is a common form of heating with natural gas, propane, oil or electricity as a fuel. Air is heated in the furnace and distributed through a set of metal ducts to various areas of the house.
Fuel Cell
  – This clean fuel source converts chemical energy from hydrogen to electrical energy. Yields zero emissions.
Fully Tempered Glass
  – Flat or bent glass that has been heat-treated to a high surface and/or edge compression to meet the requirements of ASTM C 1048, kind FT. Fully tempered glass, if broken, will fracture into many small pieces (dice) which are more or less cubical. Fully tempered glass is approximately four times stronger than annealed glass of the same thickness when exposed to uniform static pressure loads.
  – A heating system that uses the principle of thermal convection. When air is heated, it rises and as the air cools it settles. Ducts are installed to carry the hot air from the top of the furnace to the rooms. Other ducts, called cold air returns, return the cooler air back to the furnace.
  – (a) Elastic strip that seals a joint between two materials. (b) Pre-formed shapes, such as strips, grommets, etc., of rubber or rubber-like composition, used to fill and seal a joint or opening either alone or in conjunction with a supplemental application of a sealant.
  – Energy extracted from the natural heat of the earth's rocks and fluids.
Geothermal Heat System (Closed Loop)
  – Geothermal heat pumps (GHPs) use the constant temperature of the earth to provide cooling and heating for a home. A loop of piping is buried in the ground and fluid circulates through the loop. In the summer, the fluid uses the cooler temperature of the ground to provide indoor cooling. During colder months, the geothermal heat pump uses the below-ground temperature, which is significantly warmer than the outside air, to warm a home.
Glazing Area
  – Total area of the glazed fenestration measured using the rough opening and including sash, curbing or other framing elements that enclose conditioned space. Glazing area includes the area of glazed fenestration assemblies in walls bounding conditioned basements. For doors where the daylight opening area is less than 50 percent of the door area, the glazing area is the daylight opening area. For all other doors, the glazing area is the rough opening area for the door including the door and the frame.
  – A hard, brittle substance, usually transparent, made by fusing silicates under high temperatures with soda, lime, etc.
Glass Load Factor
  – A number combining glass’ solar heat transmission and its heat conduction. Used for cooling load calculations.
  – (a) A generic term used to describe an infill material such as glass, panels, etc. (b) the process of installing an infill material into a prepared opening in windows, door panels, partitions, etc.
Glazing Bead
  – The strip used at the surrounding the edge of the glass, in a window or door which holds the glass in place.
Glazing Channel
  – In glazing, a three-sided, U-shaped sash detail into which a glass product is installed and retained.
Green/Living Roof
  – A roof surface covered by a water-proofing membrane, a drainage plane, a water retention medium, and plantings of drought-resistant species. The benefits of a green roof include control of storm water runoff which can reduce urban water pollution; absorption of airborne toxins and an increase in oxygen in the air, and a reduction of surface temperature of the roof (heat island effect). They also can increase the lifespan of the roof system and provide building and noise insulation. Green roofs are most common in multifamily or other large urban buildings.
Green Seal
  – A certification for construction products, such as windows, paints, and adhesives, attesting that the products were manufactured and can be used with minimal impact on the environment.
  – Falsely promoting or exaggerating the greenness of a product or service.
Grey Water
  – Water from laundry, bathing, and similar uses that can be reused for non potable activities.
Grey Water System
  – Wastewater from bathtubs, shower drains, sinks, washing machines, and dishwashers. Grey water can can be recycled for irrigation, toilets, and exterior washing, and such recycling conserves water. Incorporating plumbing systems that separate grey water from black water (toilet water) can result in water cost savings.
  – A site, such as a mall or commercial facility, which has been abandoned, leaving behind a large developed but empty area.
  – (a) The completed assembly of main and cross tees in a suspended ceiling system before the ceiling panels are installed. (b) The decorative slats (mutton) installed between glass panels. (c) Used when referring to the electric utility distribution system.
Gross Area of Exterior Walls
  – The normal projection of all exterior walls, including the area of all windows and doors installed therein (see “Exterior wall”).
Gross Floor Area
  – (a) The sum of the areas of several floors of the building, including basements, cellars, mezzanine and intermediate floored tiers and penthouses of headroom height, measured from the exterior faces of exterior walls or from the centerline of walls separating buildings, but excluding: (b) Covered walkways, open roofed-over areas, porches and similar spaces. (c) Pipe trenches, exterior terraces or steps, chimneys, roof overhangs and similar features.
  – Refers to electricity's habit of seeking the shortest route to earth. Neutral wires carry it there in all circuits. An additional grounding wire or the sheathing of the metal-clad cable or conduit protects against shock if the neutral leg is interrupted.
Ground Fault
  – Ground Fault Circuit Interrupter (GFCI, GFI) - an ultrasensitive plug designed to shut off all electric current. Used in bathrooms, kitchens, exterior waterproof outlets, garage outlets, and "wet areas". Has a small reset button on the plug.
Grounding Rod
  – Rod used to ground an electrical panel.
Ground System
  – Is the connection of current-carrying neutral wire to the grounding terminal in the main switch which in turn is connected to a water pipe. The neutral wire is called the ground wire.
Ground Water
  – Water from an aquifer or subsurface water source.
  – Acronym for Heating Seasonal Performance Factor. It is a commonly used measure of the heating efficiency of heat pumps. The cooling efficiency of a heat pump is measured by its SEER.
H Clip
  – Small metal clips formed like an "H" that fits at the joints of two plywood sheets (or wafer board) to stiffen the joint. Normally used on the roof sheeting.
  – The form of energy that is transferred by virtue of a temperature difference or a change in state of a material.
Heat Anticipator
  – A very small electric heater in a thermostat that causes the thermostat to turn off before room temperature reaches the thermostat setting, so that the house doesn’t overheat.
Heat Capacity
  – The quantity of heat required to raise the temperature of 1 cubic foot of a material 1°F. The heat capacity of a building element is the sum of the heat capacities of each of its components.
Heat Exchanger
  – A device that transfers heat via an air or liquid exchange with the device typically installed in furnaces and A/C systems.
Heat Gains
  – Heat that accumulates in homes; this is desirable during the heating season and undesirable during the cooling season.
Heat Loss
  – This is the amount of heat lost through the building shell, during given period of time, typically a year.
Heat Pump
  – (a) A mechanical device which uses compression and decompression of gas to heat and/or cool a house. (b) A refrigeration system that extracts heat from one substance and transfers it to another portion of the same substance or to a second substance at a higher temperature for a beneficial purpose.
Heat Recovery Ventilator
  – A central ventilator that transfers heat from exhaust to intake air.
Heat Rejection Equipment
  – Equipment used in comfort cooling systems such as air-cooled condensers, open cooling towers, closed-circuit cooling towers and evaporative condensers.
Heat Rise
  – The number of degrees of temperature increase that air is heated as it is blown over the heat exchanger. Heat rise equals supply temperature minus return temperature.
Heat Transmission
  – Heat flow through the walls, floor, and ceiling of a building. It does not include air leakage.
Heat Transfer Coefficient
  – See U-value.
Heat Trap
  – An arrangement of piping and fittings, such as elbows, or a commercially available heat trap that prevents thermos-syphoning of hot water during standby periods.
Heated Slab
  – Slab-on-grade construction in which the heating elements or hot air distribution system is in contact with or placed within the slab or the subgrade.
Heated Space
  – Space within a building which is provided with a positive heat supply (see “Positive heat supply”). Finished living space within a basement with registers or heating devices designed to supply heat to a basement space shall automatically define that space as heated space.
Heating Degree Day
  – Each degree that the average daily temperature is below the base temperature (usually 65°F) constitutes one heating degree day.
Heating Load
  – (a) The total number of BTU per hour of heat required to be added to a home, in order to provide indoor comfort. Heating load is based on worst-case Winter Design temperatures determined by local weather statistics. (b) The amount of heating required to keep a building at a specified temperature during the winter, usually 65° F, regardless of outside temperature.
Heating Seasonal Performance Factor (HSPF)
  – The total heating output of a heat pump during its normal annual usage period for heating, in Btu, divided by the total electric energy input during the same period, in watt hours, as determined by DOE 10 CFR Part 430, Subpart B, Test Procedures and based on Region 4.
Hermetic Seal
  – Vacuum seal (between panes of a double-paned window i.e. insulated glass unit or IGU). Failure of a hermetic seal causes permanent fogging between the panels of the IGU.
High Limit
  – This is a bimetal thermostat that turns the heating element of a furnace off if it senses a dangerously high temperature.
Home Heating Index
  – The number of Btus of energy used by a home, divided by its area in square feet, and then divided by the number of heating degree days during the time period.
House Pressure
  – The pressure difference measured by a manometer, between the indoors and outdoors.
  – An appliance normally attached to the furnace, or portable unit device designed to increase the humidity within a room or a house by means of the discharge of water vapor.
  – A control mechanism used to operate a mechanical ventilation system based upon the relative humidity in the home.
  – An automatic control that switches a fan, humidifier, or dehumidifier on and off to control relative humidity.
Humidity Ratio
  – Same as absolute humidity. The absolute amount of air’s humidity measured in pounds of water vapor per pound of dry air.
  – An abbreviation for Heat, Ventilation, and Air Conditioning
HVAC Rough
  – Work performed by the Heating Contractor after the stairs and interior walls are built. This includes installing all duct work and flue pipes. Sometimes, the furnace and fireplaces are installed at this stage of construction.
HVAC System
  – This is the combination of the conditioning equipment (AC/Furnace/Boiler), distribution network (ducting or piping) and terminals (boots and grilles) that provide either collectively or individually the processes of heating, ventilating, or air conditioning to a building.
HVAC System Components
  – HVAC system components provide, in one or more factory-assembled packages, means for chilling or heating water, or both, with controlled temperature for delivery to terminal units serving the conditioned spaces of the building. Types of HVAC system components include, but are not limited to, water chiller packages, reciprocating condensing units and water source (hydronic) heat pumps (see “HVAC system equipment”).
HVAC System Equipment
  – Heating, Ventilating, and Air Conditioning system equipment, in one (single packaged unit containing; condenser, evaporator, distribution fan and heating source) or more (split system consisting of separate; evaporator coil, air handler or furnace and condenser) factory assembled packages, which provides the means for circulation, cleaning (filtration), and conditioning of air to a controlled temperature and humidification level. It may also be used to provide humidification; either alone or in combination with a heating plant. The cooling function is either operated electrically or using heat and the refrigerant condenser is air, water or evaporatively cooled. Where the equipment is provided in more than one package, the separate packages shall be designed by the manufacturer to be used together (See AHRI matching). The equipment will provide the heating function either as a heat pump or by the use of electric elements or fossil-fuel-fired burners and heat exchangers. (The word “equipment” used without a modifying adjective, in accordance with common industry usage, applies either to HVAC system equipment or HVAC system components.)
  – A heating system using hot water or steam as the heat-transfer fluid.
  – Acronym for Indoor Air Quality.
  – Acronym for Insulated Concrete Forms, concrete construction using rigid plastic foam forms that hold concrete in place during curing and remain in place afterwards to serve as thermal insulation for concrete walls. The foam sections are lightweight and result in energy-efficient, durable construction.
  – The light level measured on a horizontal plane in foot candles.
Incandescent Lamp
  – Until 2010, this was the most common lamp employing an electrically charged metal filament that glows at white heat.
Inches of Water Column (IWC)
  – Small air pressure differences are measured in inches of water column (IWC) in the American measurement system.
  – This describes two or more materials which are not suitable to be used together.
Indoor Air Quality (IAQ)
  – This is a measurement of the overall cleanliness or “quality” of the air within a building or home.
  – The uncontrolled inward air leakage into a building and vice versa; caused by the pressure effects of wind or the effect of differences in the indoor and outdoor air density or both. In either case, heat loss results. To find the infiltration heating load factor (HLF), the formula to account for the extra BTU's needed to heat the infiltrated air is:
  – British Thermal Units per Hour: Building Volume (ft3) x air changes x BTU/cu.ft/hr x TD (TD is temperature difference)
  – Pertaining to heat rays emitted by the sun or warm objects on earth.
Input Rating
  – The rate at which an energy-using device consumes electricity or fossil fuel.
Insulated Glass
  – Two or more glass panes spaced apart and sealed in a factory.
Insulating Glass
  – Window or door in which two panes of glass are used with a sealed air space between.  See Double glass.
Insulating Glass Unit
  – Two or more panes of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between each lite.
  – (a) Any material high in resistance to heat transmission that, when placed in the walls, ceiling, or floors of a structure, and will reduce the rate of heat flow. (b) Generally referring to any material which slows down or retards the flow or transfer of heat. Building insulation types are classified according to form as loose fill, flexible, rigid, reflective, and foamed-in-place. All types are rated according to their ability to resist heat flow (R-Value).
Insulation Board (Rigid)
  – A structural building board made of coarse wood or cane fiber in ½- and 25/32-inch thickness. It can be obtained in various size sheets and densities.
Insulation (Foam in Place)
  – A foam product that may act as an air barrier and providing insulation and air sealing in one step.
Insulation Fasteners
  – Any of several specialized mechanical fasteners designed to hold insulation in place. The wire type, used to hold batt insulation in place between rafter or joists are sometimes referred to as “staves”.
Insulating Sheathing
  – Also see Insulation Board (Rigid).
Integrated Part-Load Value (IPLV)
  – This is a single measure of merit, based on part-load EER or COP expressing part-load efficiency for air-conditioning and heat pump equipment on the basis of weighted operation at various load capacities for the equipment.
Interacting Relationships
  – Changing conditions that are inter-related and therefore affect each other.
Internal Gains
  – Heat gained from sources internal to the building that must be removed during the cooling periods to maintain comfort. Some examples would be: occupant density, bathing, cooking, and operating appliances.
  – Ignition Device - A device that lights the pilot light on a gas appliance when the control system calls for heat, thus saving the energy wasted by a standing pilot.
Intermediate Zone
  – A zone located between the building’s conditioned spaces and outdoors, like a crawl space, fir down or attic.
  – The space or opening between two or more adjoining surfaces. The location between the touching surfaces of two members or components joined and held together by nails, glue, cement, mortar, or other means.
Joint Cement or Joint Compound
  – This is a powder which is usually mixed with water and used for joint treatment in gypsum-wallboard finish, i.e." spackle" or drywall mud.
  – A horizontal wood framing member that supports a floor or ceiling. Usually wooden 2 X 8's, 10's, or 12's that run parallel to one another and support a floor or ceiling, and supported in turn by larger beams, girders, or bearing walls.
Joist Hanger
  – A metal "U" shaped item used to support the end of a floor joist and attached with hardened nails to another bearing joist or beam.
  – A thermometer scale on which a unit of measurement equals the Celsius degree.
Kilowatt (kw)
  – (a) One thousand watts. A kilowatt hour is the base unit used in measuring electrical consumption. Also see watt. (b) A unit of electric power equal to 1000 joules per second or 3412 Btus per hour.
Kilowatt-hour (kWh)
  – (a) The unit of electric energy equal to 3600 kilojoules or 3412 Btus. (b) 1000 watts; 1 kWh = 3414 Btu’s.
Kinetic Energy
  – Energy in transition or motion.
Kraft Paper
  – This is the heavy, water resistant paper usually found on batt insulation.
  – A light bulb.
Latent Heat
  – The heat absorbed or released by a substance when it changes state. An example would be a substance changing from a liquid to a gas.
  – Space in a window sash for a single pane of glass, also a pane of glass (light or lite).
Light Emitting Diode Lamp (LED)
  – A technology that produces light by causing electrons to flow through the lamp and release energy in the form of light.
Light Pollution
  – This is the excessive illumination of night-skies by artificial light.
Light Quality
  – Good light quality is characterized by absence of glare and low brightness contrast.
Limit Switch
  – A safety control that automatically shuts off a furnace if it gets too hot. Most also control blower cycles.
Liquid-Applied Membrane
  – Generally applied to cast-in-place concrete surfaces in one or more coats to provide fully-adhered waterproof membranes which conform to all contours.
  – Another term for a pane of glass. Sometimes spelled "light" in industry literature but spelled "lite" in this text to avoid confusion with light as in "visible light."
Low-Flow Aerators
  – A device that affixes to a sink faucet to limit flow. Low flow aerators can generally range in size from approximately 1.0 to 1.5 gallons/minute.
Low-Flow Showerhead
  – Restrictive showerhead that limits water flow to a lower gallon/minute flow that usually ranges from 1.5 - 2.0 = gallons/minute.
Low-Voltage Lighting
  – Lighting equipment powered through a transformer such as a cable conductor, a rail conductor and track lighting.
Low-Water Cutoff
  – This is the float-operated control for turning the burner off if a steam boiler is low on water.
  – A unit of light output from a lamp. Unit of measure for total light output, based on the amount of light falling on a surface of one square foot.
  – A lighting fixture or lamp. A complete lighting unit consisting of at least one lamp and the parts designed to distribute the light, to position and protect the lamp, to connect the lamp to the power supply and ballasting, when applicable. Luminaires are commonly referred to as “lighting fixtures.”
  – Short for low emissivity, which means the characteristic of a metallic glass coating to resist the flow of radiant heat.
Main Panel Box
  – The service box containing a main switch, and the fuses or circuit breakers located inside the home.
Make-Up Air
  – Air supplied to a space to replace exhausted air. Air brought in to replace air displaced by combustion or exhaust appliances.
  – A section of pipe with multiple openings.
  – Measuring device for fluid/air pressures.
  – (a) A non-toxic, low volatile organic compound (VOC), air duct sealant used for permanently sealing the fabricated joints and seams of sheet metal air ducts, rigid fiberglass air ducts, flexible air ducts and thermal insulation. (b) Heavy-consistency compound that may remain adhesive and pliable with age. Is typically a waterproof compound applied to exterior walls and roof surfaces. (c) Pasty material used as a cement (as for setting tile) or a protective coating (as for thermal insulation or waterproofing).
Mechanical Ventilation
  – The intentional ventilation of a building, that allows the homeowner some control in the amount and timing of the air exchange in the home.
Mechanical Ventilation System (Balanced)
  – A system of inlets and outlets that prevents pressure differences while ventilating the home.
Mechanical Ventilation System (Supply Only)
  – A type of mechanical ventilation that uses a fan assembly to bring air into the home, but which relies on building leakage or planned outlet dampers to remove moisture and contaminants.
Metering Device
  – In refrigeration, an orifice or capillary tube that meters refrigerant into an evaporator
  – A very specific localized climatic area, usually of a small site or habitat.
  – Spreading or creeping of a constituent of a compound onto/into adjacent surfaces. See bleeding.
Mock-Up Testing
  – Controlled air, water and structural performance testing of existing or new glazing systems.
Nameplate Horsepower
  – The nominal motor horsepower rating stamped on the motor nameplate.
National Fenestration Rating Council (NFRC)
  – This is the national organization which establishes standards for windows and doors.
Natural Ventilation
  – This is a method of ventilation using only natural air movement, without fans.
  – A landscaping method that uses native plants to conserve and create natural habitats that provides nurturing environments for wildlife.
Net Free Area
  – The area of a vent after that area has been adjusted for insect screen, louvers, and weather coverings. The net free area is always less than the actual area.
Net Metering
  – This is the method of gaining a credit for excess electricity produced by a consumer, often by means of a wind turbine or solar paneling.
  – A phrase describing a method of examining the interior of a component whereby no damage is done to the component itself.
Non-Drying (Non-Curing)
  – This is a sealant that does not set up or cure solid. See Butyl.
  – A sealant formulation having a consistency that will permit application in vertical joints without appreciable sagging or slumping.
  – Descriptive of a product that does not form a surface skin.
  – (a) The orifice of a heating system that sprays the fuel of fuel-air mixture into the combustion chamber. (b) The tubular tip of a caulking gun through which the compound is extruded.
OHM Meter
  – A device used to measure the resistance across a load. They are never used on a live circuit. It is used to track down broken wires.
OHM's Law
  – States that, in a given electrical circuit, the amount at current in amps is equal to the pressure in volts divided by the resistance in ohms. The formula is: I (Current) = V voltage or V = I x R. R resistance or R = V/I
On Center
  – The measurement of spacing for studs, rafters, and joists in a building from the center of one member to the center of the next.
Opaque Areas
  – All exposed areas of a building envelope which enclose conditioned space, except openings for windows, skylights, doors and building service systems.
Open-Combustion Heater
  – A heater that takes its combustion air from the surrounding room and dose not employ a flue to remove the combustion gases.
  – A term designating any chemical compound which contains carbon and hydrogen.
  – A small hole in piping where gas or oil exits to be mixed with air before combustion.
Outdoor Air
  – Air taken from the outdoors and, therefore, not previously circulated through the system.
  – The useful energy that a device produces after accounting for waste involved in the energy transfer.
Oxygen Depletion Sensor (ODS)
  – A safety device for unvented combustion heaters that shuts gas off when oxygen is depleted.
Packaged Air Conditioner
  – This is an air conditioner that contains the compressor, evaporator, and condenser in a single cabinet.
Packaged Terminal Air Conditioner (PTAC)
  – A factory-selected wall sleeve and separate un-encased combination of heating and cooling components, assemblies or sections (intended for mounting through the wall to serve a single room or zone). It includes heating capability by hot water, steam or electricity. (For the complete technical definition, see ARI 310/380.)
Packaged Terminal Heat Pump
  – A PTAC capable of using the refrigeration system in a reverse cycle or heat pump mode to provide heat. (For the complete technical definition, see ARI 310/380.)
  – This is a unit of measurement for air pressure. (See Inch of water.)
Passive Solar
  – The type of construction design, utilizing the sun's energy to help warm the home in winter and redirects or blocks that energy to reduce cooling needs in the summer.
Payback Period
  – This is the number of years that an investment in energy conservation will take to repay its cost in energy savings.
  – A heat-expanded mineral used for insulation. An aggregate formed by heating and expanding siliceous volcanic glass.
  – A measurement of how much water vapor a material will let pass through it per unit of time.
  – A measure of the ease with which water penetrates a material or the measure or rating of a material’s ability to permit moisture to pass through it.
Photo Resistor
  – Electronic sensing device used to sense flame, daylight, artificial light.
Photovoltaic (PV)
  – This system captures light from the sun and converts it into electricity through solar panels usually installed on roofs.
  – The electric cord that the electrician provides and installs on an appliance such as a garbage disposal, dishwasher, or range hood.
  – A column of masonry, usually rectangular in horizontal cross section, used to support other structural members. Also see Caisson.
  – A powdered solid used in paint or enamel to give it a color.
Pilot Light
  – A small, continuous flame (in a hot water heater, boiler, or furnace) that ignites gas or oil burners when needed.
Plenum Chamber
  – Chamber or container for moving air under a slight positive pressure to which one or more ducts are connected.
  – Polymer plastic used for vapor barriers, air barriers, and foam backer rod.
  – Also referred to as PIR, polyiso, or ISO, is a thermoset plastic typically produced as a foam and used as rigid thermal insulation. Its chemistry is similar to polyurethane (PUR) except that the proportion of methylene diphenyl diisocyanate (MDI) is higher and a polyester-derived polyol is used in the reaction instead of a polyether polyol.
  – A substance consisting of large molecules which have been formed from smaller molecules of similar make-up.
  – A synthetic aromatic polymer made from the monomer styrene and is used as a type of foam insulation; available in sheet or spray form.
Polystyrene Insulation
  – Is a type of rigid plastic foam insulation, usually white or blue in color and sold in 1/8” - 3’ 4’x8’ sheets. Form board insulation is referred to as extruded polystyrene, due to the manufacturing process used to create it it.
Polysulfide Sealant
  – Polysulfide liquid polymer sealant which is mercaptan terminated, long chain aliphatic polymers containing disulfide linkages. They can be converted to rubbers at room temperature without shrinkage upon addition of a curing agent.
  – Polyurethane is a resilient, flexible and durable polymer composed of organic units joined by carbamate links. While most polyurethanes are thermosetting polymers that do not melt when heated, thermoplastic polyurethanes are also available. It is a material that can take the place of paint, cotton, rubber, metal or wood in thousands of applications across virtually all fields.
Polyurethane Insulation
  – This is the most commonly used spray expanding foam application. It is applied using a two component high pressure system and spray gun in new home construction. It is spray applied directly to the surface being insulated and adheres due to its glue like adhesiveness. After contacting the surface the gases released in the mixing process cause the foam to expand to 2-3 times it original depth, filling the cavity. It typically requires shaving the over fill to the top of the studs, in order for the interior wall sheathing to be applied. Low pressure slow rise spray foam is used primarily for remodel jobs, where there are existing walls with drywall already in place, so the expansion of the foam does not buckle wall surfaces. Also see Polyurethane Open and Closed Cell Insulation.
Polyurethane Insulation (Closed Cell)
  – Closed cell foam insulation is much denser than open cell. It has a smaller, more compact cell structure. It is a very good air barrier as well as a water vapor barrier. It is often used in roofing projects or other outdoor applications, but can be used anywhere in the home. Caution should be taken when applying to surfaces where moisture migration is required in order to dissipate. Closed cell insulation does not allow for this and may trap moisture in porous surfaces.
Polyurethane Insulation (Open Cell)
  – Open cell is a type of foam where the tiny cells are not completely closed. Open cell is less expensive because it uses fewer chemicals. It is a very good air barrier but does not provide any type of water vapor barrier. It is much more sponge-like in appearance. It is often used for interior walls because it provides sound reduction. It is not recommended for outdoor applications.
Polyurethane Sealant
  – This is versatile plastic foam sealant material directly applied the surface. It is usually yellow in color.
  – The density of substance and its capacity to pass liquids.
Positive Cooling Supply
  – Mechanical cooling deliberately supplied to a space, such as through a supply register. Also, mechanical cooling indirectly supplied to a space through uninsulated surfaces of space-cooling components, such as evaporator coil cases and cooling distribution systems which continually maintain air temperatures within the space of 85°F (29°C) or lower during normal operation. To be considered exempt from inclusion in this definition, such surfaces shall comply with the insulation requirements of this code.
Positive Heat Supply
  – Heat deliberately supplied to a space by design, such as a supply register, radiator or heating element. Also, heat indirectly supplied to a space through uninsulated surfaces of service water heaters and space-heating components, such as furnaces, boilers and heating and cooling distribution systems which continually maintain air temperature within the space of 50°F (10°C) or higher during normal operation. To be considered exempt from inclusion in this definition, such surfaces shall comply with the insulation requirements of this code.
  – A variable resistor used as a controller or sensor.
Potential Energy
  – Energy in a stored or packaged form.
  – The energy rate, usually measured in watts. Power equals voltage times amps or: W = E (voltage) x 1 (amps). The heavier the flow of amps at a given supply, the higher the rate at which energy is being supplied and used.
Power Vent
  – This is a vent that includes a fan to speed up air flow out of the pipe and is often installed on roofs to ventilate attics.
Power-Vented System
  – System that uses positive vent pressure to remove combustion by-products to the outside. A power vent located on the appliance pulls air through the heat exchanger and pushes byproducts out through the vent pipe.
  – Any pesticide substance that, for a reasonable length of time, will prevent the action of wood-destroying fungi, insect borers, and similar destructive agents when the wood has been properly coated or impregnated with it. Normally an arsenic derivative, such as Chromated Copper Arsenate (CCA) is an example.
  – A force encouraging flow by virtue of a difference in some condition between two areas. Typically measured or expressed in Pounds per Square Inch (PSI), Inches of Water Column (IWC), or Pascals (PA).
Pressure Boundary
  – (a) The primary air barrier installed on a home. (b) Refers to the location of the barrier that separates indoor air from outdoor air. It should be continuous and aligned with a thermal boundary.
Pressure Diagnostics
  – The practice of measuring air pressures and flows in buildings.
Pressure Pan
  – A device used to block a duct register, while measuring the static pressure behind it, during a blower door test.
Pressure Relief Valve (PRV)
  – A safety device valve mounted on hot water heater or boiler storage tanks which is designed to release any high pressure in the tank to prevent tank explosions.
  – A control that turns a steam boiler’s burner on and off as steam pressure changes.
Proposed Design
  – A description of the proposed building used to estimate annual energy use for determining compliance based on total building performance.
  – The science of the relationship between air, water vapor, and heat.
  – The acronym for Revolutions per Minute. The measurement used to determine the speed of motor.
  – The measured resistance of a material to heat transfer. Every material used for construction has an R-Value and the R-Value is the amount of resistance to heat flow through any given construction material. The higher the R value, the less heat is transmitted throughout the material. The R-value is the reciprocal of the U-value. To determine the U-Value divide 1 by the R-Value (U=1/R) or to determine the R-Value divide 1 by the U-Value (R=1/U).
R-Value (Thermal Resistance)
  – The inverse of the time rate of heat flow through a body from one of its bounding surfaces to the other surface for a unit temperature difference between the two surfaces, under steady state conditions, per unit area (h x ft2 x °F/Btu).
Radiant Barrier
  – A foil sheet or coating designed to reflect heat rays or retard their emission.
Radiant Heating
  – A method of heating, usually consisting of a forced hot water system with pipes placed in the floor, wall, or ceiling. This may also include electrically heated panels.
Radiant Temperature
  – This is the average temperature of objects in a home like walls, ceiling, floor, furniture, and other objects.
  – (a) Heat energy, which originates on a hot body like the sun, and travels from place to place through the air. Energy transmitted from a heat source to the air around it. Radiators actually depend more on convection than radiation. (b) Heat transfer from a warm object to a cold object, where the objects are not in contact with each other. Unlike convection or conduction, radiation does not require a “medium” to carry the heat. The objects must be “in sight” of one another. Any heated surface will lose heat to cooler surrounding space or surfaces through radiation. The earth receives its heat from the sun by radiation. The heat rays are turned into heat as they strike an object which will absorb some or all of the heat transmitted.
  – A heating unit which is supplied heat through a hot water system.
  – A naturally-occurring, heavier than air, radioactive gas common in many parts of the country.  Radon gas exposure is associated with lung cancer. Mitigation measures may involve crawl space and basement venting and various forms of vapor barriers.
Radon System
  – A ventilation system beneath the floor of a basement and/or structural wood floor and designed to fan exhaust radon gas to the outside of the home
Rain Water Catchment/Collection
  – Systems that harvest water during periods of rain. The water the can be saved and used during droughts.
Rain/Freeze Sensors
  – Sensors prevent automatic sprinkler systems from watering during rain or cold weather.
  – Thermometer scale on which unit of measurement equals the Fahrenheit degree.
Rate of Return
  – The percentage of savings from an energy investment accrued each year.
  – An electrical outlet.  A typical household will have many 120 volt receptacles for plugging in lams and appliances and 240 volt receptacles for the range, clothes dryer, air conditioners, etc.
Recirculating Water Heater
  – Systems that use a thermostat or timer to automatically turn on the pump whenever water temperature drops below a set-point, or when the timer reaches a setting. Hot water recirculation systems can be activated by the push of a button or by a thermostat, timer or motion sensor. Such systems ensure that hot water is always available without any waiting time. Hot water recirculation systems generally consist of a pump, an integrated electronic controller, and a zone valve. When the activation button is pushed, or when another type of control turns the system on, the pump starts re-circulating cooled water that has been sitting in the hot water line and sends it back to the water heater through the cold water line. When the water reaches a desired temperature, a control closes the zone valve and turns off the pump. It is much like turning on the hot water faucet and letting the water run until it gets hot, but instead of the water going down the drain it is simply returned back to the water heater.
Recycled Components
  – Materials used in a home that were salvaged or are made from recycled materials. One example is wood flooring made from salvaged timber from old barns.
Recyled Construction / Household Waste
  – A strategy in which homeowners, remodeling a house in anticipation of selling it, recycle old materials and demolition waste rather than sending them to a landfill
  – The ability of a material’s surface to reflect radiant heat, and may also be referred to as reflectivity.
Reflective Glass
  – Glass with a metallic coating to reduce solar heat gain.
Reflective Insulation
  – Sheet material with one or both faces covered with aluminum foil.
Recovery Efficiency
  – Recovery rate or recovery efficiency refers to the amount of water heated to a set temperature, per hour. Gas water heaters have 75-80% recovery efficiency, while electric typically have 99% recovery efficiency, since the element in in contact with the water.
  – (a) A substance utilized to produce refrigeration by its expansion or vaporization or absorption. (b) A special fluid used in air conditioners and heat pumps that heats air when it condenses and cools air when it evaporates. (c) A substance that remains a gas at low temperatures and pressure and can be used to transfer heat. Freon is an example and is used in air conditioning systems.
  – A grill placed over a HVAC duct outlet or air return.
  – To replace a broken window.
  – The replacement of an existing lamp with a lower wattage lamp.
Relative Heat Gain
  – The amount of heat gain through a glass product taking into consideration the effects of solar heat gain (shading coefficient) and conductive heat gain (U-value).
Relative Humidity (RH)
  – The percentage of moisture vapor present in the air, relative to the total amount of moisture the air could hold at a specific temperature and/or pressure, expressed as a percentage.
  – An automatic, electrically-operated switch.
Relief Valve
  – A device designed to open if it detects excess temperature or pressure.
  – Remote electrical, gas, or water meter digital readouts that are installed near the front of the home in order for utility companies to easily read the home owners usage of the service.
Renewable Energy Source
  – Sources of energy (excluding minerals) derived from incoming solar radiation, including natural daylighting and photosynthetic processes; from phenomena resulting therefrom, including wind, waves and tides, lake or pond thermal differences; and from the internal heat of the earth, including nocturnal thermal exchanges.
Reset Controller
  – A device that adjusts fluid temperature or pressure in a central heating system according to outdoor air temperature.
  – (a) The property of a material resisting the flow of electrical energy or heat energy. (b) The internal structure of wires even in the best conductors opposes the flow of electric current and converts some current into heat. This internal friction-like effect is called resistance and is measured in ohms. Resistance equals Voltage divided by Amperage.
  – A personal safety device designed to protect against inhalation of airborne particles.
Retaining Wall
  – This is a structure that holds back a slope and prevents erosion.
  – An energy conservation measure that is applied to an existing building. Also means the action of improving the thermal performance or maintenance of a building.
Return or Return Air
  – (a) The HVAC system vent, that returns air to the furnace or air handler to be conditioned. (b) Air circulating back to the furnace or handler from the house, to be conditioned and supplied to the rooms.
R-Factor or Value
  – This is the unit of measure of a materials ability to resist the flow heat. New homes walls are usually insulated with 4" of batt insulation with an R value of R-13, and a ceiling insulation of R-30.
Rock Wool®
  – A brand of Mineral Wool insulation made from byproduct molten rock or slag fiber.
Room Air Conditioner
  – (a) A unitary air conditioner installed through a wall or window, which cools the room by removing heat from the room and releasing it outdoors. (b) An encased assembly designed as a unit for mounting in a window or through a wall, or as a console. It is designed primarily to provide free delivery of conditioned air to an enclosed space, room or zone. It includes a prime source of refrigeration for cooling and dehumidification and means for circulating and cleaning air, and shall be permitted to also include means for ventilating and heating.
Room Heater
  – A heater located within a room and used to heat that room.
Rough Opening
  – (a) The opening in a wall into which a door or window is to be installed. (b) The horizontal and vertical measurement of a window or door opening before drywall or siding is installed.
  – A natural form of bringing debris and sediment into water, runoff is the natural formation of streams after precipitation that carries contaminants to a larger water source.
  – An acronym for “Seasonal Energy Efficiency Ratio”.
  – Acronym for Savings-to-Investment Ratio.
  – Describing vapor and liquid at the phase-change point.
Savings to Investment Ratio (SIR)
  – (a) Measures how many times an energy retrofit pays for itself during its lifetime. (b) The life-cycle savings of an energy improvement divided by the initial investment. (For every dollar invested in an energy improvement, how many dollars will be saved over the life of the improvement in today’s dollars?)
  – (a) Dissolved minerals that precipitate inside boilers and storage tanks. (b) The relationship between actual measurements on a page of plans or blue prints and the actual measurements of the building represented by the plans or blue prints.
Screw Lamp Holders
  – A lamp base that requires a screw-in-type lamp, such as a compact-fluorescent (CFL), incandescent, or tungsten-halogen bulb.
  – An elastomeric material with adhesive qualities applied between components of a similar or dissimilar nature to provide an effective barrier against the passage of the elements.
Sealed Combustion Appliance
  – An appliance such as a room or wall heater, furnace or water heater that draws combustion air from outdoors and has a sealed exhaust system.
Sealed Combustion Venting System
  – Uses either a concentric or a two-pipe vent. (A concentric vent is one in which there is a small pipe inside a larger pipe.) One pipe is designated to bring in combustion air, and the other is designated for removal of combustion by-products out of the home. No combustion air comes from inside the home.
Seasonal Efficiency
  – Total system efficiency, which includes Annual Fuel Utilization Efficiency (AFUE) and distribution losses. This is the average efficiency over the course of a heating season.
Seasonal Energy Efficiency Ratio (SEER)
  – (a) This is a laboratory measurement of energy efficiency for central air conditioners, less distribution system loss. The SEER is computed by dividing cooling capacity, measured in Btuh, by the equipment watts. (b) The total cooling output of an air conditioner during its normal annual usage period for cooling, in Btu/h (W), divided by the total electric energy input during the same period, in watt-hours, as determined by DOE 10 CFR Part 430, Subpart B, Test Procedures.
Sensible Heat
  – The heat absorbed by a substance which raises its temperature.
  – A bimetal switch that turns on the elements of an electric furnace in sequence.
Service Systems
  – All energy-using systems in a building that are operated to provide services for the occupants or processes housed therein, including HVAC, service water heating, illumination, transportation, cooking or food preparation, laundering and similar functions.
Service Water Heating
  – The supply of hot water for purposes other than comfort heating.
Setback Thermostat
  – Thermostat with an integrated clock, which can be programmed at various temperature set points and at different times of the day/week. Usually used as the heating or cooling system thermostat. It may also be referred to as a “Programmable Thermostat”.
Shading Coefficient (SC)
  – (a) A decimal describing how much solar energy is transmitted through a window opening, compared to clear single glass, which has an SC of 1.0.
Sheet Metal Duct Work
  – The HVAC ducting system, usually consisting of round or rectangular metal pipes and sheet metal (for Return Air) and installed for distributing warm (or cold) air from the furnace to rooms in the home.
  – The exterior building envelope, including the walls, floor, and roof assemblies.
  – The finished exterior covering of the outside walls of a frame building.
Silicone Sealant
  – Sealant made of silicone rubber. An elastomer composed of silicone, itself a polymer containing silicon together with carbon, hydrogen, and oxygen. Silicone rubbers are widely used in industry, and there are multiple formulations. Silicone rubbers are often one- or two-part polymers, and may contain fillers to improve properties or reduce cost.
Simple Payback
  – The number of years it takes for annual savings from an energy improvement to equal the initial investment.
Simulation Tool
  – (a) An approved software program or calculation-based methodology that projects the hour-by-hour loads and annual energy use of a building. (b) Software used to simulate conditions that may occur in a building.
Sky Dome
  – A type of sky lite exhibiting a characteristic translucent plastic domed top.
  – A glass or other transparent or translucent glazing material or structure on a roof that is designed to admit light and is somewhat above the plane of the roof surface. They are installed at a slope of 15 degrees (0.26 rad) or more from vertical. Glazing material in skylights, including unit skylights, solariums, sunrooms, roofs and sloped walls is included in this definition.
  – (a) Concrete foundation or pavement, i.e. driveways, garages, and floors. (b) A rectangular door without hinges or frame.
Slab on Grade
  – A type of foundation with a concrete floor which is placed directly on the soil, in which footings are needed but little or no foundation wall is poured. The edge of the slab is usually thicker and acts as the footing for the walls.
Slab on Grade Floor Insulation
  – Insulation applied around the perimeter of the floor slab or its supporting foundation, where the top edge of the floor perimeter slab is above the finished grade or 12” – 24” below the finished grade.
Sling Psychrometer
  – A device holding two thermometers that is slung through the air to measure relative humidity.
Solar Assisted Water Heating
  – This is a solar hot water array on the roof that supplements (but does not exclusively supply) the hot water to the home. Water warmed by solar energy is pumped into the hot water heater where less energy is required to get it hot or less cold water needs to be warmed to fill the tank.
Solar Energy Source
  – Source of natural daylighting and of thermal, chemical or electrical energy derived directly from conversion of incident solar radiation.
Solar Gain
  – Heat from the sun that is absorbed by a building and contributes to the need for cooling.
Solar Heat
  – (a) This is radiant energy from the sun with wavelengths between 0.7 and 1 micrometer. (b) Active solar space-heating systems consist of collectors that collect and absorb solar radiation combined with electric fans or pumps to transfer and distribute that solar heat. Active systems also generally have an energy-storage system to provide heat when the sun is not shining. The two basic types of active solar space-heating systems use either liquid or air as the heat-transfer medium in their solar energy collectors.
Solar Heat Gain Coefficient (SHGC)
  – (a) The ratio of the solar heat gain entering the space through the fenestration assembly to the incident solar radiation. (b) The percentage of solar heat that is absorbed vs. reflected when it contacts a window. Solar heat gain includes directly transmitted solar heat and absorbed solar radiation which is then transferred via radiation, conduction or convection into the space.
Solar Transmittance
  – The percent of total solar energy transmitted by a material. Solenoid - A magnetic device that moves a switch or valve stem.
Space Conditioning
  – Heating, cooling, or ventilation of an indoor space.
Space Heat(ing)
  – Heat supplied to the living space, for example, to a room or the living area of a building.
  – The distance between individual members or shingles in building construction.
Specific Heat
  – This is the ratio of a material’s heat storage capacity to the heat storage capacity of water.
  – Temporary flow of combustion gases from a dilution device.
Split System Air Conditioner
  – An air conditioner that has the condenser and compressor outdoors and the evaporator indoors.
Stack Effect
  – The draft established in a building from air infiltration enter low and exfiltration exiting high. This occurs when the air inside the building is heated and becomes less dense rising up and out of any holes in the upper portions of the envelope. The escaping air is replaced with outside air that enters through holes in the lower portions.
Standard Reference Design
  – A version of the proposed design home that meets the minimum requirements of a code or standard and is used to determine the maximum annual energy use requirement for compliance based on total building performance.
Standing Losses
  – Heat lost from a hot water storage tank through its shell.
State Point
  – Air at a particular temperature and humidity occupies a single point on the psychrometric chart called a state point.
Static Vent
  – This type of vent does not include a fan and relies on static pressure to evacuate air or gases.
STC (Sound Transmission Class)
  – The measure of sound stopping of ordinary noise.
Steady State Efficiency
  – The efficiency of a heating appliance, after an initial start-up period, that measures how much heat crosses the heat exchanger. The steady-state efficiency is measured by a combustion analyzer.
Straw Bale Construction
  – A construction method that uses waste straw left over from crops, such as wheat, oats, barley, rye, rice and flax, after all the food has been extracted. Straw is gathered, baled, compressed and tied together. Bales are placed over a "stem wall" to protect the straw from the ground soil and the straw bales are covered with stucco and plastered over for finishing.
Steam Trap
  – An automatic valve that closes to trap steam in a radiator until it condenses.
Steam vent
  – A bimetal-operated air vent that allows air to leave steam piping and radiators, but closes when exposed to steam itself.
Storm Door
  – A panel or sash door placed on the outside of an existing door to provide additional protection from the elements.
Storm Window or Sash
  – An extra glazed panel or sash placed on the inside or outside of an existing sash or window as additional protection against the elements.
  – That part of a building between any floors or between the floor and roof.
  – The number of degrees Fahrenheit that a condenser and nearby piping cools the liquid refrigerant below its saturation temperature.
  – A one-story structure attached to or added to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure’s exterior walls and roof.
Sun Screen(s)/Solar Shades
  – These are window treatments which effectively block the sun's heat.
Super Heat
  – The number of degrees Fahrenheit that an evaporator and nearby piping heats gaseous refrigerant above its saturation temperature.
Supply Air
  – Air that has been heated or cooled and is then moved through the ducts and out the supply registers of a home.
  – Renewable sources such as building materials, utilities, and resources that have increased environmental benefits.
Sustainable Flooring
  – Bamboo, cork or flooring that is made from reclaimed or rapidly renewable sources.
  – A device that completes or disconnects an electrical circuit.
  – The combination of central or terminal equipment, components, controls, accessories, interconnecting means, and terminal devices by which energy is transformed so as to perform a specific function, such as HVAC, service water heating or illumination.
Take Off
  – The detailed material list necessary to complete a job.
Task Lighting
  – Lighting provided at the area where a visual task is performed.
  – A measurement related to the amount of kinetic energy within a material or substance. The greater the kinetic energy, the higher the temperature recorded.
  – A unit of energy equaling 100,000 British thermal units (Btus) or 29.3 kilowatt-hours. Ten therm(s) is equal to one dekatherm (dkt).
Thermal Break
  – A piece of relatively low conducting material between two high conducting materials.
Thermal Bridging
  – Rapid heat conduction resulting from direct contact between very thermally conductive materials like metal and glass.
Thermal Boundary
  – The insulation boundary that separates conditioned from non-conditioned spaces in a building. It should be continuous and aligned with the pressure boundary.
Thermal Bypass
  – A material or component breach that allows more heat transfer to another material or component, when compared to adjoining component pieces.
Thermal Conductance
  – (a) General term applied to K-value, meaning conduction heat-flow rate or the ability to conduct heat. (b) Time rate of heat flow through a body (frequently per unit area) from one of its bounding surfaces to the other for a unit temperature difference between the two surfaces, under steady conditions (Btu/(hr x ft2 x°F).
Thermal Isolation
  – Physical separation of unconditioned space(s) from conditioned space(s). An example would be the separation between a sunroom addition and a dwelling unit, consisting of existing or new wall(s), doors and/or windows. They would be controlled as separate zones for heating and cooling conditioning by using separate equipment.
Thermal Movement
  – The measured amount of dimensional change that a material exhibits as it is warmed or cooled.
Thermal Resistance (R)
  – Same as R-value, expresses the ability to retard heat flow. The reciprocal of thermal conductance (h x ft2 x °F/Btu)
Thermal Resistance Overall (Ro)
  – The overall thermal resistance of the gross area or individual component of the exterior building envelope (such as roof/ceiling, exterior wall, floor, crawl space wall, foundation, window, skylight, door, opaque wall, etc.), which includes the area weighted R-values of the specific component assemblies (such as air film, insulation, drywall, framing, glazing, etc.).
Thermal Shock
  – The stress built up by sudden and appreciable changes in temperature.
Thermal Transmittance
  – Expressed as U-value, thermal transmittance is heat flow by conduction, convection, and radiation through a non-uniform layered building component like a wall. The coefficient of heat transmission (air to air), is the time rate of heat flow per unit area and unit temperature difference between the warm-side and cold-side air films (Btu/h x ft2 x°F). The U-factor applies to combinations of different materials used in series along the heat flow path, single materials that comprise a building section, cavity airspaces and surface air films on both sides of a building element. To determine the U-Factor, divide 1 by the R-Value. U=1/R
Thermal Transmittance Overall (Uo)
  – This is the overall (average) heat transmission of a gross area of the exterior building envelope (Btu/h x ft2 x °F). The Uo-factor applies to the combined effect of the time rate of heat flow through the various parallel paths, such as windows, doors and opaque construction areas, comprising the gross area of one or more exterior building components, such as walls, floors or roof/ceilings.
  – An electronic resistor used to sense temperature.
  – A bimetal-junction electric generator used to keep the safety valve of an automatic gas valve open.
  – A branch of physics that explains the effect of temperature and heat, and the conversion of energy from one form to another.
  – A control device which regulates the temperature of a room or building by switching heating or cooling equipment on or off to achieve a desired set point temperature.
Tinted Glass
  – Glass with colorants added to the basic glass batches that give the glass color as well as light and heat-reducing capabilities. The color extends throughout the thickness of the glass.
Title 24
  – A set of California laws which regulates the construction industry to conserve energy.
Tracer gas
  – A harmless gas used to measure air leakage in a building.
  – A double coil of wire that reduces or increases voltage from a primary circuit to a secondary circuit.
Treated Lumber
  – This is a wood product which has been impregnated with chemical pesticides such as CCA (Chromated Copper Arsenate), to reduce damage from wood rot or insects. Often used for the portions of a structure which are likely to be in contact with soil and water. Wood may also be treated with a fire retardant.
Trombe Wall
  – Also referred to as a "solar wall", a Trombe wall consists of an 8-to-16-inch-thick masonry wall on the south side of a house. A single or double layer of glass is mounted about 1 inch or less in front of the wall's surface. Solar heat is absorbed by the wall's dark-colored outside surface and stored in the wall's mass, where it radiates into the living space.
Two-Part Sealant
  – A product composed of a base and curing agent or accelerator, necessarily packages in two separate containers which are uniformly mixed just prior to use.
U-Factor (Thermal Transmittance)
  – The coefficient of heat transmission (air to air) through a building component or assembly, equal to the time rate of heat flow per unit area and unit temperature difference between the warm side and cold side air films (Btu/h x ft2 x °F) and also known as U-value.
  – The measure of the amount of heat that will flow through a square foot of building cross-section with multiple slabs of materials. As the U-value decreases, so does the amount of heat that is transferred through the glazing material. The lower the U-value, the more restrictive the fenestration product is to heat transfer. It is the reciprocal of the R-value. It is also referred to as U-factor when applied to windows.
  – The invisible rays of the spectrum of light which are at its violet end is sometimes abbreviated UV.
Ultraviolet Radiation
  – This is the solar radiation having wavelengths just shorter than visible light.
Unconditioned Space
  – An area or zone within the building envelope that is not intentionally heated or cooled.
Unitary Cooling and Heating Equipment
  – One or more factory-made assemblies which include an evaporator or cooling coil, a compressor and condenser combination, and which shall be permitted to include a heating function as well. When heating and cooling equipment is provided in more than one assembly, the separate assemblies shall be designed to be used together.
Unitary Heat Pump
  – One or more factory-made assemblies which include an indoor conditioning coil, compressor(s) and outdoor coil or refrigerant-to-water heat exchanger, including means to provide both heating and cooling functions. When heat pump equipment is provided in more than one assembly, the separate assemblies shall be designed to be used together.
Urban Infill
  – Redevelopment of sites, in the core of metropolitan areas, for commercial and residential purposes.
  – A common foam insulation; available in sheet or spray form.
  – Acronym for Volatile Organic Compounds are organic chemicals, an organic substance with harmful effects on air or water quality. VOCs are frequently associated with paint, pesticides, carpet, and adhesives.
  – The gaseous form of any substance.
Vapor Barrier
  – A building product with low permeability, installed on exterior walls, floors and/or ceilings to retard the passage of water vapor into walls and prevent condensation within them.
Vapor Diffusion
  – The flow of water vapor through a solid material.
Vapor Diffusion Retarder
  – A material with, used to reduce moisture migration through building components.
  – Change from a liquid to a gas.
  – A pipe or duct which allows the flow of air and gasses to the outside. Also, another word for the moving glass part of a window sash, i.e. window vent.
Vent Connector
  – The vent pipe carrying combustion gases from the appliance to the chimney.
Vent Damper
  – An automatic damper powered by heat or electricity that closes the chimney while a heating device is off.
Vent Pipe
  – A vertical pipe of relatively small dimensions which protrudes through a roof to provide for the ventilation of gasses.
Vent Stack
  – A vertical vent pipe installed for the purpose of providing circulation of air to and from any part of a drainage system.
Vent System
  – In plumbing, a system to provide a flow of air to or from a drainage system or to provide circulation of air within such system to protect traps seals from siphoning and back pressure.
  – (a) The movement of air through an area for the purpose of removing moisture, air pollution, or unwanted heat. (b) The natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from, any space. (c) The process of supplying or removing air by natural or mechanical means to or from any space. Such air shall be permitted to be conditioned or unconditioned. (d) Air turnover (intentional and unintentional) in the home.
Ventilation Air
  – That portion of supply air which comes from outside (outdoors) plus any recirculated air that has been treated to maintain the desired quality of air within a designated space.
  – Device installed on the roof for the purpose of ventilating the interior of the building.
  – The process of installing roof vents in a roof assembly to relieve vapor Pressure; the process of water in the insulation course of the roof assembly evaporating and exiting via the roof vents. The removal of combustion gases by a chimney or other type of combustion vent.
  – (a) A heat-expanded mineral used for insulation. Sometimes contains asbestos. (b) A mineral used as bulk insulation and also as aggregate in insulating and acoustical plaster and in insulating concrete floors. (c) An aggregate somewhat similar to perlite that is used as an aggregate in lightweight roof decks and deck fills. It is formed from mica, a hydrous silicate.
  – The internal frictional resistance offered by a fluid to change of shape or to the relative motion or flow of its parts.
Visible Light Transmittance
  – (a) The percentage of visible light (390 to 770) nanometers) within the solar spectrum that is transmitted through glass. (b) The percent of visible light transmitted by a glass assembly.
  – (a) Cardboard rectangular boxes that are installed between the earth (between caissons) and the concrete foundation wall. Used when expansive soils are present. (b) Area lacking insulation in a ceiling, wall or floor.
  – The energy contained in each unit of charge in joules per coulomb.
  – (a) A measure of electrical potential. Most homes are wired with 110 and 220 volt lines. The 110 volt power is used for lighting and most of the other circuits. The 220 volt power is usually used for the kitchen range, hot water heater and dryer. (b) The driving force behind the flow of electricity somewhat like pressure is in a water pipe.
  – Measures the voltage flowing through a circuit. The circuit must be closed to allow the voltage to flow.
Water Footprint
  – An estimation of the amount of water used.
Water Heater (Instantaneous/Tankless)
  – A water heater with an input rating of at least 4,000 Btu/h per gallon (310 W/L) stored water and a storage capacity of less than 10 gallons (38 L).
Water Heater (Storage)
  – This is a water heater with an input rating less than 4,000 Btu/h per gallon (310 W/L) of stored water or storage capacity of at least 10 gallons (38 L).
Water Proofing
  – The process where a building component is made totally resistant to the passage of water and/or water vapor.
Water Repellent Coating
  – Transparent coating or sealer applied to the surface of concrete and masonry surfaces to repel water.
Water Repellent Preservative
  – A liquid applied to wood to give the wood water repellant properties
Watershed Protection
  – An environmental movement that monitors our daily actions and their effects toward the conservation, development, utilization and proper disposal of water in order to maintain safe and effective drainage for the various water systems surrounding us.
Water Vapor
  – Moisture existing as a gas in air. Water vapor is transported by air movement caused by pressure differences.
  – This is the electrical unit of power equivalent to one joule per second or 3.4 Btuh. A Kilowatt is equal to1000 watts and electric customers are billed on the kilowatts of power they have used.
  – A unit of electrical energy equivalent to 3,600 joules or 3.4 Btus.
  – The process of reducing energy consumption and increasing comfort by improving the energy efficiency of the building. Work typically involves air sealing the building shell, adding insulation, weather-stripping windows and doors, sealing the duct system and tuning the HVAC equipment.
  – Narrow sections of thin metal or flexible gaskets mounted in rigid metal strips installed to prevent the infiltration of air and moisture around windows and doors.
Weep Hole
  – (a) Small holes drilled in window frames for the purpose of allowing water to drain out of an area in a building where it has collected. (b) A hole which allows for drainage of entrapped water from masonry or glazing structures.
Wet-bulb Temperature
  – The temperature of a dampened thermometer of a sling psychrometer used to determine relative humidity, dew point, and enthalpy.
  – Areas that serve as links and buffers between land and water resources by collecting and filtering runoff.
Whole House Fan
  – A fan designed to move air through and out of a home and normally installed in the ceiling.
Wind Power
  – Power supplied by a wind turbine.
Wind Washing
  – Reductions in R-Value of insulation caused by air movement through insulation, commonly occurring in attics where baffles have not been installed.
Window Films
  – Plastic films, coated with a metallized reflective surface that are adhered to window glass to reflect heat rays from the sun.
Window Projection Factor
  – A measure of the portion of glazing that is shaded by an eave or overhang.
Winter Design Temperature
  – Is a regional calculated average indoor temperature designed to determine the heating and cooling load for a specific home.
With Reference To (WRT)
  – Is used when referencing the air pressures between two areas or locations being measured and compared.
Worst-Case Depressurization Test
  – A safety test, performed by specific procedures, designed to assess the probability of chimney back drafting.
  – A landscaping method used in arid areas that incorporates native plants that can tolerate infrequent watering.
Z-bar Flashing
  – Bent, galvanized metal flashing that's installed above a horizontal trim board of an exterior window, door, or brick run. It prevents water from getting behind the trim/brick and into the home.
  – (a) the section of a building that is served by one heating or cooling loop because it has noticeably distinct heating or cooling needs. (b) Systems with separate thermostat controls in different parts of a structure that allow for independent temperature control of each area.
Zone Valve
  – A device usually placed near the heating or cooling zone, which controls the flow of water or steam to parts of the building; it is controlled by a zone thermostat.

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