Green Building Glossary
Note: Numbers in brackets refer to the definition citation listed at the bottom of the page.
ABS Acrylonitrile butadiene styrene: a lightweight, black, durable plastic used for piping due to its high strength. It is recyclable, but not many recycling centers accept it. It needs to be shielded from the sun as it is not completely UV stable. It is better overall than cast iron and PVC for risks for health and environment.
Absorption Chiller: A water chilling process in which cooling is accomplished by the evaporation of a fluid (usually water), which is then absorbed by a different solution (usually lithium bromide), then evaporated under heat and pressure. The fluid is then condensed with the heat of condensation rejected through a cooling tower. [Definition: Washington State University Cooperative Extension Energy Program]
Acid Rain: The precipitation of dilute solutions of strong mineral acids, formed by the mixing in the atmosphere of various industrial pollutants (primarily sulfer dioxide and nitrogen oxides) with naturally occurring oxygen and water vapor. 
Active solar: A system using mechanical devices (pumps, fans, etc.) that transfers collected heat to the storage medium and/or the end-use. 
Active system: Traditional heating, cooling and ventilating systems which use mechanical means to artificially condition (cool, heat, ventilate) the air supply in buildings, and draw power for these mechanical processes from electricity or gas.
Adaptability: Design strategy that allows for multiple future uses in a space as needs evolve and change. Adaptable design is considered a sustainable building strategy as it reduces the need to resort to major renovations or tearing down a structure to meet future needs.
Adapted (Introduced) Plants: Plants that reliably grow well in a given habitat with minimal attention from humans in the form of winter protection, pest protection, water irrigation, or fertilizer once root systems are established in the soil. Adapted plants are considered to be low maintenance but not invasive. 
Adaptive Reuse: Renovation of a building or site to include elements that allow a particular use or uses to occupy a space that originally was intended for a different use. 
Adhesive: Any substance that is used to bond one surface to another surface by attachment. Adhesives include adhesive bonding primers, adhesive primers, adhesive primers for plastics, and any other primer. 
Adobe: Mud bricks reinforced with straw. Used particularly in
Advanced framing: Refers to a variety of framing techniques designed to reduce the amount of lumber used and waste generated in the construction of a wood-framed structure while increasing space available for insulation.
Aerosol Adhesive: An adhesive packaged as an aerosol product in which the spray mechanism is permanently housed in a non-refillable can designed for hand-held application without the need for ancillary hoses or spray equipment. Aerosol adhesives include special purpose spray adhesives, mist spray adhesives and web spray adhesives. 
Aerator: A faucet aerator mixes air with a flow of water and is used to oxygenate water, to smooth the flow of water and to reduce splashing.
Agricultural Waste: Materials left over from agricultural processes (e.g., wheat stalks, shell hulls, etc.). Some of these materials are finding new applications as building materials and finishes. Examples include structural sheathing and particleboard alternatives made from wheat, rye and other grain stalks, and panels made from sunflower seed hulls.
Agrifiber Board: A composite panel product derived from recovered agricultural waste fiber from sources including, but not limited to, cereal straw, sugarcane bagasse, sunflower husk, walnut shells, coconut husks, and agricultural prunings. The raw fibers are processed and mixed with resins to produce panel products with characteristics similar to those derived from wood fiber. The products must comply with the following requirements:
1. The product is inside of the buildings waterproofing system.
2. Composite components used in assemblies are to be included (e.g., door cores, panel substrates, etc.)
3. The product is part of the base building systems. 
Air Changes Per Hour (ACH): The movement of a volume of air in a given period of time; if a house has one air change per hour, it means that the air in the house will be replaced in a one-hour period. 
Air Change Effectiveness: A measurement of the performance of a ventilation system, by measuring the age of air in a volume. Often accomplished by using a tracer gas decay technique.
Air Cleaning: Indoor-air quality-control strategy to remove various airborne particulates and/or gases from the air. Most common methods are particulate filtration, electrostatic precipitation, and gas sorption. 
Air Conditioning: The process of treating air to meet the requirements of a conditioned space by controlling its temperature, humidity, cleanliness and distribution. (ASHRAE 62.1 – 2004) 
Air Exchange Rate: The rate at which outside air replaces indoor air in a given space. 
Airborne Particulates: Total suspended particulate matter found in the atmosphere as solid particles or liquid droplets. Chemical composition of particulates varies widely, depending on location and time of year. Sources of airborne particulates include dust, emissions from industrial processes, combustion products from the burning of wood and coal, combustion products associated with motor vehicle or non-road engine exhausts, and reactions to gases in the atmosphere. 
Air Handling Unit: Equipment that includes a fan or blower, heating and/or cooling coils, regulator controls, condensate drain pans, and air filters. 
Air Plenum: Any space used to convey air in a building, furnace, or structure. The space above a suspended ceiling is often used as an air plenum. 
Air Pollutant: Any substance in air that could, in high enough concentration, harm man, other animals, vegetation, or material. Pollutants may include almost any natural or artificial composition of airborne matter capable of being airborne. They may be in the form of solid particles, liquid droplets, gases, or in combination thereof. Generally, they fall into two main groups: (1) those emitted directly from identifiable sources, and (2) those produced in the air by interaction between two or more primary pollutants, or by reaction with normal atmospheric constituents, with or without photoactivation. Exclusive of pollen, fog, and dust, which are of natural origin, about 100 contaminants have been identified. Air pollutants are often grouped in categories for ease in classification; some of he categories are: solids, sulfur compounds, volatile organic chemicals, particulate matter, nitrogen compounds, oxygen compounds, halogen compounds, radioactive compound, and odors. 
Air Quality Construction Management Plan: A systematic plan for addressing construction practices that can impact air quality during construction and continuing on to occupation.
Albedo: Synonymous with solar reflectance. 
Alternative Energy: Energy from a source other than the conventional fossil-fuel sources of oil, natural gas and coal (i.e., wind, running water, the sun). Also referred to as "alternative fuel." 
Alternative Fuels: Substitutes for traditional liquid, oil-derived motor vehicle fuels like gasoline and diesel. Includes mixtures of alcohol-based fuels with gasoline, methanol, ethanol, compressed natural gas, and others. 
Alternative Fuel Vehicles: Vehicles that use low-polluting, non-gasoline fuels such as electricity, hydrogen, propane or compressed natural gas, liquid natural gas, methanol, and ethanol. Efficient gas-electric hybrid vehicles are included in this group for LEED purposes. 
Alternative Refueling Station: Location that provides the service of refueling an alternative fuel vehicle (e.g., electricity, compressed natural gas). Providing access to alternative fuels with a refueling station is considered a sustainable building strategy in that it encourages the use of alternative fuels and the vehicles that use them.
Angle of Maximum Candela: The direction in which the luminaire emits the greatest luminous intensity. 
Anti-corrosive Paints: Coatings formulated and recommended for use in preventing the corrosion of ferrous metal substrates. 
Aquatic Systems: Ecologically designed treatment systems that utilize a diverse community of biological organisms (e.g., bacteria, plants and fish) to treat wastewater to advanced levels. 
Aquifer: An underground water-bearing rock formation or group of formations, which supplies groundwater, wells or springs. 
Asbestos: A mineral fiber that can pollute air or water and cause cancer or asbestosis when inhaled. EPA has banned or severely restricted its use in manufacturing and construction. 
ASHRAE: American Society of Heating, Refrigeration and Air Conditioning Engineers. 
Assembly Recycled Content: Includes the percentages of post-consumer and pre-consumer content. The determination is made by dividing the weight of the recycled content by the overall weight of the assembly. 
Automatic Fixture Sensors: Motion sensors that automatically turn on/off lavatories, sinks, water closets, and urinals. Sensors may be hard wired or battery operated. 
Baseline Building Performance: The annual energy cost for a building design intended for use as a baseline for rating above standard design, as defined in ASHRAE 90.1 – 2004 Informative Appendix G. 
Basis of Design (BOD): Includes design information necessary to accomplish the owner’s project requirements, including system descriptions, indoor environmental quality criteria, other pertinent design assumptions (such as weather data), and references to applicable codes, standards, regulations and guidelines. 
Benefit/Cost Analysis: An economic method for assessing the benefits and costs of achieving alternative health-based standards at given levels of health protection. 
Best Management Practice (BMP): Methods that have been determined to be the most effective, practical means of preventing or reducing pollution from non-point sources. 
Bicycle Storage: Covered and/or secured storage for building occupants commuting by bicycle. This amenity is considered a sustainable building technique in that it encourages human-powered transportation options. Some local governments offer subsidies or incentives to include bicycle storage in an existing or proposed building project.
Bioaccumulants: Substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted. 
Biochemical Oxygen Demand (BOD): A measure of the amount of oxygen consumed in the biological processes that break down organic matter in water. The greater the BOD, the greater the degree of pollution. 
Bioconcentration: The accumulation of a chemical in tissues of a fish or other organism to levels greater than in the surrounding medium. 
Biodegradable: Capable of decomposing under natural conditions. 
Biodiversity: Refers to the variety and variability among living organisms and the ecological complexes in which they occur. Diversity can be defined as the number of different items and their relative frequencies. For biological diversity, these items are organized at many levels, ranging from complete ecosystems to the biochemical structures that are the molecular basis of heredity. Thus, the term encompasses different ecosystems, species, and genes. 
Biological Contamination: Contamination of a building environment caused by bacteria, molds and their spores, pollen, viruses, and other biological materials. It is often linked to poorly designed and maintained HVAC systems. People exposed to biologically contaminated environments may display allergic-type responses or physical symptoms such as coughing, muscle aches and respiratory congestion. 
Biomass: All of the living material in a given area; often refers to vegetation. 1 Plant material such as trees, grasses and crops that can be converted to heat energy to produce electricity 
Biome: Entire community of living organisms in a single major ecological area. 
Bioremediation: The cleanup of a contaminated site using biological methods, i.e., bacteria, fungi, plants, etc. Organisms are used to either break down contaminants in soil or water, or accumulate the contaminants in their tissue for disposal. Many bioremediation techniques are substantially less costly than traditional remediation methods using heat, chemical or mechanical means.
Bioswale: A technology that uses plants and soil and/or compost to retain and cleanse runoff from a site, roadway, or other source.
Blackwater: Does not have a single definition that is accepted nationwide. Wastewater from toilets and urinals is, however, always considered blackwater. Wastewater from kitchen sinks (perhaps differentiated by the use of a garbage disposal), showers, or bathtubs may be considered blackwater by state or local codes. Project teams should comply with the blackwater definition as established by the authority having jurisdiction in their areas. 
Breathing Zone: The region within an occupied space between planes 3 and 6 feet above the floor and more than 2 feet from the walls or fixed air-conditioning equipment. 
Brownfields: Abandoned, idled, or under used industrial and commercial facilities/sites where expansion or redevelopment is complicated by real or perceived environmental contamination. They can be in urban, suburban, or rural areas. EPA's Brownfields initiative helps communities mitigate potential health risks and restore the economic viability of such areas or properties. 
Building Cooling Load: The hourly amount of heat that must be removed from a building to maintain indoor comfort (measured in British thermal units [Btu]). 
Building Density: The floor area of the building divided by the total area of the site (square feet per acre). 
Building Envelope: The exterior surface of a building's construction--the walls, windows, floors, roof, and floor. Also called building shell. 
Building Flush-Out: See Flush-Out.
Building Footprint: The area on a project site that is sued by the building structure and is defined by the perimeter of the building plan. Parking lots, landscapes and other non-building facilities are not included in the building footprint. 
Building Related Illness: Diagnosable illness whose cause and symptoms can be directly attributed to a specific pollutant source within a building (e.g., Legionnaire's disease, hypersensitivity, pneumonitis). (See: sick building syndrome; biological contamination). 
Carbon Dioxide Monitoring: A method for determining indoor air quality by using the concentration of carbon dioxide as an indicator. Although the level of CO2 is a good general indicator of air quality, it is reliant on the presence of certain conditions and must be applied accordingly.
Carbon Dioxide Sensor: Device for monitoring the amount of carbon dioxide in an air volume.
Carbon Monoxide (CO): A colorless, odorless, poisonous gas produced by incomplete fossil fuel combustion. 
Carcinogen: Any substance that can cause or aggravate cancer. 
Carpool: An arrangement in which two or more people share a vehicle for transportation. 
Carrying capacities: The uppermost limit on the number of species and ecosystems or habitats possible given the supply and availability of nutrients in a given area.  In human settlements, this term also refers to the upper limits beyond which the quality of life, community character, or human health, welfare, and safety will be impaired, such as the estimated maximum number of people that can be served by existing and planned infrastructure systems, or the maximum number of vehicles that can be accommodated on roadway. 
Car Sharing: A system under which multiple households share a pool of automobiles, either through cooperative ownership or through some other mechanism. 
Cellulose Insulation: Insulation alternative to glass fiber insulation. Cellulose insulation is most often a mixture of waste paper and fire retardant, and has thermal properties often superior to glass fiber. Glass fiber batt insulation often contains formaldehyde, which can adversely affect indoor air quality and human health, and the glass fibers themselves are hazardous if inhaled and irritating to the skin and eyes. Specify cellulose insulation with high recycled content for maximum environmental benefit.
CERCLA: Refers to the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), commonly known as Superfund. CERCLA addresses abandoned or historical waste sites and contamination. It was enacted in 1980 to create a tax on the chemical and petroleum industries and provided federal authority to respond to releases of hazardous substances. 
Certified Lumber: General shorthand term for lumber that has been certified sustainable harvest by an independent certification authority. See Forest Stewardship Council.
Chain of Custody: A document that tracks the movement of a wood product from the forest to a vendor and is used to verify compliance with FSC guidelines. A “vendor” is defined as the company that supplies wood products to project contractors or subcontractors for on-site installation. 
Charrette: A meeting held early in the design phase of a project, in which the design team, contractors, end users, community stakeholders, and technical experts are brought together to develop goals, strategies, and ideas for maximizing the environmental performance of the project. Research and many projects’ experience has indicated that early involvement of all interested parties increases the likelihood that sustainable building will be incorporated as a serious objective of the project, and reduces the soft costs sometimes associated with a green design project.
Chiller: A device that generates a cold liquid that is circulated through an air-handling unit's cooling coil to cool the air supplied to the building. 
Chlorofluorocarbons (CFCs): A family of inert, nontoxic, and easily liquefied chemicals used in refrigeration, air conditioning, packaging, insulation, or as solvents and aerosol propellants. Because CFCs are not destroyed in the lower atmosphere they drift into the upper atmosphere where their chlorine components destroy ozone. 
Cistern: Small tank or storage facility used to store water for a home or farm; often used to store rainwater. 
Climate-dominated Building: A building in which the energy consumption is driven by the heat loss or gain that moves across the building’s envelope. The internally generated energy requirements from machines, appliances or people are smaller than the energy requirements created by heat or cold moving through the building’s envelope. This means that heating, cooling and ventilation are the building’s biggest energy requirements. 
CO2: Carbon dioxide
Cogeneration: The joint production and use of electricity and heat. Typically, electricity is the primary output of such large facilities as power plants. As a byproduct, heat can be used in food processing, district heating, or oil recovery. In contrast, industrial or small systems (e.g., Laundromats, health clubs, and car washes) may be designed primarily to heat water while the generation of electricity is secondary. 
Comfort: An important design objective in sustainable building. Designing for comfort aims to create a space where people enjoy being; such qualitative, performance-based objectives are a hallmark of sustainable building.
Comfort Criteria: Specific original design conditions that shall at a minimum include temperature (air, radiant and surface), humidity and air speed as well as outdoor temperature design conditions, outdoor humidity design conditions, clothing (seasonal) and activity expected. (ASHRAE 55-2004) 
Commissioning (Building): The process of ensuring that systems are designed, installed, functionally tested, and capable of being operated and maintained to perform in conformity with the owner’s project requirements. 
Commissioning Plan: A document defining the commissioning process, which is developed in increasing detail as the project progresses through its various phases. 
Commissioning Report: The document that records the results of the commissioning process, including the as-built performance of the HVAC system and unresolved issues. 
Commissioning Specification: The contract document that details the objective, scope and implementation of the construction and acceptance phases of the commissioning process as developed in the design-phase commissioning plan. 
Commissioning Team: Includes those people responsible for working together to carry out the commissioning process. 
Community: A factor with increased emphasis in sustainable building and sustainable development. Design and building related practices enhancing and supporting community ideals and functions are considered more sustainable than those that do not, all else being equal. An interacting population of individuals living in a specific area. 
Compact Fluorescent Lamp (CFL): Small fluorescent lamps used as more efficient alternatives to incandescent lighting. Also called PL, CFL, Twin-Tube, or BIAX lamps. 
Completed Design Area: The total area of finished ceilings, finished floors, full height walls and demountable partitions, interior doors and built-in case goods in the space when the project is completed: exterior windows and exterior doors are not considered. 
Composite Wood: A product consisting or wood or plant particles or fibers bonded together by a synthetic resin or binder (i.e., plywood, particle-board, OSB, MDF, composite door cores). For the purposes of LEED requirements, products must comply with the following conditions:
1. The product is inside of the building’s waterproofing system.
2. Composite wood components used in assemblies are included (e.g., door cores, panel substrates, plywood sections of I-beams).
3. The product is part of the base building systems. 
Compost: The relatively stable humus material that is produced from a composting process in which bacteria in soil mixed with degradable materials break down the mixture into organic fertilizer. 
Composting: Controlled biological decomposition of organic material in the presence of air to form a humus-like material. Controlled methods of composting include mechanical mixing and aerating, ventilating the materials by dropping them through a vertical series of aerated chambers, or placing the compost in piles out in the open air and mixing it or turning it periodically. 
Composting Toilet Systems: Dry plumbing fixtures that contain and treat human waste via microbiological processes. 
Compressed Natural Gas (CNG): An alternative fuel for motor vehicles; considered one of the cleanest because of low hydrocarbon emissions and its vapors are relatively non-ozone producing. However, vehicles fueled with CNG do emit a significant quantity of nitrogen oxides. 
Conditioned Space: The part of a building that is heated or cooled, or both, for the comfort of occupants. (ASHRAE 62.1-2004) 
Conservation Easement: Easement restricting a landowner to land uses that are compatible with long-term conservation and environmental values. 
Construction and Demolition Waste: Waste building materials, dredging materials, tree stumps, and rubble resulting from construction, remodeling, repair, and demolition of homes, commercial buildings and other structures and pavements. May contain lead, asbestos, or other hazardous substances.  (Land clearing debris including soil, vegetation, rocks, etc. are not to be included) 
Construction IAQ Management Plan: A document specific to a building project that outlines measures to minimize contamination in the building during construction, and to flush the building of contaminants prior to occupancy. 
Construction Site Recycling: See Construction Waste Management
Construction Waste Management: General term for strategies employed during construction and demolition to reduce the amount of waste and maximize reuse and recycling. Construction waste management is a sustainable building strategy in that it reduces the disposal of valuable resources, provides materials for reuse and recycling, and can promote community industries.
Contaminant: An unwanted airborne constituent that may reduce acceptability of the air. (ASHRAE 62.1-2004).
Conventional Irrigation: Refers to the most common irrigation system used in the region where the building is located. A common conventional irrigation system uses pressure to deliver water and distributes it through sprinkler heads above the ground. 
Cooling Load: See Building Cooling Load.
Cooling Tower: Device which dissipates the heat from water-cooled systems by spraying the water through streams of rapidly moving air.  Cooling towers can be substantial water users, and provide an opportunity for water conservation. Many local water providers can supply technical information on water use reduction and may provide incentives for measures with substantial water savings.
Cradle-to-Cradle: A term used in life-cycle analysis to describe a material or product that is recycled into a new product at the end of its defined life. 
Cradle-to-Grave: A term used in life-cycle analysis to describe the entire life of a material or product up to the point of disposal. Also refers to a system that handles a product from creation through disposal. 
Cubic Feet Per Minute (CFM): A measure of the volume of a substance flowing through air within a fixed period of time. With regard to indoor air, refers to the amount of air, in cubic feet, that is exchanged with outdoor air in a minute's time; i.e., the air exchange rate. 
Cullet: Crushed glass. 
Curfew Hours: Locally determined times when greater lighting restrictions are imposed. When no local or regional restrictions are in place, 10:00 p.m. is regarded as a default curfew time. 
Daylighting: The controlled admission of natural light into a space through glazing with the intent of reducing or eliminating electric lighting. By utilizing solar light, daylighting creates a stimulating and productive environment for building occupants. 
Degree-Day: A rough measure used to estimate the amount of heating required in a given area; is defined as the difference between the mean daily temperature and 65 degrees Fahrenheit. Degree-days are also calculated to estimate cooling requirements. 
Demand Hot Water System: Hot water heaters designed to provide instantaneous hot water, rather than storing preheated hot water in a tank. Such devices can serve an entire home, or be "point-of-use", serving an individual water use. Benefits include elimination of "standby losses", or energy wasted keeping stored water warm, and with point of use devices, reduction or elimination of water wasted waiting for water to get warm, as well as conductive losses as water travels through pipes. Electric demand systems tend to use a large amount of energy; gas-fired units with standing pilot lights lose much of their efficiency due to the ongoing pilot light.
Demand-side Waste Management: Prices whereby consumers use purchasing decisions to communicate to product manufacturers that they prefer environmentally sound products packaged with the least amount of waste, made from recycled or recyclable materials, and containing no hazardous substances. 
Depressurization: A condition that occurs when the air pressure inside a structure is lower that the air pressure outdoors. Depressurization can occur when household appliances such as fireplaces or furnaces, that consume or exhaust house air, are not supplied with enough makeup air. Radon may be drawn into a house more rapidly under depressurized conditions.  Backdrafting of furnaces and vented appliances can also occur with depressurization, introducing exhaust gases into the house.
Development Footprint: The area on the project site that has been impacted by any development activity. Hardscape, access roads, parking lots, non-building facilities and building structure are all included in the development footprint. 
Dioxin: Any of a family of compounds known chemically as dibenzo-p-dioxins. Concern about them arises from their potential toxicity as contaminants in commercial products. Tests on laboratory animals indicate that it is one of the more toxic anthropogenic (man-made) compounds. 
Disassembly: Taking apart an assembled product. Design for disassembly in buildings allows building components to be readily reused and recycled.
Displacement Ventilation: Ventilation that uses natural convection processes to move warm air up and out of a volume. Displacement ventilation tends to use less energy than conventional forced air ventilation, as it works with natural convection processes.
Dose-response: Relationship between exposure levels and adverse effects. 
Drought Tolerance: The capacity of a landscape plant to function well in drought conditions.
Durability: A factor that affects the life cycle performance of a material or assembly. All other factors being equal, the more durable item is environmentally preferable, as it means less frequent replacement. However, durability is rendered moot as a factor if the material is replaced for aesthetic reasons prior to it actually wearing out.
Dynamic Environmental Chamber: Well-controlled system (including temperature, relative humidity (RH) and air quality/purity) that utilizes realistic air flows for the assessment of chemical emissions from products and materials. 
Ecosystem: A basic unit of nature that includes a community of organisms and their non-living environment linked by biological, chemical and physical processes. 
Embodied Energy: The total amount of energy used to create a product, including energy expended in raw materials extraction, processing, manufacturing and transportation. Embodied energy is often used as a rough measure of the environmental impact of a product. Energy that is used during the entire lifecycle of the commodity for manufacturing, transporting and disposing of the commodity as well as the inherent energy captured within the product itself 
Encapsulation: The treatment of asbestos-containing material with a liquid that covers the surface with a protective coating or embeds fibers in an adhesive matrix to prevent their release into the air. 
Endangered Species: Animals, birds, fish, plants, or other living organisms threatened with extinction by anthropogenic (man-caused) or other natural changes in their environment. Requirements for declaring a species endangered are contained in the Endangered Species Act. 
End-use: The task or purpose for which energy is required. Examples include lighting dark spaces, cooking food, and powering vehicles. 
• Primary – That contained in fossil fuels in the form of coal, oil or natural gas or in nuclear energy or hydroelectricity.
• Delivered – That in the fuel at its point of use after allowing for extraction (or generation) and transmission losses.
• Useful – The portion of the delivered energy that is of benefit after allowing for the efficiency of the consuming appliance. 
Energy Analysis: Analysis of the energy use of a structure.
Energy or water conservation: Using less energy or water. Conservation can imply a lifestyle change or a reduced level of service. Lowering thermostat settings or installing a shower flow restrictor aer examples of energy conservation. 
Energy or water efficiency: Using less water or energy to perform the same tasks. A device is energy-efficient if it provides comparable or better quality of service while using less energy than a conventional technology. Building weatherization or high-efficiency showerheads are efficiency technologies. 
Energy Management System: A control system capable of monitoring environmental and system loads and adjusting HVAC operations accordingly in order to conserve energy while maintaining comfort. 
Energy Modeling: Process to determine the energy use of a building based on software analysis. Also called building energy simulation. Common simulation software are DOE-2 and Energy Plus.
Energy Star: Program administered by the Environmental Protection Agency that evaluates products based on energy efficiency. ENERGY STAR Rating is the rating a building earns using the ENERGY STAR Portfolio Manager to compare building energy performance to similar buildings in similar climates. A score of 50 represents average building performance. 
Engineered Lumber/Wood: Composite wood products made from lumber, fiber or veneer, and glue. Engineered wood products can be environmentally preferable to dimensional lumber, as they allow the use of waste wood and small diameter trees to produce structural building materials. Engineered wood products distribute the natural imperfections in wood fiber over the product, making them stronger than dimensional lumber. This allows for less material to be used in each piece, another environmental benefit. Potential environmental drawbacks with engineered wood include impacts on indoor environmental quality due to offgassing of chemicals present in binders and glues, and air and water pollution related to production.
Environmental Footprint: For an industrial setting, this is a company's environmental impact determined by the amount of depletable raw materials and nonrenewable resources it consumes to make its products, and the quantity of wastes and emissions that are generated in the process. Traditionally, for a company to grow, the footprint had to get larger. Today, finding ways to reduce the environmental footprint is a priority for leading companies.  An environmental footprint can be determined for a building, city, or nation as well, and gives an indication of the sustainability of the unit.
Environmental Impact Statement: A document required of federal agencies by the National Environmental Policy Act for major projects or legislative proposals significantly affecting the environment. A tool for decision making, it describes the positive and negative effects of the undertaking and cites alternative actions. 
Environmental Tobacco Smoke: Mixture of smoke from the burning end of a cigarette, pipe, or cigar and smoke exhaled by the smoker. 
Erosion: The wearing away of land surface by wind or water, intensified by land-clearing practices related to farming, residential or industrial development, road building, or logging.
Exfiltration: Uncontrolled outward air leakage from conditioned spaces through unintentional openings in ceilings, floors and walls to unconditioned spaces or the outdoors caused by pressure differences across these openings due to wind, inside-outside temperature differences (stack effect), and imbalances between supply and exhaust airflow rates. (ASHRAE 62.1-2004) 
Fluorocarbons (FCs): Any of a number of organic compounds analogous to hydrocarbons in which one or more hydrogen atoms are replaced by fluorine. Once used in the United States as a propellant for domestic aerosols, they are now found mainly in coolants and some industrial processes. FCs containing chlorine are called chlorofluorocarbons (CFCs). They are believed to be modifying the ozone layer in the stratosphere, thereby allowing more harmful solar radiation to reach the Earth's surface. 
Flush-Out: A period after finish work and prior to occupation that allows the building’s materials to cure and release volatile compounds and other toxins. A building flush-out procedure is normally followed, with specified time periods, ventilation rate, and other criteria.
Fly Ash: A fine, glass-powder recovered from the gases of burning coal during the production of electricity. These micron-sized earth elements consist primarily of silica, alumina and iron. When mixed with lime and water the fly ash forms a cementitious compound with properties very similar to that of portland cement. Because of this similarity, fly ash can be used to replace a portion of cement in the concrete, providing some distinct quality advantages. The concrete is denser resulting in a tighter, smoother surface with less bleeding. Fly ash concrete offers a distinct architectural benefit with improved textural consistency and sharper detail.
Fly ash with a low LOI (carbon content) is used as a substitute for portland cement in concrete. Regulations vary from state to state, however, ASTM suggests that fly ash must not contain more than 6% unburned carbon to be used for its cementitious qualities. Otherwise, concrete companies use it as a fine aggregate in concrete block. Others use it for filling old coal mines, seaside docking areas and as a lining for hazardous waste dumps. 
Substitution of fly ash for portland cement in concrete is considered a sustainable building strategy, as it reduces the amount of energy-intensive (and CO2-producing) cement in the mix, as well as providing the performance enhancements described above.
Footprint (Building): The area of a building formed by the perimeter of the foundation. Shrinking the footprint of a building allows for more open space and pervious surface on a site.
Footprint (Environmental): See Environmental Footprint
Forest Stewardship Council (FSC): A third-party certification organization, evaluating the sustainability of forest products. FSC-certified wood products have met specific criteria in areas such as forest management, labor conditions, and fair trade.
Formaldehyde: A colorless, pungent, and irritating gas, CH20, used chiefly as a disinfectant and preservative and in synthesizing other compounds like resins. 
Functional Performance Testing: The process of determining the ability of the commissioned systems to perform in accordance with the owner’s project requirements, basis of design, and construction documents. 
Fungus (Fungi): Molds, mildews, yeasts, mushrooms, and puffballs, a group of organisms lacking in chlorophyll (i.e., are not photosynthetic) and which are usually non-mobile, filamentous, and multicellular. Some grow in soil, others attach themselves to decaying trees and other plants whence they obtain nutrients. Some are pathogens; others stabilize sewage and digest composted waste. 
Geothermal/Ground Source Heat Pump: These heat pumps are underground coils to transfer heat from the ground to the inside of a building. (See: heat pump; water source heat pump)  This type of heat pump can realize substantial energy savings over conventional heat pumps, by using the naturally more stable temperature of the earth as its heat source.
Glazing: Translucent or transparent element of a window assembly. Glazing can have properties that increase its thermal performance, including Low-Emissivity coatings, multiple panes, thermally broken spacers, etc.
Glazing Factor: The ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance, and window height. 
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. 
Global Warming Potential: The ratio of the warming caused by a substance to the warming caused by a similar mass of carbon dioxide. CFC-12, for example, has a GWP of 8,500, while water has a GWP of zero. 
Graywater (also spelled greywater and gray water): Defined by the Uniform Plumbing Code (UPC) in its Appendix G, titled “Gray water Systems for Single-Family Dwellings,” as “untreated household wastewater which has not come into contact with toilet waste. Grey water includes water from bathtubs, showers, bathroom wash basins, and water from clothes-washer and laundry tubs. It shall not include wastewater from kitchen sinks or dishwashers.” The International Plumbing Code (IPC) defines graywater in its Appendix C, titled “Graywater Recycling Systems,” as “wastewater discharged from lavatories, bathtubs, showers, clothes washers, and laundry sinks.” Some states and local authorities allow kitchen sink wastewater to be included in graywater. Other differences with the UPC and IPC definitions can probably be found in state and local codes. Project teams should comply with the graywater definitions as established by the authority having jurisdiction in their areas. 
Gray Water Reuse: A strategy for reducing wastewater outputs from a building, by diverting the gray water into productive uses such as subsurface irrigation, or on-site treatment and use for non-potable functions such as toilet flushing. Gray water reuse is restricted in many jurisdictions; check with local health and building officials.
Green Design: A design, usually architectural, conforming to environmentally sound principles of building, material and energy use. A green building, for example, might make use of solar panels, skylights and recycled building materials. 
Green Development: A sustainable approach to real estate development that incorporates such environmental issues as: efficient and appropriate use of land, energy, water, and other resources; protection of significant habitats, endangered species, archeological treasures and cultural resources; and integration of work, habitat and agriculture. Green development supports human and natural communities and cultural development while remaining economically viable for owners and tenants. 
Green Label: A certification program by the Carpet and Rug Institute for carpet and adhesives meeting specified criteria for release of volatile compounds.
Green Roof: Contained green space on, or integrated with, a building roof. Green roofs maintain living plants in a growing medium on top of a membrane and drainage system. Green roofs are considered a sustainable building strategy in that they have the capacity to reduce stormwater runoff from a site, they modulate temperatures in and around the building, have thermal insulating properties, can provide habitat for wildlife and open space for humans, and other benefits.
Greenfields: Sites that have not been previously developed or graded and remain in a natural state. 
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 Gases: Gases such as carbon dioxide, methane and CFCs that are relatively transparent to the higher-energy sunlight, but trap lower-energy infrared radiation. 
Greenwash: Disinformation disseminated by an organization so as to present an environmentally responsible public image. 
Ground Cover: Low-growing plants often grown to keep soil from eroding and to discourage weeds.
Halogen: A type of incandescent lamp with higher energy-efficiency that standard ones. 
Halon: Bromine-containing compounds with long atmospheric lifetimes whose breakdown in the stratosphere causes depletion of ozone. Halons are used in fire suppression systems and fire extinguishers. 
Heat Exchanger: Device for exchanging heat present in wastewater or stale air to preheat incoming water or air. See Heat Recovery Ventilator for more information on air-to-air heat exchangers.
Heat Island Effect: Occurs when warmer temperatures are experienced in urban landscapes compared to adjacent rural areas as a result of solar energy retention on constructed surfaces. Principal surfaces that contribute to the heat island effect include streets, sidewalks, parking lots, and buildings. 
Heat Pump: An electric device with both heating and cooling capabilities. It extracts heat from one medium at a lower (the heat source) temperature and transfers it to another at a higher temperature (the heat sink), thereby cooling the first and warming the second. (See: geothermal, water source heat pump.) 
Heat Recovery Unit/Ventilator: An air-to-air heat exchanger with balanced exhaust and supply fans that meet all necessary ventilation needs without producing drafts or air pressure imbalance on a heating or cooling system. (Definition: Washington State University Cooperative Extension Energy Program)
Heavy Metals: Metallic elements with high atomic weights; (e.g., mercury, chromium, cadmium, arsenic, and lead); can damage living things at low concentrations and tend to accumulate in the food chain. 
High Efficiency: General term for technologies and processes that require less energy, water, or other inputs to operate. A goal in sustainable building is to achieve high efficiency in resource use when compared to conventional practice. Setting specific targets in efficiency for systems (e.g., using only EPA Energy Star certified equipment, furnaces with an AFUE rating above 90%, etc.) and designs (e.g., watts per square foot targets for lighting) help put this general goal of efficiency into practice.
High-Heeled Truss: Roof truss design that allows space for insulation near the eaves. Conventional truss design limits the amount of insulation that can be applied in this area.
High Intensity Discharge: A generic term for mercury vapor, metal halide, and high-pressure sodium lamps and fixtures. 
High Performance Glazing: Generic term for glazing materials with increased thermal efficiency.
Household Hazardous Waste: Hazardous products used and disposed of by residential as opposed to industrial consumers. Includes paints, stains, varnishes, solvents, pesticides, and other materials or products containing volatile chemicals that can catch fire, react or explode, or that are corrosive or toxic. 
Human Health Risk: The likelihood that a given exposure or series of exposures may have damaged or will damage the health of individuals. 
HVAC (Heating, Ventilation, and Air Conditioning): General term for the heating, ventilation and air conditioning system in a building. System efficiency and design impact the overall energy performance of a home and its indoor environmental quality.
Hybrid Vehicles: Vehicles that use a gasoline engine to drive an electric generator and use the electric generator and/or storage batteries to power electric motors that drive the vehicle’s wheels. 
Hydrocarbons (HC): Chemical compounds that consist entirely of carbon and hydrogen. 
Hydro (electric): Electricity that is produced when falling water turns generators. It is a renewable energy source derived from gravity and rain. Very small generation facilities, producing up to 50 kilowatts, are called micro-hydro. 
Hydrochlorofluorocarbons (HCFCs): Refrigerants used in building equipment that deplete the stratospheric ozone layer, but to a lesser extent than CFCs. 
Hydrofluorocarbons (HFCs): Refrigerants that do not deplete the stratospheric ozone layer. However, some CFCs have high global warming potential and, thus, are not environmentally benign. 
Hydrologic Cycle: Movement or exchange of water between the atmosphere and earth. 
Hydrology: The science dealing with the properties, distribution, and circulation of water. 
Hydrolysis: The decomposition of organic compounds by interaction with water. 
Hydronic Heating (Hydronic System): A space heating system that uses water circulated through a radiant floor or baseboard system or a convection or fan coil system.
Hypersensitivity Diseases: Diseases characterized by allergic responses to pollutants; diseases most clearly associated with indoor air quality are asthma, rhinitis, and pneumonic hypersensitivity. 
Impervious Surface: A surface that sheds the precipitation falling on it, rather than infiltrating. Impervious surfaces can lead to excessive stormwater runoff and limit the amount of stormwater that remains onsite or recharges local aquifers.
Indigenous Planting: Landscaping strategy that uses native plants. Provided the natives are placed in the proper growing conditions; such plantings can have low, or zero supplemental water needs. Indoor Adhesive, Sealant and/or Sealant Primer Product: Defined as an adhesive or sealant product applied on-site, inside of the building’s weatherproofing system. 
Indoor Air Pollution: Chemical, physical, or biological contaminants in indoor air. 
Indoor Air Quality (IAQ): ASHRAE defines acceptable indoor air quality as air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which 80% or more people exposed do not express dissatisfaction.  The nature of air inside the space that affects the health and well-being of building occupants. 
Infiltration: a. The penetration of water through the ground surface into sub-surface soil or the penetration of water from the soil into sewer or other pipes through defective joints, connections, or manhole walls. b. The technique of applying large volumes of waste water to land to penetrate the surface and percolate through the underlying soil. 1 Uncontrolled inward air leakage to conditioned spaces through unintentional openings in ceilings, floors and walls from unconditioned spaces or the outdoors caused by the same pressure differences that induce exfiltrations (ASHRAE 62.1-2004) 
Infiltration Rate: The quantity of water that can enter the soil in a specified time interval. 
Inflow: Entry of extraneous rain water into a sewer system from sources other than infiltration, such as basement drains, manholes, storm drains, and street washing. 
Installation Inspection: The process of inspecting components of the commissioned systems to determine if they are installed properly and ready for systems performance testing. 
Insulated Concrete Form: Expanded polystyrene forms that are left in place after the concrete is poured for a foundation or wall. The foam increases the thermal performance of the structure over non-insulated concrete.
Integrated Design: A holistic process that considers the many disparate parts of a building project, and examines the interaction between design, construction, and operations to optimize the energy and environmental performance of the project. The strength of this process is that all relevant issues are considered simultaneously in order to “solve for pattern” or solve many problems with one solution. The goal of integrated design is developments that have the potential to heal damages environments and become net producers of energy, healthy food, clean water and air, and healthy human and biological communities. 
Integrated Pest Management (IPM): A mixture of chemical and other, non-pesticide, methods to control pests. 
Integrated Waste Management: The complementary use of a variety of practices to handle solid waste safely and effectively. Techniques include source reduction, recycling, composting, combustion and landfilling. 
Integration: An essential concept in sustainable building. Viewing a building as a system allows the discovery of synergies and potential tradeoffs or pitfalls with design choices. An integrated design approach helps maximize synergies and minimize unintended consequences.
Invasive Plants: Both indigenous and non-indigenous species or strains that are characteristically adaptable, aggressive, have a high reproductive capacity and tend to overrun the ecosystems they inhabit. Collectively they are one of the great threats to biodiversity and ecosystem stability. 
Joint and Several Liability: Under CERCLA, this legal concept relates to the liability for Superfund site cleanup and other costs on the part of more than one potentially responsible party (i.e., if there were several owners or users of a site that became contaminated over the years, they could all be considered potentially liable for cleaning up the site). 
Landscape Area: Area of the site equal to the total site area less the building footprint, paved surfaces, water bodies, patios, etc. 
Leachate: Water that collects contaminants as it trickles through wastes, pesticides or fertilizers. Leaching may occur in farming areas, feedlots, and landfills, and may result in hazardous substances entering surface water, ground water, or soil. 
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. 
LEED™: A self-assessing green building rating system developed by the U.S. Green Building Council. LEED™ stands for Leadership in Energy and Environmental Design, and evaluates a building from a systems perspective. By achieving points in different areas of environmental performance, a building achieves a level of "certification" under the system.
Life Cycle (of a Product): All stages of a product's development, from extraction of fuel for power to production, marketing, use, and disposal. 
Life Cycle Analysis (LCA): The assessment of a product's full environmental costs, from raw material to final disposal, in terms of consumption of resources, energy and waste.  Life cycle analysis is used as a tool for evaluating the relative performance of building materials, technologies, and systems.
Life Cycle Cost Method: A technique of economic evaluation that sums over a given study period the costs of initial investment (less resale value), replacements, operations (including energy use), and maintenance and repair of an investment decision (expressed in present or annual value terms). 
Life Cycle Inventory (LCI): An accounting of the energy and waste associated with the creation of a new product through use and disposal. 
Light-Emitting Diode (LED): A long-lasting illumination technology used for exit signs which requires very little power. 
Light Shelf: A horizontal shelf positioned (usually above eye level) to reflect daylight onto the ceiling and to shield direct flare from the sky.
Linoleum: A resilient flooring product developed in the 1800s, manufactured from cork flour, linseed oil, oak dust, and jute. Linoleum’s durability, renewable inputs, anti-static properties, and easy-to-clean surface often make it classified as a "green" building material.
Local/Regional Materials: Building products manufactured and/or extracted within a defined radius of the building site. For example, the US Green Building Council defines local materials as those that are manufactured, processed and/or extracted within a 500-mile radius of the site. Use of regional materials is considered a sustainable building strategy due to the fact that these materials require less transport, reducing transportation-related environmental impacts. Additionally, regional materials support local economies, supporting the community goal of sustainable building.
Load-dominated Building: A building whose energy use is driven by the internal loads like lighting, plug loads and heat from people. You can usually distinguish a climate-dominated building from a load-dominated building by whether or not air conditioning is running year round, in a cool/cold climate. If the air conditioning runs throughout the year, it is probably load-dominated. 
Low Emissivity (low-E) Windows: Window technology that lowers the amount of energy loss through windows by inhibiting the transmission of radiant heat while still allowing sufficient light to pass through. 
Low Toxic: Generic term for products with lower levels of hazard than conventional products. Specific criteria need to be applied to this term to make it meaningful in the selection of sustainable building materials.
Low VOC: Building materials and finishes that exhibit low levels of "offgassing," the process by which VOCs (Volatile Organic Compounds) are released from the material, impacting health and comfort indoors and producing smog outdoors. Low (or zero) VOC is an attribute to look for in an environmentally preferable building material or finish. See "Volatile Organic Compound (VOC)" for more information.
Maintenance: An overlooked element of a product, system, or design strategy that impacts cost over the life cycle. Selecting products and designing for easy maintenance enhances durability and lessens the likelihood that maintenance is overlooked. Establishing and adhering to a maintenance protocol ensures that materials and systems function to specifications.
Makeup Air: Any combination of outdoor and transfer air intended to replace exhaust air and exfiltration. (ASHRAE 62.1-2004) 
Mass Transit Vehicles: Vehicles typically capable of serving 10 or more occupants, such as buses, trolleys, light rail, etc. 
Material Safety Data Sheet (MSDS): A compilation of information required under the OSHA Communication Standard on the identity of hazardous chemicals, health, and physical hazards, exposure limits, and precautions. Section 311 of SARA requires facilities to submit MSDSs under certain circumstances. 
MDF (Medium Density Fiberboard): A composite wood fiberboard, used for cabinetry and other interior applications. MDF containing urea formaldehyde can contribute to poor indoor air quality.
Mechanical Ventilation: Ventilation provided by mechanical powered equipment, such as motor-driven fans and blowers, but not by devices such as wind-driven turbine ventilators and mechanically operated windows. 
Mercury: A metal that is an odorless silver liquid at room temperature, converting to an odorless, colorless gas when heated. Mercury readily combines with other elements, and accumulates in the environment. Mercury is toxic, and causes a range of neurological, organ, and developmental problems. Fluorescent lights and old thermostats are two building related products that can contain significant amounts of mercury. Newer fluorescent lights are available with substantially reduced amounts of mercury.
Methane: A colorless, nonpoisonous, flammable gas created by anaerobic decomposition of organic compounds. A major component of natural gas used in the home.  Methane has also been found to be a potent greenhouse gas. Methane from landfills, livestock, and composting operations can be captured and used as a fuel source for alternative energy production.
Mixed Mode Ventilation: A ventilation strategy that combines natural ventilation with mechanical ventilation, allowing the building to be ventilated either mechanically or naturally; and at times both mechanically and naturally simultaneously. 
Modular Building: Building technique using modular, or pre-constructed components. Building on a "module" also refers to the concept of using standardized dimensions that reduce the amount of construction waste. Building in four-foot increments is one strategy.
Montreal Protocol: Treaty, signed in 1987, governs stratospheric ozone protection and research, and the production and use of ozone-depleting substances. It provides for the end of production of ozone-depleting substances such as CFCs. Under the Protocol, various research groups continue to assess the ozone layer. The Multilateral Fund provides resources to developing nations to promote the transition to ozone-safe technologies. 
Mulch: A layer of material (wood chips, straw, leaves, etc.) placed around plants to hold moisture, prevent weed growth, and enrich or sterilize the soil. 
Multiple Chemical Sensitivity: A diagnostic label for people who suffer multi-system illnesses as a result of contact with, or proximity to, a variety of airborne agents and other substances. 
Mutagen/Mutagenicity: An agent that causes a permanent genetic change in a cell other than that which occurs during normal growth. Mutagenicity is the capacity of a chemical or physical agent to cause such permanent changes. 
Natural Ventilation: Ventilation design that uses existing air currents on a site and natural convection to move and distribute air through a structure or space. Strategies include placement and operability of windows and doors, thermal chimneys, landscape berms to direct airflow on a site, and operable skylights. (See ASHRAE 62.1-2004)
Net Metering: A metering and billing arrangement that allows on-site generators to send excess electricity flows to the regional power grid. These electricity flows offset a portion of the electricity flows drawn from the grid. For more information on net metering in individual states, visit the DOE’s Green Power Network Web site at www.eere.energy.gov/greenpower/netmetering. 
Night Flushing: The process of removing hot air from a building during the cool evening hours, to cool elements with thermal mass within the building and flush stale air.
Nonrenewable Energy: Energy derived from depletable fuels (oil, gas, coal) created through lengthy geological processes and existing in limited quantities on the earth. 
Nonrenewable Resource: A resource that cannot be replaced in the environment (e.g., fossil fuels) because it forms at a rate far slower than its consumption. 
Non-water-using Urinal: A urinal that uses no water, but instead replaces the water flush with a specially designed trap that contains a layer of buoyant liquid that floats above the urine layer, blocking sewer gas and urine odors from the room. 
Off-gassing: Release of volatile chemicals from a product or assembly. Many chemicals released from materials impact indoor air quality and occupant health and comfort. Offgassing can be reduced by specifying materials that are low- or no-VOC and by avoiding certain chemicals (e.g., urea formaldehyde) entirely. Controlling indoor moisture, and specifying pre-finished materials, can also reduce offgas potential.
On-Demand Hot Water: See Demand Hot Water Systems
On-Site Stormwater Management: Building and landscape strategies to control and limit stormwater pollution and runoff. Usually an integrated package of strategies, elements can include vegetated roofs, compost-amended soils, pervious paving, tree planting, drainage swales, and more.
On-site Wastewater Treatment: Uses localized treatment systems to transport, store, treat, and dispose of wastewater volumes generated on the project site. 
Open Space Area: Open Space Area is defined by local zoning requirements. If local zoning requirements do not clearly define open space, it is defined for the purposes of LEED calculations as the property area minus the development footprint; and it must be vegetated and pervious, with exceptions only as noted in the credit requirements section. For projects located in urban areas that earn SS Credit 2, open space also includes non-vehicular, pedestrian-oriented hardscape spaces. 
Open-grid Pavement: Defined for LEED purposes as pavement that is less than 50% impervious and contains vegetation in the open cells. 
Operations Manual (O&M Manual): Manual developed to assist building occupants in maintaining and operating a green building and its features. Many features’ effectiveness can be reduced or eliminated by the actions (or inaction) of occupants and maintenance crews. An operations manual usually includes product and system information and warranties, contact information, and other information required for effective operations and maintenance.
Organic Compound: Vast array of substances typically characterized as principally carbon and hydrogen, but that may also contain oxygen, nitrogen and a variety of other elements as structural building blocks. 
Orientation (Solar): Orientation of a structure for controlled solar gain is essential to the success of passive and active solar design elements. Sun charts and software assist in orienting a building for maximum solar benefit. Designing for solar considerations can substantially reduce both heating and cooling.
OSB: Oriented Strand Board. A high strength, structural wood panel formed by binding wood strands with resin in opposing orientations. OSB is environmentally beneficial in that it uses small dimension and waste wood for its fiber; however, resin type should be considered for human health impact, and the production process monitored for air pollutant emissions.
OSHA: Occupational Safety and Health Administration . Federal agency created in 1971 with the mission of preventing work-related injury, illness and death.
Outdoor Air Supply: Air brought into a building from outside. 
Overhangs: Architectural elements on roofs and above windows that function to protect the structure from the elements or to assist in daylighting and control of unwanted solar gain. Sizing of overhangs should consider their purpose, especially related to solar control.
Owner’s Project Requirements (OPR): An explanation of the ideas, concepts and criteria that are determined by the owner to be important to the success of the project (previously called the Design Intent). 
Ozone Depletion: Destruction of the earth's ozone layer, which can be caused by the photolytic breakdown of certain chlorine- and/or bromine-containing compounds (e.g., chlorofluorocarbons), which catalytically decompose ozone molecules. 
Ozone Hole: A thinning break in the ozone layer. Designation of amount of such depletion as an "ozone hole" is made when the detected amount of depletion exceeds 50 percent. Seasonal ozone holes have been observed over the Antarctic and arctic regions, part of Canada, and the extreme northeastern United States. 
Ozone Layer: The protective layer in the atmosphere, about 12-15 miles above sea level, that absorbs some of the sun's ultraviolet rays, thereby reducing the amount of potentially harmful radiation that reaches the earth's surface. 
Ozone (O3): A naturally occurring, highly reactive, irritating gas comprising triatomic oxygen formed by recombination of oxygen in the presence of ultraviolet radiation. This gas builds up in the lower atmosphere as smog pollution, while in the upper atmosphere it forms a protective layer that shields the earth and its inhabitants from excessive exposure to damaging ultraviolet radiation. 
Particulate Pollution: Pollution made up of small liquid or solid particles suspended in the atmosphere or water supply. 
Particulate: a. Fine dust or particles (e.g., smoke). b. Of or relating to minute discrete particles. c. A particulate substance. 
Passive Solar: Strategies for using the sun’s energy to heat (or cool) a space, mass, or liquid. Passive solar strategies use no pumps or controls to function. A window, oriented for solar gain and coupled with massing for thermal storage (e.g., a Trombe wall) is an example of a passive solar technique.
pH: An expression of the intensity of the basic or acid condition of a liquid; may range from 0 to 14, where 0 is the most acid and 7 is neutral. Natural waters usually have a pH between 6.5 and 8.5. 
Photocell: A device that measures the amount of incident light present in a space. 
Photovoltaic (PV) Cell: An electronic device consisting of layers of semiconductor materials fabricated to form a junction (adjacent layers of materials with different electronic characteristics) and electrical contacts and being capable of converting incident light directly into electricity (direct current). 
Photovoltaic (PV) Module: An integrated assembly of interconnected photovoltaic cells designed to deliver a selected level of working voltage and current at its output terminals, packaged for protection against environment degradation, and suited for incorporation in photovoltaic power systems. 
Phytoremediation: Low-cost option for site cleanup when the site has low levels of contamination that are widely dispersed. Phytoremediation (a subset of bioremediation) uses plants to break down or uptake contaminants.
Pollution: Generally, the presence of a substance in the environment that, because of its chemical composition or quantity, prevents the functioning of natural processes and produces undesirable environmental and health effects. Under the Clean Water Act, for example, the term has been defined as the man-made or man-induced alteration of the physical, biological, chemical and radiological integrity of water and other media. 
Pollution Prevention: Techniques that eliminate waste prior to treatment, such as changing ingredients in a chemical reaction. Identifying areas, processes and activities that create excessive waste products or pollutants in order to reduce or prevent them through alteration or elimination of a process. The EPA has initiated a number of voluntary programs in which industrial or commercial "partners" join with the EPA in promoting activities that conserve energy, conserve and protect the water supply, reduce emissions or find ways of utilizing them as energy resources, and reduce the waste stream. 
Porous Paving: Paving surfaces designed to allow stormwater infiltration and reduce runoff.
Post-Consumer Recycling: Use of materials generated from residential and consumer waste for new or similar purposes; e.g. converting wastepaper from offices into corrugated boxes or newsprint. 
Post-Consumer Recycle Content: A product composition that contains some percentage of material that has been reclaimed from the same or another end use at the end of its former, useful life. 
Post-Industrial Material: Industrial manufacturing scrap or waste; also called pre-consumer material. 
Post-Industrial Recycle Content: A product composition that contains some percentage of manufacturing waste material that has been reclaimed from a process generating the same or a similar product. Also called pre-consumer recycle content. 
Precautionary Principle: When information about potential risks is incomplete, basing decisions about the best ways to manage or reduce risks on a preference for avoiding unnecessary health risks instead of on unnecessary economic expenditures. 
Pre-Consumer Materials/Waste: Materials generated in manufacturing and converting processes such as manufacturing scrap and trimmings and cuttings. Includes print overruns, overissue publications, and obsolete inventories. 
Public Transportation: Mass transit, including bus and light rail systems. Siting a building near public transit is considered a sustainable building strategy, as it facilitates commuting without the use of single occupancy vehicles.
Pyrolysis: Decomposition of a chemical by extreme heat. 
Radon: A colorless naturally occurring, radioactive, inert gas formed by radioactive decay of radium atoms in soil or rocks. Design strategies help reduce the amount of radon infiltration into a building and remove the gas that does infiltrate. 
Rainwater Catchment/Harvest: On-site rainwater harvest and storage systems used to offset potable water needs for a building and/or landscape. Systems can take a variety of forms, but usually consist of a surface for collecting precipitation (roof or other impervious surface) and a storage system. Depending on the end use, a variety of filtration and purification systems may also be employed.
Rapidly Renewable Materials: Material considered to be an agricultural product, both fiber and animal, that takes 10 years or less to grow or raise, and to harvest in an ongoing and sustainable fashion. 
Receptacle Load: Refers to all equipment that is plugged into the electrical system, from office equipment to refrigerators. 
Reclamation: Restoration of materials found in the waste stream to a beneficial use that may be other than the original use. 
Recycled Content: The content in a material or product derived from recycled materials versus virgin materials. Recycled content can be materials from recycling programs ("post-consumer") or waste materials from the production process or an industrial/agricultural source ("pre-consumer" or "post-industrial").
Recycling: Process by which materials that would otherwise become solid waste are collected, separated or processed and returned to the economic mainstream to be reused in the form of raw materials or finished goods. 
Recycling Areas: Space dedicated to recycling activities is essential to a successful recycling program, both on the construction site and in the building after occupation. For strategies related to determining recycling area configuration and placement, see the Business and Industry Resource Venture site.
Recycling Bins: Containers to temporarily hold recyclable materials until transferred to a larger holding facility of pick-up by a recycling service. Conveniently located bins increase recycling rates by allowing occupants to recycle more easily. Designing space for recycling bins is a physical reminder of a commitment to recycling.
Re-entry: (In indoor air program) Refers to air exhausted from a building that is immediately brought back into the system through the air intake and other openings. 
Refurbished: Products that have been upgraded to be returned to active use in their original form. Refurbishing is considered a form of reuse, and is preferable to recycling as it requires less processing and inputs to return a product to useful service.
Regional Manufacture: Goods produced within a certain radius of the project site. Using regionally produced goods is considered a sustainable building strategy in that it reduces the transportation impacts associated with the product, it often allows for a better understanding of the production process and increases the likelihood that the product was manufactured in accordance with environmental laws, and it supports regional economies.
Relative Humidity: Ratio of the amount of water vapor in air at a specific temperature to the maximum capacity of the air at that temperature. 
Relite: Windows or translucent panels above doors or high in a partition wall intended to allow natural light to penetrate deeper into a building.
Renewable Energy Certificates (RECs): RECs are a representation of the environmental attributes of green power, and are sold separately from the electrons that make up the electricity. RECs allow the purchase of green power even when the electrons are not purchased. 
Renewable Resources: A resource that can be replenished at a rate equal to or greater than its rate of depletion; e.g., solar, wind, geothermal and biomass resources. 
Renovation: Upgrade of an existing building or space that maintains the original structure of a building.
Resource Conservation: Practices that protect, preserve or renew natural resources in a manner that will ensure their highest economic or social benefits. 
Respirable: Particles or aerosols capable of being inhaled into the deep lung, less than 3 microns in diameter. 
Retrofit: The replacement, upgrade, or improvement of a piece of equipment or structure in an existing building or facility. 
Reuse: Using a product or component of municipal solid waste in its original form more than once; e.g., refilling a glass bottle that has been returned or using a coffee can to hold nuts and bolts.  Reuse is a sustainable building strategy in that it reduces the strain on both renewable and nonrenewable resources, and when materials are reused on or near the site of salvage, they reduce transportation-related environmental impacts.
Risk: A measure of the probability of an adverse effect on a population under a well-defined exposure scenario. 
Risk Assessment: Qualitative and quantitative evaluation of the risk posed to human health and/or the environment by the actual or potential presence and/or use of specific pollutants. 
Risk Factor Characteristics (e.g., race, sex, age, obesity) or variables (e.g., smoking, occupational exposure level) associated with increased probability of a toxic effect. 
Route of Exposure: The avenue by which a chemical comes into contact with an organism, e.g., inhalation, ingestion, dermal contact, injection. 
R-value: A unit of thermal resistance used for comparing insulating values of different materials; the higher the R-value, the greater its insulating properties. 
Salvage: Building materials diverted from the waste stream intended for reuse. Commonly salvaged materials include structural beams and posts, flooring, doors, cabinetry, brick, and decorative items. 
Sick Building Syndrome: Building whose occupants experience acute health and/or comfort effects that appear to be linked to time spent therein, but where no specific illness or cause can be identified. Complaints may be localized in a particular room or zone, or may spread throughout the building. 
Shower Facilities: In buildings that house workers, shower facilities are considered a green building feature in that they allow occupants that elect to travel by bicycle and other human powered modes of transportation to exercise this option.
Sisal: A durable natural fiber used as a floor covering, derived from leaves of the sisal plant.
Small: All else being equal, smaller is usually preferable in sustainable building. Larger buildings and spaces require more materials and energy to construct and use more resources to heat, cool and maintain.
Solar Collector: Any device used to capture or concentrate the sun’s energy. The leaves on a tree can be considered a solar collector, as can a window, solar panel, or dark surfaced thermal mass.
Solar Orientation: See Orientation (solar).
Solar Panels: General term for an assembly of photovoltaic modules. See photovoltaic. Use of solar panels is a sustainable building strategy in that it lessens a building’s reliance on nonrenewable sources of power distributed through the grid system.
Source Reduction: The design, manufacture, purchase or use of materials to reduce the amount or toxicity of waste in an effort to reduce pollution and conserve resources (i.e., reusing items, minimizing the use of products containing hazardous compounds, extending the useful life of a product and reducing unneeded packaging).
Practices that reduce the amount of any hazardous substance, pollutant or contaminant entering any waste stream or otherwise being released into the environment. Such practices also reduce the risk to public health and the environment associated with such releases. Term includes equipment or technology modifications, substitution of raw materials, and improvements in housekeeping, maintenance, training or inventory control. 
Stack Effect: Air, as in a chimney, that moves upward because it is warmer than the ambient atmosphere. 
Staging: The sequencing and physical positioning of building materials on a construction site. Sustainable building pays particular attention to staging in order to minimize the impact to the construction site and protect materials from damage.
Stakeholder: Any organization, governmental entity, or individual that has a stake in or may be impacted by a given approach to environmental regulation, pollution prevention, energy conservation, etc. 
Straw-Bale Construction: Alternative building method using bales of straw for wall systems. The method uses an agricultural waste product in place of diminishing dimensional lumber, and achieves high insulation values. It is a building method most appropriate for regions with relatively little precipitation.
Structural Insulated Panel (SIP): Manufactured panels consisting of a sandwich of polystyrene between two layers of engineered wood paneling. Can be used for walls, roof, or flooring, and result in a structure very resistant to air infiltration.
Subsidies: Economic incentives to engage in an activity or purchase a product. Subsidies can work for or against environmental protection. Governments and utilities will sometimes offer subsidies for technologies that decrease energy or water use.
Sulfur Dioxide (SO2): A heavy, smelly gas that can be condensed into a clear liquid; used to make sulfuric acid, bleaching agents, preservatives and refrigerants; a major source of air pollution in industrial areas. 
Sunshades: Devices for blocking unwanted solar gain.
Sustainability: Practices that would ensure the continued viability of a product or practice well into the future. 
Sustainable Development: An approach to progress that meets the needs of the present without compromising the ability of future generations to meet their needs. 
Sustainable Forestry: The practice of managing forest resources to meet the long-term forest product needs of humans while maintaining the biodiversity of forested landscapes. The primary goal is to restore, enhance and sustain a full range of forest values-economic, social and ecological. 
Superfund: The program operated under the legislative authority of CERCLA and SARA that funds and carries out EPA solid waste emergency and long-term removal and remedial activities. These activities include establishing the National Priorities List, investigating sites for inclusion on the list, determining their priority, and conducting and/or supervising cleanup and other remedial actions. 
Superinsulation: Insulating a building to minimize the amount of heat that can escape from (or, in a hot climate, enter) a building. 
Sustainability: Meeting the needs of the present without compromising the ability of future egenrations to meet their own needs. 
Teratogenesis: The introduction of nonhereditary birth defects in a developing fetus by exogenous factors such as physical or chemical agents acting in the womb to interfere with normal embryonic development. 
Thermal Break: Method of increasing the thermal performance of a material or assembly by reducing conductive heat loss. By inserting a less thermally conductive material in a material or assembly that bridges conditioned and unconditioned space, the conductive path is reduced or broken. An example is the thermal break featured in aluminum-framed windows.
Thermal Bridging: Unwanted heat loss or gain due to conduction through a material. An example of thermal bridging is heat loss that occurs with structural steel framing that is insufficiently insulated between conditioned and unconditioned space.
Thermal Mass: A mass (often stone, concrete, or brick) used to store heat and reduce temperature fluctuation in a space, by releasing heat slowly over time.
Thermal Pollution: The addition of heat to a body of water that may change the ecological balance. 
Tipping Fee: Charge for the unloading or dumping of waste at a recycling facility, composting facility, landfill, transfer station or waste-to-energy facility. 
Total Volatile Organic Compounds: The total mass, typically in milligrams per cubic meter, of the organic compounds collected in air. 
Toxic: Capable of having an adverse effect on an organism; poisonous; harmful or deadly. 
Toxic Release Inventory: Database of toxic releases in the United States compiled from SARA Title III Section 313 reports. 
Transpiration: The process by which water vapor is lost to the atmosphere from living plants. The term can also be applied to the quantity of water thus dissipated. 
Trombe Wall: Thermal storage system used in passive solar design. A high-mass wall that stores heat from solar gain during the day and slowly radiates the heat back into the living space at night.
Truck Tire Wash Down Area: A strategy for removing dirt and other contaminants from construction vehicles in order to prevent stormwater contamination related to transport of contaminants offsite on vehicle tires. A specified area is created for wash down, with structural controls in place to prevent wash down waters from entering the storm system or the larger environment.
U (U-Value): A measure of the amount of heat that flows in or out of a substance under constant conditions when there is a one degree difference between the air within and outside a building. U-values are used in determining the performance of a glazing system or window assembly.
Ventilation Control (by Occupants): The ability of building occupants to control ventilation rates. A strategy for giving control of comfort back to occupants, this can be achieved through access to individual electronic controls or by operable windows in workspaces. Studies show that giving increased control to occupants over their environment results in greater occupant tolerance for variability in the indoor environment.
Ventilation Rate: The rate at which indoor air enters and leaves a building. Expressed as the number of changes of outdoor air per unit of time: air changes per hour (ACH), or the rate at which a volume of outdoor air enters in cubic feet per minute (CFM). 
Visual DOE: See Energy Modeling
Volatile Organic Compounds (VOCs): Carbon compounds that participate in atmospheric photochemical reactions (excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides and carbonates, and ammonium carbonate). The compounds vaporize (become a gas) at normal room temperatures. 
Walk-off Mat: Design strategy for reducing the amount of contaminants introduced into an interior space by providing grating or other material to remove contaminants from shoes. A significant portion of contaminants in a building are brought in this way, impacting indoor environmental quality.
Wastewater: The spent or used water from a home, community, farm, or industry that contains dissolved or suspended matter. 
Waste Management Plan: See Construction Waste Management
Water-Source Heat Pump: Heat pump that uses wells or heat exchangers to transfer heat from water to the inside of a building. Most such units use ground water. (See groundsource heat pump; heat pump.) 
Waterless Urinal: Urinal with no water line. Most designs use a specialized material that allows fluid to drain one-way into the sewer system.
Watts per Square Foot: A shorthand measure of the energy use of a building, often applied to indoor lighting. Energy codes often limit the watts per square foot based on building type and function.
Weatherization: The process of reducing the leaks of heat from or into a building. It may involve caulking, weatherstripping, adding insulation, and other similar improvements to the building shell. 
Wetlands: An area that is saturated by surface or ground water with vegetation adapted for life under those soil conditions, as swamps, bogs, fens, marshes, and estuaries. 
Wind Power: Systems that convert air movement into mechanical or electrical energy. Driven by the wind, turbine blades turn a generator or power a mechanical pump. 
Wind Turbine: Device for generating electricity from wind; windmill.
Window Shading: Any device for reducing unwanted heat gain from a window.
Worm Bin: System for on-site management of food scraps and other organic materials. Similar to a compost bin, a worm bin uses worms to digest organic wastes, in a process known as "vermicomposting".
4: Thomas, R. and M. Fordham (ed.), 2003. Sustainable Urban Design: An Environmental Approach. London: Spon Press.
5: Lopez Barnett, D. and W. Browning, 1995. A Primer on Sustainable Building. CO: Rocky Mountain Institute.
6: U.S. Green Building Council, 2006. New Construction & Major Renovation (Version 2.2) Reference Guide.
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