Glossary

Abatement

A measure or set of measures designed to perma­nently eliminate a hazard

Absolute humidity

Air’s moisture content expressed in weight of water vapor per standard weight (pounds, grams) of dry air.

Absorptance

The ratio of a solar energy absorbed to incident solar. Also called absorbtivity.

Absorption

A solid material’s ability to draw in and hold liquid, gas, or radiant energy.

Accent lighting

Illumination of walls or other surfaces, to spread light and reduce contrast in an indoor or outdoor area.

Acoustical Sealant

Sealing agent used to minimize sound trans­mission through a joint.

ACH50

The number of times in one hour that all of the air in a home is replaced by outside air during a 50-pascal blower door test.

Adsorption

Adhesion of a thin layer of molecules to a surface they contact.

Air barrier

Any part of the building shell that offers resistance to air leakage. The air barrier is effective if it stops most air leak­age. The primary air barrier is the most effective of a series of potential air barriers.

ACH₅₀

Air changes per hour at 50 pascals. The number of times the volume of air in a structure will change in one hour at the induced blower door house pressure of 50 pascals.

ACHnat

Air changes per hour natural. The number of times the indoor air is exchanged with the outdoor air in one hour under natural driving forces, often written as just ACH.

Air conditioning

Cooling buildings with a refrigeration system. More generally means both heating and cooling.

Air Conditioning Contractors of America (ACCA)

Industry group that promotes best practices and lobbies for the industry.

Air exchange

The process whereby indoor air is replaced with the outdoor air through air leakage and ventilation.

Air-free carbon monoxide (ppm)

A measurement of CO in an air sample or flue gas that accounts for the amount of excess air (oxygen, O₂) in the sample. It adjusts the as-measured CO ppm value, thus simulating air-free (oxygen-free) conditions in the sample. Measured in parts per million (ppm).

Air handler

A steel cabinet containing a blower with cooling and/or heating equipment, connected to ducts that transport indoor air to and from.

Air-handling unit (AHU)

See air handler.

Air leakage

Uncontrolled ventilation through gaps in the air barrier. Typical sites of air leakage include around windows, pipes, wires and other penetrations.

Air-impermeable insulation

An insulation having an air perma­nence equal to or less than 0.02 L/s-m² at 75 Pa pressure differ­ential tested according to ASTM E 2178 or E 283.

Air sealing

The systematic approach to reducing air leakage in a building.

Albedo

The ratio of reflected light to incident light.

Altitude adjustment

The input modification for a gas appliance installed at a high altitude. When a gas appliance is installed more than 2000 feet above sea level, The installer may reduce its input rating according to manufacturers’ specifications.

Ambient

Of the surrounding area or environment.

Ambient air

Air in the habitable space. Also the air around a human observer.

Ambient lighting

Lighting spread throughout the lighted space for safety, security, and aesthetics.

American Gas Association (AGA)

A trade association represent­ing American natural gas supply companies. AGA collaborates with ASC and NFPA on the National Fuel Gas Code.

American National Standards Institute, Inc. (ANSI)

A private non-profit organization that oversees the development of volun­tary consensus standards for products, services, processes, sys­tems, and personnel in the United States.

American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE)

A technical society for individuals and organizations interested in heating, ventilation, air-condition­ing, and refrigeration. ASHRAE publishes standards and guide­lines relating to HVAC systems and issues.

American Society for Testing and Materials (ASTM)

A stan­dards organization that develops and publishes voluntary con­sensus technical standards for a wide range of materials, products, systems, and services.

Amperage

The rate that electrical current flows through an appliance at any given time; also called current.

Ampere

A unit that measures the rate that electrons move through a conductor.

Anemometer

A device that measures air speed, used in HVAC work to determine flow rates at registers.

Annual Fuel Utilization Efficiency (AFUE)

A laboratory-derived efficiency for heating appliances that accounts for chimney losses, jacket losses, and cycling losses, but not distribution losses, fan energy, or pump energy.

Annual return

The annual savings divided by the initial cost of an ECM, expressed as a percent.

Appliance

Any device powered by electricity or combustible fuel.

Approach temperature

The temperature difference between the fluid inside a heat exchanger and the fluid outside of it.

Aquastat

A heating control device that controls the burner or the circulator in a hydronic heating system.

Arc-fault circuit interrupter (AFCI)

A circuit breaker that dis­connects a circuit when it detects an electrical arc.

Area

Length x width = area.

As-measured carbon monoxide

A calculation of CO in parts per million (ppm) of a combustion-gas sample with the excess air (oxygen, O2), diluting the CO concentration removed by the calculator in the fuel-gas analyzer.

ASHRAE

American Society of Heating, Refrigerating, and Air-Conditioning Engineers. International technical society which develops standards for those concerned with refrigeration pro­cesses and the design and maintenance of indoor environments.

ASHRAE 62.2-20xx

Indoor air quality standard developed for low-rise residential buildings. Defines the roles of, and mini­mum requirements for mechanical and natural ventilation sys­tems and the building envelope.

Asbestos

A fibrous mineral with fireproofing and insulating characteristics manufactured into a variety of building materi­als. Small, sharp, asbestos fibers are a known carcinogen when inhaled.

Association of Energy Engineers (AEE)

A professional organiza­tion for energy engineers. AEE offers many certification pro­grams, including energy auditors and other energy experts.

Association of Home Appliance Manufacturers (AHAM)

Trade association representing the appliance manufacturing industry

Asthma

An acquired respiratory illness with strong correlation to buildings, moisture problems, and pets.

Atmospheric appliance

A combustion appliance that burns and exhausts its combustion gases at atmospheric pressure.

Atmospheric pressure

The weight of air and its contained water vapor on the surface of the earth. At sea level this pressure is 101,325 pascals or 14.7 pounds per square inch.

Attic

The unfinished space directly between the ceiling assem­bly of the top story and the roof assembly.

Attic, habitable

A finished or unfinished area, not considered a story. See the IRC for specific requirements.

Audit

The process of identifying energy conservation opportu­nities in buildings.

Auxiliary heat

Electric resistance heat in a heat pump that heats the building when the compressor isn’t able to provide the entire heat capacity needed for cold weather.

Awning window

Awning windows are essentially casement win­dows that swing vertically.

B-vent

A double-wall pipe for gas and propane-fired combus­tion appliances.

Backdrafting

Continuous spillage of combustion gases from a vented combustion appliance into the conditioned space.

Backdraft 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.

Baffle

1. A lightweight plate that directs air from a soffit over attic insulation and along the bottom of the roof deck to venti­late the attic and cool the roof deck. 2. A plate or strip designed to retard or redirect the flow of flue gases.

Balance point

The outdoor temperature at which no heating is needed to maintain indoor comfort.

Ballast

A coil of wire or electronic device that provides a high starting voltage for a lamp and also limits the current flowing through it

Balloon framing

A method of construction in which the vertical framing members (studs) are continuous pieces running the entire height of the wall.

Band joist

See - Rim joist

Barometric vent damper

A device installed in the heating unit vent system to control draft. Usually used on oil-fueled heaters or gas heaters with power burners

Barrier

Material used to block passage or movement.

Basement

The portion of a building that is partly or completely below grade.

Batt

A blanket of preformed fibrous insulation designed to fill cavities.

Beam

A strong horizontal building support used to carry the weight of a floor or roof.

Belly blow

A process for re-insulating floor cavities with blown-in insulation.

Belly return

A configuration found in some mobile homes that uses the belly cavity as the return side of the heating/cooling dis­tribution system.

Belt rail

A horizontal wall support for fastening siding.

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.

Blocking

A construction element or material used to strengthen or to prevent the movement of air or insulation into or out of building cavities.

Block frame

A non-finned window frame for new or retrofit installation in a rough opening.

Blower door

A diagnostic tool used to quantify and locate air leakage in the building envelope and to help prioritize the air sealing protocols.

Blow-down

The act of removing water from a boiler to remove sediment and suspended particles from the boiler water.

Blower

A squirrel-cage fan in a furnace or air handler.

Blown insulation

A loose-fill insulation that is blown into attics and building cavities using an insulation blowing machine.

Board foot

An American measurement of lumber volume. A board foot equals 144 cubic inches of wood, or 12”x12”x1”.

Boiler

A fossil fuel appliance used for producing hot water or steam as the medium to distribute heat to the dwelling unit.

Boot

A duct section that connects between a duct and a register or between round and square ducts

Bonus room

A room that is substandard in some way and not listed in a home’s salable features.

Borescope

A flexible tube with a light and camera or viewer at one end. Inspectors use borescopes to look into wall cavities and other tight spaces, otherwise impossible to inspect.

Boundary

Defines where one area ends and another begins.

Branch circuit

An electrical circuit used to power receptacles and lights within a home.

Branch duct

An air duct which branches from a main duct.

Brightness

The intensity of the sensation derived from viewing a lit surface. Measured in footlamberts or candelas per square meters. It is also called 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.

BTUh

British Thermal Units per hour.

Building cavities

The spaces inside walls, floors, and ceilings between the interior and exterior sheeting

Building envelope

The area of the building that encloses its con­ditioned and unconditioned spaces.

Building Performance Institute (BPI)

Organization supporting the development of a highly professional building performance industry through individual and organizational credentialing and a quality assurance program.

Building science

A complex perspective on buildings, using con­temporary technology to analyze and solve problems of design, construction, maintenance, safety, and energy efficiency.

Building shell

Separates a building’s indoors from the outdoors.

Bulk moisture

Large amounts of water intrusion, for example from wind-driven rain or sub-surface water.

Burner

A device that facilitates the burning of a fossil fuel, like gas or oil.

Butyl-backed tape

Heavy-duty, pressure-sensitive sealant or gas­ket.

Bypass

An air leakage site that allows air to leak into or out of a building flowing around the air barrier and insulation.

Cad cell

A flame sensor composed of the chemical compound cadmium sulfide. Its purpose is to sense whether a flame is pres­ent during a burner cycle. If the cad cell doesn’t detect a flame, it shuts the burner off.

Calibration

Comparison of the test results of an instrument to a known reference point.

Call-back

Having a weatherization team return to a job site to perform work not done or to redo work done unsatisfactorily.

Can light

A light fixture (or can) that is set into the ceiling. Also called a recessed light fixture.

Cantilever

A projecting structure, such as a beam, that is sup­ported at one end and carries a load at the other end or along its length.

Cantilevered floor

A floor that extends beyond the foundation of the framed structure below it.

Cape Cod

A house design featuring a finished attic space, also called a one-and-a-half story.

Capillary action

The ability of water to move through materials, even upward against gravity, through small tubes or spaces.

Capillary barrier

A material or air space designed to stop capil­lary action from carrying water into a building.

Carbon dioxide (CO2)

A heavy, colorless, nonflammable gas formed by the oxidation of carbon, by combustion, and by the respiration of plants and animals. One of two main products of complete combustion of a hydrocarbon (the other is water vapor).

Carbon monoxide (CO)

Carbon monoxide is a tasteless, odor­less, colorless and poisonous gas that is a by-product of incom­plete combustion of fossil fuels. It is usually caused by a lack of air to support combustion or impingement of the flame.

Carcinogen

A material known to cause cancer.

Casement window

Casement windows have a single operable hopper style sash that swings upward horizontally, or more commonly that swings outward on a vertical plane. Casement window frames that have gone out of square due to settling can stick and quite possibly render these types of windows inopera­ble.

Casing

Decorative molding or trim around a window or door.

Cathedral ceiling

A sloped ceiling insulated between the roof deck and the finish ceiling material.

Cathedralized attic

An attic that is insulated at the underside of the roof deck rather than at the ceiling.

Caulking

Mastic compound for filling joints and cracks.

Celsius (°C)

The metric temperature scale used in Europe and most other countries. Water freezes at 0°C and boils at 100°C.

Cellulose insulation

Insulation, packaged in bags for blowing, made from newspaper or wood waste and treated with a fire retardant.

Centigrade

Another word for Celsius (°C)

Central heating system

The primary heating system of the dwelling unit including the heat producing appliance along with the return and supply system for heat distribution.

Certification

Recognition by an independent person or group that someone can competently complete a job or task, frequently demonstrated by passing an exam.

Certified renovator

A person authorized by the EPA to perform repair and renovation projects that disturb lead-based paint.

CFM₅₀

The amount of cubic feet per minute of air moving through a structure. Measured at 50-pascals pressure during a blower door test.

CFMn

The amount of cubic feet of air moving through a struc­ture under typical, natural conditions.

CFM - Cubic feet per minute

An American measurement of air­flow equal to 0.472 liters per second.

Chaseway

Cavity within a building with a purpose of conveying pipes, ducts, etc. through the building. Chaseways, such as plumbing walls, are common sites for air leakage.

Chimney

A building component designed for the sole purpose of assuring combustion by-products are exhausted to the exte­rior of the building.

Chimney connector

A pipe that connects a fuel-burning appli­ance to a chimney. Also see vent connector.

Chimney flue

A passageway in a chimney for conveying com­bustion gases to the outdoors.

Chimney chase

The framing and other building materials that surround the chimney.

Circuit breaker

A device found in a Circuit Panel Box that com­pletes an electrical circuit. This breaker disconnects the circuit from electricity when it senses an overload of current.

Cladding

The exterior covering or coating on a structure, such as wood siding, stucco, or brick veneer.

Clean and tune (C&T)

A procedure performed on a heating or cooling system by a qualified technician to optimize its effi­ciency.

Cleanout

An opening in a chimney (usually at its base) to allow inspection and the removal of ash or debris.

Clearances

Allowable distances between heat-producing appli­ances, chimneys, or vent systems and combustible surfaces.

Climate zone

An area with a prevailing climate that distin­guishes it from other areas by parameters such as temperature, rainfall, and humidity.

Codes

Any set of standards set forth and enforced for the pro­tection of public health and building durability.

Co-efficient of performance (COP)

A dimensionless number representing the ratio of a heat pump or air conditioner’s output in watt-hours of heat moved divided by watt-hours of electrical input.

Coil

A snake-like piece of copper tubing surrounded by rows of aluminum fins that clamp tightly to the tubing and aid in heat transfer.

Coil stock

Sheet metal packaged as a coil in various widths.

Cold-air return

Ductwork that draws house air into the air han­dler for reheating by a furnace.

Cold roof

A roof design where the roof temperature is equalized from top to bottom by roof ventilation and/or roof insulation to prevent ice damming.

Collar beam

A horizontal piece in roof framing that provides structural strength by connecting opposite rafters.

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

A measurement of the warmness (redness or yellowness) or coolness (blueness or whiteness) of a light source in the Kelvin temperature scale.

Column

A vertical building support usually made of wood or steel.

Combustible

Means something will burn, although not neces­sarily readily.

Combustible gas leak detector

 A device for determining the presence and general location of combustible gases in the air.

Combustion

The act or process of burning. Oxygen, fuel, and a spark must be present for combustion to occur.

Combustion air

Air that chemically combines with a fuel during the combustion process to produce heat and combustion gases, mainly carbon dioxide and water vapor.

Combustion analyzer

A device used to measure and analyze combustion gases for efficiency and safety.

Combustion appliance

 Any appliance in which combustion occurs.

Combustion appliance zone (CAZ)

The closed space or area that holds one or more combustion appliances.

Combustion appliance zone (CAZ) testing

Diagnostics per­formed to ensure that combustion appliances work properly and that house pressures allow combustion gases to vent.

Combustion byproducts

Gases, vapors, and particulates pro­duced whenever carbon-based fuels are burned.

Combustion chamber

The area inside the heat exchanger where the flame burns.

Combustion efficiency

Synonymous with steady-state efficiency.

Combustion gases

Combustion byproducts.

Commissioning

The process of testing and adjusting building mechanical systems.

Common vent

The portion of the vent or chimney that the combustion products of multiple appliances pass through.

Compact fluorescent lamp (CFL)

A small fluorescent light engi­neered to fit in an Edison base of an incandescent fixture.

Compartmentalization

Air-sealing that prevents air from migrating from one dwelling or zone of a multifamily building to another.

Competency

Demonstrated ability to perform a job or task.

Compressor

A motorized pump that compresses the gaseous refrigerant and sends it to the condenser where heat is released.

Concentrically constructed direct-vent

A direct-vent appliance that has an exhaust-gas vent and a combustion-supply-air vent arranged in a concentric fashion: one pipe is inside the other with a space between the walls of each.

Condensate

Vapor condensed back to a liquid. For example: water or refrigerant.

Condensate receiver

A tank for catching returning condensate water from a steam heating system or condensed refrigerant from a condenser.

Condense

When a gas turns into a liquid as it cools, it con­denses. When a gas condenses into a liquid it releases heat.

Condenser

The coil in a refrigeration system where the refriger­ant condenses and releases heat.

Condensing furnace

A high-efficiency furnace that removes latent heat from combustion gases by condensing water vapor out of the combustion gases.

Conditioned

Intentionally heated or cooled areas of a building.

Conditioned air

Air that has been heated, cooled, humidified, or dehumidified to provide comfort.

Conditioned space

For energy purposes, space within a building that is provided with heating and/or cooling equipment or sys­tems, or that communicates directly with a conditioned space. For mechanical purposes, an area, room or space being heated or cooled by any equipment or appliance.

Conductance

The quantity of heat, in BTUs, that flows through one square foot of material in one hour, when there is a one degree Fahrenheit temperature difference between both sur­faces. Conductance values are given for a specific thickness of material.

Conduction

Conduction is the transfer of heat through a mate­rial by molecular vibration.

Conductivity

The quantity of heat that flows through one square foot of homogeneous material, one inch thick, in one hour, when there is a temperature difference of one degree Fahr­enheit between its surfaces.

Confined space

A space, defined for the purpose of evaluating combustion air, with a volume of less than 50 cubic feet per 1,000 BTU per hour of the total input rating of all combustion appliances installed in that space.

Contractor

Any person or entity that provides services under contract, and not as employees of the purchasing agency.

Contrast

Difference in brightness measured by the relationship between an object’s brightness and the brightness of its back­ground.

Control circuit

An electrical circuit that activates or deactivates a power circuit or opens and shuts a valve.

Convection

The transfer of heat caused by the movement of a fluid like water or air. When a fluid becomes warmer it becomes lighter and rises.

Convective loop

Heat flow resulting from fluid flow between surfaces of different temperatures.

Cooling load

The maximum rate of heat removal required of an air conditioner when the outdoor temperature and humidity are at a standard worst-case outdoor condition.

Core competencies

Essential skills for weatherization workers, defined by the Weatherization Trainers Consortium.

Cost effective

Having an acceptable payback, return-on-invest­ment, or savings-to-investment ratio.

Crawl space

The low space beneath the ground floor of a build­ing that gives workers access to wiring and plumbing.

Crew leader

A crew leader is a residential energy professional who supervises weatherization tasks specified in the scope of work.

Critical framing juncture

An intersection of framing members and envelope components that require special attention during air-sealing and insulation.

Cross section

A view of a building component drawn or imag­ined by cutting through the component.

Crosswise floor-joists

 Mobile home joist configuration where the main duct is located beneath the floor joists and connected by boots to the sub-floor.

Cubic foot per minute (CFM)

A measurement of volumetric air­flow rate. See also CFM₅₀ and CFMn.

Curtain wall

A wall between columns and beams that supports no weight but its own.

Dado

A rectangular groove cut into wood to create a structural joint.

Decatherm

One million BTUs or 10 therms.

Decking

The wood material structural sheathing installed over the rafters to support the roofing.

Decommissioning

Removing or retiring equipment from active service including disposing of hazardous material in an approved way.

Deferral of services

Postponement or denial of weatherization services to the client.   

Dehumidification

The removal of water from the air. Excess humidity can cause mold.

Degree days (DD)

A cumulative measurement of outdoor tem­perature calculated by adding the temperature differences between an indoor temperature of 65°F and the daily average outdoor temperature for a one-year period.

Delta-T

Temperature difference.

Demand

The peak need for electrical energy. Some utilities levy a monthly charge for demand.

Demand-side management (DSM)

The planning and imple­mentation of utility-sponsored conservation of electricity or gas.

Dense packing

Blowing insulation with sufficient force to create a high density to reduce settling and minimize air leakage and air convection.

Density

The weight of a material divided by its volume, usually measured in pounds per cubic foot.

Depressurization tightness limit (DTL)

A calculation procedure, expressed in units of CFM₅₀, performed to estimate the building tightness level at which combustion appliances might backdraft when the house is under conditions of worst-case depressuriza­tion. The DTL sets a low limit for air sealing that may or may not be lower than the BTL for the same house.

Depressurize

Cause to have a lower pressure or higher vacuum with respect to a pressure reference point such as the outdoors.

Desiccant

A liquid or solid material used to absorb water or water vapor.

Design temperature

A high or low temperature, based on cli­mate history, used for designing heating and cooling systems when calculating heating and cooling loads.

Desk monitoring

Weatherization monitoring activities per­formed through review of paperwork.

De-superheater

A heat exchanger that removes the superheat from a compressed refrigerant and transfers that heat to another fluid, usually water.

Dew point

The warmest temperature of an object in an environ­ment where water condensation from the surrounding air would form on that object.

Diffusion

Movement of water vapor through a material as a function of the vapor pressure across a material and the vapor permeability of that material. See also: vapor permeable

Dilution air

Air that enters through the dilution device—an opening where the chimney joins to an atmospheric-draft com­bustion appliance

Dilution device

A draft diverter, draft hood, or barometric draft control between an atmospheric-draft combustion appliance and its chimney.

Direct current

An electric current flowing in only one direction.

Direct leakage

Air enters and exits at same location; occurs at direct openings to outdoors.

Direct-vent appliance

A combustion appliance for which all combustion gases are vented to the outdoors through an exhaust vent pipe and all combustion supply air is supplied to the com­bustion chamber from the outdoors through a separate, dedi­cated supply-air pipe. See also sealed-combustion

Discount rate

The interest rate at which expected future cash savings can be discounted for the time value of money.

Distribution system

A system of wires, pipes, or ducts that dis­tributes energy.

DOE

The United States Department of Energy.

Domestic hot water (DHW)

Refers to a separate, closed system to heat potable (drinkable) water and supply it to the dwelling unit for washing, bathing, etc.

Dominant duct leakage

To identify either dominant supply or return leaks in a forced-air distribution system by measuring house pressure.

Door casing

A wooden trim around doors that covers the seam between the jamb and the wall.

Door stop

The wood trim fastened to the inside of the door jamb that stops the door’s swing.

Dose

The amount of pollutant that enters a human body, exposed to the pollutant.

Dormer

A framed structure projecting above a sloping roof sur­face, and normally containing a vertical window.

Double-hung window

Double-hung windows have operable upper and lower sashes that slide vertically in a channel.

Downflow

Airflow configuration in a furnace where air flows from above the air handler and discharges from the bottom.

Downflow furnace

Furnace type where the blower is located at the top of the furnace cabinet and air is forced downwards across the heat exchanger and into the ducts located in below the furnace.

Downstream

Away from the source of the flow.

Draft

A pressure difference that causes combustion gases or air to move through a vent connector, flue, chimney, or combustion chamber.

Draft diverter

A device located in gas appliance flue pipe. Used to moderate or divert draft that could extinguish the pilot or interfere with combustion.

Draft fan

A mechanical fan used in a venting system to aug­ment the natural draft in gas- and oil-fired appliances. These electrically operated, paddle-fan devices are installed in fur­naces.

Draft gauge

Device for testing chimney draft.

Draft hood

See draft diverter.

Draft inducer

A fan that depressurizes the combustion chamber or venting system to move combustion products toward the out­doors.

Draft regulator

A self-regulating damper attached to a chimney or vent connector for the purpose of controlling draft.

Drainage plane

A space that allows water storage and drainage in a wall cavity, adjacent to or part of the water-resistive barrier.

Dropped-down belly

 Mobile home configuration where a hump is formed in the floor by the rodent barrier and insulation going around the main duct attached to the floor’s bottom.

Dropped soffit

A lowered part of the ceiling in a home.

Drywall

Gypsum interior wallboard used to produce a smooth and level interior wall surface and to resist fire. Also called gyp­sum wall board or sheetrock.

Dry-bulb temperature

Normal ambient air temperature mea­sured by a thermometer.

Duct blower

A blower-door-like device used for testing duct leakiness and airflow.

Duct board

Rigid board composed of insulation material with one or both sides faced with a finishing material, usually alumi­num foil.

Duct boot

Transition piece that connects the main duct to the floor and is often vulnerable to failure.

Duct-induced pressure differences

Pressure differences between rooms in a building caused by the ducted air delivery system, can be due to supply ducts, return ducts, or both.

Duplex

Any structure which consists of two separate dwelling units in one building.

Dwelling unit

A house, including a stationary mobile home, an apartment, a group of rooms, or a single room occupied as sepa­rate living quarters.

Eave

The part of a roof that projects beyond its supporting walls (See - Soffit).

Eave chute

Device that maintains air space between the insula­tion blanket and the roof sheathing and prevents insulation from clogging eave vents.

Eave vent

Vent opening located in the soffit under the eaves of a house to allow the passage of air through the attic and out the roof vents.

Economizer

A subsystem in an HVAC system that caves energy by using favorable outdoor temperature and humidity to condi­tion building air.

Efficiency

The ratio of output divided by input.

Efficacy

The number of lumens produced by a watt used for lighting a lamp. Used to describe lighting efficiency. Synonym: Effectiveness.

Egress window

A window with a defined opening size for the purpose of fire escape.

Elastomeric

A characteristic of a material that is flexible and permits joint movement.

Elastomeric coating

Polymeric material, such as acrylic, that is used to coat roof leaks and to reduce solar heat gain.

Electrical load

Term for the wattage drawn by a electrical device or the device itself.

Electric service

The electric meter and main switch, usually located outside the building.

Electro-mechanical

Describes controls where an automatic mechanical device like a bimetal or bulb-and-bellows does the switching.

Emergency heat

1. A heating device that doesn’t require electric­ity used during an emergency. 2. Or electric-resistance heating elements used for heating in case a heat pump’s compressor fails.

Emittance

The rate that a material emits radiant energy from its surface. Also called emissivity.

Encapsulation

Any covering or coating that acts as a barrier between the hazard, such as lead-based paint, and the indoor environment.

Enclosure

The building shell or building envelope. The exterior walls, floor, and roof assembly of a building.

Energy

A quantity of heat or work

Energy audit

The process of identifying energy conservation opportunities in buildings.

Energy auditor

One who inspects and surveys the energy use of buildings in order to promote energy conservation.

Energy conservation measures (ECM)

Building components or products installed to reduce the building's energy consumption.

Energy consumption

The conversion or transformation of potential energy into kinetic energy for heat, light, electricity, etc.

Energy education

Communication used by weatherization staff to inform customers of ways to reduce energy consumption by altering their behavior.

Energy efficiency

Term used to describe how efficiently a build­ing component uses energy.

Energy efficiency ratio (EER)

A measurement of energy effi­ciency for room air conditioners. The EER is computed by dividing cooling capacity, measured in British Thermal Units per hour (Btuh), by the watts of electrical power. (See - Seasonal Energy Efficiency Rating or SEER)

Energy factor

The fraction of water heater input remaining in 64 gallons per day of hot water flowing from a water heater.

Energy Information Administration (EIA)

Section of the U.S. Department of Energy providing statistics, data, and analysis on resources, supply, production, and consumption for all energy sources.

Energy rater

A person who evaluates the energy efficiency of a home and assigns a performance score, a certification received from HERS (Home Energy Rating System).

Energy-recovery ventilator (ERV)

A ventilator that recovers latent and sensible energy from the exhaust airstream and imparts it to the incoming airstream.

Enthalpy

The internal heat of a material measured in Btus per pound.

Entropy

Heat unavailable to a closed thermodynamic system during a heat transfer process.

Envelope

The building shell. The exterior walls, floor, and roof assembly of a building. Also referred to as the enclosure.

Environmentally sensitive

Highly susceptible to adverse effects of pollutants.

EPA, U.S. Environmental Protection Agency

EPA protects human health and safeguards the natural environment.

Equivalent length

The length of straight pipe or duct that has equivalent resistance to a pipe fitting or duct fitting. Used for piping and duct design.

Equivalent duct length (EDL)

A measure of how much static pressure a fan has to overcome.

Equivalent leakage area (ELA)

Calculation, in square inches, of the total area of all holes and cracks in a structure. The leakage area is then combined to represent one total leakage area.

Evaporation

The change of a liquid to a gas. Evaporation is the key process in the operation of air conditioners and evaporative coolers. Evaporation absorbs heat.

Evaporative cooler

A device for cooling homes in dry climates by reducing the temperature of incoming air by the evaporation of water.

Evaporator

The heat transfer coil of an air conditioner or heat pump that cools the passing air as the refrigerant inside the coil evaporates and absorbs the air’s heat.

Excess air

Air in excess of what is needed for combustion.

Exfiltration

The movement of air out of a building.

Expanded polystyrene

White polystyrene insulation.

Expanding foam

An insulation product designed to expand and harden upon contact with the air. Available in canisters with spray nozzles that make it easy to apply foam in a wide variety of situations.

Expansion valve

A valve that meters refrigerant into the evapo­rator.

Exposure

A specific assessment of pollutant amount and dura­tion that a human is exposed to.

Fahrenheit

A temperature scale used in the United States and a few other countries. On the Fahrenheit scale, water boils at 212 degrees and freezes at 32 degrees.

Fan-assisted combustion

A combustion appliance with an inte­gral fan to draw combustion supply air through the combustion chamber.

Fan control

A bimetal thermostat that turns the furnace blower on and off as it senses the presence of heat.

Fan-off temperature

In a furnace, the supply-air temperature at which the fan control shuts down the blower fan.

Fan-on temperature

In a furnace, the supply air temperature at which the fan control activates the blower fan.

Federal Energy Management Program (FEMP)

A program of DOE that implements energy legislation and presidential direc­tives. FEMP provides project financing, technical guidance and assistance, coordination and reporting, and new initiatives for the federal government.

Feeder wires

The wires connecting the electric meter and main switch with the main panel box indoors.

Fenestration

Window and door openings in a building's wall.

Fiberglass

A fibrous material made by spinning molten glass used as an insulator and heat loss retardant.

Field testing

Evaluation of a trainee’s abilities conducted on-site, rather than in a classroom.

Fill tube

A plastic or metal tube used to blow insulation inside a building cavity.

Fin comb

A comb-like tool used to straighten bent fins in air conditioning and heat-pump coils.

Final inspection

An evaluation of a weatherization job at or after its completion.

Finished attic

An attic that was converted to living space by the construction of dormers and knee walls.

Finned tube

A length or coil of pipe with heat transfer fins attached for heat transfer.

Fire barrier

A fire-resistance-rated building assembly, designed to contain a fire for a particular time period.

Fire blocking

Building materials installed to resist the free pas­sage of flames and smoke, to adjacent areas of the building.

Fire resistance

The property of building materials or assemblies that prevents or retards the passage of heat, hot gases, or flames during a fire.

Fire resistance rating

The period of time a building element, component or assembly maintains the ability to confine a fire, continues to perform a given structural function, or both.

Fire stop

Framing member designed to stop the spread of fire within a wall cavity.

Fire tape

Tape and drywall-finishing compound applied to cre­ate a fire-resistant assembly.

Firewall

A fire-resistance-rated smoke-tight wall with protected openings that restricts the spread of fire. A firewall extends con­tinuously from the foundation to or through the roof. The fire­wall is designed to remain standing even if the assemblies on either side collapse during a fire.

Flame impingement

The contact of flame against an object, such as a metal heat exchanger.

Flame rectification

A modern method of flame sensing that uses the flame itself as a conductor in the flame-safety circuit.

Flame-retention head burner

A high efficiency oil burner that produces a hotter flame and operates with a lower airflow, com­pared to older oil burners.

Flame roll-out

Fuel gas combustion process occurring outside the normal combustion area of a combustion appliance.

Flame safety control

A control device used to stop the flow of fuel to the burner if the fuel doesn’t ignite.

Flame spread

A fire rating for materials in a fire test that com­pares the spread of flame to red oak, which has a flame spread of 100.

Flammability

The rating for building materials that will burn readily when exposed to a flame.

Flammable

Combustible; readily set on fire.

Flashing

Waterproof material used to prevent leakage at inter­sections between building assemblies or penetrations through the building envelope.

Floor joists

The framing members that support the floor.

Flue

The channel or pipe that conveys combustion gases.

Flue gas

Combustion gases, mainly carbon dioxide, water vapor, nitrogen, and oxygen.

Flush flange

A window frame designed to provide a finished exterior appearance over a flat exterior surface like stucco.

Foam board

Plastic foam insulation manufactured most com­monly in sheets.

Foam compatible adhesive

Adhesive that is manufactured to safely adhere foam to itself and other materials.

Foot candle

A measure of light striking a surface.

Footing

The part of a foundation system that actually transfers the weight of the building to the ground.

Forced draft

A vent system for which a fan installed at the com­bustion appliance moves combustion gases to the outdoors with positive static pressure in the vent pipe. Because of this positive pressure, the vent connector must be air-tight.

Fouling

The deposit of particles and fluids on a heat exchanger or other HVAC component.

Friable

Easily broken into small fragments or reduced to pow­der, as with asbestos.

Frost line

The maximum depth of the soil where water will freeze during the coldest weather.

Fuel escalation rate

Annual escalation rate of fuel prices based on the annual energy price forecasts of DOE's Energy Informa­tion Administration.

Furnace

An appliance that produces and distributes warm air throughout the dwelling unit.

Furring

Thin wood strips fastened to a wall or ceiling surface as a nailing base for finish materials.

Fuse

A current carrying element that melts if too much current flows in an electric circuit.

Gable

The triangular section of an end wall formed by the pitch of the roof.

Gable roof

A roof shape that has a ridge at the center and slopes in two directions.

Gable vent

A screened vent installed at or near the peak of a roof gable that allows air exchange between the attic and out­doors.

Gallons per minute (GPM)

The unit for measuring water flow in a supply pipe or heat-distribution pipe or oil flow in a burner.

Gasket

Elastic strip that seals a joint between two materials.

General heat waste

Pertaining to general weatherization materi­als that DOE believes are cost-effective.

Glare

Any bright light or light reflection that annoys, distracts, or reduces visibility.

Glass load factor

A number combining glass’s solar heat trans­mission and its heat conduction. Used for cooling load calcula­tions.

Glazing

Pertaining to glass assemblies, installation or windows.

Glazing compound

A flexible, putty-like material used to seal glass in its sash or frame.

Grade

The level of the ground around a building.

Grantee

The individual or organization that receives a grant.

Gravity furnace

A central heating system that uses natural grav­ity to distribute heated air or water throughout the dwelling unit as opposed to forced circulation, using pumps or blowers.

Ground fault circuit interrupter (GFI or GFCI)

An electrical connection device that breaks a circuit if current flows in a grounding wire.

Ground-moisture barrier

A plastic material covering the ground that is both a vapor barrier and a water barrier, which protects building materials from excessive relative humidity.

Gusset

A metal or wood plate added to the surface of a joint to strengthen the connection.

Gypsum board

A common interior sheeting material for walls and ceilings made of gypsum rock powder packaged between two sheets of heavy building paper. Also called drywall, sheet­rock, gyprock, or gypboard.

Habitable space

A building space intended for continual human occupancy. Examples include areas used for sleeping, dining, and cooking, but not bathrooms, toilets, hallways, storage areas, closets, or utility rooms. See occupiable space and conditioned space.

Hallway return or hallway return system

A type of mobile home air distribution system. The mobile home heating or cooling system receives return air through a central trunk line beneath the hallway.

Hatch

 A rectangular hole in a horizontal building assembly like a floor or ceiling that allows access

Hazardous Material

A particular substance that is considered a danger to the client or crew.

Head

Foot pounds of mechanical energy per pound of fluid cre­ated by a pump to overcome gravity or friction.

Head jamb

Groove at the top of the window that allows the window sashes to slide into place and sit inside the window frame.

Health and safety (H&S)

Provision included in a 1976 law change for the Weatherization Assistance Program. WAP now considers the health and safety of low-income families, as well as reducing their energy costs.

Heat

Molecular movement

Heat anticipator

A device in a thermostat that causes the ther­mostat to turn off before room temperature reaches the thermo­stat setting, so that the house doesn’t overheat from heat remaining in the heater and distribution system after the burner shuts off.

Heat capacity

The quantity of heat required to raise the tem­perature of 1 cubic foot of a material 1 degree F.

Heat exchanger

The device in a heating unit that separates the combustion chamber from the distribution medium and trans­fers heat from the combustion process to the distribution medium.

Heat gains

Term used to mean unwanted heat that accumulates in homes, making mechanical cooling desirable or necessary.

Heat loss

The amount of heat escaping through the building shell as measured for a specific period of time (month, year, etc.)

Heat pump

A type of heating/cooling unit, usually electric, that uses a refrigeration system to heat and cool a dwelling.

Heat-recovery ventilator

A central ventilator that transfers heat from exhaust to intake air.

Heat transmission

Heat flow through the walls, floor, and ceil­ing of a building, not including air leakage.

Heat transfer coefficient

See U-factor.

Heating degree day(s) (HDD)

See: Degree days

Heating load

The maximum rate of heat conversion needed by a building during the coldest weather.

Heating seasonal performance factor (HSPF)

Rating for heat pumps describing how many Btus of heat they transfer per watt-hour of electricity they consume.

High-efficiency particulate air (HEPA) vacuum

A vacuum cleaner that uses a high-efficiency particulate air (HEPA) filter.

High limit

A thermostat that turns the heating element of a fur­nace or boiler off if it senses a dangerously high temperature.

Hinges

The metal objects that attach a door to a door jamb, nor­mally with screws.

Hip roof

A roof with two or more adjacent roof surfaces, joined along a sloping “hip.”

Home energy index

The number of BTUs or kWh of energy used by a home, divided by its area of conditioned square feet.

Home energy rating systems (HERS)

A nationally recognized energy rating program that give builders, mortgage lenders, sec­ondary lending markets, homeowners, sellers, and buyers a pre­cise evaluation of energy losing deficiencies in homes.

Home heating index

The number of Btus of energy used by a home divided by its area in square feet, then divided by the number of heating degree days during the time period.

HOME Program

A program created under Title II (the Home Investment Partnership Act) of the National Affordable Hous­ing Act of 1990. Provides funds for states to expand the supply of decent and affordable housing for low-income people.

Home Ventilating Institute (HVI)

A non-profit association of manufacturers of residential ventilating products offering a vari­ety of services including testing, certification, verification, and marketing programs.

Hot roof

An unventilated roof with insufficient insulation to prevent snow melting on the roof and the creation of ice dams.

House as a system

The concept that many components of a house interact, affecting the home’s comfort and performance.

House depressurization limit

A selected indoor negative pres­sure; expressed in Pascals, immediately around vented combus­tion appliances that use indoor air for combustion supply air.

House pressure

The difference in pressure between the indoors and outdoors measured by a manometer.

House wrap

A generic term for the modern version of the building’s water-resistive barrier.

HUD

U.S. Department of Urban Housing and Development

Humidistat

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 or grains of water vapor per pound of dry air.

HVAC

Heating, ventilation, and air-conditioning system. All components of the appliances used to condition a building’s indoor air.

Hydronic system

A heating system that uses hot water or steam as the heat-transfer fluid. Commonly called a hot-water heating system.

Hygrometer

A tool for measuring relative humidity. A psy­chrometer, which uses two thermometers, one with a dry bulb and one with a wet bulb, is a simple hygrometer.

IAQ

Indoor Air Quality. The quality of indoor air relative to its acceptability for healthful human habitation.

I-beam

A rolled or extruded metal beam having a cross section resembling a capital I.

IC rated

Insulation Contact rating for light fixtures. IC housings may be in direct contact with fibrous insulation.

Ice dam

Ice that forms at the roof eaves during differential tem­peratures of a roof deck causing freezing and thawing.

IECC

International Energy Conservation Code

Ignition barrier

A material installed to prevent another mate­rial, often plastic foam, from catching fire.

Illumination

The light level measured on a horizontal plane in Foot Candles.

Inaccessible cavity

An area that is too confined to enter and/or maneuver in by an average worker.

Incandescent light

The common light bulb found in residential lamps and light fixtures and known for its inefficiency.

Inches of Water Column (IWC)

A non-metric unit of pressure difference. One IWC equals about 250 Pascals.

Incidental repairs

Under DOE rules, this term refers to the repairs on a dwelling unit to protect the performance and dura­bility of energy conservation measures.

Indirect leakage

Describes how air leaks into the home at one point and out at a different point. Indirect leakage is more diffi­cult to discover compared to direct leakage. Indirect leakage occurs through a dwelling’s bypasses or chaseways.

Indoor air quality (IAQ)

The quality of indoor air relative to its acceptability for healthful human habitation.

Induced draft

A vent system or combustion appliance for which a fan, installed at or very near the termination point of the appli­ance or the vent pipe, moves the combustion gases.

Infiltration

Infiltration refers to the movement of air into a building through cracks and penetrations in the building enve­lope.

Infrared

Pertaining to heat rays emitted by the sun or warm objects on earth.

Infrared camera

A special camera that “sees” temperature dif­ferences on surfaces, allowing the user to determine if a building assembly is insulated properly. This instrument is also useful for detecting air leakage if used with a blower door.

Infrared thermography

The science of using infrared imagers to detect radiant energy on building surfaces, which visualizes a building’s heat loss.

Input rating

The measured or assumed rat at which an energy-using device consumes electricity or fossil fuel.

Insolation

The amount of solar radiation striking a surface.

Inspector

A weatherization worker responsible for quality con­trol or quality assurance by making final inspections and in-progress inspections.

Inspection gap

A gap in foundation insulation left for the pur­pose of inspecting for insect infestation.

Instantaneous water heater

A water heater with no storage tank that heats water instantaneously as the water flows through it.

Insulated flex duct

A round duct composed of two flexible plas­tic tubes with tubular insulation and air barrier between the two.

Insulated glass

Two or more glass panes spaced apart and sealed in a factory.

Insulated glass unit (IGU)

Two or more glass panes spaced apart and sealed in a factory.

Insulation

A material used to resist heat transmission.

Insulation dam

A material that prevents fibrous insulation from flowing into an area where it isn’t necessary or wanted.

Insulation restrainer

A flexible material, such as netting or fab­ric, use to hold blown fibrous insulation in place.

Insulation shield

A fire-barrier erected around a heat producing device to prevent insulation from covering or contacting hot surfaces.

Intentionally conditioned

Conditioned by design and fitted with radiators, registers, or other devices to maintain a comfortable temperature.

Intermediate zone

A zone located between the building’s condi­tioned space and the outdoors, like a crawl space or attic.

Intermittent ignition device (IID)

A device that lights the burner on a gas appliance when the control system calls for heat, thus saving the energy wasted by a pilot light.

Internal gains

The heat generated by bathing, cooking, and operating appliances, that must be removed during the summer to promote comfort.

International Association of Plumbing and Mechanical Officials (IAPMO)

The industry trade group that develops the Uniform Mechanical Code and the Uniform Plumbing Code.

International Codes Council (ICC)

An international non-gov­ernmental organization for developing building safety, fire pre­vention, and energy efficiency codes (I-codes).

International Fuel Gas Code (IFGC)

Code that addresses the design and installation of fuel gas systems and gas-fired appli­ances through requirements that emphasize performance.

International Residential Code (IRC):

The most prominent building code in the US managed by the International Codes Council.

Interstitial space

Building cavity. Space between framing and other building components.

Intrusion

Air moving into and out of insulation without going through the wall or ceiling assembly.

Jalousie windows

A type of window usually associated with mobile homes with two or more panes of glass that pivot on a horizontal axis.

Jamb

The side or top piece of a window or door frame.

Jamb clips or plates

Structural devices used to fasten a block-frame window to its opening.

Job task analysis

A prioritized list of knowledge, skills, and abil­ities derived from analysis of a job.

Joist

A horizontal wood framing member that supports a floor or ceiling.

Joule

A unit of energy. One thousand joules equals 1 BTU.

Kerf

A slit made by cutting, often with a saw.

Kilowatt

A unit of electric power equal to 1000 joules per sec­ond or 3412 Btus per hour.

Kilowatt-hour

The most commonly used unit for measuring the amount of electricity consumed over time; one kilowatt of elec­tricity supplied for one hour. A unit of electric energy equal to 3600 kilojoules.

Knee wall

A short wall, often less than three feet in height. Knee walls are common in old houses with finished attic spaces.

Knee-wall attic

An triangular attic with short walls, usually under three feet in height.

Knob-and-tube wiring

Early standardized electrical wiring in homes consisting of insulated copper conductors supported by porcelain knobs and tubes.

Lamp

A light bulb.

Latent heat

The amount of heat energy required to change the state of a substance between a solid and a liquid, or from a liquid to a gas.

Lath

A support for plaster, consisting of thin strips of wood, metal mesh, or gypsum board.

Lawrence Berkeley National Laboratory (LBNL)

Member of the national laboratory system supported by DOE though its Office of Science. LBNL conducts research on building energy effi­ciency.

Lead RRP Program (RRP)

Firms that work on projects that dis­turb lead-based paint in homes, child care facilities and pre-schools built before 1978 must have their firm certified by EPA (or an EPA authorized state), use certified renovators who are trained by EPA-approved training providers and follow lead-safe work practices.

Leadership in Energy and Environmental Design (LEED)

A building certification system developed by the U.S. Green Build­ing Council.

Leakage ratio

Measurement of total square inches of air leakage area per 100 feet of building envelope surface area.

Light quality

The relative presence or absence of glare and brightness contrast. Good light quality has no glare and low brightness contrast.

Local ventilation

Ventilation at the source of building pollut­ants, also called spot ventilation. For example: kitchen and bath­room exhaust fans.

Loose-fill insulation

Fibrous insulation in small fibers that installers blow into a building assembly using a blowing machine.

Low-flow rings

Part of a blower door that forces air past the sen­sors fast enough to obtain a reliable reading.

Low-E

Short for “low emissivity”, which means the characteris­tic of a metallic glass coating to resist the flow of radiant heat.

Low expanding foam

Liquid-applied form that expands 20-30 times its liquid size.

Low water cutoff

A float-operated control to turn the burner off if a steam boiler is low on water.

Lumen

A unit of light output from a lamp.

Luminaire

A light fixture.

Main panel box

The electric 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.

Manifold

A tube with one inlet and multiple outlets, or multi­ple inlets and one outlet.

Manometer

A differential gauge used for measuring pressure.

Manufactured homes

Transportable homes that are faster and less expensive to build compared to site-built homes.

Mastic

A thick creamy substance used to seal seams and cracks in building materials, especially ducts.

Masonry

Stone, brick, or concrete block construction.

Mean radiant temperature (MRT)

The area-weighted mean temperature of all the objects in an environment.

Mechanical draft

A combustion appliance with induced draft of forced draft.

Meeting rails

The rail of each sash that meets a rail of the other when the window is closed.

Membrane

A barrier that separates two environments. Mem­branes may be permeable to the flow of air, water, and other flu­ids or particles.

Microclimate

A very localized climatic area, usually a small site or habitat.

Micron

A micrometer or 1/100,000 of a meter.

Mildew

Fungi that colonize organic building materials.

Minimum Efficiency Rating Value (MERV)

The dominant industry rating of the ability of HVAC air filters to remove parti­cles.

Mitigate

To make better or reduce some negative effect.

Mobile home belly

Part of a home that contains the insulation, duct system, and plumbing. It is enclosed by the sub- and fin­ished floor, with a rodent barrier underneath.

Mobile Home Energy Audit (MHEA)

A software tool that pre­dicts manufactured home energy consumption and recom­mends weatherization retrofit measures.

Moisture meter

An instrument for measuring the percentage of water in a substance.

Mold

A growth of minute fungi forming on vegetable or animal matter and associated with decay or dampness.

Monitor

The process through which a person, frequently a rep­resentative of a State or Federal agency, visits completed units to ensure that weatherization funding is spent appropriately.

Mortar

A mixture of sand, water, and cement used to bond bricks, stones, or blocks together.

Mortise

A recessed area cut into the wood framing member where a hinge or wood tongue fits.

Mud sill

A wood component attached to the foundation of a building that creates a means of attaching various components of the framing to the foundation.

Mullion

Vertical framing members that don't run the full length of the door.

Multifamily (MF) housing

A building with five or more residen­tial units.

Mushroom vent

A vent that has at the top of a vertical shaft a broad rounded cap that can be screwed down to close it.

Nail fin or flange

Semi-flexible strips of metal or plastic used to attach a window frame to the outside of a rough opening.

National Association for State Community Services Programs (NASCSP)

Assists States in responding to poverty issues. NASCSP members are state administrators of the Community Services Block Grant (CSBG) and U.S. Department of Energy's Weatherization Assistance Program (DOE/WAP).

National Electric Code (NEC)

A safety code regulating the elec­tricity use. The NEC is a product of the National Fire Protection Association.

National Energy Audit Tool (NEAT)

Created by Oak Ridge National Laboratories as a DOE approved audit qualifying for the 40% materials waiver. It is a computerized auditing tool for prioritizing energy conservation measures for houses.

National Fenestration Rating Council (NFRC)

NFRC is a non-profit organization that administers the only uniform, indepen­dent rating and labeling system for the energy performance of windows, doors, skylights, and attachment products.

National Fire Protection Association (NFPA)

Creates and main­tains minimum standards and requirements for fire prevention, training, and equipment, developing and publishing codes and standards such as the NFPA 70, the National Electric Code, and NFPA 54, the National Fuel Gas Code.

National Institute for Occupational Safety and Health (NIOSH)

 A federal agency responsible for conducting research and mak­ing recommendations for the prevention of work-related injury and illness to help ensure safe and healthful working conditions.

Natural draft

Draft that relies on the buoyancy of heated gases (not a fan) to move combustion gases up a chimney.

Natural gas

A hydrocarbon gas that is usually obtained from underground sources, often in association with petroleum and coal deposits.

Natural ventilation

Ventilation using only natural air movement without fans.

Net-free vent area (NFVA)

The area of a vent after that area has been adjusted for insect screen, louvers, and weather covering. The free area is always less than the actual area.

Netting

An open weave fabric or plastic mesh that supports fibrous insulation. See insulation restrainer

NFPA

National Fire Protection Association.

NFPA 211

National Fire Protection Association's Standard for Chimneys, Fireplaces, Vents, and Solid-Fuel-Burning Appli­ances includes installation procedures for vents and chimneys that serve wood-burning stoves and fireplaces.

NFPA 31

National Fire Protection Association's Standard for the Implementation of Oil-Burning Equipment, dictating that chimneys must be at least 2 feet higher than any portion of the building within 10 feet.

NFPA 54

National Fire Protection Association's National Fuel Gas Code.

Noncombustible material

Materials that pass the test procedure for defining noncombustibility of elementary materials set forth in ASTM E 136.

Nonconditioned space

A space that isn’t heated or cooled.

Non-expanding foam

Spray foam that doesn’t expand. Used in window and door jambs, and other constricted spaces where expanding foam may distort building window or door frames.

Nozzle

An orifice for spraying a liquid like fuel oil.

O₂

Oxygen

Oak Ridge National Laboratory (ORNL)

Laboratory where the Mobile Home Energy Audit (MHEA) software was developed.

Occupants

People of any age living in a dwelling. Animals are not defined as occupants.

Occupational Safety and Health Administration (OSHA)

An agency of the United States Department of Labor, with a mission to prevent work-related injuries, illnesses, and occupational fatalities by issuing and enforcing standards for workplace safety and health.

Off-gas

Off-gassing is the evaporation of volatile chemicals in non-metallic materials at normal atmospheric pressure. This means that building materials can release chemicals into the air through evaporation.

Ohm

A unit of measure of electrical resistance. One volt can produce a current of one ampere through a resistance of one ohm.

One-part foam

One-part foam comes in spray cans (e.g., Great Stuff) and spray guns with screw-on cans. One-part foam is best suited for filling gaps and holes less than ¾-inch.

Open-combustion appliance

An appliance that does not have a sealed combustion chamber and draws its combustion air from the surrounding room.

Orifice

A hole in a gas pipe or nozzle fitting where gas or fuel oil exits to be mixed with air before combustion occurs in the heat­ing chamber. The diameter of the orifice determines the flow rate.

Orphaned water heater

A gas water that formerly shared a chimney with a gas furnace or boiler but now is the only appli­ance venting into the naturally drafting chimney.

Oscillating fan

A fan, usually portable, that moves back and forth as it operates, changing the direction of the air movement.

OSHA

Occupational Safety and Health Administration

Output capacity

The useful heat in BTUH that a heating unit produces after accounting for waste.

Over-fired

When a burner burns too much fuel caused by over-sized fuel nozzles or excessive fuel pressure.

Oxidation

The chemical reaction of a substance with oxygen.

Oxygen content

A measure of the amount of oxygen in the air or combustion gases as a percent.

Oxygen-depletion sensor

A safety device on a heating unit that shuts off the fuel supply when oxygen content of the combustion air is inadequate.

Packaged air conditioner

An air conditioner that contains the compressor, evaporator, condenser, and air handler in a single cabinet.

Packaged terminal (PT)

A self-contained space heating and/or cooling system, usually powered with electricity, .

Packaged terminal air conditioner or heat pump (PTAC or PTHP)

A self-contained space heating and/or cooling system, frequently installed in a sleeve through the exterior wall of a building, using heat pump technology. Common in hotels and apartment buildings.

Panel

Parts of a door between rails and stiles or mullions.

Parapet walls

A low wall at the edge of a low-sloping roof.

Parts per million (ppm)]

The unit commonly used to represent the degree of pollutant concentration, where the concentrations are small.

Pascal (Pa)

A unit of measurement of air pressure. One inch of water column equals 249 pascals. Atmospheric pressure (29.92 inches of mercury) is equivalent to 102,000 Pa.

Passive attic venting

Takes advantage of the natural buoyancy of air by providing inlets and outlets low and high on the roof.

Payback period

The number of years that an investment in energy conservation requires to repay its cost through energy savings.

Performance standard

Specification of the conditions that exist when a someone performs a job in an approved manner.

Perimeter basement drain

An indoor drain cut into the floor and around the perimeter of a basement or crawl space to inter­cept and remove water from the basement.

Perlite

A heat-expanded non-combustible mineral used for insulation.

Perm

A measurement of how much water vapor a material transmits per hour. Specifically: diffusion of 1 grain of water vapor per hour, per square foot, per inch of mercury pressure.

Permeance rating

Number that quantifies the rate of vapor dif­fusion through a material.

Personal fall arrest system

A system used to arrest an employee in a fall from a working level. It consists of an anchor point, con­nectors, a body belt or body harness and may include a lanyard, deceleration device, lifeline, or combinations of these.

Personal protective equipment (PPE)

Accessories such as safety glasses, ear plugs, and respirators worn to protect individuals from workplace hazards.

Phase change

The act of changing from one state of matter to another, for example: solid to liquid or liquid to gas.

Photoresistor

Electronic sensing device used to sense flame, sunlight, artificial light.

Photovoltaic (PV)

A solid-state electronic device that converts light into direct current electricity.

PIC

Polyisocyanurate foam insulation.

Picture window

Picture windows have no operable sashes and are used primarily for outdoor viewing and daylighting.

Pier and beam foundation

Housing base that uses a concrete footing and a pier to support the floor, walls, and roof.

Pitch

The slope of a roof expressed as the rise over the run or by an angle in degrees.

Plaster

A plastic mixture of sand, lime, and Portland cement spread over wood or metal lath to form the interior surfaces of walls and ceilings.

Plastic tie band

A ratcheting plastic band used to clamp wires or flexible ducts to metal ducts or to attach insulation to round metal ducts.

Plate

A framing member installed horizontally to which the vertical studs in a wall frame are attached.

Platform framing

A system of framing a building in which floor joists of each story rest on the top plates of the story below or on the foundation sill for the first story, and the bearing walls and partitions rest on the subfloor of each story.

Plenum

The large duct that connects the air handler to the main ducts.

Plumb

Absolutely vertical at a right angle to the earth’s surface.

Plywood

Laminated wood sheeting with layers cross-grained to each other.

PM

Particulate matter or particle pollution. PM2.5 particles are less than 2.5 microns in diameter. PM10-2.5 are between 2.5 and 10 microns in diameter.

Pocket doors

Doors that slide into a wall cavity and typically leak a lot of air.

Polyethylene

A plastic made by the polymerization of ethylene, used in making, lightweight, and tough plastics, films, insula­tions, and vapor barriers.

Polyisocyanurate (PIC)

A plastic foam insulation sold in sheets, similar in composition to polyurethane.

Polystyrene insulation

A rigid plastic foam insulation, usually white, pink, green, or blue in color.

Polyurethane

A versatile plastic spray-foam insulation, usually yellow in color.

Porosity

Measure of the void spaces in a material, expressed as either a fraction or a percentage of the total volume of material.

Positive-pressure, supplied-air respirator

Has its own air com­pressor to supply fresh air to the worker through a sealed mask or hood.

Potential energy

Energy in a stored form, like fuel oil, coal, wood, or water stored in a reservoir.

Potentiometer

A variable resistor used as a controller or sensor.

Pounds per square inch (psi)

Units of measure for the pressure a gas or liquid exerts on the walls of its container.

Power burner

A burner that moves combustion air at a pressure greater than atmospheric pressure. Most oil-fired burners and many larger gas burners are power burners.

Power venter

A blower located on the inside or outside of an exterior wall that pulls the combustion gases out of the appli­ance and exhausts these gases outdoors.

Prescriptive standard

Specifies in detail the requirements and procedures to be followed rather than specifying a performance outcome.

Present value (PV)

The amount that a future sum of money is worth today considering a specific discount rate.

Pressure

A force encouraging movement of a fluid by virtue of a difference in density, elevation, or some other condition between two places.

Pressure-and-temperature relief valve

A safety component required on boilers and water heaters, designed to relieve excess pressure or temperature in the tank by discharging water.

Pressure balancing

To equalize house or duct pressure by adjust­ing supply and return airflow in ducted forced-air distribution systems.

Pressure boundary

The surface that separates indoor air from outdoor air. Also called the air barrier.

Pressure diagnostics

The evaluation of building pressures and airflows in order to control air leakage and to ensure sufficient airflow for heating, cooling, and ventilation.

Pressure-equalized rain screen

A space between the water-resis­tive barrier and the exterior cladding in a wall that connects to the outdoors so that no pressure difference exists between the space and the outdoors. This assembly gives superior resistance to wind and wind-driven rain.

Pressure-pan testing

One method for determining duct leakage. Uses a pressure pan, manometer, and a blower door to quantify pressure differences and verify improvements after duct sealing.

Pressuretrol

A control that turns a steam boiler’s burner on and off as steam pressure changes.

Pressure-reducing valve

An adjustable valve that reduces the building’s water pressure to provide water to hydronic and steam heating systems and potable-water systems.

Primary air

Air mixed with fuel before combustion.

Prime window

The main window installed in the rough open­ing consisting of fixed or moveable sashes (not to be confused with a storm window).

Priority list

The list or ranking of energy-conservation mea­sures developed by a program to produce the most cost-effective energy savings results based on a savings to investment ratio cal­culation.

Propane (liquefied petroleum gas, or LPG)

A colorless, flamma­ble gas occurring in petroleum and natural gas.

Psychrometer

An instrument for determining atmospheric humidity by the reading of two thermometers, the bulb of one being kept moist and ventilated.

Psychrometric chart

A chart presenting the physical and ther­mal properties of moist air in graphical form. Used in conjunc­tion with a psychrometer to determine relative humidity, dew point, enthalpy, and other characteristics of humid air.

Psychrometrics

The study of the relationship between air, water vapor, and heat.

Pull-down stairs

Staircase that folds up into the attic until pulled down for use.

Pulley seals

A component of a double-hung window sash that minimizes air leakage through the pulley hole.

Purlins

Framing members that sit on top of rafters, perpendicu­lar to them, designed to spread support to roofing materials.

Quality assurance (QA)

The systematic evaluation of a product or service to ensure quality standards are being met.

Quality control (QC)

Review of the final work product to ensure that it was correctly done.

QCI or Quality control inspection

Detailed inspection of the final work product and its relationship to the energy audit and work order.

R-Value

A measurement of thermal resistance of materials, especially layered materials.

Radiant barrier

A metalized sheet or coating designed to reflect radiant heat or to resist the emission of radiant heat.

Radiant temperature

The surface temperature of objects in a home, like walls, ceiling, floor, and furniture.

Radiation

Heat energy that is transferred by electromagnetic energy or infrared light, from one object to another. Radiant heat can travel through a vacuum, through air, or through other transparent and translucent materials.

Radon

A carcinogenic radioactive gas that decomposes into radioactive particles.

Rafter

A roof support that supports the roof deck and follows the roof’s slope.

Rain screen

The combination of a water-resistive barrier and a space, used to keep wall assemblies dry in climates with substan­tial rainfall.

Rater

A person who performs energy ratings. Same as energy rater.

Recovery efficiency

A water heater’s efficiency at actually heat­ing water to the water heater’s rated capacity without consider­ing standby or distribution losses.

Reflectance

The ratio of radiant heat reflected from a given sur­face to the total radiation falling on the surface. Also called reflectivity.

Reflective glass

Glass that has a mirror-like coating on its exte­rior surface to reflect solar heat. The solar heat gain coefficient of reflective glass ranges from 0.10 to 0.30.

Refrigerant

A fluid used in air conditioners and heat pumps that heats air when it condenses from a gas to a liquid and cools air when it evaporates from a liquid to a gas.

Register

The grill cover over a duct outlet for forced-air distri­bution systems and may control the airflow.

Relamping

The replacement of an existing, standard light bulbs with lower wattage energy-efficient bulbs.

Relative humidity

The percent of water vapor that air contains, compared to the maximum amount of water vapor the air can hold. Air that is completely saturated has 100% relative humid­ity.

Relay

An automatic, electrically-operated switch.

Reset controller

Adjusts fluid temperature or pressure in a HVAC system according to the outdoor air temperature.

Residential Load Calculation: Manual J

Allows the user to prop­erly size building HVAC systems.

Resistance

The property of a material resisting the flow of elec­trical energy or heat energy.

Respirable

Able to be breathed deeply into human lungs.

Retrofit

An energy conservation measure applied to an existing building.

Return air

Air circulating back to an air handler from the build­ing, to be heated or cooled and supplied back to the building’s conditioned areas.

Return plenum

A large main duct that brings return air back to the air handler.

Revolutions per minute

Number of times the crankshaft of an combustion engine, or the shaft of an electric motor, rotates in one minute.

Reweatherized unit

Any unit that received weatherization ser­vices prior to September 30, 1994 and has received additional services under subsequent grants or allowed by current DOE regulations.

Ridge venting

Ridge venting is a continuous vent (or two strips of vents) along the roof ridge. Usually combined with continu­ous soffit or eave vents as part of an overall attic-ventilation sys­tem.

Rim joist

The outermost joist around the perimeter of the floor framing. Also known as band joist.

Riser

Transition piece that connects the main duct to the floor and is often vulnerable to failure. Also the vertical part of a stair step. See also duct boot.

Rodent barrier

Guard used to keep rodents from entering a mobile home through its belly.

Roof jack

Chimney assembly that penetrates the roof and includes the flashing and chimney cap assemblies.

Roof vent

A screened and louvered opening to allow air exchange between the attic and outdoors.

Room air conditioner

An small air conditioning unit installed through a wall or window, which cools a room by removing heat and releasing it outdoors.

Room heater

A heater located within a room and used to heat that room.

Rough opening

The framed opening in a wall into which a door or window is installed.

SDS

Safety Data Sheet.

Safety Data Sheet (SDS)

A sheet containing data regarding the properties of a particular substance, intended to provide work­ers with procedures for handling or working with that substance in a safe manner, including information such as physical data, toxicity, health effects, first aid, storage, disposal, and protective equipment.

Safety glass

Glass that is toughened or laminated so that it is less likely to splinter when broken.

Sash

A movable or stationary part of a window that frames the glass.

Saturation

Describing a mixture of vapor and liquid at the phase-change point. The condition in which the air can’t hold any more moisture, as a function of temperature and vapor pres­sure.

Savings-to-investment ratio (SIR)

SIR is the cash savings divided by the initial investment over the lifespan of energy-conserva­tion measures. SIRs of greater than one are considered cost effective according to DOE WAP.

Scale

Dissolved minerals that precipitate inside boilers and stor­age tanks.

Sealed-combustion heater

A heater that draws air for combus­tion from outdoors and has a sealed exhaust system. Also called a direct-vent appliance.

Seasonal efficiency

Refers to the overall efficiency of the central heating system including AFUE and distribution losses.

Seasonal energy efficiency ratio (SEER)

A measurement of energy efficiency for central air conditioners. The SEER is com­puted by dividing cooling capacity, measured in BTUh, by the Watts (see also Energy Efficiency Rating).

Seasonal heating performance factor (SHPF)

Ratio of useful heat output of a heat pump to the electricity input, averaged over a heating season.

Secondary air

Combustion air surrounding a flame.

Sensible heat

The heat required to change the temperature of a material.

Sequencer

A bimetal switch that turns on the elements of an electric furnace in sequence.

Service equipment

The electric meter and main switch, usually located outside the building.

Service wires

The wires coming from the utility transformer to the service equipment of the building.

Set-point

The temperature setting of a thermostat or other tem­perature-based control.

Shading coefficient (SC)

A decimal describing how much solar energy is transmitted through a window opening compared to clear single glass having an SC of 1.0. For example, reflective glass has an SC of 0.20 to 0.40.

Sheathing

Structural sheeting, attached on top of the framing, underneath the siding and roofing of a building. Any structural building material used for covering a building surface.

Sheet Metal and Air Conditioning Contractors' National Associa­tion (SMACNA)

An international association of contractors who specialize in heating, ventilation and air conditioning.

Sheeting

Common term for any building material used for cov­ering a building surface.

Sheetrock

See drywall.

Shell

The building’s exterior envelope including walls, floor, and roof.

Shingle

A modular waterproof roofing material, that installs in overlapping rows to cover the roof surface.

Short circuit

A dangerous malfunction in an electrical circuit where electricity flows through conductors and into the ground without going through an electrical load.

Sill

The bottom of a window or door frame.

Sill box

The outer area of the floor bound by the rim joist, floor joist, sill plate, and floor.

Sill pan

A flashing device that sits on a rough-framed window sill to prevent water penetration if water infiltrates the cladding and sealant around the finished window.

Single-family (SF) home

A free-standing residential building, occupied by one family unit.

SIR

See savings-to-investment ratio.

Skirting

A non-structural screening built around the exterior of an open crawl space to exclude animals, wind, and sunlight. Also has aesthetic value.

Slab-on-grade foundation

Building foundation using a concrete slab usually poured at one time.

Slider window

A slider window is essentially a double-hung window turned on its side so the sashes move horizontally.

Sling psychrometer

A device holding two thermometers that is slung through the air to measure wet-bulb temperature and dry-bulb temperature for calculating relative humidity, enthalpy, and other psychrometric factors.

Slope

The roof section of an attic with the roof and ceiling sur­faces attached to the rafters. See also: pitch.

Smoke-developed index

The level of smoke that a material pro­duces when burning in a fire test compared to red oak, which has an index of 100.

Smoke tester

Device to test the amount of smoke being pro­duced by an oil-burning furnace or boiler. High smoke means the fuel-to-air ratio is incorrect, and combustion is inefficient.

Soffit

The underside of a roof overhang or a small lowered ceil­ing, as above cabinets or a bathtub.

Solar absorption

The ratio of absorbed solar radiation to inci­dent solar radiation.

Solar control film

Plastic films, coated with a metallic reflective surface, that are adhered to window glass to reflect solar heat gain. See also window film.

Solar gain

Heat from the sun that is absorbed by a building's materials and contributes to the heating and cooling require­ments of the dwelling.

Solar heat

Radiant energy from the sun with wavelengths between 0.7 and 1 micrometers.

Solar heat gain coefficient (SHGC)

The ratio of solar heat gain through a window to incident solar heat, including both trans­mitted heat and absorbed/radiated heat.

Solar reflectance

The ratio of reflected solar radiation to inci­dent solar radiation. See also albedo.

Solar screen

A framed screen, installed on the window’s exte­rior, designed to absorb solar heat before it strikes window glass.

Solar transmittance

The percent of total solar energy transmit­ted by a transparent or translucent material.

Solar water heater

Water-heating system where solar radiation heats the water.

Solenoid

An electromagnetic device that moves a switch or valve stem.

Sone level

An international unit used to measure sound levels. One sone is equivalent to the sound of a quiet refrigerator in a quiet kitchen.

Space conditioning

Heating, cooling, or ventilation of an indoor space.

Space heating

Heating of the building’s living spaces with a room heater or central heating system.

Spalling

Surface degradation of masonry materials because of moisture movement.

Span

Horizontal distance between supports.

Specific heat

The ratio of the heat storage capacity of a particu­lar material to the heat storage capacity of water.

Spillage

Temporary flow of combustion gases from a dilution device.

Spline

A strip of vinyl, rubber, or plastic that, when inserted into a groove, holds a screen or plastic film in place on a frame.

Split-system air conditioner

An air conditioner having the con­denser and compressor outdoors and the evaporator indoors.

Spray foam

Liquid-applied foam that expands forming a rigid foam material with millions of insulating cells.

Spot ventilation

Spot ventilation includes kitchen exhaust fans and bathroom exhaust fans. See also local ventilation.

Stack effect

The draft established in a building from outdoor air infiltrating low and exfiltrating high.

Standard Work Specifications

Voluntary guidelines for quality work for residential energy upgrades. These specifications define the minimum requirements for high-quality installation of energy-conservation measures.

Standing loss

Heat loss 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 pressure

Measurement of pressure in a fluid filled cham­ber at a specific location, and at a right angle to the fluid flow.

Steady-state efficiency (SSE)

The heating-efficiency percentage calculated by a combustion analyzer by measurements of oxy­gen and flue-gas temperature.

Steel chassis

Supporting under-frame for the mobile home.

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 steam arrives at the vent.

Stiles

Full-length vertical framing members of a door.

Stop

A thin, trim board for windows and doors to close against or slide against.

Strapping

Similar to furring. A nailer applied to a building sur­face.

Strike plate

The metal plate attached to the door jamb that the latch inserts into upon closing.

Strip heat

An electric-resistance heating cable or element as in a heat pump for electric resistance heater.

Stucco

Plaster applied to the building’s exterior walls.

Stud

A vertical wood or metal framing member used to build a wall.

Subfloor

The sheathing over the floor joists and under the floor covering.

Subspace

A space or zone located partially or completely below grade, such as a basement or crawl space.

Subcooling

The number of degrees Fahrenheit that a condenser and nearby piping cools the liquid refrigerant below its satura­tion temperature.

Subgrantee

An agency—usually a community action agency—that is awarded a sub-grant and is accountable to the grantee (State government) for managing weatherization at a local level.

Substrate

A layer of material to which another layer is applied.

Sulfur dioxide (SO₂)

A colorless, nonflammable, water-soluble gas air pollutant.

Sump pump

A pump that removes water from underneath a building.

Superheat

The number of degrees Fahrenheit that an evapora­tor and nearby piping heats gaseous refrigerant above its satura­tion temperature.

Supply air

Heated or cooled air that moves out of an air handler through the ducts and to the supply registers of a building.

Suspended ceiling

Modular ceiling panels supported by a hang­ing frame.

Tankless water heater

A water heater with no storage tank that heats water instantaneously as the water flows through it. Also called: instantaneous water heater.

Task lighting

Lighting provided at the area where a visual task is performed.

Temperature

A measure of the heat present.

Temperature and pressure relief valve

A safety component required on boilers and water heaters, designed to relieve excess pressure or temperature in the tank by discharging water.

Temperature rise

The number of degrees of temperature that the heating fluid increases as it moves through the heat exchanger.

Therm

A unit of energy equal to 100,000 Btus or 29.3 kilowatt-hours.

Thermal barrier

A material that protects materials behind it from flame impingement or from reaching 250° F during a fire. Drywall is a 15-minute thermal barrier.

Thermal boundary

A line or plane where insulation and air bar­rier(s) exist in order to resist thermal transmission and air leak­age through or within a building shell.

Thermal break

A relatively poor heat-conducting material sepa­rating two highly conductive materials, installed to reduce heat flow through the assembly.

Thermal bridging

Rapid heat conduction resulting from direct contact between very thermally conductive materials like metal and glass.

Thermal bypass

A large air leak that allows air to flow around insulation.

Thermal conductance

A homogeneous material’s ability to con­duct heat, denoted by the letter k.

Thermal emittance

Thermal emittance or thermal emissivity is the ratio of the radiant emittance of heat of a specific object or surface to that of a standard object called a black body.

Thermal enclosure/envelope

The insulated and air-sealed boundaries of a dwelling that surround the conditioned space.

Thermal mass

A solid or liquid material that absorbs and stores heating or cooling energy until it is needed.

Thermal resistance

R-value; a measurement expressing the abil­ity to resist heat flow.

Thermal transmittance

Expressed as U-factor, thermal trans­mittance is heat flow by conduction, convection, and radiation through a layered building component like a wall.

Thermistor

An electronic resistor used to sense temperature.

Thermocouple

A bimetal-junction electric generator used to keep the safety valve of an automatic gas valve open.

Thermodynamics

The science of heat.

Thermostat

A device used to control a heating or cooling sys­tem to maintain a setpoint temperature.

Threshold

The raised part of a floor underneath a door that acts as an air and dust seal.

Ton of refrigeration

The capacity to remove 12,000 BTUs per hour of heat from a building.

Total solar energy rejected

The percent of incident solar energy rejected by a glazing system equals solar reflectance plus the part of solar absorption that is reradiated outward.

Tracer gas

A harmless gas used to measure air leakage in a building.

Training and technical assistance (T&TA)

Formal technical communication that ensures that all work in the field meets State standards.

Transformer

A double coil of wire that increases or decreases voltage from a primary circuit to a secondary circuit.

Trim

Decorative wood that covers cracks around window and door openings and at the corners where walls meet floors and ceilings. Sometimes called molding.

Truss

A braced framework usually in the shape of a triangle to form and support a roof.

Tuck-under garage

Architectural style in which the garage is sit­uated underneath a room of the house.

Turbine vent

Vent usually mounted on the roof of a building. The vent has at its head a globular, vaned rotor that is rotated by wind, conveying air through a duct to and from a chamber below.

Two-part foam

A triple-expanding foam that insulates and seals air leaks. Two-part foam comes in portable low-pressure two-tank kits and high-pressure truck-mounted spray systems.

Type IC recessed electrical fixture

An recessed light fixture that is rated to be in direct contact with fibrous insulation.

Type-S fuses

Fuse type with a rejection base that prevents tam­pering as well as mismatching.

U-factor

The total heat transmission of a building assembly in BTUs per square feet per hour per degree Fahrenheit between the indoor and the outdoors.

U.S. Department of Agriculture (USDA)

United States govern­ment agency responsible for agricultural programs, USDA also administers some housing programs.

U.S. Department of Energy (DOE)

United States government agency whose mission is to advance energy technology and pro­mote related innovation in the United States.

U.S. Department of Housing and Urban Development (HUD)

United States government agency charged with rule-making and enforcement of the HUD Code for manufactured homes.

U.S. Environmental Protection Agency (EPA)

The mission of the U.S. Environmental Protection Agency is to protect human health and the environment.

U-value

See U-factor. An international term for U-factor.

Ultraviolet Radiation

Light radiation having wavelengths beyond the violet end of the visible spectrum; high frequency light waves.

Unconditioned crawl space

A crawl space without a supply of heat from a forced-air register or other heat emitter.

Unconditioned space

An area within the building envelope not intentionally heated.

Underlayment

Sheeting installed to provide a smooth, sound base for a finish material.

Under-fired

Describes a burner that isn’t receiving a sufficient flow rate of fuel.

Underwriter’s Laboratory (UL)

A private laboratory that tests materials and lists their fire-resistance characteristics.

Uniform Mechanical Code (UMC)

A model code developed by the International Association of Plumbing and Mechanical Offi­cials to govern the installation and inspection of mechanical sys­tems.

Uniform Plumbing Code (UPC)

A model code developed by the International Association of Plumbing and Mechanical Officials to govern the installation and inspection of plumbing systems.

Unintentionally conditioned

A space that is heated or cooled by energy that escapes the heating or cooling system. For example: a cooled attic or heated crawl space, which have no intentional space conditioning or comfort needs.

Unitary

Refers to an HVAC system that has all its components in one cabinet. See also: Packaged

Unvented attic

An attic space without intentional vents to venti­late it.

Upduct

An automatic vent, between the conditioned space and the attic, that operates by the pressure created by an evaporative cooler. Upducts exhaust room air into the attic. Used when open windows are a security problem.

Upflow furnace

A furnace in which the heated air flows upward as it leaves the furnace.

Upstream

Toward the source of the flow.

Vapor barrier

A material that controls water-vapor diffusion to less than 0.1 perms.

Vapor diffusion

The flow of water vapor through a solid mate­rial.

Vapor permeable

A material with a water vapor permeance of more than 10 perms.

Vapor pressure

The pressure exerted by a vapor, which increases with temperature.

Vapor retarder

A material that limits water-vapor diffusion to less than 10 perms.

Vaporize

To change from a liquid to a gas.

Vaulted attic/ceiling

An attic bounded by a sloped ceiling and sloped roof, which is created by a roof truss and typically has more than 16 inches of space between the ceiling and roof.

Veiling reflection

Light reflection from an object or task that obscures visibility.

Veneer

The outer layer of a building component that protects or beautifies the component.

Vent connector

The vent pipe carrying combustion gases from the appliance to a vent or chimney.

Vent chute

A lightweight plate that directs air from a soffit over attic insulation and along the bottom of the roof deck to venti­late the attic and cool the roof deck. A baffle.

Vent damper

An automatic damper powered by heat or electric­ity that closes the chimney while a heating device is off.

Vent pipe

The pipe carrying combustion gases from the appli­ance to the chimney.

Vent terminations

A fitting that prevents moisture intrusion, detritus, or pests into the building, and allows safe exhaust of vented gases.

Vented crawl space

Crawlspace with grilles or vents installed to allow for passive ventilation beneath the home.

Venting

The removal of combustion gases by a chimney or hor­izontal vent.

Venting system

A continuous passageway from a combustion appliance to the outdoors through which combustion gases can safety pass.

Ventilation

Refers to the controlled air exchange within a struc­ture such as local ventilation, whole-house ventilation, attic ven­tilation, and crawl space ventilation.

Vermiculite

A heat-expanded fire-resistant mineral used for insulation.

Visible transmittance

The percent of visible light transmitted by a glass assembly.

Visqueen

Polyethylene film vapor barrier.

Volt

The amount of electromotive force required to push a cur­rent of one ampere through a resistance of one ohm.

Voltage drop

The reduction of voltage in a circuit caused by resistance.

Volume

The amount of space occupied by a three-dimensional object or region of space, expressed in cubic units.

Water-resistive barrier

A water-resistant material used to pre­vent water from wetting a building’s structural sheathing and other vulnerable components.

Watt (W)

A unit of measure of electric power at a point in time, as capacity or demand. One Watt of power is equal to one joule per second.

Watt-hour

One Watt of power used continuously for one hour. One thousandth of a kilowatt-hour.

Watt meter

An instrument for measuring watts of electric power in a circuit.

Weatherization

The process of reducing energy consumption and increasing comfort in buildings by improving the energy efficiency of the building while maintaining health and safety.

Weatherization Assistance Program (WAP)

DOE’s Weatheriza­tion program.

Weatherization program notices (WPN)

Guidance documents issued by the U.S. Department of Energy for the weatherization program.

Weather-resistant barrier

See water-resistive barrier.

Weatherstripping

Flexible gaskets, often mounted in rigid metal strips, for limiting air leakage at openings in the building enve­lope such as doors and windows.

Webbing

A reinforcing fabric used with mastics and coatings to prevent the coating from cracking.

Weep holes

Holes drilled for the purpose of allowing water to drain out of an area in a building where it accumulates.

Wet-bulb temperature

The temperature of a dampened ther­mometer of a sling psychrometer used to determine relative humidity, dew point, and enthalpy.

Wet spray

Fibrous insulation mixed with water and sometimes also a binder during installation.

Whole-house fan

A fan that draws fresh outside air into the liv­ing space, flushes hot air up the attic and exhausts it to the out­side.

Whole-building ventilation

Controlled air exchange using one or more fans and ducts to maintain good indoor air quality and to keep the building sufficiently dry.

Wind effect

Building pressure and airflow between indoor and outdoors caused by the wind.

Wind washing

Wind-driven air passing over and through build­ing materials, particularly insulation.

Window films

Plastic films coated with a metallic reflective sur­face that adhere to window glass in order to reflect solar radia­tion.

Window frame

The sides, top, and sill of the window forming a box around window sashes and other components.

With reference to (WRT)

Compared to another measurement. In weatherization, a way to assess pressure differences between ducts and the rest of the home.

Work order

An order authorizing workers to complete specified tasks. Sometimes called the work scope.

Workforce Guidelines

DOE guidance on specific energy conser­vation measures; also called Standardized Work Specifications.

Work scope

The summary of energy conservation measures, materials lists and labor estimates that is prepared by an energy auditor as part of an energy audit. Same as: work order.

Worst-case depressurization test

A safety test, performed by spe­cific procedures, designed to evaluate the probability of chim­ney back-drafting.

Zone

A room or portion of a building separated from other rooms by an air barrier.

Zone pressure diagnostics (ZPD)

Using a blower door to deter­mine the interconnectivity of various building components, which helps the practitioner locate the air barrier and know if the insulation and air barrier are aligned. Also called zonal pres­sure diagnostics.