AC, HVAC, Air Filter Related Terms D-I

GLOSSARY
Air Filter Related TERMS D-I

D
Dado: A rectangular groove cut into wood.
Dander. Minute scales of animal skin.
Data-logger: An instrument which accepts and stores environmental or other data electronically ready for subsequent downloading into a computer for analysis.
Data set: A set of subjective and physical data obtained simultaneously in a comfort survey.
DAMPERS: Controls that vary airflow through an air outlet, inlet, orduct.Adamper position may be immovable, manually adjustable or part of an automated control system.
Dampproofing: the process of coating the interior or exterior of a foundation wall, f1oor, etc., with bituminous emulsions or plastic cements. The purpose of dampproofing is to prevent or interrupt the capillary draw of moisture into the wall or floor system and to the interior of the foundation.
Data Quality Objectives (DQOs) - Qualitative and quantitative statements of the overall level of uncertainty that a decision-maker will accept in results or decisions based on environmental data. They provide the statistical framework for planning and managing environmental data operations consistent with user's needs.
Daylight: visible part of global solar radiation. (Note: when dealing with the thermal effects of optical radiations, this term is commonly used for radiations extending beyond the visible region of the spectrum.)
Daylight Factor : ratio of the illuminance at a given point on a given plane due to the light received directly or indirectly from a sky of assumed or known illuminance distribution, to the illuminance on a horizontal plane due to an unobstructed hemisphere of this sky. The contribution of direct sunlight to both illuminances is excluded. (Notes: (1) glazing, dirt effects, etc. are included. (2) when calculating the lighting of interiors, the contribution of direct sunlight must be considered separately.)
Decking: The wood material installed under roofing material to support the roofing.

Declination of sun: the angle of the sun above or below the equatorial plane. This is plus if north of the plane and minus if below and varies day by day throughout the year from +23.47o to June 21 to -23.47o to December 21.

Degree days for cooling calculations: the sum, over a stated period of days, e.g. month, of positive values of the arithmetic difference between a stated reference 'base temperature' and the daily mean dry bulb air temperature. The base temperature for assessing cooling requirements is normally set above that used for assessing heating requirements to allow for the fact that acceptable comfort temperatures in summer are higher than those adopted for winter heating assessments.

Degree days for heating calculations: the product of the number of degrees below a given base temperature and the number of days when that difference occurs. The base temperature is usually defined between 15.5o to 21oC. Different base temperatures are required to estimate heating demands, frost protection, and for relating insulation standards to internal gains.

Dehumidification: (1) condensation of water vapour from air by cooling below the dew point, (2) removal of water vapour from air by chemical or physical methods.

Dehumidifier, surface: an airconditioning unit, designed primarily for cooling and dehumidifying air through the action of passing the air over wet cooling coils.

Dehumidifying effect, air cooler: product of the weight of moisture condensed in the cooler by the constant 1060.

Dehydration: (1) removal of water vapour form air by the use of absorbing or adsorbing materials, (2) removal of water from stored goods.

Demand for Energy: The peak need for electrical energy. Some utilities levy a monthly charge for demand.
Demand Side Management (DSM): The planning and implementation of those utility sponsored activities designed to influence customer use of electricity or gas in ways that will produce desired changes in the utility's load shape, such as changes in the pattern and magnitude of the utility's load. DSM study has resulted in a variety of utility-sponsored programs to redirect their customer's usage patterns, especially in the peak load periods. While mainly an electric utility applied concept, there is some application to gas utilities as well. The ultimate goal for most utilities is to avoid the need to invest in new power plants or distribution due to excessive demands on current capacity.

Denier. A unit of fineness for fibers based on a standard of 50 milligrams per 450 meters of fiber.

Density (D): the mass of a unit of volume of material. [Kg/m3]

Der p I. A purified mite allergen from Dermatophagoides pteronyssinus, a species of mite commonly fou nd in house dust accumulations and thought to be a contributory cause of atopic house dust asthma.
Degree Days: A measure of the temperature element of climate produced by multiplying temperature difference by time.
Depressurize: Cause to have a lower pressure or vacuum with respect to a reference of a higher pressure.
Desiccant: A liquid or solid material used to absorb water or water vapor.
Descriptive scale: A subjective scale in which the subject is asked to choose between a given list of descriptions in casting a comfort vote

Design heat losses: a term expressing the total predicted envelope losses over the heating season for a particular house design in a particular climate.
Design Temperature: A high or low temperature used for designing heating and cooling systems.
Dewpoint: the temperature at which a given air/water vapor mixture is saturated with water vapor (i.e. 100% relative humidity). Consequently , if air is in contact with a surface below this temperature, condensation (dew) will form on the surface.
Diffuse lighting: a form of lighting where the light is received from a number of different directions such that a precise shadow is not formed.
Diffuse solar radiation: the component of solar radiation that has been scattered by atmospheric molecules, aerosol particles, and by cloud or other particles. The diffuse radiation is somtimes assumed to be isotropic, that is, equally intense from all points of the sky . Also solar radiation scattered by transmission through diffusing glazing, See diffuse transmission.
Diffuse transmission: the type of transmission through a diffusing or translucent glazing or other material. Transmited radiation that is scattered by interaction with the glazing material.
Diffuser: a device object or surface used to alter the spacial distribution of light by diffusing it.
Diffusion, scattering : process by which the spatial distribution of a beam of radiation is changed when it is deviated in many directions by a surface or by a medium, without change of frequency of its monochromatic components. (Note: a distinction is made between selective diffusion and non-selective diffusion according to whether or not the diffusion properties vary with the wavelength of the incident radiation.)
Diluent - Any liquid or solid material used to dilute or carry an active ingredient.
Dilution air: the air required by some combustion heating systems in order to isolate the furnace from outside pressure fluctuations and to maintain an effectively constant chimney draft.
Dilution Device: A draft diverter or barometric draft control on an atmospheric-draft combustion appliance.
Dioctylphthalate (DOP). A chemical used to thermally generate consistent particles of 0.3 microns in size. The chemical is also a known carcinogen.
Dioxin: is the common name for a family of 75 chemicals that are the unintended by-products of industrial processes involving chlorine. For example, in the paper pulp industry, dioxin forms when chlorine reacts with lignin, the substance that holds the wood of trees together.
Direct method of cooling : a system in which the evaporator is in direct contact with the material or space refrigerated or is located in aircirculation passages communicating with such spaces.

Direct gain: the directly transmitted solar radiation absorped within a room.

Direct glare: glare caused by selfluminous objects situated in the visual field, especially near the line of sight.

Direct solar gains: see Direct gain.

Direct solar radiation: solar radiation which reaches the Earth's surface after selective attenuation by the atmosphere as a collimated beam (i.e. the solar radiation which is not absorbed or diffused).

Direct sunlight: direct solar radiation in the visible wavelengths.

Directional lighting: a form of lighting where light is received from a single direction.
Disinfectants: One of three groups of antimicrobials registered by EPA for public health uses. EPA considers an antimicrobial to be a disinfectant when it destroys or irreversibly inactivates infectious or other undesirable organisms, but not necessarily their spores. EPA registers three types of disinfectant products based upon submitted efficacy data: limited, general or broad spectrum, and hospital disinfectant.
Distribution System: This term refers to that part of a central heating system used to deliver heated transfer media to the living space, and return the cooled transfer media to the appliance for re-heating. In a forced air system this includes the blower, ducts, registers, dampers, and cold air returns. In a hot water system this includes circulators, supply lines, radiators, and return lines.
Domestic Hot Water (DHW): Refers to a separate, closed system to heat potable (drinkable) water and supply it to the dwelling unit for washing, bathing, etc.
Dormer: A vertical window projecting from a roof.
Double-blind study. A type of clinical trial study design in which the study participants and the investigators do not know the identity of the interventions (or lack of interventions) until data collection has been completed.
Draft Diverter: A device located in gas appliance flue pipe. Used to moderate or divert draft that could extinguish the pilot or interfere with combustion
Drain Tile Loop: A continuous length of drain tile or perforated pipe extending around all or part of the internal or external perimeter of a basement or crawlspace footing.
Drain Trap: A dip in the drain pipe of sinks, toilets, floor drains, etc., which is designed to stay filled with water, thereby preventing sewer gases from escaping into the room.
Draught: air movement causing potential discomfort .
Drill Hole Casings: The drilling hole is fitted with a series of tubes, or casings, to prevent the collapse of the hole and contamination of the petroleum from falling dirt. Similarly, the casings prevent the contamination of the surrounding soil and water from the extraction process. These casings also guide a special mud made up of clay, water and some chemicals down the shaft to the drill bit. This mud lubricates and keeps the bit cool, as well as moves rock debris from the drilling process up the shaft and out of the way. It also prevents the oil and gas from escaping out of the hole and into the atmosphere when the reservoir is finally reached.
Dry-bulb temperature : the temperature of a gas or mixture or gases indicated by an accurate thermometer
Draft Diverter A device located in gas appliance flue pipe. Used to moderate or divert draft that could extinguish the pilot or interfere with combustion
E
Eaves: The edges of a roof system (See - Soffit)
Efficiency: The ratio of output divided by input
EC: Environment Canada
Ecliptic: the great circle cut in the celestial sphere by an extension of the plane of the sun's apparent orbit around the earth. The great circle drawn on a terrestrial globe makes an angle of about 23.27o with the equator.
Effective Temperature: the temperature of a black enclosure at 50% relativehumidity (sea level), in which a solid body or occupant would exchange the same heat by radiation, convection, and evaporation as in the existing non-uniform environment.
Efficacy The number of lumens produced by a watt used for lighting a lamp. Used to describe lighting efficiency.
Eight-Hour Ozone Standards - Since 1971, the U.S. Environmental Protection Agency (EPA) has established national air quality standards for ozone. Revised in 1997, the current national air quality standard for ozone is 0.08 parts per million (ppm), or 80 parts per billion (ppb), averaged over 8 hours. For a given geographic area to be in compliance, its fourth highest 8-hour concentration in a year, averaged over three years, must be equal to or less than that amount.
Electret Air Filter: An Electret Air Filter is a type of electronic air filter. The Filter, known as an Electret, is given a positive charge that causes air borne particles to stick to it as they pass through.
Electricity Supplier: As states restructure their electricity markets, an increasing number of customers will be able to choose from a range of energy suppliers who market different types of power products, including green power from renewable energy. Restructured local utilities offer electricity products generated exclusively from renewable resources or, more frequently, electricity produced from a combination of fossil and renewable resources. In states without restructured electricity markets, local utilities may offer green pricing programs, where customers may elect to have their utility generate a portion of their power from renewable sources.
Electromagnetic radiation: (1) emission or transfer of energy in the form of electromagnetic waves or photons. (2) these electromagnetic waves or these photons.
Electronic Air Purifier
Electronic Air Purifiers do not use air filters like conventional air purifiers. Instead, they use electricity to charge the air travelling though them. Electronic air purifiers come in three basic types: Negative Ionizing Purifiers, Electret Air Filters, and Electrostatic Precipitators.
Electrostatic Precipitators
Electrostatic Precipitators are special electronic filters that use a fan to blow air into a cell where it is given a positive electrical charge. The air is then blown through special aluminum plates which carry a negative charge and attract nearly all of the durst and debris. Since they do nothing to destroy viruses, spores, and moulds, however, these plates can become a breeding ground for air born organisms.
Eligible Multi-Family Dwelling Units: A multi-family building qualifies to be weatherized in its entirety when 66% (50% for 2 and 4 unit buildings) or more of the total dwelling units in the building are determined to be eligible as per DOE rules.
Eligible Unit: A unit occupied by a household that is categorically eligible or income eligible by DOE and/or LIHEAP standards.
Emission - Release of pollutants into the air from a source. We say sources emit pollutants. Continuous emission monitoring systems (CEMS) are machines that some large sources are required to install, to make continuous measurements of pollutant release.
Emission Factor - The relationship between the amount of pollution produced and the amount of raw material processed. For example, an emission factor for a blast furnace making iron would be the number of pounds of particulates per ton of raw materials.
Emission Inventory - A listing, by source, of the amount of air pollutants discharged into the atmosphere of a community; used to establish emission standards.
Emissivity: the ratio of the radiant energy emitted from a surface at a given temperature to the energy emitted by a black body at the same temperature.

Emittance : the ratio of the radiant energy emitted (in the absence of incident radiation) from a given plane surface at a given temperature to the radiant energy that would be emitted by a perfect black body at that same temperature.
Emphysema: is characterized by disabling breathlessness caused by loss of the thin walls dividing the air spaces (alveoli), which reduces the area available for the exchange of oxygen and carbon dioxide.
Endocrine system: the endocrine system is a series of glands that secretes hormones into the bloodstream to regulate your body's processes. The main endocrine glands are: adrenal, ovary, pancreas, pituitary, testes, and thyroid.

Energy: A quantity of heat or work
Energy Consumption: The conversion or transformation of potential energy into kinetic energy for heat, light, electricity, etc.
Energy: A quantity of heat or work
Energy demand: Amount of energy required (e.g. for indoor climate control).
Energy Efficiency: Energy efficiency refers to products or systems using less energy to do the same or better job than conventional products or systems. Energy efficiency saves energy, saves money on utility bills, and helps protect the environment by reducing the amount of electricity that needs to be generated. When buying or replacing products or appliances for your home, look for the ENERGY STAR® label - the national symbol for energy efficiency.
Energy Consumption: The conversion or transformation of potential energy into kinetic energy for heat, light, electricity, etc.
Energy Education: The process used by WAP staff to inform customers of the ways they can further reduce energy consumption through altering their behavioral patterns. The most effective protocol includes multiple interaction and reinforcement with the household residents and use of a negotiated and written action plan.
Energy Efficiency: Term used to describe how efficiently a building component uses energy.
Energy Efficiency Ratio (EER): A measurement of energy efficiency for room air conditioners. The EER is computed by dividing cooling capacity, measured in British Thermal Units per hour (Btuh), by the watts of power. (See - Seasonal Energy Efficiency Rating or SEER)

Energy use: The amount of energy used (e.g. for indoor climate control), including losses of the installation.

Energy use for cooling: see cooling load.

Energy use for heating: The amount of energy needed to cover the heating demand, including losses of the installation.
Enforcement - The legal methods used to make polluters comply with air quality regulations. Enforcement methods include citations of polluters for violations of the law (citations are much like traffic tickets), fines and even jail terms. EPA and the state and local governments are responsible for enforcement of the Clean Air Act, but if they don't enforce the law, members of the public can sue EPA or the states to get action. Citizens can also sue violating sources, apart from any action EPA or state or local governments have taken. Before the 1990 Clean Air Act, all enforcement actions had to be handled through the courts. The 1990 Clean Air Act gave EPA authority so that, in some cases, EPA can fine violators without going to court first. The purpose of this new authority is to speed up violating sources' compliance with the law and reduce court time and cost.
Enhanced Recovery of Coalbed Methane (ECBM): The process of injecting a gas (carbon dioxide or nitrogen) into deep and unmineable coalbeds in order to stimulate methane production.
Enhanced Oil Recovery (EOR): The process of injecting a gas,water or some other substance into petroleum reservoirs, forcing out further product. This process extends the useful life of the reservoir.
Energy: The capacity for doing work as measured by the capability of doing work (potential energy) or the conversion of this capability to motion (kinetic energy). Energy has several forms, some of which are easily convertible and can be changed to another form useful for work. Most of the world's convertible energy comes from fossil fuels that are burned to produce heat that is then used as a transfer medium to mechanical or other means in order to accomplish tasks. Electrical energy is usually measured in kilowatt-hours, while heat energy is usually measured in British thermal units.
Energy Source: The primary source that provides the power that is converted to electricity through chemical, mechanical, or other means.
Enteric Fermentation - The natural digestive process in ruminant animals (e.g. cattle and sheep) that produces methane as a by-product.
Enthalpy: The internal heat of a material measured in Btus per pound. Total energy in a fluid (usually air) including both sensible energy (dry heat) and the latent energy associated with the water vapour in the air.
Entropy: Heat unavailable to a closed thermodynamic system during a heat transfer process.
ENVIRONMENTAL AGENTS: Conditions other than indoor air contaminants that cause stress, comfort, and/or health problems (e.g., humidity extremes, drafts, lack of air circulation, noise, and over-crowding).
Environmental controls: means by which the physical environment can be controlled: these may be active, e.g. heating or cooling systems, fans etc which use energy, or passive, such as openable windows, blinds, etc
ENVIRONMENTAL TOBACCO SMOKE (ETS): Mixture of smoke from the burning end of a cigarette, pipe, or cigar and smoke exhaled by the smoker (also secondhand smoke (SHS) or passive smoking).
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Environmental variables (thermal environment): Thermal characteristics of the environment; generally the air temperature (Ta), the radiant temperature (Tr), the water vapor pressure (Pa) (or humidity) and the air velocity (Va).

Envelope: the exterior surface of a building including all external additions e.g. chimneys, bay windows, etc.
ENVIRONMENTAL AGENTS: Conditions other than indoor air contaminants that cause stress, comfort, and/or health problems (e.g., humidity extremes, drafts, lack of air circulation, noise, and over-crowding).
ENVIRONMENTAL TOBACCO SMOKE (ETS): Mixture of smoke from the burning end of a cigarette, pipe, or cigar and smoke exhaled by the smoker (also secondhand smoke (SHS) or passive smoking).
EPA: the Environmental Protection Agency. A U.S. agency that researches and sets standards for a variety of environmental issues.
ERGONOMICS: Applied science that investigates the impact of people's physical environment on their health and comfort (e.g., determining the proper chair height for computer operators).
Estrogen: Any of several steroid hormones produced chiefly by the ovaries and responsible for promoting estrus and the development and maintenance of female secondary sex characteristics.
Eutrophication - The slow aging process during which a lake, estuary, or bay evolves into a bog or marsh and eventually disappears. During the later stages of eutrophication the water body is choked by abundant plant life due to higher levels of nutritive compounds such as nitrogen and phosphorus. Human activities can accelerate the process.
Evaporation: change of state from liquid to vapor.

Evaporative cooling: involves adiabatic heat exchange between air and water spray or wetted surface. The water is cooled by evaporation and assumes the wet-bulb temperature of the air.
Evaporative equilibrium (of a wet bulb instrument): the condition attained when the wetted wick has reached a stable and constant temperature. When the instrument is exposed to air at velocities over 4.6m/s, this temperature may be considered to approach the true wet bulb temperature.
Exfiltration: the uncontrolled leakage of air out of a building e.g. through cracks.
EXHAUST VENTILATION: Mechanical removal of air from a portion of a building (e.g., piece of equipment, room, or general area).
Exhaust Gas Recirculation System (EGR) - The controlled diversion of some of the combustion gases back into the combustion chamber, lowering the combustion temperature and reducing nitrogen oxides in the engine. This is a very effective process, because oxides of nitrogen tend to rise disproportionately with increased combustion temperatures. There are two methods of exhaust gas recirculation internally through overlap of valve opening times and externally with recirculation valves and manifolds.
Exposure - The amount of radiation or pollutant present in a given environment that represents a potential health threat to living organisms.
Extinction coefficient: a property of glazing material that characterizes the solar absorption in the material, namely, the fraction of radiation that is absorbed per unit of path length through the material.

Extraterrestrial radiation: in this context solar radiation impinging on the earth's outer atmosphere.
F
Fabric Filter - A cloth device that catches dust particles from industrial emissions.
Fahrenheit: A temperature scale used in the United States and a few other countries. On the Fahrenheit scale, water boils at 212 degrees and freezes at 32 degrees.
Family Unit: All persons living together in a dwelling unit
Fan Control ; A bimetal thermostat that turns the furnace blower on and off as it senses the presence of heat.
FEMP - Federal Energy Management Program ; A program of DOE that implements energy legislation and presidential directives. FEMP provides project financing, technical guidance and assistance, coordination and reporting, and new initiatives for the federal government. It also helps federal agencies identify the best technologies and technology demonstrations for their use.
Fenestration: Window and door openings in a building's wall.
Fiberglass: A fibrous material made by spinning molten glass used as an insulator and heat loss retardant
Fill Tube: A plastic or metal tube used for its stiffness to blow insulation inside a building cavity.
Filter: Filter is any porous device that allows the passage of air but traps air born particles, thus cleaning the air.
Fin Comb: A comb-like tool used to straighten bent fins in air conditioning coils.
Fine Particles: Minute particles dust with a diameter of less than 10µm (micrometers), namely ten times smaller than the diameter of a human hair.
Firebox: the compartment of a stove or fireplace where the wood is burned.
Fire Stop: Framing member designed to stop the spread of fire within a wall cavity.
Flame Safety Control: A control device used to stop the flow of fuel to the burner assembly in the event of no ignition.
Flashing: Waterproof material used to prevent leakage at intersections between the roof surface at walls or penetrations.
Flat plate collector: This is a solar collector, a flat assembly containing a panel of metal or other suitable material, usually a mat black colour on its sunny side, that absorbs sunlight and converts it into heat. This panel is usually in an insulated box, covered with glass or plastic to take advantage of the greenhouse effect. In the collector , this heat transfers to a circulating fluid, such as air, water or oil.

Floor heating: Heated floor, which gives off heat to the room.
Floor Joists: The framing members that support the floor area.
FLOW HOOD: Device that easily measures airflow quantity, typically up to 2,500 cfm.
Flow Rate - The rate, expressed in gallons -or liters-per-hour, at which a fluid escapes from a hole or fissure in a tank. Such measurements are also made of liquid waste, effluent, and surface water movement.
Flue: The channel of pipe used to control air flow of combustion gases.
Flue Gas - The air coming out of a chimney after combustion in the burner it is venting. It can include nitrogen oxides, carbon oxides, water vapor, sulfur oxides, particles and many chemical pollutants.
Flue Gas Desulfurization (FGD) - A technology that employs a sorbent, usually lime or limestone, to remove sulfur dioxide from the gases produced by burning fossil fuels. Flue gas desulfurization is current state-of-the art technology for major SO2 emitters, like power plants.
Fly Ash: Particle matter from coal ash in which the particle diameter is less than 1 x 10-4 meter. This is removed from the flue gas using flue gas particulate collectors such as fabric filters and electrostatic precipitators.
Foam Board: Plastic foam insulation manufactured most commonly in 4'x8' sheets in thickness of 1/4" to 3".

Focussing collector: a collector that has a reflector which focuses sunlight onto a smaller area for collection. A reflector of this type can obtain relatively high temperatures. The system is most effective for solar radiation not diffused by clouds.
Foot Candle: A measure of light striking a surface
Forced convection: convection heat transfer between a surface and an adjacent fluid (air in the present context)resulting from forced circulation of a liquid or a gas, as by a fan, jet or pump.
Fossil Fuel: Any naturally occurring organic fuel, such as petroleum, coal, and natural gas.
Fossil-Fuel Plant: A plant using coal, petroleum, or gas as its source of energy.
Fractional Distillation: input definition
Free convection : See Convective heat transfer
Free radicals: a molecule or atom with an unpaired electron. This makes it highly reactive and able to destroy other molecules.
Free-running building: A building which is neither being mechanically heated nor cooled.
Frost Line: The maximum depth of the soil where water will freeze during the coldest weather

Fuel: Any substance that can be burned to produce heat; also, materials that can be fissioned in a chain reaction to produce heat.
Fuel Cell - An electrochemical engine (no moving parts) that converts the chemical energy of a fuel, such as hydrogen, and an oxidant, such as oxygen, directly to electricity. The principal components of a fuel cell are catalytically activated electrodes for the fuel (anode) and the oxidant (cathode) and an electrolyte to conduct ions between the two electrodes.
Fugitive Emissions - Emissions not caught by a capture system.
FUNGI: Any of a group of parasitic lower plants that lack chlorophyll, including molds and mildews.
Furans: are one of a group of colorless, volatile, toxic chlorinated chemicals.

G
Gable: The triangular section of an end wall formed by the pitch of the roof.
Gas: A fuel burned in boilers and by internal combustion engines for electric generation. These include natural, manufactured, and waste gas.
Gas Heating System: A heating system that uses natural gas or bottled liquid propane gas as fuel.
Gaseous state: one of three states of matter charactemed by the greatest freedom of molecules and lack of any inherent fixed shape or volume.
Gasket: Elastic strip that seals a joint between two materials.
GAS SORPTION: Devices used to reduce levels of airborne gaseous compounds by passing the air through materials that extract the gases. The performance of solid sorbents is dependent on the airflow rate, concentration of the pollutants, presence of other gases or vapors, and other factors.
Gas Turbine Plant: A plant in which the prime mover is a gas turbine. A gas turbine consists typically of an axial-flow air compressor, one or more combustion chambers, where liquid or gaseous fuel is burned and the hot gases are passed to the turbine and where the hot gases expand to drive the generator and are then used to run the compressor.
Generating Unit: Any combination of physically connected generator(s), reactor(s), boiler(s), combustion turbine(s), or other prime mover(s) operated together to produce electric power.
Generation (Electricity): The process of producing electric energy by transforming other forms of energy; also, the amount of electric energy produced, expressed in watt-hours (Wh).
Generator: A machine that converts mechanical energy into electrical energy.
Generator Nameplate Capacity: The full-load continuous rating of a generator, prime mover, or other electric power production equipment under specific conditions as designated by the manufacturer. Installed generator nameplate rating is usually indicated on a nameplate physically attached to the generator.
Geoseismic Surveying: Geoseismic (sound) surveying and imaging is a more common and effective method of locating oil and gas reserves. Intense sound waves are sent into the earth from a series of points using dynamite, vibrator trucks, and air guns in water. These sound waves travel through the earth and are reflected back to the surface in different ways depending on the composition of the soils and how deep the rock deposits are located. Monitoring devices record the reflected sounds in terms of their movement patterns and how fast they travel through the earth. Computers can take this information and create multi-dimensional images of the subsurface landscape in order to reveal hidden reservoirs of oil and gas.
Gigawatt (GW): One billion watts.
Gigawatthour (GWh): One billion watt-hours.
Gigatonne (Gt): One Gigatonne is equivalent to a billion tonnes.
Glare: condition of vision in which there is discomfort or a reduction in the ability to see details or objects, caused by an unsuitable distribution or range of luminance, or to extreme contrast.
Glare, disability: glare that impairs the vision of objects without necessarily causing discomfort.
Glare, discomfort: glare that causes discomfort without necessarily impairing the vision of objects.
Glass Load Factor: A number combining glass's solar heat transmission and its heat conduction. Used for cooling load calculations.
Glazing: glass used in a window.
Global Climate Change
Global climate change could result in sea level rises, changes to patterns of precipitation, increased variability in the weather, and a variety of other consequences. These changes threaten our health, agriculture, water resources, forests, wildlife, and coastal areas. For more information on the science and impacts of global climate change, visit EPA's Global Warming Web site.
Global illuminance (g): illuminance [W/m2] produced by daylight on a surface.
Global radiation: the total solar radiation projected on a surface, (i.e. the sum of the direct and diffuse radiation) [W/m2].
Global Warming - An increase in the near surface temperature of the Earth. Global warming has occurred in the distant past as the result of natural influences, but the term is most often used to refer to the warming predicted to occur as a result of increased emissions of greenhouse gases. Scientists generally agree that the Earth's surface has warmed by about 1 degree Fahrenheit in the past 140 years. The Intergovernmental Panel on Climate Change (IPCC) recently concluded that increased concentrations of greenhouse gases are causing an increase in the Earth's surface temperature and that increased concentrations of sulfate aerosols have led to relative cooling in some regions, generally over and downwind of heavily industrialized areas. (See climate change)
GOVERNMENTAL: In the case of building codes, these are the State or local organizations/agencies responsible for building code enforcement.
Grain Loading - The rate at which particles are emitted from a pollution source (i.e., number of grains per cubic foot of gas emitted).
Gravity Furnace: A central heating system that uses natural gravity to distribute heat throughout the dwelling unit as opposed to forced circulation, pumps, or circulation blowers.
Green Buildings: The building industry is increasingly focused on making its buildings greener, which includes using healthier, less polluting and more resource-efficient practices. Indoor environmental quality (IEQ) refers to the quality of the air and environment inside buildings, based on pollutant concentrations and conditions that can affect the health, comfort and performance of occupants -- including temperature, relative humidity, light, sound and other factors. Good IEQ is an essential component of any building, especially a green building.
Greenhouse Effect - The warming of the Earth's atmosphere attributed to a buildup of carbon dioxide or other gases. Some scientists think that this build-up allows the sun's rays to heat the Earth, while making the infra-red radiation atmosphere opaque to infra-red radiation, thereby preventing a counterbalancing loss of heat.
Greenhouse Gas - A gas, such as carbon dioxide or methane, which contributes to potential climate change.
Green Power
Electricity that is generated from renewable energy sources is often referred to as "green power." Green power products can include electricity generated exclusively from renewable resources or, more frequently, electricity produced from a combination of fossil and renewable resources. Also known as "blended" products, these products typically have lower prices than 100 percent renewable products. Customers who take advantage of these options usually pay a premium for having some or all of their electricity produced from renewable resources. To find out more about green power, visit EPA's Green Power Partnership Web site
Green Power Marketers
Due to increased customer awareness of the environmental implications associated with power generation, a growing number of utilities and other types of energy service providers have begun offering green power products. The term "green power marketers" usually refers to energy providers operating in states that permit retail competition in the electricity markets. In states that do not allow this retail competition, many utilities have begun offering green power options under what are typically referred to as green pricing programs.
Green Power Purchasing
Green power can be purchased nationwide from several sources. Green power marketers offer green power products to consumers in deregulated markets-such as New Jersey, Pennsylvania, and New England. In states that do not allow retail competition in the electricity markets, many utilities offer renewable energy products through green pricing programs. In addition, all customers nationwide have the opportunity to buy renewable energy and stimulate the development of renewable generation sources through renewable energy certificates. Finally, customers can choose to install on-site renewable generation, such as solar panels..

Green Pricing
Green pricing refers to an optional utility service that allows customers of traditional utilities support a greater level of utility investment in renewable energy by paying a premium on their electric bill to cover any above-market costs of acquiring renewable energy resources. To find out if your utility offers a green pricing program.
Ground-level ozone: is a colorless and highly irritating gas that forms just above the earth's surface. It is called a secondary pollutant because it is produced when two primary pollutants react in sunlight and stagnant air. These two primary pollutants are nitrogen oxides (NOx) and volatile organic compounds (VOC). NOx and VOC come from natural sources as well as human activities. When ozone is combined with particulate matter it forms smog.
Gusset: A metal or wood plate added to the surface of a joint to strengthen the connection.
Gypsum Board: A common interior sheeting material for walls and ceilings made of gypsum rock powder packaged between two sheets of heavy building paper. Also called sheetrock, gyprock, or gypboard.

H
Handicapped Person: Any individual who is: 1) handicapped as defined in Section 7 (6) of the Rehabilitation Act of 1973; 2) under a disability as defined in Section 1614 (1) (3) (A) or 223 (d) (i) of the Developmental Disabilities Services and Facilities Construction Act; or 3) who is receiving benefits under Chapter 11 or 15 of Title 38, U.S.C. Other conditions may apply state to state, which can deem an individual as handicapped for the purposes of the WAP.
Hardwood: Hard tree species with dense wood that contains more energy per piece than softwood. (E.g. Elm, Hickory, Oak, Maple, Beech, Birch, Ash...)
Hazardous Air Pollutants (HAPs) - Chemicals that cause serious health and environmental effects. Health effects include cancer, birth defects, nervous system problems and death due to massive accidental releases such as occurred at the pesticide plant in Bhopal, India. HAPs are released by sources such as chemical plants, dry cleaners, printing plants, and motor vehicles (cars, trucks, buses, etc.)Heavy Fuel Oil (HFO): Industrial fuels suitable for use in boiler plant (includes Type 4, 5, 6). Heavy fuel oils are the last to be distilled during the refining process. Except for start-up and flame stabilization, virtually all petroleum used in steam plants is heavy oil.
Haze: Haze consists of sufficient smoke, dust, moisture, and vapor suspended in air to impair visibility. The term regional haze means haze that impairs visibility in all directions over a large area.
Heat: form of energy that is transferred by virtue of a temperature difference. see latent heat, radiant heat, sensible heat.

Heat accumulation : Heat Heat stored in the thermal mass (of a building). See Thermal mass.

Heat Balance Model (of thermal comfort): A model of human thermal response based on the assumption that a necessary condition for thermal comfort is a balance between the metabolic heat production and the heat loss from the body (generally an analytical model).

Heat Capacity: the amount of heat necessary to raise the temperature of a body by one degree. Numerically, the mass multiplied by the specific heat.

Heat demand : The amount of energy needed to keep the temperature of a room or building at a given value.

Heat Exchanger: a device, usually consisting of an arrangement of metal tubing used to transfer heat from one fluid to another, often used to conserve energy by heating incoming air using the heat from outgoing air.

Heat gain : Sum of internal heat gains (like heat gains from persons, lighting and apparatus) and solar heat gains.

Heat load: The heat flux which has to be removed from a room to maintain (or prevent to exceed) a required air temperature or humidity.
Heat loss (from the body): the loss of heat from the surface of the human body by conduction, convection, radiation and evaporation.

Heat loss (from a building): heat flow through building envelope components (walls, windows, roof).

Heat pump: Apparatus that transfers heat from a low (unusable) temperature level to a (usable) higher temperature level.

Heat recovery: the process of extracting heat, (usually from a fluid, gas or air) that would otherwise be wasted. For example heat recovery using a heat exchanger between incoming and exhaust air.

Heat transmission : Heat transfer through a construction, due to conduction, convection and radiation.

Heat transmission coefficient: heat transmission per unit temperature difference per area unit (usually used for total constructions).
Heating: The process of active heat supply for the benefit of climate control.

Heating degree-days (DD): The number of degrees per day that the daily average temperature (the mean of the maximum and minimum recorded temperatures) is below a base temperature, usually 65 degrees Fahrenheit, unless otherwise specified; used to determine indoor space heating requirements and heating systme sizing. Total HDD is the cumulative total for the year/heating season. The higher the HDD for a location, the colder the daily average termperature(s).

Heat Anticipator: A very small electric heater in a thermostat that causes the thermostat to turn off before room temperature reaches the thermostat setting, so that the house does not overheat from heat remaining in the furnace and ducts after the burner shuts off.
Heat Capacity: The quantity of heat required to raise the temperature of 1 cubic foot of a material 1 degree F.
Heat Gains: Term used to mean unwanted heat that accumulates in homes, making mechanical cooling desirable or necessary.
Heat Loss: The amount of heat escaping through the building shell as measured for a specific period of time (month, year, etc.)
Heat Rise; The number of degrees of temperature increase that air is heated as it is blown over the heat exchanger. Heat Rise equals supply temperature minus return temperature.
Heating season: the period of the year during which heating the building is required to maintain comfort conditions
Heat Transmission: Heat flow through the walls, floor, and ceiling of a building, not including air leakage.
Heat Transfer Coefficient: See U-value.
Heating Degree Day; Each degree that the average daily temperature is below the base temperature (usually 65 degrees F) constitutes one heating degree day.
Heating Load: The maximum rate of heat conversion needed by a building during the very coldest weather.
Heating Seasonal Performance Factor (HSPF): Rating for heat pumps describing how many Btus they transfer per kilowatt-hour of electricity consumed.
HERS: Home Energy Rating Systems: A nationally recognized energy rating program that give builders, mortgage lenders, secondary lending markets, homeowners, sellers, and buyers a precise evaluation of energy losing deficiencies in homes. Builders can use this system to gauge the energy quality in their home and also to have a star rating on their home to compare to other similarly built homes.
HEPA Filter: HEPA stands for High Efficiency Particulate Arrestance. HEPA filters were developed during World War Two as a safety device for the Manhattan Project, the American effort to develop nuclear weapons. HEPA filters use glass fibre as a filter and can clean 99.7 per cent of particles above 0.3 microns in diameter. Though brittle, these filters are now widely used in a variety of filtration devices, and are widely considered to be the best air filter available to the public.
High Limit: A bimetal thermostat that turns the heating element of a furnace off if it senses a dangerously high temperature.
Histamine: Histamine is a substance your body injects into your bloodstream to help you stay alert. However, it is often triggered by allergens. It causes fluid to be released into the skin (which causes swelling and hives), and when released into the sinuses can cause a runny nose and watery eyes.
Home Heating Index: The number of Btus of energy used by a home divided by its area in square feet, then divided by the number of heating degree days during the time period.
HOME Program: A program created under Title II (the Home Investment Partnership Act) of the National Affordable Housing Act of 1990. Provides funds for states to expand the supply of decent and affordable housing for low-income people. This program can be easily coordinated with a state's WAP efforts.
Household: Any individual or group of individuals who are living together as one economic unit for whom residential energy is customarily purchased in common or who make undesignated payments for energy in the form of rent.
House Pressure: The difference in pressure between the indoors and outdoors measured by a manometer.

HUD - U.S. Department of Urban Housing and Development

Humidifying/Dehumidifying effect: latent heat of water vaporization at the average evaporating temperature times the number of pounds of water evaporated or condensed in watts.

Humidity: the "dampness" of the air expressed either as a subjective sensation or as a physical measure of the water vapour in the air (see relative humidity, water vapour pressure).
HUMIDIFIER FEVER: A respiratory illness caused by exposure to toxins from microorganisms found in wet or moist areas in humidifiers and air conditioners. Also called air conditioner or ventilation fever.
Humidity Ratio: Same as "absolute humidity." The absolute amount of air's humidity measured in pounds of water vapor per pound of dry air.
HVAC: Heating, ventilation, and air-conditioning system.

HVAC (heating ventilating and air conditioning): A term generally applied to the hardware or the industry concerned with the supply of environmental control in buildings.

Hybrid solar heating system: solar heating system that combines active and passive techniques.
Hydrocarbons: In order to understand how crude oil and natural gas can be made up of all of these parts at the same, it helps to know that fossil fuels are composed of hydrocarbons. Hydrocarbons (CnH2n+2) are molecules which contain many carbon (C) and hydrogen (H) atoms linked together. Not all hydrocarbons are the same in shape, size and weight - some are short chains such as methane (CH4) as is the case for natural gas, and some form rings such as benzene (C6H6). Gasoline is really a collection of a specific range of hydrocarbon sizes (around C9H20) which are smaller than the hydrocarbons that make up diesel (around C14H30). (also see boiling points of hydrocarbons)
Hydroelectric Plant: A plant in which the turbine generators are driven by falling water.
Hydrogen Sulfide (H2S) - Gas emitted during organic decomposition. Also a by-product of oil refining and burning. Smells like rotten eggs and, in heavy concentration, can kill or cause illness.
Hydronic: A heating system that uses hot water or steam as the heat-transfer fluid.
HYPERSENSITIVITY DISEASES: Diseases characterized by allergic responses to pollutants. The hypersensitivity diseases most clearly associated with indoor air quality are asthma, rhinitis, and hypersensitivity pneumonitis. Hypersensitivity pneumonitis is a rare but serious disease that involves progressive lung damage as long as there is exposure to the causative agent.
HYPERSENSITIVITY PNEUMONITIS: A group of respiratory diseases that cause inflammation of the lung (specifically granulomatous cells). Most forms of hypersensitivity pneumoni are caused by the inhalation of organic dusts, including m IAQ: Indoor air quality.
IAQ BACKGROUNDER: A component of the IAQ Tools for Schools Action Kit that provides a general introduction to IAQ issues, as well as IAQ program implementation information.
I
IAQ COORDINATOR: An individual at the school and/or school district level who provides leadership and coordination of IAQ activities.
IAQ CHECKLIST: A component of the IAQ Tools for Schools Action Kit containing information and suggested easy-to-do activities for school staff to improve or maintain good indoor air quality. Each Activity Guide focuses on topic areas and actions that are targeted to particular school staff. The Checklists are to be completed by the staff and returned to the IAQ Coordinator as a record of activities completed and assistance as requested.
IAQ MANAGEMENT PLAN: A component of the IAQ Tools for Schools Kit, specifically, a set of flexible and specific steps for preventing and resolving IAQ problems.
IAQ TEAM: People who have a direct impact on IAQ in the schools (school staff, administrators, school board members, students and parents) and who implement the IAQ Action Packets.
IIllumination: The light level measured on a horizontal plane in Foot Candles
Illuminance (at a point of a surface): quotient of the luminous flux dX incident on an element of the surface containing the point, by the area dA of that element. Equivalent definition. Integral, taken over the hemisphere visible at a given point, of the expression Lv.cosY.dX. where Ly. is the luminance at the given point in the various directions of the incident elementary beams of solid angle dX and Y is the angle between any of these beams and the normal to the surface at the given point.

Impermeable not permitting gas or water pass through.
Inch of Water: Small air pressure differences caused by wind, blower doors, furnace fans, and chimneys are measured in inches of water (in.-H2O) in the American measurement system.

Incident angle: in this context the angle between the beam of solar radiation and a line perpendicular (normal) to the irradiated surface
Incidental Repairs: Under DOE rules, this term refers to the repairs on a dwelling unit necessary for the effective performance or preservation of the allowable energy conservation measures to be installed. Usually, a specific dollar amount is set by a state to limit such incidental repairs.
Incineration - A treatment technology involving destruction of waste by controlled burning at high temperatures; e.g., burning sludge to remove the water and reduce the remaining residues to a safe, non-burnable ash that can be disposed of safely on land, in some waters, or in underground locations.
INDICATOR COMPOUNDS: Chemical compounds, such as carbon dioxide, whose presence at certain concentrations may be used to estimate certain building conditions (e.g., airflow, presence of sources).

Indirect cooling : a system in which a liquid, such as brine or water, cooled by the refrigerant, is circulated to the material or space refrigerated or is used to cool air so circulated.

Indirect gain - the indirect transfer of solar heat into the space to be heated from a collector that is coupled to the space by an uninsulated, conductive or convective medium (such as thermal storage wall or roof pond).

Indirect lighting: lighting achieved by reflection, usually from wall and/or ceiling surface.

INDOOR AIR POLLUTANT: Particles and dust, fibers, mists, bioaerosols, and gases or vapors.
Indoor Air Pollution: Indoor Air Pollution is the term used to describe the amount of contaminants in the air inside a building. Indoor air pollution can often be worse than outside air pollution due to poor ventilation. Unfortunately, it is often ignored. About 80 per cent of all indoor air pollution is human skin. The remaining 20 per cent is usually made up of dust mites, pet dander, smoke, pollen, sweat, and chemical compounds from various substances.
Indoor Air Quality: Indoor Air Quality (IAQ) is a term used to describeThe quality of indoor air relative to its acceptability for healthful human habitation. It is based upon determining the level of pollution of the inside air. The IAQ of any building is measured according to guidelines set by the government and is used as a measuring stick for the efficiency of air purification and filtration systems.
Induced draft flue system: a term referring to a type of gas heating system equipped with a fan downstream of the fumace. The fan pulls gases from the fumace and propels them to the flue.
Industrial Air Pollution: This term refers to the emissions of the following pollutants: sulfur oxides, nitrogen oxides, mercury, and carbon dioxide. These air emissions contribute to such environmental concerns as urban smog; acid deposition; excessive nutrient loads to important bodies of water, such as the Chesapeake Bay; haze in national parks and wilderness areas; and global climate change.

Industrial Energy Customer: Industrial energy customers include businesses involved in manufacturing or industrial processing.

Infiltration: the uncontrolled movement of outdoor air into the interior of a building through cracks around windows and doors or in walls, roofs and floors. This may work by cold air leaking in during the winter, or the reverse in the summer.
Infrared Thermography: The science of using infrared imaging to detect radiant energy or heat loss characteristics of a building. The infrared camera or scanner electronically senses heat radiated by objects and converts that thermal energy into images visible to the human eye. The camera or scanner, similar to a camcorder in appearance, produces varying shades of black and white images of the building structure. The darker the image, the colder the corresponding surface; the lighter areas are the hotter surfaces. Some scanners can automatically record these images on video, as well as allow the operator to record audio commentary as he/she scans the building. A certain degree of interpretation skill is required to properly assess the images being recorded. Used in conjunction with a blower door, the scanner can provide valuable data, since the pressurization or depressurization can magnify air leakage sites and thermal bypasses.
Infrared radiation: electromagnetic radiation with wavelengths longer than that for light (>700 nanometers). Infrared is often divided into the near infrared (wavelength 800-2000 nm) and the far infrared (>2000nm). Almost all energy radiated by surfaces with a temperature beneath 6000 K is heat radiance. Glass, which is most transparent for visual light radiance (400 nm to 800 nm), is not always transparent to heat radiance. This is the preponderant form of radiation emitted by bodies with moderate temperatures such as the elements of a passive building.
Inhalable Particles - All dust capable of entering the human respiratory tract.
Input Rating: The measured and assigned rating indicating the level at which an energy-using device consumes electricity or fossil fuel.
Insolation: The amount of solar radiation striking a surface
Inspection and Maintenance Program (I/M program) - Auto inspection programs that are required for some polluted areas. These periodic inspections, usually done once a year or once every two years, check whether a car is being maintained to keep pollution down and whether emission control systems are working properly. Vehicles that do not pass inspection must be repaired. Enhanced I/M programs, using special machines to check for such things as how much pollution a car produces during actual driving conditions, are required for some severely polluted areas.
Insulated Glass: Two or more glass panes installed in windows and doors, spaced apart and sealed in a factory.

Insulation material : A material with a low thermal conductivity (e.g. below 0.2 W/m2K) applied to reduce thermal losses through building envelope (e.g. walls, roofs, floors).

Intermittent Ignition Device: A device that lights the pilot on a gas appliance when the control system calls for heat, thus saving the energy wasted by a standing pilot.

Internal (heat) gains: the energy dissipated inside the heated space by people (body heat) and appliances (lighting, cooker, etc.). A proportion of this energy contributes to the space heating requirements (kWh).
Internal sources: the sources of internal heat such as appliances, lights and people . See internal heat.
International Air Pollution - Pollution that moves across national borders. The 1990 Clean Air Act includes provisions for cooperative efforts to reduce pollution that originates in one North American country and affects another.
Interstate Air Pollution - Pollution that moves across state borders. Because often, air pollution moves out of the state in which it is produced into another state, the 1990 Clean Air Act includes many provisions, such as interstate compacts, to help states work together to protect the air they share.
Intrinsic Heat: heat from human bodies, electric light bulbs, cooking stoves, and other objects not intended specifically for space heating.

Irradiance (at a point of a surface): quotient of the radiant flux dX, incident on an element of the surface containing the point, by the area dA of that element. Equivalent definition: Integral, taken over the hemisphere visible from the given point, of the expression Le cos Y.dX. where Le is the radiance at the given point in the various directions of the incident elementary beams of solid angle dX where Y is the angle between any of these beams and the normal to the surface at the given point.
Irradiation: see radiation.
Irritant - A substance that causes irritation of the skin, eyes, or respiratory system. Effects may be acute from a single high-level exposure, or chronic from repeated low-level exposures to such compounds as chlorine, nitrogen dioxide, and nitric acid.
Isentropic: an adjective describing a reversible adiabatic process a change taking place at constant entropy.

ISO:The International Standards Organisation, based in Geneva.

ISO/CEN 7730:The Standard for calculating the effect of indoor environments using the PMV/PPD indices of Fanger, produced by the International Standards Organisation, based in Geneva.

Iso-: The (l) prefix meaning constant: as in isothermal (constant temperature); isentropic (constant entropy); isobaric (constant pressure); etc.; and (2) in chemicals, one having different characteristics but with the same number and kind of atoms.

Isobaric: an adjective used to indicate a change taking place at constant temperature.

Isolated gain: the transfer of heat into the space to be heated from a collector that is thermally isolated from the space to be heated by physical separation or insulation (such as an attached sunspace with an insulated common wall).
Isoconcentration - More than one sample point exhibiting the same isolated concentration.
Isothermal: an adjective used to indicate a change taking place at constant temperature