Honeywell Furnace Filters Terms Related to Air Filters J-Z

GLOSSARY
Air Filter RelatedTERMS J-Z

J
Jamb: The side or top piece of a window or door frame.
Joist: A horizontal wood framing member that supports a floor or ceiling.
K
Kata Thermometer: A special thermometer designed to measure the cooling power of the environment. Often used as an anemometer
Kilowatt (kW): One thousand watts.
Kilowatt-hour (kWh): One thousand watt-hours.
Kyoto Protocol: An international agreement adopted in December 1997 in Kyoto, Japan. The Protocol sets binding emission targets for developed countries that would reduce their emissions on average 5.2 percent below 1990 levels.
L
Lag: Time delay between, say, the peak outdoor temperature and the indoor temperature, also applied to the time required for the sensing element of a control system to reach equilibrium with the property being controlled.

Laminar airflow. Non-turbulent flow of air in one direction at a uniform speed.
Landlord/Tenant Agreement: Document required for completed application when applicant is a renter. The Agreement is legally binding contract, signed by the tenant, the landlord (or property owner), and the local agency specifying the role and responsibilities of each party. The basic goal of the WAP is to ensure that the benefits of the program accrue to the low-income family. A variety of standard clauses can be incorporated into the Agreement, including clauses on landlord's inability to raise rents for specified period of time, eviction prohibition, and landlord required "participation." Participation can take the form of actual cash, provided labor, and/or in-kind contributions.

Latent heat: the energy required to change the state of a unit mass of material from solid to liquid (fusion) or liquid to gas (evaporation), without a change in temperature. This energy is then released, again without change of temperature (provided super cooling does not occur), when the material reverts from gas to liquid or from liquid to solid. (Wh/kg, kJ/kg)
Latitude: the angular distance north (+) or south (-) of the equator, measured in degrees of arc
(Large) Hydroelectric Power: The process of generating electricity by harnessing the power of moving water is called hydroelectricity. Hydroelectric power (hydropower) is generated by forcing water that is flowing downstream, often from behind a dam, through a hydraulic turbine that is connected to a generator. The water exits the turbine and is returned to the stream or riverbed. Much of the hydroelectricity in the United States is generated at large facilities and in the Pacific Northwest, where it meets about two-thirds of the electricity demand. In the U. S., hydroelectricity contributes about 10 percent of the total electricity supply.
Lead (Pb) - A heavy metal that is hazardous to health if breathed or swallowed. Its use in gasoline, paints, and plumbing compounds has been sharply restricted or eliminated by federal laws and regulations.
Leakage Ratio: Measurement of total square inches of infiltration area per 100 feet of building envelope surface area.
Leverage Activity: The actions of the state and local agencies to obtain and account for resources provided to supplement or supplant federal funding being used to weatherize dwelling units.
Light: Electromahgnetic radiation within the visible spectrum (wavelengths between approx 400-800 nm)
Light Fuel Oil: (LFO): Fuel suitable for use in liquid-fuel burning equipment without preheating, primarily domestic-type burners (includes Type 0, 1 and 2). Virtually all petroleum used in internal combustion and gas turbine engines is light oil.
Light, perceived: Universal and essential attribute of all perceptions and sensations that are peculiar to the visual system. (Notes: light is normally, but not always, perceived as a result of the action of a light simulation of the visual system.)
Lightwell absorption fraction: the fraction of solar radiation that directly heats the air after it is transmitted through the glazing and after each reflection from interior surfaces. It is intended to simulate the presence of lightweight objects that absorb solar radiation and rapidly convect heat to the air.
Lignite: A brownish-black coal of low rank with high inherent moisture and volatile matter (used almost exclusively for electric power generation). It is also referred to as brown coal. Comprises two groups classified according to the following ASTM Specification D388-84 for calorific values on a moist material-matter-free basis:
Liquid state : one of three states of matter characterized by limited freedom of molecules and by substantial incompressibility
Line Losses
The amount of energy lost during transmission and distribution of electricity, including unaccounted for uses.
Load: see heat load.

Load Collector Ratio (LCR): the ratio of the building load coefficient to the projected area.

Load factor: the ratio of actual mean load to a maximum load of maximum production capacity in a given period.

Leverage Activity: The actions of the state and local agencies to obtain and account for resources provided to supplement or supplant federal funding being used to weatherize dwelling units.

Local Agency: Also referred to as the subgrantee, contractor, service delivery network member, or local service provider, a local agency is a nonprofit organization or unit of local government responsible for providing WAP services in a specified political subdivision.

Longitudinal sampling: A method of sampling a population in which a large number of comfort votes is sought from each of relatively few subjects (cf Transverse sampling).

Long-wave radiation: radiation emitted between roughly 5000 and 30000 nm wavelength, as in thermal radiation from the surfaces of a room, or from the outside surface of the roof.

Longitude: the arc of the equator between the meridian of a place and the Greenwich meridian measured in degrees east or west.

Louvre (system): an assembly of sloping vanes intended to permit air to pass through and to inhibit transfer of water droplets. Also used as an solar control, either external to the building or internally (e.g. venetian blinds)

Low energy building: A very good insulated and passive solar building, with a very low remaining heating and cooling demand.
Low-e glass : Glazing with a low thermal transmittance (U-value), due to a heat reflecting coating(s) applied in the gap of double glazing. The applied coatings are visually transparant.
Low NOx Burners - One of several combustion technologies used to reduce emissions of nitrogen oxides.
Lowest Achievable Emission Rate (LAER) - Under the Clean Air Act, the most stringent emission limitation derived from either (1) the most stringent emission limitation in the implementation plan of any state for such source or category of source; or (2) the most stringent emission limitation achieved in practice by such class or category of sources.
Low Water Cutoff: A float-operated control for turning the burner off if a steam boiler is low on water.
Lumen (lm): SI unit of luminous flux: luminous flux emitted in unit solid angle (steradian) by a uniform unit source having a luminous intensity of 1 candela. Equivalent definition: luminous flux of a beam of monochromatic radiation whose frequency is 540 x 1012 hertz and whose radiant flux is 1/683 watt.

Luminance: The physical measure of the brightness of a surface such as a lamp, a reflecting material or the sky in a given direction. Luminance is the luminous intensity emitted by an area of a surface. Units : candela per square meter (cd/ m2)

Luminous efficacy of radiation: quotient (K) of the luminous flux by the corresponding radiant flux.
Luminous environment: lighting considered in relation to physiological and phychological effects.
Luminous flux: quantity derived from radiant flux evaluating the radiation according to its action upon the CIE stand photometric observer.

Luminous intensity (of a source in a given direction): quotient of the luminous flux dFv leaving the source and propagated in the element of solid angle containing the given direction, by the element of solid angle.
Lux: SI unit of illuminance: illuminance produced on a surface, area 1 square metre by a luminous flux of 1 lumen uniformly distributed over that surface lm/m2
M
Make-up Air: Air supplied to a space to replace exhausted air.
Manometer: Measuring device for small gas pressures.
Masonry: concrete, concrete block brick, adobe, stone and other similar materials.
Map of Radon Zones: A U.S. EPA publication depicting areas of differing radon potential in both map form and in state specific booklets.
Mastic: A thick creamy substance used to seal seams and cracks in building materials.
Mass: the quantity of matter in body as measured by the ratio of the force required to produce a unit acceleration.
Mass-area-to-glazing-area ratio: the ratio of the total surface area of massive elements to the glazing area. Massive elements including in this definition are all floors, walls ceilings, or other interior objects with densities comparable to high-density concrete provided their surfaces are exposed and located in a room that is at least partially illuminated by direct solar gains.
Material Safety Data Sheets (MSDS) - Product safety information sheets prepared by manufacturers and marketers of products containing toxic chemicals. These sheets can be obtained by requesting them from the manufacturer or marketer. Some stores, such as hardware stores, may have material safety data sheets on hand for products they sell.
Maximum Available Control Technology (MACT) - The emission standard for sources of air pollution requiring the maximum reduction of hazardous emissions, taking cost and feasibility into account. Under the Clean Air Act Amendments of 1990, the MACT must not be less than the average emission level achieved by controls on the best performing 12 percent of existing sources, by category of industrial and utility sources.
MHEA - Mobile Home Energy Audit: A software tool that predicts manufactured home energy consumption and recommends weatherization retrofit measures.

Mean radiant temperature (MRT): the area weighted mean temperature of all surrounding surfaces, i.e. sum of (s.t)/ sum of (s), where 't' is the temperature of each surface of angular area 's'. Also the temperature of a uniform black enclosure in which a solid body or occupant would exchange the same amount or radiant heat as in the existing nonuniform environment. It is an approximate indication of the effect that the surface temperatures of surrounding objects have on human comfort.
Mechanical Air Purifier: The most common air filters available on the market; Mechanical Air Purifiers use a fan to draw air through a filter. Common mechanical air filters are activated carbon filters, high density fibre filters, and HEPA filters.
Mechanical systems: a term widely used in commercial and industrial construction, referring to all the mechanical components of the building. i.e. plumbing, heating, ventilation, air conditioning and heat recovery.
Mechanically Ventilated Crawl Space: A system designed to increase ventilation within a crawlspace, achieve higher air pressure in the crawlspace relative to air pressure in the soil beneath the crawlspace, or achieve lower air pressure in the crawlspace relative to air pressure in the living spaces, by use of a fan.
Media - Specific environments--air, water, soil--which are the subject of regulatory concern and activities.
Megawatt> (MW): One million watts.
Megawatthour> (MWh): One million watt-hours.
Mercury/Mercury Compounds
Mercury is a toxic heavy metal that is a byproduct of the combustion of fossil fuels, especially coal. Mercury and compounds containing mercury can accumulate in the environment and are highly toxic to humans and animals if inhaled or swallowed. Exposure can permanently damage the brain, kidneys, and fetuses.
Metals: any class of chemical elements with specific physical and chemical qualities. The ratios of metal elements such as potassium and iron have been shown to be an indicator of wood combustion.
Metabolic rate: The rate of heat production by the body when engaged in various tasks, often defined in terms of the resting metabolism (Mets).

Methane (CH4)
A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 23 times that of carbon dioxide (CO2). Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion. The global warming potential (GWP) is from the Intergovernmental Panel on Climate Change's (IPCC's) Third Assessment Report (TAR).
Micro-climate: The climate in the immediate vicinity of a building.
Mixed systems: a solar heating system that combines two or more passive solar heating types.
Mixed-mode systems: heating or cooling systems which combine passive and mechanical systems
Microbiologicals: See "Biological Contaminants."
Mitigate: To make less severe or to mollify.
Mobile Sources - Moving objects that release pollution; mobile sources include cars, trucks, buses, planes, trains, motorcycles and gasoline-powered lawn mowers. Mobile sources are divided into two groups on-road vehicles, which include cars, trucks and buses, and nonroad vehicles, which includes trains, planes, lawn mowers, and some portable equipment.
MODEL CODE ORGANIZATIONS: Includes the following agencies and the model building codes they promulgate:
"Building Officials and Code Administrators International, Inc. (BOCA National Building Code/1993 and BOCA National Mechanical Code/1993);
"International Conference of Building Officials (Uniform Building Code/1991 and Uniform Mechanical Code/1991);
"Southern Building Code Congress, International, Inc. (Standard Building Code/1991 and Standard Mechanical Code/1991);
"Council of American Building Officials (CABO One- and Two-Family Dwelling Code/1992 and CABO Model Energy Code/1993).
Monitoring (monitor) - Measurement of the types and amounts of air pollution. The 1990 Clean Air Act requires states to monitor community air in polluted areas to check on whether the areas are being cleaned up according to schedules set out in the law. Also, the 1990 Clean Air Act requires certain large polluters to perform enhanced monitoring to provide an accurate picture of their pollutant releases such as keeping detailed records, participating in periodic inspections, and installing Continuous Emissions Monitoring Systems (CEMS).
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.
MUC: Montr�al Urban Community
Multiple Chemical Sensitivity (MCS): A condition in which a person reports sensitivity or intolerance (as distinct from "allergic") to a number of chemicals and other irritants at very low concentrations. There are different views among medical professionals about the existence, causes, diagnosis, and treatment of this condition.
N
Nano-meters (nm): unit used to measure short wavelengths in electromagnetic radiation 1 nm = 10-9m. See also infra-red radiation, visible radiation.
NASCSP - National Association for State Community Services Programs NASCSP's mission is to assist state in responding to poverty issues. NASCSP memebers are state administrators of the Community Services Block Grant (CSBG) and U.S. Department of Energy's Weatherization Assistance Program (DOE/WAP). The CSBG, administered by the states, provides core funding to local agencies to reduce poverty, revitalize low-income communities and to empower low-income families to become self-sufficient. The DOE/WAP helps low-income families reduce their energy costs by making homes more energy efficient. The local agencies funded by these programs provide a wide range of services such as weatherization, energy assistance, child care, job training, and housing. NASCSP keeps its memebers, the federal government, and other interested parties informed about issues related to CSBG and DOE/WAP through its publications.
National Emissions Standards for Hazardous Air Pollutants (NESHAPS) - Emissions standards set by EPA for an air pollutant not covered by NAAQS that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness. Primary standards are designed to protect human health, secondary standards to protect public welfare (e.g. building facades, visibility, crops, and domestic animals).
National Low Emissions Vehicle Program (NLEV) - A program that creates voluntary requirements that U.S. automakers can adopt in lieu of compliance with other vehicle emission control measures. The program applies to the manufacture of new light-duty vehicles and new light-duty trucks up to 6,000 lb gross vehicle weight rating (GVWR).
National Pollutant Release Inventory (NPRI) - A Canadian program, created in 1992, to provide information on pollutants released to the environment and transferred for disposal. Reporting of NPRI is mandated under the Canadian Environmental Protection Act (CEPA) and is due by June 1 of the following year. Each year, Environment Canada updates the NPRI substance list and revises reporting criteria after consultation with stakeholders.
Natural convection: heat transfer between a surface and adjacent fluid (usually air) and by the flow of fluid from one place to another, induced by temperature differences rather than by mechanical means, also called free convection. Compare with forced convection.
Natural convection air cooler: an air cooler depending on natural convection for air circulation.
Natural Gas: A naturally occurring mixture of hydrocarbon and nonhydrocarbon gases found in porous geological formations beneath the earth's surface, often in association with petroleum. The principal constituent is methane.
Natural Ventilation: Ventilation using only natural air movement without fans or other mechanical devices.
NEAT - National Energy Audit: 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.
Net Free Area: 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.
Neurological: relating to the nervous system ? the entire integrated system of nerve tissue in the body, brain, brainstem and spinal cord.
Natural Gas: Underground deposits of gases consisting of 50 to 90 percent methane (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H8) and butane (C4H10).
Natural light: visible part of direct solar radiation. (Note: when dealing with actinic effects of optical radiations, this term is commonly used for radiations extending beyond the visible region of the spectrum.)
Natural lighting system: component or a series of components joined in a specific building for natural daylighting.
Natural ventilation : Air which enters a building controlled, through open windows or other openings, due to wind pressue or temperature differences between the outdoor and indoor air.
Needlepoint Ionizers
Needle ionizers use high voltage electricity to create negative electrons. These electrons run up the length of a pointed spike, or needle, where they stream into the air and attract oxygen molecules. At this point, they become negative ions and are attracted to airborne particles. These molecules build up around the particles until they become too heavy to remain air borne and float to the ground. This process is known as agglomeration.
Negative Ion
Negative ions are odorless, tasteless, and invisible molecules that we inhale in abundance in certain environments. Think mountains, waterfalls, and beaches. Once they reach our bloodstream, negative ions are believed to produce biochemical reactions that increase levels of the mood chemical serotonin, helping to alleviate depression, relieve stress, and boost our daytime energy.
Negative Ionizing Filter
A Negative Ionizing Filter is a device which electrically charges the air inside it and uses a fan to blow it out into the room. This charged air causes particles in it to become attracted to the walls and furniture in the room. This can lead to a process known as the Black Wall Effect.
Negative pressure: a pressure below atmospheric. In residential construction negative pressure often refers to pressures around the house that is less than the indoor or the pressures on e.g. the windward side of the house : such variations in pressure will encourage infiltration by cross ventilation.
Net load coefficient (NLC): net reference load per degree of indoor-minus-outdoor temperature difference per day
Net reference load: steady-state heat loss from a building, excluding the solar wall, assuming constant indoor temperature. Compare with net load coefficient (J).
Neurological Disorders - Disorders of the central nervous system (brain, brainstem and cerebellum), the peripheral nervous system (including cranial nerves), and the autonomic nervous system (parts of which are located in both central and peripheral nervous system). Major conditions include, headache; dementia, including Alzheimer's disease; seizures and epilepsy; sleep disorders; infections; movement disorders such as Parkinson's disease; and spinal cord disorders.
Neutral temperature: see Comfort temperature.
New Source Performance Standards (NSPS) - U.S. federal standards promulgated for major and minor sources on a category-category basis. NSPS are national emission standards that are progressively tightened over time to achieve a steady rate of air quality improvement without unreasonable economic disruption. The NSPS imposes uniform requirements on new and modified sources through the nation. These standards are based on the best demonstrated technology (BDT).
New Source Review (NSR) - A program used in development of permits for new or modified industrial facilities which are in a nonattainment area, and which emit criteria air pollutants. The two major requirements of NSR are Best Available Control Technology (BACT) and emission offset.
Night insulation: movable insulation that covers a glazing at night and is removed during the day.
Night radiance : Heat radiance which appears at night: When the sky is clear at night a surface facing the sky sends and receives heat radiance to and from the sky. The radiant temperature of a clear sky is usually well below zero, particularly at night. Because of this the surface temperature can easily descend below the ambient outdoor air temperature.
Night ventilation: Ventilation which takes place outside the normal operating time of the building.
Nitrogen oxides (NOx): gases composed of nitrogen and oxygen that can transform into acidic air pollutants. NOx are released into the air through the use of chemical fertilizers for agriculture and the combustion of fuel. They play a major role in the formation of smog.
Nonattainment Area - A geographic area in which the level of a criteria air pollutant is higher than the level allowed by the federal standards. A single geographic area may have acceptable levels of one criteria air pollutant but unacceptable levels of one or more other criteria air pollutants; thus, an area can be both attainment and nonattainment at the same time. It has been estimated that 60% of Americans live in nonattainment areas.
Non-Methane Hydrocarbon (NMHC) - The sum of all hydrocarbon air pollutants, excluding methane; significant precursors to ozone formation.
Non-Methane Organic Gases (NMOG) - The sum of all organic air pollutants, excluding methane. NMOG account for aldehydes, ketones, alcohols, and other pollutants that are not hydrocarbons but are precursors of ozone.
Non-Point Source - Diffuse pollution source (i.e. without a single point of origin or not introduced into a receiving stream from a specific outlet). The pollutants are generally carried off the land by storm water. Common nonpoint sources are agriculture, forestry, urban, mining, construction, dams, channels, land disposal, saltwater intrusion, and city streets. May be referred to as area source.
Non-Road Emissions - Pollutants emitted by combustion engines on farm and construction equipment, gasoline-powered lawn and garden equipment, powerboats, outboard motors, and some portable equipment.
Normal distribution: A frequency distribution that predicts the probability that a variable will take a certain value; the distribution is symmetrical about the mean value. Based on statistical theory, the normal distribution underlies much statistical analysis
Notice of Intent on Cleaner Vehicles, Engines and Fuels: The federal government's 10-year agenda on vehicles and fuels, publishe in the Canada Gazette on February 17, 2001.
Nuclear Energy: Nuclear energy originates from the splitting of uranium atoms in a process called fission. At the power plant, the fission process is used to generate heat for producing steam, which is used by a turbine to generate electricity. Because nuclear power plants do not burn fuel, they do not emit air pollutant emissions. All of the nuclear power plants in the United States collectively produce about 2,000 metric tons per year of radioactive waste. Abandoned uranium mines contaminated with high-level radioactive waste can continue to pose radioactive risks for as long as 250,000 years after closure. There are more than 60 nuclear power plants currently in operation in the U.S., which accounts for approximately 20 percent of the country's electricity production. No nuclear power plants have been built since 1996, mostly due to economic factors and environmental concerns.

Nuclear Fuel: Fissionable materials that have been enriched to such a composition that, when placed in a nuclear reactor, will support a self-sustaining fission chain reaction, producing heat in a controlled manner for process use.
Nuclear Power Plant>: A facility in which heat produced in a reactor by the fissioning of nuclear fuel is used to drive a steam turbine.
Nozzle: An orifice for spraying a liquid.

O
Obstruction: (in daylight calculations) anything outside a building which prevents the direct view of part of the sky
Octane: is a measure of a gasoline's ability to resist "knocking" or pre-ignition. When gasoline enters the engine it is compressed within a cylinder and then ignited by a spark plug to initiate the combustion process and release energy. This energy is then captured by the engine piston, and so on. However, when fuel is compressed it also increases in temperature, which may high be enough to ignite the fuel before the engine is ready to capture the energy. This premature firing or pre-ignition is called "knocking," and it is not good for the vehicle or fuel performance. High performance vehicles need high octane fuels because of the high compression within their engines.
Offset - A method used in the 1990 Clean Air Act to give companies which own or operate large (major) source in a non-attainment area flexibility in meeting overall pollution reduction requirements when changing production processes. If the owner or operator of the source wishes to increase release of a criteria air pollutant, an offset (reduction of a somewhat greater amount of the same pollutant) must be obtained either at the same plant or by purchasing offsets from another company.
Off-gassing: The production of gases from the chemical deterioration of a substance over time.
Oil: a liquid fossil fuel, is formed from layers of buried plants and animals that have been subjected to geologic heat and pressure over a long period of time. The energy that the plants and animals originally obtained from the sun is stored in the oil in the form of carbon. In addition to carbon, oil contains elements such as nitrogen, sulfur, mercury, lead, and arsenic. Oil is a nonrenewable resource because it cannot be replenished on a human time frame.

Oil Heating System: Refers to a central heating system that uses #2 fuel oil, kerosene, or residual oil as the primary fuel for heat generation.
Opacity - The amount of light obscured by particulate pollution in the air; clear window glass has zero opacity, a brick wall is 100 percent opaque. Opacity is an indicator of changes in performance of particulate control systems.
Open-Combustion Heater: A heating device that takes its combustion air from the surrounding room air
Organic Chemicals/Compounds - Naturally occurring (animal or plant-produced or synthetic) substances containing mainly carbon, hydrogen, nitrogen, and oxygen.
Orientation: The azimuth of a particular surface or the major axis of a building. see Azimuth
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
Outdoor Air Supply: Air brought into a building from the outdoors (often through the ventilation system) that has not been previously circulated through the system. Also known as "Make-Up Air."
Output Capacity: The conversion rate of useful heat that a heating unit produces after accounting for any waste caused by the conversion of energy into heat.
Outside air: external air , atmosphere exterior to refrigerated or conditioned space, ambient (surrounding) air.
Overcast sky: A sky in which there is no direct solar radiation. NOTE: The measured temperature data and solar radiation tables for overcast skies within this Handbook refer to days when the cloud cover was 8/8 during all the daylight hours. Night-time temperature data are related to the same 'overcast' days, i.e. night-time cloud cover was not taken into account.
Oxidant - A collective term for some of the primary constituents of photochemical smog.
Oxygen Depletion Sensor: A safety device on a heating unit that shuts off the fuel supply to the combustion chamber when oxygen is depleted.
Oxygenated Fuel (oxyfuel) - A special type of gasoline, which burns more completely than regular gasoline in cold start conditions; more complete burning results in reduced production of carbon monoxide, a criteria air pollutant. In some parts of the country, where carbon monoxide release from cars starting up in cold weather makes a major contribution to pollution, gasoline refiners must market oxygenated fuels, which contain higher oxygen content than regular gasoline.
Ozone - A gas that is a variety of oxygen. The oxygen gas found in the air consists of two oxygen atoms stuck together; this is molecular oxygen. Ozone consists of three oxygen atoms stuck together (O3) into an ozone molecule. Ozone occurs in nature; it produces the sharp smell you notice near a lightning strike. High concentrations of ozone gas are found in a layer of the atmosphere -- the stratosphere -- high above the Earth. Stratospheric ozone shields the Earth against harmful rays from the sun, particularly ultraviolet B. Smog's main component is ozone; this ground-level ozone is a product of reactions among chemicals produced by burning coal, gasoline and other fuels, and chemicals found in products including solvents, paints, hairsprays, etc.
Ozone Hole - Thin place in the ozone layer located in the stratosphere high above the Earth. Stratospheric ozone thinning has been linked to destruction of stratospheric ozone by CFCs and related chemicals. The 1990 Clean Air Act has provisions to reduce and eliminate ozone destroying chemicals' production and use. Ozone holes have been found above Antarctica and above Canada and northern parts of the United States, as well as above northern Europe.

P
Packaged Air Conditioner: An air conditioner that contains the compressor, evaporator, and condenser in a single cabinet.
PA - Pascal: A unit of measurement of air pressure. One column inch of water equals 247 pascals. Atmospheric pressure (29.92 inches of mercury) is equivalent to 102,000 PA.
PAH: Polycyclic aromatic hydrocarbons (PAH): natural products from the incomplete combustion of carbon compounds - forest fires, volcanic eruptions and decomposing organic matter are all natural sources of PAH. Certain industrial processes are man made sources.
Particulates; Particulate Matter (PM-10) - A criteria air pollutant. Particulate matter includes dust, soot and other tiny bits of solid materials that are released into and move around in the air. Particulates are produced by many sources, including burning of diesel fuels by trucks and buses, incineration of garbage, mixing and application of fertilizers and pesticides, road construction, industrial processes such as steel making, mining operations, agricultural burning (field and slash burning), and operation of fireplaces and woodstoves. Particulate pollution can cause eye, nose and throat irritation and other health problems.
Parts per million> (ppm): A measure of concentration, or how much substance is in a given sample.
Passive solar energy : Solar energy collected by non active systems e.g. windows, atria etc..
Parts Per Billion (ppb)/Parts Per Million (ppm) - Units commonly used to express contamination ratios, as in establishing the maximum permissible amount of a contaminant in Passive solar energy : Solar energy collected by non active systems e.g. windows, atria etc..
Pascal: unit of pressure. House air tightness tests are typically conducted with a pressure difference of 50 Pascals between the inside and outside. 50 Pascals is equal to 5.008 mm (0.2 in) of water at 12.9oC.

Payback Period: The number of years that an investment in energy conservation will take to repay its cost through energy savings.
Peak Load Plant: A plant usually housing old, low-efficiency steam units, gas turbines, diesels, or pumped storage hydroelectric equipment normally used during the peak-load periods.
Peaking Capacity: Capacity of generating equipment normally reserved for operation during the hours of highest daily, weekly, or seasonal loads. Some generating equipment may be operated at certain times as peaking capacity and at other times to serve loads on an around-the-clock basis.
PEFR. Peak expiratory flow rate. A measure of lung function and the fastest rate at which air moves through the airways during a forced expiration.
PELs: Permissible Exposure Limits (standards set by the Occupational, Safety and Health Administration - OSHA).
Pellet: fuel made from dried ground wood or other biomass waste (such as corn) compressed into 25mm x 6mm (1" x �") cylinders.
Percent of possible sunshine: the actual number of hours of sunshine expressed as a percentage for the month (or other period of time).
Percent radiation received: the monthly mean Global Radiation of a horizontal plane, expressed as a percentage of the monthly mean radiation on a horizontal plane outside the atmosphere.
Perlite: A heat-expanded mineral used for insulation.
Perm: A measurement of how much water vapor a material will let pass through it per unit of time.
Permeance: water vapour permeance is the rate of water vapour diffusion through a sheet of any thickness of material (or assembly between parallel surfaces). It is the water vapour flow to the differences of the vapour pressures on the opposite surfaces. Permeance is measured in perms (m2.K/W).
Permeability: water vapour permeability is a property of a substance which permits passage of water vapour. When permeability varies with psychrometric conditions, the 'spot' or 'specific permeability' defines the property at a specific condition.
Permit - A document that resembles a license, required by the Clean Air Act for big (major) sources of air pollution, such as power plants, chemical factories and, in some cases, smaller polluters. Usually permits will be given out by states, but if EPA has disap
Permit Fees - Fees paid by businesses required to have a permit. Permit fees are like the fees drivers pay to register their cars. The money from permit fees will help pay for state air pollution control activities.
Petroleum>: A mixture of hydrocarbons existing in the liquid state found in natural underground reservoirs often associated with gas.Petroleum includes fuel oil No. 2, No. 4, No. 5, No. 6; topped crude; kerosene; and jet fuel.
Petroleum (Crude Oil)>: A naturally occurring, oily, flammable liquid composed principally of hydrocarbons. Crude oil is occasionally found in springs or pools but usually is drilled from wells beneath the earth's surface.
pH: a scale from 0 to 15 for measuring alkalinity or salinity.
Phase-change materials: materials with a phase change point close to the desired room temperature which can be used either to reduce temperature fluctuations within a room or to store energy in the phase change process (usually melting) and re-releasing it to the system when its temperature falls below the transition point. Phase change materials may be surface mounted as in phase change tiles or storage based as in latent heat stores for active solar systems (see latent heat).
Physical adsorption. The assimilation of gas, vapor, or dissolved matter by the surface of another substance resulting from the electrostatic interaction between molecules of gas or vapor and a surface.
Physical environment (thermal environment): The environment in a room or building defined by its the environmental variables.
Photochemical Oxidants or Smog - Air pollutants formed by the action of sunlight on oxides of nitrogen and hydrocarbons.
PICOCURIE (pCi): A unit for measuring radioactivity, often expressed as picoCuries per liter (pCi/L) of air.
Plant: A facility at which are located prime movers, electric generators, and auxiliary equipment for converting mechanical, chemical, and/or nuclear energy into electric energy. A plant may contain more than one type of prime mover.
Plant Use: The electric energy used in the operation of a plant. Included in this definition is the energy required for pumping at pumped storage plants.
Plant-Use Electricity: The electric energy used in the operation of a plant. This energy total is subtracted from the gross energy production of the plant; for reporting purposes the plant energy production is then reported as a net figure. The energy required for pumping at pumped storage plants is, by definition, subtracted, and the energy production for these plants is then reported as a net figure.
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.
Plate: A piece of lumber installed horizontally to which the vertical studs in a wall frame are attached.
Plenum: The piece of ductwork, usually found above the heat exchanger of a hot air furnace, that connects the air handler to the main supply duct.
Plumb: Absolutely vertical at a right angle to the earth's surface.
Plywood: Laminated wood sheeting with layers cross-grained to each other.
PM: Preventive Maintenance.
PM10/PM2.5 - PM10 is measure of particles in the atmosphere with a diameter of less than 10 or equal to a nominal 10 micrometers. PM2.5 is a measure of smaller particles in the air.
Point Source - A stationary location or fixed facility from which pollutants are discharged; any single identifiable source of pollution; e.g. a pipe, ditch, ship, ore pit, factory smokestack.
Pollutant Pathways: Avenues for distribution of pollutants in a building. HVAC systems are the primary pathways in most buildings; however all building components interact to affect how air movement distributes pollutants. Also - a term used in the IAQ Tools for Schools: IAQ Coordinator's Guide.
Polyethylene: Polymer plastic used for vapor barriers, air barriers, and foam backer rod.
Polyisocyanurate: A plastic foam insulation sold in sheets, similar in composition to polyurethane.
Polystyrene Insulation: A rigid plastic foam insulation, usually white or blue in color.
Polyurethane: A versatile plastic foam insulation, usually yellow in color.
Pollutant Release and Transfer Register (PRTR) - A Mexican program, created in 2001, requiring mandatory reporting by industrial facilities of potentially hazardous polluted materials emitted or passed into the environment from various media. Similar to the Toxic Release Inventory (TRI) in U.S. and the National Pollutant Release Inventory (NPRI) in Canada.
POSITIVE PRESSURE: Condition that exists when more air is supplied to a space than is exhausted, so the air pressure within that space is greater than that in surrounding areas. Under this condition, if an opening exists, air will flow from the positively pressurized space into surrounding areas.
Potential Energy: Energy in a stored or packaged form, like fuel oil, coal, wood, etc.
Power: The rate at which energy is transferred. Electrical energy is usually measured in watts. Also used for a measurement of capacity.
Power Generation : A process of converting thermal, mechanical, chemical or nuclear energy into electric energy.
Precipitator - Pollution control device that collects particles from an air stream.
Precursor - In photochemistry, a compound antecedent to a pollutant. For example, volatile organic compounds (VOCs) and nitrogen oxides react in sunlight to form ozone or other photochemical oxidants. As such, VOCs and oxides of nitrogen are precursors.
PPD - predicted percentage dissatisfied: The percentage of subject population who will be dissatisfied (uncomfortable) in a given environment as predicted by a theoretical index (generally that of Fanger). see PMV
Preference vote: The response by a subject as to their preference at the time of asking; this may be a preference for a warmer or cooler environment, or for a particular response on a comfort scale.
Preheating: in air conditioning: to heat the air before other processes.
Pressed Wood Products: A group of materials used in building and furniture construction that are made from wood veneers, particles, or fibers bonded together with an adhesive under heat and pressure
Pressure: the normal force exerted by a homogeneous liquid or gas, per unit of area, on the wall of the container .
Pressure Diagnostics
The practice of measuring pressures and flows in buildings to control air leakage, and also to ensure adequate heating and cooling air flows and ventilation.
Pressure difference: the difference in pressure of the volume of air enclosed by the building envelope and the air surrounding the envelope.
Pressure drop. The loss of force applied over a filtering surface due to restriction of airflow.
Pressure Pan: A device used to block a duct register while measuring the static pressure behind it.
Pressure, Static: In flowing air, the total pressure minus velocity pressure. The portion of the pressure that pushes equally in all directions.
Pressure, Total: In flowing air, the sum of the static pressure and the velocity pressure.
Pressuretrol; A control that turns a steam boiler's burner on and off as steam pressure changes.
Pressure, Velocity: In flowing air, the pressure due to the velocity and density of the air.
Prevention of Significant Deterioration (PSD) - EPA program in which state and/or federal permits are required in order to restrict emissions from new or modified sources in places where air quality already meets or exceeds primary and secondary ambient air quality standards.
Preventive Maintenance: Regular and systematic inspection, cleaning, and replacement of worn parts, materials, and systems. Preventive maintenance helps to prevent parts, material, and systems failure by ensuring that parts, materials and systems are in good working order.
Primary Standard - A pollution limit based on health effects. Primary standards are set for criteria air pollutants.
Probit analysis: A statistical analysis whereby the proportion of people casting different comfort votes at a particular temperature can be estimated for a population from the results from a sample.
Profile angle (vertical shadow angle): the angle between the direction of the sun resolved in a vertical plane perpendicular to the face of the solar aperture, on the normal of the solar aperture. This angle is used to predict the effect of shading devices in sectional drawings.
Prime Mover>: The engine, turbine, water wheel, or similar machine that drives an electric generator; or, for reporting purposes, a device that converts energy to electricity directly (e.g., photovoltaic solar and fuel cells).
Prime Window: The main window installed on the outside wall consisting of fixed or moveable lights that slide on permanently fixed tracks (not to be confused with a storm window).
Priority List: The list or ranking of installation measures developed by a program to produce the most cost effective energy savings results based on a savings to investment ratio calculation.
Program Income: Income earned by the grantee from grant-supported activities, including but not limited to, income from service fees, sale of commodities, usage or rental fees, and royalties on patents and copyrights.
Psycogenic Illness: This syndrome has been defined as a group of symptoms that develop in an individual (or a group of individuals in the same indoor environment) who are under some type of physical or emotional stress. This does not mean that individuals have a psychiatric disorder or that they are imagining symptoms.
Psychosocial Factors: Psychological, organizational, and personal stressors that could produce symptoms similar to those caused by poor indoor air quality.
Psychrometrics: The study of the relationship between air, water vapor, and heat.
Psychophysics: The branch of psychology dealing with the relationship between our sensations and the stimuli from the physical world.
Psychometry: the study of the interactions between temperature and water vapour in air. Includes relative humidities, wet and dry bulb temperatures, enthalpy, and so on
Purifier: A purifier is a device that cleans the air of viruses and microscopic organisms as well as dust and allergens. Purifiers are especially useful for people who suffer from allergies and wish to live an allergy-free lifestyle.
Pumped Storage Hydroelectric Plant>: A plant that usually generates electric energy during peak-load periods by using water previously pumped into an elevated storage reservoir during off-peak periods when excess generating capacity is available to do so. When additional generating capacity is needed, the water can be released from the reservoir through a conduit to turbine generators located in a power plant at a lower level.
Purlins: Framing members that sit on top of rafters, perpendicular to them, designed to spread support to roofing materials.
PV - Photovoltaic: A solid-state electrical device that converts light directly into direct current electricity of voltage-current characteristics that are a function of the characteristics of the light source and the materials in and design of the device. Solar photovoltaic devices are made of various semi-conductor materials including silicon, cadmium sulfide, cadmium telluride, and gallium arsenide, and in single crystalline, multi-crystalline, or amorphous forms.

Q
Quality Assurance/Quality Control (QA/QC) - A system of procedures, checks, audits, and corrective actions to ensure that all research design and performance, environmental monitoring and sampling, and other technical and reporting activities achieve the program's desired data quality objectives (DQOs).
R
'R' Value : the thermal resistance to heat flow across a sample material of a unit area and known thickness caused by a temperature difference across it. This is often used to give a comparative value of the effect of different insulating materials. (m2.K/W)
Radiance of the sky (Ls) : the radiant flux emitted in a small solid angle from a specific area of the sky in the direction of the observer expressed as the flux received normal to the beam per unit solid angle. (W/m2.sr)
Radiant Barrier: A foil sheet or coating designed to reflect heat producing sun rays.
Radiant flux, radiant power: power emitted, transmitted or received in the form of radiation. (Unit: W)
RADIANT HEAT TRANSFER: Radiant heat transfer occurs when there is a large difference between the temperatures of two surfaces that are exposed to each other, but are not touching.
Radiant Temperature: The average reflective temperature of objects in a home, like walls, ceiling, floor, and furniture.
Radiant heat transfer : the transfer of heat energy from a location of higher temperature to a location of lower temperature by means of electromagnetic radiation. Radiant heating is due to infrared radiation and its use is very prevalent in passive systems. see also infra-red radiation
Radiative heat transfer : Heat transfer by electromagnetic radiation. Often divided into short-wave radiation - generally taken as those wavelengths associated with the solar spectrum (300-3,000nm) and longwave radiation (>3,000nm).
Radiator: Apparatus for heating of a room, which gives off heat to the space by radiation and convection.
Radiation: Heat energy originating on a hot body like the sun and traveling from place to place through the air.
RADON (Rn) AND RADON DECAY PRODUCTS: Radon is a radioactive gas formed in the decay of uranium. The radon decay products (also called radon daughters or progeny) can be breathed into the lung where they continue to release radiation as they further decay.
Reactive metabolites: are substances that interfere with the body's ability to build up and break down complex molecules used to help the
Reasonably Available Control Technology (RACT) - Control technology that is reasonably available, and both technologically and economically feasible. Usually applied to existing sources in nonattainment areas; in most cases is less stringent than New Source Performance Standards (NSPS).
Recirculated air: return air passed through the conditioner before being resupplied to the conditioned space. The air contditioning unit takes in outdoor air but also a part from the rooms.
RE-ENTRAINMENT: Situation that occurs when the air being exhausted from a building is immediately brought back into the system through the air intake and other openings in the building envelope.
RE-ENTRY: Situation that occurs when the air being exhausted from a building is immediately brought back into the system through the air intake and other openings in the building envelope.
Reference design: a detailed specification of the passive solar features of a hypothetical passive solar building used as the subject of performance analysis.
Reference temperature: a fixed indoor temperature in the definition of the net reference load. also the fixed indoor temperature in the reference nonsolar building used in the definition of solar savings.
Reflectance: ratio of the reflected radiant or luminance flux to the incident flux in the given conditions. Can be defined for a incident radiatior of given spectral composition polarization and geometrical distribution)
Reflectance (visible): the ratio or percentage of the amount of light reflected by surface to the amount incident upon it. Good light reflectors are not necessarily good heat reflectors.
Reflective Glass: radiant energy is reflected from both inside and outside surfaces of a sheet of parallel sided glazing. Multiple inter-reflections occur within the glazing. The ratio of the overall reflected radiant energy to the incident radiant energy is known a the reflectance. Its value depends on the angle of incidence. Energy inter-reflected from the inside face is dependent on the absorbability of the material and so is also dependent on wavelength. For any wavelength and angle of incidence, absorptance reflectance + transmittance = 1. The solar heat gain coefficient of reflective glass ranges from 0.10 to 0.40.
Reflectance of opaque materials: the proportion of radiation reflected by surface. the reflectance varies for different wavelengths and angles of incidence: for instance white paint has an average reflectance of 0.71 for normal incidence solar radiation and 0.11 for long-wave (thermal) radiation. For any wavelength and angle of incidence, absorbance + reflectance = 1.
Reflected (global) so1ar radiation: radiation that results from reflection of the global solar radiation by the surface of the Earth and by an surface intercepting that radiation.
Reformulated Gasoline - Specially refined gasoline with low levels of smog-forming volatile organic compounds (VOCs) and hazardous air pollutants. The 1990 Clean Air Act requires sale of reformulated gasoline in the nine smoggiest areas in the U.S.
Refractive index: a property of glazing materials that determines the reflection/refraction characteristics of the glazing.
Refrigerant: A special 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.
Regenerative cooling: process of utilizing heat which is rejected or absorbed in one part of the cycle to function usefully in another part of the cycle by heat transfer .
Regional Greenhouse Gas Initiative (RGGI) - A cooperative effort by Northeastern and Mid-Atlantic states to reduce carbon dioxide emissions. The RGGI states will develop a regional strategy by April 2005 for controlling emissions. This strategy will more effectively control interstate transport and international transport of greenhouse gases, and will require electric power generators in participating states to reduce carbon dioxide emissions.
Regional Haze - The haze produced by a multitude of sources and activities, which emit fine particles and their precursors across a broad geographic area. The U.S. regulations require states to develop plans to reduce the regional haze that impairs visibility in Class I areas.
Register: The grille cover over a duct outlet for warm air distribution or cold air return.

Regression (linear): A statistical technique by which the variation of a dependent variable can be predicted from the value of an independent variable (or variables) through a Regression Coefficient (or coefficients) plus a constant term. (y = a.x + b)
Reheating of air : in an air conditioning system, the final step in treatment in the event the temperature is too low.
RELs: Recommended Exposure Limits (recommendations made by the National Institute for Occupational Safety and Health (NIOSH)).
Relamping: The replacement of an existing, standard light bulbs with lower wattage energy efficient bulbs like compact fluorescent lamps.
Relative humidity (RH): the water vapour pressure in the air expressed as a proportion of the saturated water vapour pressure (ie the highest possible value) at the current air temperature. Air that is completely saturated has 100% relative humidity.
Relative sunshine duration: ratio of sunshine duration to possible sunshine duration within the same period
Relay: An automatic, electrically-operated switch.
Remote Sensing - The collection and interpretation of information about an object without physical contact with the object; e.g., satellite imaging, aerial photography, and open path
Renewable Energy: The term renewable energy generally refers to electricity supplied from renewable energy sources, such as wind and solar power, geothermal, hydropower, and various forms of biomass. These energy sources are considered renewable sources because they are continuously replenished on the Earth.

Reset Controller: Adjusts fluid temperature or pressure in a central heating system according to outdoor air temperature.
Resistance: The property of a material resisting the flow of electrical energy or heat energy.
Resistance value (RSI): thermal resistance value. Measurement of the ability of a material to resist heat transfer
Resistivity : the thermal resistance of unit area of a material of unit thickness to heat flow caused by a temperature difference across the material. (m2K/W)

Retail Competition: In states with retail competition, consumers have the opportunity to choose their energy provider and purchase products based on the price or on the source of power supplied to their home or business.
Residential wood combustion (RWC): the process of burning wood for home heating purposes.
Residual Fuel Oil>: The topped crude of refinery operation, includes No. 5 and No. 6 fuel oils as defined in ASTM Specification D396 and Federal Specification VV-F-815C; Navy Special fuel oil as defined in Military Specification MIL-F-859E including Amendment 2 (NATO Symbol F-77); and Bunker C fuel oil. Residual fuel oil is used for the production of electric power, space heating, vessel bunkering, and various industrial purposes. Imports of residual fuel oil include imported crude oil burned as fuel.
Residuum: input definition
Respiration: production of carbon dioxide and heat by ripening of perishables in storage; also the breathing process of animals
Respiratory Disease - A disease affecting the respiratory system.
Return Air: Air circulation back to the furnace from the house to be heated by the furnace and supplied to the rooms.
Re-Weatherized Unit: Any unit that received weatherization services prior to September 30, 1985 and has received additional services under subsequent grants or allowed by current DOE regulations.
Retrofit: An energy conservation measure applied to an existing building or the action of improving the thermal performance or maintenance of a building.
Rhinitis. Inflammation of the lining of the nose.
Rim Joist: The outermost joist around the perimeter of the floor framing.
Room temperature : used colloquially to mean the ordinary temperature one is accustomed to find in dwellings. Technically it can mean the temperature of (l) a room in which a refrigerator is being operated or tested; (2) a room being conditioned for the occupant's comfort.
Running Losses - Evaporation of motor vehicle fuel from the fuel tank while the vehicle is in use.
RMQA, 1998: A 1998 study led by the Regroupement Montr�alais pour la qualit� de l'air. The study assessed the impact of air pollution on health and the environment in the Greater Montreal area and identified wood combustion as a major source of air pollution.
S
Sampling program: a field measurement study during which data is collected through samples and analyzed.
Saturated air: moist air in which the partial pressure of water vapour equals the vapour pressure of water at the existing temperature. This occurs when dry air and saturated water vapour coexist at the same dr -bulb temperature.
Saturated temperature : of a fluid, the boiling point corresponding to a given pressure; evaporation temperature, condensation temperature.
Saturation ratio : the ratio of the specific humidity of humid air to that of saturated air at the same temperature and pressure, usually expressed as a percentage .
Saturation pressure: the saturation pressure for a pure substance for any given temperature is that pressure at which vapour and liquid, or vapour and solid, can coexist in stable equilibrium.
SANITIZER: One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an anti-microbial to be a sanitizer when it reduces but does not necessarily eliminate all the microorganisms on a treated surface. To be a registered sanitizer, the test results for a product must show a reduction of at least 99.9% in the number of each test microorganism over the parallel control.
Savings-to-Investment Ratio (SIR): They are computed over the lifetimes of the retrofit measures installed and expressed in terms of the net present value of the retail cost of the dwelling's fuel. Under some methodologies, other benefits, etc. Investment usally takes into account materials, labor, and support costs. SIRs of greater than one are counted as cost effective under this DOE WAP method of determining cost-effectiveness.
Scrubber - An air pollution device that uses a spray of water or reactant or a dry process to trap pollutants in emissions.
Sealants : flexible materials used on the inside of a building to seal gaps in the building envelope thereby preventing uncontrolled air infiltration and exfiltration.

Sealed Combustion Heater: A heater that draws air for combustion from outdoors and has a sealed exhaust system.
Seasonal Efficiency: Refers to the overall efficiency of the central heating system including on and off cycle fuel utilization and heat loss. The calculation of these factors is represented in the Annual Fuel Utilization Efficiency (AFUE) rating for the appliance. Distribution system loss is not factored into the AFUE.
Seasonal Energy Efficiency Ratio (SEER): A measure of seasonal or annual efficiency of a central air conditioner or air conditioning heat pump. It takes into account the variations in temperature that can occur within a season and is the average number of Btu of cooling delivered for every watt-hour of electicity used by the heat pump over a cooling season.
Seasonal Performance Factor (SPF): Ratio of useful energy output of a device to the energy input, averaged over an entire heating season.
Secondary Standard - A pollution limit based on environmental effects such as damage to property, plants, visibility, etc. Secondary standards are set for criteria air pollutants.
Sedimentary rocks: Sedimentary rocks have their origins in the bottom of oceans, lakes, rivers and swamps such as was found millions of years ago when the plants and animals that eventually would become petroleum were deposited.
Selective coating : finishes applied to materials to improve their performance in relation to radiation of different wavelengths: for example those applied to solar absorbers would seek to have a high absorptance of solar radiation and a low emittance of long-wave (thermal) radiation, while those for glazing have a high transmittance to solar radiation and high reflectance of long wavelengths.
Selective surface (absorber) : a surface absorbing essentially all incident solar radiation (short wave high temperature source), while emitting a small fraction of thermal radiation (long wave low temperature source).
Semantic differential: A technique for obtaining a value for subjective response in which the subject is asked to denote the intensity of a stimulus by choosing a subdivision between two extremes.
Semi-enclosed sunspace: a sunspace that shares common walls with the associated building.
Sensible heat: heat which is associated with a change in temperature in contrast to a heat interchange associated with a change of state (latent heat).
Sensitivity date: date that express the dependence of the heating performance of a passive solar heating system on individual parameters of the system design.
Sequencer: A bimetal switch that turns on the elements of an electric furnace in sequence.
Sequestration: A term that is used to refer to the uptake of CO2 from the atmosphere by plants and its subsequent storage as biomass.
Settling: This term refers to the effect of insulation depressing over time and, thereby, reducing the overall energy efficiency of the materials. This process is primarily the result of using too much air when installing the blown-in insulation - commonly called "fluffing," or the effect of long periods of time on the materials. One reason to re-inspect some work several months after installation to assess the settling factor. Settling can also occur during the installation of sidewall insulation when the cavity is not completely filled. This is usually avoided if "dense pack" protocols are followed during the installation.
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 .20 to .45.
Sheathing: A structural sheeting, attached on top of the framing, underneath siding, or on the roof of a building.
Sheeting: Common term for any building material used for covering a building surface.
Shell: The building's exterior envelope including walls, floor, and roof.
Shingle: A modular roofing material, usually asphalt, that is installed in overlapping rows to cover the entire roof.
Short Circuit: A dangerous malfunction in an electrical circuit where electricity is flowing through conductors and into the ground without going through an electric load, like a light or motor.
SHORT-CIRCUITING: Situation that occurs when the supply air flows to return or exhaust grilles before entering the breathing zone (area of a room where people are). To avoid short-circuiting, the supply air must be delivered at a temperature and velocity that results in mixing throughout the space.
SICK BUILDING SYNDROME (SBS): Term that refers to a set of symptoms that affect some number of building occupants during the time they spend in the building and diminish or go away during periods when they leave the building. Cannot be traced to specific pollutants or sources within the building.
Sidewall Insulation: The process of installing insulation material, usually blown cellulose, into the non-insulated wall stud cavities of a structure to reduce heat loss. Installation is achieved by drilling one or more rows of holes into the wall, one in each stud cavity. To achieve the most effective results, a dense pack protocol is used to install "high density" insulation materials. The "packing" of the materials should be tight enough that the installer cannot move the insulation when complete. It is common to install materials at 3.5 pounds per square foot.
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.
Sinusitis. Inflammation of a sinus membrane, especially in the nasal region
SI units: (Systeme International d'Unites) the International System of Units being adopted throughout the world.
Skin temperature: The average temperature of the skin surface.
Skin wettedness: A theoretical measure of the coverage of the skin by sweat needed to explain the rate of evaporation of sweat as a proportion of the total skin surface area.
Skylight: horizontal or sloping window in the ceiling of a room.
Sling Psychrometer: device holding two thermometers that is slung through the air to measure relative humidity.
Small Hydro: In addition to very large hydro plants in the West, the United States has many smaller hydro plants. Like large plants, small-scale hydroelectric systems capture the energy in flowing water and convert it to electricity. Although the potential for small hydroelectric systems depends on the availability of suitable water flow, these systems can provide cheap, clean, reliable electricity where the resource exists.

Smog - A mixture of pollutants, principally ground-level ozone, produced by chemical reactions in the air involving smog-forming chemicals. A major portion of smog-formers comes from burning of petroleum-based fuels such as gasoline. Other smog-formers, volatile organic compounds, are found in products such as paints and solvents. Smog can harm health, damage the environment and cause poor visibility. Major smog occurrences are often linked to heavy motor vehicle traffic, sunshine, high temperatures and calm winds or temperature inversion (weather condition in which warm air is trapped close to the ground instead of rising). Smog is often worse away from the source of the smog-forming chemicals, since the chemical reactions that result in smog occur in the sky while the reacting chemicals are being blown away from their sources by winds.
Softwood: A soft tree species with less density and energy per piece of wood than hardwood. (E.g. Pine, Spruce, Fir, Balsam, Hemlock...)

Soffit: The underside of a roof overhang or a small lowered ceiling, as above cabinets or a bathtub.
SOIL GAS: The gas present in soil which may contain radon.
SOIL-GAS-RETARDER: A continuous membrane or other comparable material used to retard the flow of soil gases into a building.
Sol-air temperature: the hypothetical temperature which would give the same temperature distribution and heat flow in a building element that would result from the impact of the actual combination of the absorbed short wave radiation, long wave exchange with sky and ground, forced convection due to wind at the given external air temperature . It is used to assess transfer of heat through a specific building element of a given surface colour. Different sol-air temperatures are encountered on differently orientated surfaces for materials of the same surface properties.
Solar absorptance : the fraction of incident solar radiation that is absorbed upon striking a surface.
Solar aperture : that portion of the solar wall covered by glazing.
Solar collection area : the projected area of a collector normal to the direction of the sun.
Solar collector: -a device for capturing solar energy, ranging from ordinary windows to complex mechanical devices.See also flat plate collector, focussing collector
Solar constant : the irradiance of solar radiation beyond the earth's atmosphere at the average earth-sun distance on a surface perpendicular to the sun's rays. The value for the solar constant is 1.353 kW/m2.
Solar fraction (or percentage solar) : the percentage of the total heat load supplied by the solar heating system, including useful losses from the storage .
Solar gain: Heat from the sun, entering a room through transparent surfaces (kW/m2).
Solar Heat: Radiant energy from the sun with wavelengths between 0.7 and 1 micrometers.
Solar heat gain : in passive solar heating a term referring to the amount of heat gained through windows over the heating season. Net solar gain refers to the solar heat gain less the heat losses through the windows (kWh/m2).
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 Heat Gain Factor (SHGF): Solar heat gain amount on a surface with a particular angle and orientation expressed in Btus per square foot per hour.
Solar load ratio (SLR) : ratio of solar gain to building load used in SLR correlations.
Solar radiation : radiation emitted by the sun, including infrared radiation, visible light and ultraviolet radiation.
Solar savings fraction (SSF) : the ratio of the solar savings to the energy requirement of the reference nonsolar building.
Solar spectrum : the radiation emitted by the sun outside the atmosphere approximates to that emitted by a black body at 6000oK. At the surface of the earth, the majority of the radiation falls within a range of wavelengths from 300 to 2,500 nm and typically about ha1f the energy comes in the form of visible light (380 to 700 nm wavelength). Ultra violet radiation has wavelengths shorter than 380 nm and only forms a very small proportion of the spectrum. Due to water vapour and carbon dioxide and other absorbing gases in the atmosphere, several bands of long wave radiation are substantially removed.
Solar time : a time scale based on the movement of the sun, such that noon is when the sun is at the highest of its arc and is true south, as opposed to local standard time.
Solar Transmittance: The percent of total solar energy transmitted by a material.
Solenoid: A magnetic device that moves a switch or valve stem.
Solid state: one of three states of matter characterized by stability of dimensions, relative incompressibility , and molecular motion held to limited oscillation. [note the term solid state is often used to talk about solid-state semiconductors].
Solution Gas: natural gas that is dissolved in the crude oil within the reservoir and is released to the atmosphere when the crude oil is pumped to the surface.
Sound insulation: The ability of building elements to reduce the sound level between internal spaces, or between outdoors and indoors. In HVAC systems: acoustical treatment of fan housings, supply ducts, space enclosures, and other parts of system and equipment to isolate vibration or to reduce noise transmission
Source - Any place or object from which pollutants are released. A source can be a power plant, factory, dry cleaning business, gas station or farm. Cars, trucks and other motor vehicles are sources, and consumer products and machines used in industry can be sources too. Sources that stay in one place are referred to as stationary sources; sources that move around, such as cars or planes, are called mobile sources.
Space Heating: Heating the living spaces of the home with a room heater or central heating system.
Span: Horizontal distance between supports.
Specific heat: the amount of heat required to raise the temperature of a unit mass of any substance one degree as a fraction of that required to raise the temperature of unit mass of a standard substance one degree (usually water at 15oC).
Specific heat capacity : a measure amount of energy required to raise a unit mass or volume of a material through a unit temperature change. (kWh/kg.K, J/kg.K. kWh/m3.K, J/m3.K)
Specific volume : the volume of a substance per unit mass; the reciprocal of density.
Spectrum (of radiation) : display or specification of the components of the radiation considered in terms of intensity and wavelength. (Notes: (l) there are line spectra, where the spectrum consists of a finite number of 'lines' at particular wavelength(s) and continuous spectra where there is an infinite number of wavelengths with no sudden discontinuities of intensity. Some spectra exhibiting both these characteristics. (2) this term is also used for spectral efficiencies [excitation spectrum, action spectrum].
Specular reflectance : proportion of incoming radiation which undergoes specular reflection.
Specular reflection : reflection at a surface where the angle of reflection (more or less) equals the angle of incidence (as happens in a mirror)
Specular surface : a surface with specular reflection properties. For example finishes such as polished aluminium, stainless steel or tin.
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.Spherical irradiance, radiant fluence rate (at a point): quantity defined by the formula

where d_ is the solid angle of each elementary beam passing through the given point and Le its radiance at that point. (Unit: W/m2)
Split-System Air Conditioner: air conditioner having the condenser and compressor outdoors and the evaporator indoors.
Spray pond: arrangement for lowering the temperature of water in contact with outside air by evaporative cooling of the water. The water to be cooled is sprayed by nozzles into the space above a body of previously cooled water and allowed to fall by gravity into it.
Stack - A chimney, smokestack, or vertical pipe that discharges used air.
Stack effect: the tendency of air or gas in a duct or other vertical passage to rise when heated due to its lower density in comparison with that the surrounding air or gas. In buildings, the tendency towards displacement (caused by an increase in temperature) of internal heated air by unheated outside air, due to the difference in density of outside and inside air. See Convective
Standard air: dry air at a pressure of 101.325 kPa at a temperature of 20oC. The density is than 1.2041 kg/m3
Standard conditions: a set of physical, chemical or other parameters of a substance or system which defines an accepted reference state or forms a basis for comparison.
Stage I Controls - Systems placed on fuel storage tanks to control and capture gasoline vapors during loading of the tanks by delivery trucks.
Stage II Controls - Systems placed on service station gasoline pumps to control and capture gasoline vapors during refueling, including vapor recovery nozzles.
Standing Loss: Heat loss from a hot water storage tank through its shell.
State Implementation Plan (SIP) - A detailed description of the programs a state will use to carry out its responsibilities under the Clean Air Act. State implementation plans are collections of the regulations used by a state to reduce air pollution in nonattainment areas. The Clean Air Act requires that EPA approve each state implementation plan. Members of the public are given opportunities to participate in review and approval of state implementation plans.
Static Pressure: Condition that exists when an equal amount of air is supplied to and exhausted from a space. At static pressure, equilibrium has been reached.
Stationary Source - A place or object from which pollutants are released and which does not move around. Stationary sources include power plants, gas stations, incinerators, houses etc.
Steady conditions: an operating state of a system, including its surroundings, in which the extent of change with time of all the significant parameters is so small that no important effects on the performance can be observed or measured.
Steady-state model (of thermal comfort): A theoretical model of thermal response based on climate chamber measurements in conditions which are held constant in time.
Stratosphere - Part of the atmosphere, the gases that encircle the Earth. The stratosphere is a layer of the atmosphere 9 to 31 miles above the Earth. Ozone in the stratosphere filters out harmful sun rays, including a type of sunlight called ultraviolet B, which has been linked to health and environmental damage.
Steady State Efficiency: the measurement of heat system balance in the on-cycle when heat into system equals heat out. Generally provided as a percentage of the maximum available heat generation capacity (100%) against the amount of usable heat being sent to the distribution system. This figure can also represent the percentage of heat being used within the system as compared to the heat lost through the flue. The reading is most valid when the stack temperature becomes constant and the distribution pumps or blowers are operating.
Steam Electric Plant (Conventional): A plant in which the prime mover is a steam turbine. The steam used to drive the turbine is produced in a boiler where fossil fuels are burned.
Steam Trap: An automatic valve that closes to trap steam in a radiator until it condenses.
Steam Ventc; A bimetal-operated air vent that allows air to leave steam piping and radiators, but closes when steam strikes the surface.
STERILIZER: One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an antimicrobial to be a sterilizer when it destroys or eliminates all forms of bacteria, fungi, viruses, and their spores. Because spores are considered the most difficult form of a microorganism to destroy, EPA considers the term sporicide to be synonymous with "sterilizer."
Stop: A thin, trim board for windows and doors to close against or slide against.
Strike Plate: The metal plate attached to the door jamb that the latch inserts into upon closing.
Stud: A vertical wood or metal framing member used to build a wall.
Sub bituminous Coal: Sub bituminous coal, or black lignite, is dull black and generally contains 20 to 30 percent moisture. The heat content of sub bituminous coal ranges from 16 to 24 million Btu per ton as received and averages about 18 million Btu per ton. Sub bituminous coal, mined in the western coal fields, is used for generating electricity and space heating.
Sub-Floor: The sheathing over the floor joists and under the floor covering.
Subject A person taking part in a comfort survey.
Subject population: A group of people who form the basis for a comfort survey.
Subject sample: A sample of the subject population who participate in the survey.
Subjective response: The sensation caused by a physical stimulus (generally a comfort vote).
SUB-SLAB DEPRESSURIZATION SYSTEM (ACTIVE): A system designed to achieve lower sub-slab air pressure relative to indoor air pressure by use of a fan-powered vent drawing air from beneath the slab.
SUB-SLAB DEPRESSURIZATION SYSTEM (PASSIVE): A system designed to achieve lower sub-slab air pressure relative to indoor air pressure by use of a vent pipe routed through the conditioned space of a building and connecting the sub-slab area with outdoor air, thereby relying solely on the convective flow of air upward in the vent to draw air from beneath the slab.
SUB-MEMBRANE DEPRESSURIZATION SYSTEM: A system designed to achieve lower sub-membrane air pressure relative to crawlspace air pressure by use of a fan-powered vent drawing air from under the soil-gas-retarder membrane.
Sun effect: solar energy transmitted into interior spaces through windows and building materials.
Sunlight: visible part of direct solar radiation. (Note: when dealing with actinic effect of optical radiations, this term is commonly used for radiations extending beyond the visible region of the spectrum
Sulphur: One of the elements present in varying quantities in coal which contributes to environmental degradation when coal is burned. In terms of sulphur content by weight, coal is generally classified as low (less than or equal to 1 percent), medium (greater than 1 percent and less than or equal to 3 percent), and high (greater than 3 percent). Sulphur content is measured as a percent by weight of coal on an "as received" or a "dry" (moisture-free, usually part of a laboratory analysis) basis.
Sulfur Dioxide - A criteria air pollutant and gas produced by burning coal, most notably in power plants. Some industrial processes, such as production of paper and smelting of metals, produce sulfur dioxide. Sulfur dioxide is closely related to sulfuric acid, a strong acid. Sulfur dioxide plays an important role in the production of acid rain.
Supply Air: Air that has been heated or cooled and is moved through the ducts and to the supply registers of a home.
Surface film conductance: the rate of heat flow per unit area under steady conditions between a surface and a fluid for unit temperature difference between the surface and fluid [in W/m2.K].
Sunshine (possible percentage): the actual number of hours of sunshine expressed as a percentage of the maximum possible duration for the month (or other period).
Sunshine duration [S] : sum of time intervals within a given time period (hour, day, month, year) during which the irradiance from direct solar radiation on an plane normal to the sun direction is equal to or greater that 200 W/m2.
Sunspace : see attached sunspace or semienclosed sunspace.
Suntempered building : a minimal solar building derived from a conventional building by orienting its long axis east-west and placing a substantial fraction of its window area on the south side.
Surface cooling: method used to cool air or other gas by passing it over cold surfaces.
Surface resistance : With the transition from air to material and material to air a surface resistance has to be overcome. It has two components, the surface resistance for convection/conduction Rc whose value depends on the rate of air flow over the surface and radiative surface resistance for long wave radiation heat transfer Rr whose value depends on the surface emittance and the surface temperature. These two components are assumed to act in parallel so that the overall surface resistance Ro is give by
Survey (comfort survey, field survey): An experimental investigation of subjective responses of a group of subjects in the field, generally assumed to be undertaken in such a way as to disrupt the normal pattern of the subject's lives as little as possible, and to leave subjects to decide their own dress and activity, use of environmental controls and so on
Suspended Ceiling: Modular ceiling panels supported by a hanging frame.
Sweat rate: the rate at which sweat is produced by the body.
System (Electric): Physically connected generation, transmission, and distribution facilities operated as an integrated unit under one central management, or operating supervision.
Systematic errors: Errors in the underlying assumptions of a theoretical comfort model which are temperature-dependent, and will therefore give rise to errors in its predictions
T
Taped Duct Test (TDT): A procedure using the blower door to measure the "potential" for leakage reduction of the duct system. All supply registers and return grills are taped shut following the initial blower door reading and a subsequent air leakage test taken. if closing off the duct system in this manner causes an appreciable reduction in the air leakage rate, this is an indication that there are significant duct leaks.
TCF: trillion cubic feet, a measurement used to define the production of natural gas.
Temperature : the thermal state of matter with reference to its tendency to communicate heat to matter in contact with it
Temperature difference, diffusion : temperature difference between the air temperature at supply opening and design outdoor temperature.
Temperature difference, effective : difference between the room air temperature and the supply air temperature at the outlet to the room.
Temperature difference, mean: mean of difference between temperatures of a fluid receiving and a fluid yielding heat.
Temperature Inversion - One of the weather conditions that are often associated with serious smog episodes in some portions of the country. In a temperature inversion, air does not rise because it is trapped near the ground by a layer of warmer air above it. Pollutants, especially smog and smog-forming chemicals, including volatile organic compounds, are trapped close to the ground. As people continue driving, and sources other than motor vehicles continue to release smog-forming pollutants into the air, the smog level keeps getting worse.
Temperature swing (indoor) : the range of indoor temperatures in a building (K).
Temperature swing (outdoor) : the range of outdoor temperature between day and night.
Temperature standards: Recommended values for temperature (and other environmental parameters) in buildings or rooms, values generally defined by the expected use of the room.
Therm: The unit of energy equal to 100,000 Btus or 29.3 kilowatt-hours.
Thermal break : a material of low conductivity used in an assembly to prevent flow of heat by conduction from one side of the assembly to the other . Often used to refer to materials used for this purpose in the frame of metal windows.
Thermal bridge : Non- or relative low-insulated connections between indoor and outdoor environment and may compromise the effect of thermal insulation: for example, framing members in insulated frame walls or metal ties in cavity wall and panel construction.
Thermal Bridging: Rapid heat conduction resulting from direct contact between very thermally conductive materials like metal and glass.
Thermal Bypass: Similar to a convection loop, this structural heat loss is characterized by heated air traveling up exterior or interior stud cavities and leaking out the top of that cavity to the attic through joints and cracks in the framing, wiring and plumbing holes, etc. These types of heat loss sources are sometimes the most difficult to locate.
Thermal comfort: The study of the relationship between man's thermal sensation and the stimulus in the form of the thermal environment in conditions of moderate heat stress (generally taken to include thermal discomfort).
Thermal conductance: rate of heat flow through a body per unit area from one of its bounding surfaces to the other for a unit temperature difference between the two surfaces, under steady conditions [e.g. W/m2.K]. See also U-Value.
Thermal conduction: process of heat transfer through a material medium in which kinetic energy is transmitted through the material from particle to particle without displacement of the particles.
Thermal conductivity: rate of heat flow through unit area and unit thickness of a homogeneous material under steady conditions when a unit temperature gradient is maintained in the direction perpendicular to area. Materials are considered homogeneous when the value of the thermal conductivity is not affected by variation in thickness or in size of the sample within the range normally used in construction. (W/m2.K)
Thermal controls: see Environmental Controls
Thermal experience: The different thermal environments experienced by a subject taking account of the order in which they occurred.
Thermal insulation: a material having a relatively high resistance to heat flow and used principally to retard heat flow.
Thermal mass: the ability of a building to accumulate heat effectively. A construction with a low thermal mass is heated quickly; a construction with a big thermal mass is heated slowly. This way construction with a big thermal mass, like concrete or brick, can store heat or cold and release it many hours later. 'Primary thermal mass' receives direct sunlight; 'secondary thermal mass' is in sight of the primary thermal mass and so receives radiative and convective energy from the primary thermal mass; 'remote thermal mass' os hidden from view of both the primary and secondary thermal mass and so receives energy by convection only.See Heat accumulation.
Thermal performance: the characteristic way in which a building reacts to the thermal climate
Thermal Power: Involves the combustion of primarily fossil fuels, but also biomass, to vaporize water as it passes through a boiler. The vapor passes through a turbine, where it expands to a lower pressure causing the shaft to rotate. The turbine shaft is connected to an electrical generator.
Thermal radiation : energy transfer in the form of electromagnetic waves from a body by virtue of its temperature, including infrared radiation, ultraviolet radiation, and visible light. The heat transfer between objects is according to difference of the fourth power of their temperatures. See also Infra-red radiation.
Thermal resistance : The thermal resistance (the reciprocal of thermal conductance - see above), denoted by R, of a construction layer is the quotient of thickness and conductivity. A construction layer with a high thermal resistance is a good insulator; one with a low thermal resistance is a bad insulator (m2.K/W).
Thermal resistivity : the reciprocal of thermal conductivity. (m2.K/W)
Thermal storage mass : building elements, usually masonry or water in containers, designed to absorb solar heat during daytime hours for release later when heat is needed.
Thermal storage volume ratio: ratio of the volume of thermal storage material to the projected area.
Thermal storage wall : a wall of massive material (masonry or water in containers) placed between the solar aperture and the heated space. Heat is transferred into the space by conduction through the masonry or conduction and convection through the water , and, if openings are provided, by natural convection. See also Trombe wall and water wall.
Thermal transmittance : the thermal transmission through 1 square metre area of a given structure (e.g. a wall consisting of bricks, thermal insulation, cavities, etc .) divided by the difference between the environmental temperature on either side of the structure. Usually called 'U-value'. (W/m2.K).
Thermocirculation : free convection from a warm zone (sunspace or Trombe-wall air space) to a cool zone through openings in a common wall.
Thermocirculation vents : openings in a common wall between cool and warm zones through which thermocirculation occurs. The vents are arranged in pairs, one of each pair near the floor and one near the ceiling.
Thermocouple: A bimetal-junction electric generator used to keep the safety valve of an automatic gas valve open.
Thermodynamics: The science of heat
Thermodynamic properties: basic qualities used in defining the condition of a substance, such as temperature, pressure, volume, enthalpy, entropy.
Thermo-regulation: the various physiological means by which the core temperature is regulated: vasoregulation, sweating and shivering.
Thermosiphon : the convective circulation of a fluid which occurs in a closed system where warm fluid uses and is replaced by a cooler fluid in the same system.
Tilt : the angle of a plane relative to a horizontal plane.
Time sampling: sampling by time of day; a wide time sample is necessary if the full experience of subjects is to be represented,
Title XVI: Term to be used interchangeably with those income groups known as SSI (Supplemental Security Income) recipients.
TLVs - Threshold Limit Values (guidelines recommended by the American Conference of Governmental Industrial Hygienists).
Toplighting : light which enters through the top part of intrior space such as clerestories, light wells or skylights.
TRACER GASES: Compounds, such as sulfur hexaflouride, which are used to identify suspected pollutant pathways and to quantify ventilation rates. Trace gases may be detected qualitatively by their odor or quantitatively by air monitoring equipment.
Transboundary Pollutants - Air pollution that travels from one jurisdiction to another, often crossing state or international boundaries. Also applies to water pollution.
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.
Transmission (light) : passage of radiation through a medium without change of frequency of its monochromatic components.
Transmission : in thermodynamics, a general term for heat travel; properly , heat transferred per unit of time.
Transmittance, radiant : the ratio of the radiant energy transmitted by parallel sided plane sheet of a given material to the radiant energy incident on the outside surface of that material: the value depends on the angle of incidence and wavelength. For any wavelength and angle of incidence, absorptance + reflectance + transmittance = 1.
Transverse sampling: A method of choosing a population sample for a survey by taking one or a few comfort votes from a large number of subjects (cf longitudinal sampling).
Trombe wall : a thermal storage wall of masonry placed between the solar aperture and the heated space. Heat is transferred into the space by conduction through the masonry and, if vents are provided, by natural convection.
Troposphere - The layer of the atmosphere closest to the earth's surface.
Toxic Release Inventory (TRI) - Database of toxic releases in the U. S. compiled from SARA Title III Section 313 reports.
Topography: the physical landscape of a region
Transformer: An electrical device for changing the voltage of alternating current.
Transmission: The movement or transfer of electric energy over an interconnected group of lines and associated equipment between points of supply and points at which it is transformed for delivery to consumers, or is delivered to other electric systems. Transmission is considered to end when the energy is transformed for distribution to the consumer.
Transmission System (Electric): An interconnected group of electric transmission lines and associated equipment for moving or transferring electric energy in bulk between points of supply and points at which it is transformed for delivery over the distribution system lines to consumers, or is delivered to other electric systems.
Truss: A lightweight, rigid framework designed to be stronger than a solid beam of the same weight.
Turbine: A machine for generating rotary mechanical power from the energy of a stream of fluid (such as water, steam, or hot gas). Turbines convert the kinetic energy of fluids to mechanical energy through the principles of impulse and reaction, or a mixture of the two.

U
UNIT VENTILATOR: A fan-coil unit package device for applications in which the use of outdoor- and return-air mixing is intended to satisfy tempering requirements and ventilation needs.
U-Value : the thermal conductance of a composite building element: see Thermal Transmittance.
Ultraviolet B (UVB) - A type of sunlight. The ozone in the stratosphere, high above the Earth, filters out ultraviolet B rays and keeps them from reaching the Earth. Ultraviolet B exposure has been associated with skin cancer, eye cataracts and damage to the environment. Thinning of the ozone layer in the stratosphere results in increased amounts of ultraviolet B reaching the Earth.
Ultraviolet radiation :electromagnetic radiation having wavelengths shorter than visible light (<380nm). This invisible form of radiation is found in solar radiation and plays a part in the deterioration of plastic glazings, paint, and furnishing fabrics.It is also the major carcenogen in sunlight.
United Nations Framework Convention on Climate Change (UNFCCC) - A treaty signed at the 1992 Earth Summit in Rio de Janeiro that calls for the "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system." The treaty includes a non-binding call for developed countries to return their emissions to 1990 levels by the year 2000. The treaty took effect in March 1994 upon ratification by more than 50 countries.
Usual" temperatures (thermal comfort): If the adaptation processes are working satisfactorily then we expect people to be comfortable in the environments they are accustomed to, for they will have had adequate opportunity to adjust the temperatures to suit their requirements, and to modify their living patterns to suit the temperatures. It follows that knowledge of these 'usual' environments would provide thermal comfort information of a basic kind.
Useful solar energy : the amount of solar energy contributing to the total heat load. It is expressed in absolute figures (kWh) or per unit collector area (kW/m2).
Utility
A utility is a municipal or private business that provides electricity to the public and is subject to governmental regulation.
V
Vapor Barrier: A material that retards the passage of water vapor.
Vapor Diffusion: The flow of water vapor through a solid material.
Vapour pressure: the pressure exerted by the molecules of a given vapour (e.g. water).
Vapor Recovery Nozzles - A special gas pump nozzles that will reduce release of gasoline vapor into the air when people put gas in their cars. There are several types of vapor recovery nozzles, so nozzles may look different at different gas stations. The 1990 Clean Air Act requires installation of vapor recovery nozzles at gas stations in smoggy areas.
VARIABLE AIR VOLUME SYSTEM (VAV): Air handling system that conditions the air to constant temperature and varies the outside airflow to ensure thermal comfort.
Vasoregulation (vasoconstriction, vasodilation): The physiological mechanism by which the body regulates the supply of blood to the periphery of the body to reduce heat loss from the skin (vasoconstriction) or enhance it (vasodilation).
Veiling Reflection: Light reflection from an object or task that obscures details.
Veneer: The outer layer of a building component (e.g., interior doors often have a wood veneer; some wood-frame houses have brick veneer walls, etc.).
Vent Connector: The vent pipe carrying combustion gases from the appliance to the chimney.
Vent Damper: An automatic damper powered by heat or electricity that closes the chimney while a heating device is off.
Ventilation: Refers to the controlled air exchange within a structure. All dwellings must "breathe" and proper ventilation rates must be determined. If the structure requires more interior/exterior air exchanges, there are mechanical and non-mechanical options for increasing those rates. The most common option is passive ventilation through the installation of roof, soffit, or gable vents.
Ventilation losses : the heat losses associated with the continuous replacement of warm, stale air by fresh cold air.
VENTILATION RATE: The rate at which indoor air enters and leaves a building. Expressed in one of two ways: the number of changes of outdoor air per unit of time (air changes per hour, or "ach") or the rate at which a volume of outdoor air enters per unit of time (cubic feet per minute, or "cfm").
Venting: The removal of combustion gases by a chimney.
Vermiculite: A heat-expanded mineral used for insulation.
Viscosity : that property of semifluids, fluids and gases by virtue of which they resist an instantaneous change of shape or arrangement of parts. It is the cause of fluid friction whenever adjacent layers of fluid move with relation to each other.
Visible radiation: see below
Visible spectrum : that part of the solar spectrum which is visible to the human eye: there are not precise limits for the spectral range of visible radiation since they depend upon the amount of radiant power reaching the retina and the responsivity of the observer. The lower limit is generally taken between 360 and 400 nm and the upper limit between 760 mm and 830 nm.
Visible Transmittance: The percent of visible light transmitted by a glass assembly.
Visqueen: Polyethylene film vapor barrier.
Visual performance : performance of the visual system as measured for instance by the speed and accuracy with which a visual task is performed.
Volatile - Any substance that evaporates readily.
Volatile Organic Compounds (VOCs) - Chemicals that produce vapors readily. At room temperature and normal atmospheric pressure, vapors escape easily from volatile liquid chemicals. Volatile organic chemicals include gasoline, industrial chemicals such as benzene, solvents such as toluene and xylene, and tetrachloroethylene (perchloroethylene) the principal dry cleaning solvent). Many volatile organic chemicals are also hazardous air pollutants; for example, benzene causes cancer.
Volumetric heat capacity (pc) : a measure of the ability of a unit of volume of material to store heat, namely, the heat stored in a unit of volume of material per degree of temperature rise (J/m3).
Volumetric heat loss coefficient (G-value) : the total heat loss of a dwelling (through the fabric and ventilation), divided by the heated volume and the temperature at which the loss occurs. (W/m3.K)
W
Warmth sensation: Subjective response to the thermal environment.
Water Vapor - Water substance in vapor (gaseous) form; one of the most important of all constituents of the atmosphere.
Water vapor pressure: The partial pressure of the water vapor in a sample of air
Water cooling :water used for condensation of refrigerant; condenser water.
Water wall : a thermal storage wall of water in containers placed between the solar aperture and the heated space . Heat is transferred into the space by conduction and convection through the water.
Watt>: The electrical unit of power. The rate of energy transfer equivalent to 1 ampere flowing under a pressure of 1 volt at unity power factor.
Watt-hour (Wh): An electrical energy unit of measure equal to 1watt of power supplied to, or taken from, an electric circuit steadily for 1 hour.
Weatherization Assistance Program (WAP): E's Weatherization Assistance (Wx) Program is the nation's largest residential energy efficiency program. Its mission is to increase the energy efficiency of dwellings occupied by low-income Americans, therby reducing their energy costs, while safeguarding their health and safety. DOE works directly with the states, the District of Columbia, and Native American Tribal Governments to carry out these goals. These agencies, in turn, contract with approximately 1,000 local governmental or non-profit agencies to deliver weatherization services to our low-income clients.
Weatherstripping: Flexible gaskets, often mounted in rigid metal strips, for limiting air leak age at opening in the shell like doors and windows.
Webbing: reinforcing fabric used with mastics and coatings to prevent patches from cracking.
Weep Holes: Holes drilled for the purpose of allowing water to drain out of an area in a building where it has accumulated.
Wet-bulb temperature, : thermodynamic wet-bulb temperature is the temperature at which liquid or solid water, by evaporating into air, can bring the air to saturation adiabatically at the same temperature. Wet-bulb temperature (without qualification) is the temperature indicated by a wet-bulb psychrometer constructed and used according to specification.see also evaporative equilibrium
WETT program: Wood Energy Technology Transfer training program
Window Films: Plastic films, coated with a metallic reflective surface, that are adhered to window glass to reflect heat rays from the sun.
Window Frame: The sides, top, and sill of the window forming a box around window sashes and other components.
Wind speed : the speed of the air measured in accordance with the recommendations of the World Meteorological Organization, normally measured ten meters above ground level (m/s).
Winter Smog: a high concentration of fine particles in the ambient air during the winter months. This particulate matter accumulates at the ground level under special temperature condition such as really cold temperature, low wind and temperature inversion which have for effect to retain pollutants at ground level for many hours
Work plane: reference surface defined as the plane at which work is usually done. (Note: in interior lighting and unless otherwise indicated, this plane assumed to be a horizontal plane 0.85 m above the floor and limited by the walls of the room. in the USA the work plane is usually assumed to be 0.76 m above the floor, in the USSR 0.8 m above the floor.)
Worst-Case Depressurization Test: A safety test, performed by specific procedures, designed to assess the probability of chimney back-drafting.

XY

Z
Zenith Angle - the angular distance from the sun to the zenith (the point directly above the observer) (at noon: latitude - solar declination).

ZONE: The occupied space or group of spaces within a building which has its heating or cooling controlled by a single thermosta
I