Active Solar Heating: Heat from the sun is absorbed by collectors and mechanically transferred by pumps or fans for storage for heating, cooling, or making electricity.

Agenda 21: A comprehensive strategy developed by the United Nations that can be implemented by national and local governments to minimize the negative impacts that humans have on the environment.

Biomass: Living and recently dead biological material that can be used as a sustainable fuel.

Blackwater: Water containing human waste from toilets and urinals. Black water contains pathogens that must be neutralized before the water can be safely reused. Typically, black water, after neutralization, is used for non-potable uses such as flushing or irrigation.

BREEAM: Building Research Establishment Environmental Assessment Method (BREEAM) is a comprehensive tool for analyzing and improving the environmental performance of buildings through design and operations. This methodology has been developed by the U.K.-based Building Research Establishment.

Brownfields: Abandoned, idled, or underused industrial and commercial facilities where expansion or redevelopment is complicated by real or perceived environmental contamination.

Building Envelope: The skin of a building—including the windows, doors, walls, foundation, basement slabs, ceilings, roof, and insulation—that separates the interior of a building from the outdoor environment.

Built Environment: Human-built structures such as single-family homes.

Carbon Dioxide (CO2): A colorless, odorless gas that naturally exists in the earth's atmosphere. The major source of manmade CO2 emissions is from the combustion of fossil fuels. Carbon dioxide is the primary greenhouse gas and is known to contribute to global warming and climate change.

Carbon Footprint: The measure of the impact human activities have on the environment in terms of the amount of greenhouse gases produced, measured in units of carbon dioxide.

Certified Sustainably Managed: Wood determined to have been harvested from a sustainable forest that exhibits the same ecological characteristics as a healthy natural forest. A number of certifying organizations have been established to oversee the harvesting of wood for lumber and provide guidelines for preservation of forests.

Chlorofluorocarbons (CFCs): A family of chemicals used in refrigeration, air conditioning, packaging, insulation, or as solvents and aerosol propellants, which drift into the upper atmosphere and destroy the Earth's protective ozone layer.

Composting: A process whereby organic wastes—food, paper, and yard wastes—decompose naturally, resulting in a product rich in minerals and ideal for gardening and farming as a soil conditioner, mulch, resurfacing material, or landfill cover.

Cradle to Cradle: A certification system and philosophy established by architect William McDonough based on the idea that products and the built environment should be designed in a closed system so that when they are no longer useful, they provide fuel for new products or natural cycles, eliminating waste. This framework seeks to create production techniques that are not just efficient, but essentially waste-free. In cradle-to-cradle production, all material inputs and outputs are seen either as technical or biological nutrients. Technical nutrients can be recycled or reused with no loss of quality and biological nutrients can be composted or consumed.

Cradle to Grave: The process whereby a company takes responsibility for the disposal of goods it has produced, but not necessarily putting products' constituent components back into service.

Daylighting: The use of natural light to supplement or replace artificial lighting. Strategies include the proper orientation and placement of windows, use of light wells, light shafts or tubes, skylights, clerestory windows, light shelves, reflective surfaces, and shading, as well as the use of interior glazing to allow light into adjacent spaces.

Daylight Harvesting: The process of using digital photo sensors to detect daylight levels and automatically adjust the output level of electric lighting to create a balance.

Domestic Hardwood: Deciduous trees that grow in the United States. This is the only type of wood in the U.S. where on a general scale the growth of new trees easily exceeds the removal rate.

Eco-assessment: An evaluation of your home or workplace with the aim of cutting your energy and water usage.

Eco-friendly: Having little or no impact on the native ecosystem.

Ecological Footprint: The area of land and water needed to produce the resources to entirely sustain a human population and absorb its waste products with prevailing technology.

Embodied Energy: The total of the energy required to produce a service or product. Included are the product's raw material extraction, transport, manufacturing, assembly, and installation, as well as capital and other costs of a specific material, in addition to disassembly, deconstruction, and/or decompostion.

Emissions: The release of a substance (usually a gas when referring to the subject of climate change) into the atmosphere.

Emissions Cap: A limit placed on corporations regarding the amount of greenhouse gases it can emit.

Emissions trading (aka Cap and Trade): A market-based approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants. A central authority (usually a governmental body) sets a limit or cap on the amount of a pollutant that can be emitted. The limit or cap is allocated or sold to firms in the form of emissions permits which represent the right to emit or discharge a specific volume of the specified pollutant. Firms are required to hold a number of permits (or credits) equivalent to their emissions. The total amount of permits cannot exceed the cap, limiting total emissions to that level. Firms that need to increase their emission permits must buy permits from those who require fewer permits. The transfer of permits is referred to as a trade. In effect, the buyer is paying a charge for polluting, while the seller is being rewarded for having reduced emissions. Thus, in theory, those who can reduce emissions most cheaply will do so, achieving the pollution reduction at the lowest cost to society.

Energy Efficiency: Ratio of energy output of a conversion process or of a system to its energy input.

Energy Smart: Meeting energy needs cost effectively and with the least impact on the environment.

Energy Star: The Energy Star program, managed by the Environmental Protection Agency and the Department of Energy, helps consumers identify energy-efficient products for their homes.

Exterior Grade Plywood: Uses phenol formaldehyde (a volatile organic compound) as an adhesive rather than the urea formaldehyde used in interior grade plywood and particleboard.

Fly Ash: The ash residue from high temperature combustion processes. Electric motor plants using western coal produce a non-toxic fly ash that because of its very high calcium content can be a substitute for Portland cement (the common bonding material in concrete).

Formaldehyde: Colorless, pungent smelling, toxic material used as an adhering component of glues used in many wood products. It can cause respiratory problems, cancer, and chemical sensitivity. At concentrations above 0.1 ppm in air, formaldehyde can irritate the eyes and mucous membranes, resulting in watery eyes. Naturally occurring but when added it is referred to as urea formaldehyde.

Fossil Fuels: Carbon-rich deposits in the Earth, such as petroleum (oil), coal, or natural gas, derived from the remains of ancient plants and animals and used for fuel. These are non-renewable resources with a finite supply. They are pollutive, but are so commonly used due to their traditionally low costs.

Fuel Cell: A technology that uses an electrochemical process to convert energy into electrical power. Often powered by natural gas, fuel cell power is cleaner than grid-connected power sources. In addition, hot water is produced as a by-product that can be used as a thermal resource.

Geothermal Energy: Heat that comes from the Earth's interior.

Global Warming: An increase in the global mean temperature of the Earth that is a result of increased emissions of greenhouse gases that are trapped within the Earth's atmosphere. Global warming is believed to have adverse consequences, such as climate change and a rise in sea levels. The scientific community is in general agreement that the Earth's surface has warmed by about 1°F over the past 140 years.

Global Warming Potential (GWP): 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. Global Warming Potential (GWP) is defined as the cumulative radiative forcing effects of a gas over a specified time horizon resulting from the emission of a unit mass of gas relative to a reference gas. The GWP-weighted emissions of direct greenhouse gases in the U.S. Inventory are presented in terms of equivalent emissions of carbon dioxide (CO2), using units of teragrams of carbon dioxide equivalents (Tg CO2 Eq.).

Graywater: Wastewater from sources such as sinks, showers, kitchens, and washers, which after purification, is used for non-potable uses such as flushing and irrigation. Rainwater from gutters can be used for this.

Green Building: A building that minimizes its impact on the environment through conservation of energy, water, and other resources, while contributing to the health of its occupants without compromising the aesthetic design.

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.

Greenhouse Gases: Any gas that absorbs infrared radiation in the Earth's atmosphere. Carbon dioxide, methane, and nitrogen oxides are of particular concern due to their length of time they remain resident in the atmosphere. Primarily, the emissions of coal-fired power plants and combustion engine automobiles produce carbon dioxide that prevents excess heat from escaping through the atmosphere, thereby raising the surface temperature of the earth. More than 80 percent of all U.S. greenhouse gases are carbon dioxide emissions from energy-related sources.

Green Power: Electricity generated from renewable energy sources. This includes solar, wind, biomass, geothermal, and hydroelectric power.

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.

Green Tag: A green tag, or Renewable Energy Certificate (REC), represents the environmental attributes created when electricity is generated using renewable resources instead of fossil fuels such as coal, oil and natural gas. RECs can be sold separately from their associated electricity and enable 
customers to ‘green’ the electricity they consume from their retail power suppliers.

Greenfields: Sites that have not been previously developed or graded and remain in a natural state.

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.

Harvested Rainwater: The rain that falls on a roof and is channeled by gutters to a storage tank or cistern.

Heat Island Effect: A phenomenon that occurs in developed areas where the replacement of natural land cover with paving, buildings, roads, parking lots, and other structures result in an increase in outdoor temperatures. The heat island effect can be mitigated by vegetation, green roofs, and light colored materials that reflect heat. Urban heat islands can be as much as 10°F hotter than the surrounding undeveloped areas.

Heat Recovery Systems: Building mechanical systems that capture waste heat from another system and use it to replace heat that would otherwise come from a primary energy source.

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 Intensity Discharge: A generic term for mercury vapor, metal halide, and high-pressure sodium lamps and fixtures.
High Performance GlazingGeneric term for glazing materials with increased thermal efficiency.

Home Area Network: Expanding the IP communications on a residential broadband network beyond computers and printers to include appliances, such as thermostats and refrigerators, to achieve energy efficiency. ‘Smart’ devices communicate as part of a ‘home grid’ utilizing the existing and expanded communications networks as a reactive function of the electric grid. Storage devices could be programmed to take in energy when it is most affordable to be used when on-demand energy is at its highest levels of expense.

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.

Hydro (electric) energy: 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.

Hydrocarbons (HC): Chemical compounds that consist entirely of carbon and hydrogen. Fossil fuels are made up of hydrocarbons.

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.

Currently used as refrigerants, HCFCs deplete the ozone layer and are being phased out in the United States. The UN Environment Programme estimates that exposure to the additional UV-B radiation resulting from 10 percent loss of global ozone could lead to 300,000 additional cases of squamous cell cancer and basal cell cancer and 4,500-9,000 additional cases of potentially fatal melanoma worldwide each year. Increased exposure to UV-B rays also poses a significant threat to animal and plant life and consequently many of the earth's food chains.
Hydrologic CycleMovement or exchange of water between the atmosphere and earth. [1] or The process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologic cycle is responsible for 25 to 30 percent of the mid-latitudes' heat transport from the equatorial to polar regions.

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.

Hydrosphere: The component of the climate system comprising liquid surface and subterranean water, such as: oceans, seas, rivers, fresh water lakes, underground water etc.  

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. Pervious or porous surfaces allow some water infiltration, thereby reducing runoff.

Indigenous Materials: Building materials that are mined, manufactured, or fabricated locally to reduce transportation cost and increase the viability of the local economy.

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 Quality (IAQ): The content of interior air that could affect the health and comfort of building occupants. Good air quality inside a building results from streaming an appropriate amount of outside air into the building and regulating proper filtration, air distribution, and removal of indoor pollutants through he use of proper ventilation.

Industrial Ecology: An approach to the design of industrial products and processes that evaluates such activities through the dual perspectives of product competitiveness and environmental interactions.

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 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.

Intelligent Materials: Materials able to adapt to their environment by altering their properties, such as thermochromic glazing that changes its transparency in response to changing temperatures.

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).

Kilowatt-hours (kWH): The most commonly known as a billing unit for energy delivered to consumers by electric utilities. A unit of energy equal to 1000 watt hours or 3.6 megajoules. Energy in watt hours is the multiplication of power in watts and time in hours.

Kyoto Protocol: In December 1997, a delegation from 160 countries came together on climate change and adopted an agreement, under which the industrialized nations agreed to reduce their greenhouse gas emissions by an average of 5.2 percent below 1990 emissions levels by 2010.

Landfill: Engineered facilities located, maintained and designed to assure compliance with federal waste disposal laws. Solid waste landfills are located away from eco-sensitive environments to protect them from contaminants in water, land and air. Often, they collect hazardous waste and gas emissions to be converted into alternative energy sources. Waste is generally spread in thin layers, compacted, and covered with a fresh layer of soil each day.

LEED (Leadership in Energy and Environmental Design): A voluntary, consensus-based national rating system for developing high-performance, sustainable buildings. Developed by the USGBC, LEED addresses all building types and emphasizes state-of-the-art strategies for sustainable site development, water savings, energy efficiency, materials and resources selection, and indoor environmental quality. LEED is a practical rating tool for green building design and construction that provides immediate, measurable results for building owners and occupants.

Life Cycle (of a Product): All stages of a product's development from extraction 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. Used as a tool for evaluating the relative performance of building materials, technologies and systems.

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 that consumes 80 percent less energy than conventional, incandescent bulbs. Common in digital clocks, remote controls, watches and appliances, they are now being produced in bulb form as a home lighting alternative.

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-E (Low-Emissive): Glass that reflect heat, not light, and therefore keeps spaces warmer in winter and cooler in summer.

Low Emission Vehicle: A vehicle that emits relatively low levels of air pollutants. The term may be used in a general sense, but in some countries it is defined in law; low emission vehicles may be given tax or other advantages, while high emission vehicles may suffer restrictions or additional taxation.

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.

Microclimate: Localized climate conditions within an urban area or building.

Minimum Efficiency Reporting Value (MERV): A rating from 1 to 16 that measures a filter’s efficiency. A higher MERV means the air filter is more efficient at removing particles.

Modular Building: Building technique using pre-constructed components. Building on a "module" also refers to the concept of using standardized dimensions that reduce the amount of construction waste.

Monitoring-Based Commissioning (MBCx): An energy efficiency methodology that identifies a prioritized list of savings opportunities based on continuous analysis of a building’s operations.

Municipal Solid Waste (MSW): Residential solid waste and some non-hazardous commercial, institutional, and industrial wastes. Generally sent to municipal landfills for disposal.

Natural Gas: Underground deposits of gases consisting of 50 to 90 percent methane (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H8) and butane (C4H10).

Natural Products Association Certified: This certification is applied to products with 95 percent of the ingredients derived from natural sources (for instance, plants, milk, honey, beeswax, minerals); synthetic ingredients are allowed only when no viable natural alternative exists. Regardless of source, the ingredients must not pose any potential human health problem, and companies can't process natural ingredients in any way that could significantly alter their purity.

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.

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.
Net-ZeroThe characteristic of requiring no additional energy input from outside sources.

Non-Renewable Energy Resources: Energy resources that cannot be restored or replenished by natural processes and therefore are depleted through use. Commonly used non-renewable energy resources include coal, oil, natural gas, and uranium.

Occupancy Sensor: A sensing device, commonly connected to a room’s lighting, but also occasionally to heating or ventilation, that shuts down these services when the space is unoccupied.

Off the Grid: A system that runs on renewable energy sources independent of a conventional public utility grid.

Offsets: Greenhouse gas reduction activities undertaken to compensate for emissions elsewhere.

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 TreatmentUses localized treatment systems to transport, store, treat and dispose of wastewater volumes generated on the project/building site.

Open-grid Pavement: Defined for LEED purposes as pavement that is less than 50% impervious and contains vegetation in the open cells. The vegetations’ evapotranspiration reduces the heat island effect caused by pavement.
Optimal Value Engineering (OVE)Represents a coordinated effort to design, plan, and build in order to reduce the amount of lumber used in framing. Careful planning, redesign of certain elements, and use of alternative materials are key to the process.

Ozone: A form of oxygen found naturally that provides a protective layer shielding the Earth from ultraviolet radiation's harmful effects on humans and the environment. Ground level ozone is the primary component of smog, produced near the Earth's surface through complex chemical reactions of nitrogen oxides, volatile organic compounds, and sunlight.

Particulate Matter: Solid material that escapes from combustion processes and can be inhaled, causing potential health problems.

Passive Design: Building design and placement in home construction that permits the use of natural thermal processes—convection, absorption, radiation, and conduction—to support comfort levels.

Passive Cooling: A system whereby a building's structure (or an element of it) permits increased ventilation and retention of coolness within the building components. The intention is to minimize or eliminate the need for mechanical means of cooling.

Passive Heating: A system whereby a building's structure (or an element of it) is designed to allow natural thermal energy flows, such as radiation, conduction, and natural convection generated by the sun, to provide heat. The home relies solely or primarily on non-mechanical means of heating.

Passive Solar: The use of natural heat transfer processes to collect, distribute, and store useable heat without the help of mechanical devices (pumps or fans). Passive solar systems have few moving parts. Trombe Walls and the use of the thermal mass of building structure to store energy are examples of passive solar systems.

Passive Ventilation: The use of convective airflows that result from the tendency of warm air to rise and cool air to sink, while also taking advantage of prevailing winds. Many passive ventilation systems rely on building occupants to control window and vents as indicated by conditions inside and outside the building.

Photocell: A device that measures the amount of incident light present in a space.

Photovoltaic (PV) Cell: Technology using solar cells (usually made of silicon) to convert sunlight into electricity. PV installations may be ground-mounted or integrated into the building structure, for instance on a roof.

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 into external power systems.

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.
Power Purchase Agreement (PPA)A legal contract between an electricity generator and a power purchaser. The power purchaser purchases energy, and sometimes also capacity and/or ancillary services, from the electricity generator. Such agreements play a key role in the financing of independently owned (i.e. not owned by utility) electricity generating assets. The seller under the PPA is typically an independent power producer, or "IPP." PPAs are often regarded as the central document in the development of independent electricity generating assets, and are key to obtaining financing for many alternative energy projects.

Property Assessed Clean Energy (PACE): An experimental retrofit financing program in which municipalities with PACE legislation (currently 23 states in the US) help home and business owners pay for the upfront costs of green initiative, such as solar, by offering a bond to investors and then loaning that money to the consumers and businesses that put it towards an energy retrofit or small alternative energy project. Under the assumption that the project will increase the value of the home, the loans are repaid over the assigned term (typically 15 or 20 years) via an annual property tax bill assessment, and then the municipality pays back the bondholder. PACE bonds can be issued by municipal financing districts or finance companies, and the proceeds can be used to help both commercial and residential properties become more energy efficient. One of the most notable characteristics of PACE programs is that the loan is attached to the property rather than an individual.

Prefabricated: Standardized building sections that are created in a factory to be shipped and assembled in another location.

Radiant Heating: An efficient heating system that warms cold objects, which then radiate heat into the surrounding space evenly.

Rainwater Harvesting: The collection, storage, and reuse of rainwater.

Regeneration: Renewal of sites or habitats that have become unfit for human, animal, or plant habitation, bringing them back into productive use. The term most commonly refers to urban and industrial land.

R-Value: A measure of the thermal resistance of material, especially insulation.

Radiant Heat: Heat transferred in the form of light energy (including non-visible spectra). Distinct from conductive heat, occurring with the direct contact between two materials.

Radiation: Energy transfer in the form of electromagnetic waves or particles that release energy when absorbed by an object.

Rainwater Catchment/Harvest (or Cistern): On-site rainwater harvest and storage systems used to offset potable water needs for a building and/or landscape. They catch and store rainwater for uses such as irrigation, plumping, or cooling towers, thereby reducing stormwater runoff. 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 take 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.
Reclaimed woodFlooring and other wood products remilled from salvaged timbers previously used as railroad ties, flooring or other building purposes. Its use prevents this lumber from becoming waste, while also preserving living trees.

Reclamation: Restoration of materials found in the waste stream to a beneficial use that may be other than the original use.
Recycled ContentThe 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").

Reclaim: To use a product again after its initial use. This commonly refers to materials such as tile, brick, and stone.

Recycling: The reprocessing of materials into new products, which generally prevents the waste of potentially useful materials, reduces the consumption of raw materials, lowers energy usage, and decreases greenhouse gas emissions compared to virgin production.

Reforestation: Planting of forests on lands that have previously contained forests but that have been converted to some other use.

Regeneration: Renewal of sites or habitats that have become unfit for human, animal, or plant habitation, bringing them back into productive use. The term most commonly refers to urban and industrial land.

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.

Renewable Energy Credit/Certificates:  Retradable commodities representing renewable energy. RECs are purchased in addition to grid electricity to offset non-renewable energy used with renewable sources. RECs fund renewable energy sources and contribute renewable energy to the national grid, thereby reducing fossil fuel based energy production. Rocs purchased to achieve LEED points must be certified Green-e (a third-party certifier) or meet equivalent standards. Green power is another term often used for Rocs.

Renewable Energy Sources: Energy sources that replenish themselves naturally within a short period of time. Sources of renewable energy include solar energy, hydroelectric power, geothermal energy, wind power, ocean thermal energy, wave power, wind power and fuel wood.

Renewable Portfolio Standard (RPS): A regulation that requires energy suppliers (utility companies) to utilize an increased percentage of power from renewable energy sources, such as wind, solar, biomass, and geothermal. Other common names for the same concept Renewable Electricity Standard (RES) at the United States federal level and Renewables Obligation in the UK.

The RPS mechanism generally places an obligation on electricity supply companies to produce a specified fraction of their electricity from renewable energy sources. Certified renewable energy generators earn certificates for every unit of electricity they produce and can sell these along with their electricity to supply companies. Supply companies then pass the certificates to some form of regulatory body to demonstrate their compliance with their regulatory obligations.

Retrofit: The replacement, upgrade, or improvement of a piece of equipment or structure in an existing building or facility, usually with the intent of decreasing overall energy consumption.

Reuse: To use products, such as glass bottles or shipping crates, repeatedly in the same form.

Renewable Energy: Energy resources, such as wind, solar, hydroelectric, biomass, geothermal, ocean thermal, and wave power, that replenish themselves within a short period. Although non-pollutive, some displace habitats and require large tracts of land.

(Rapidly) Renewable resource: Organic materials, like bamboo or corn, that have a short regeneration period to full maturation, usually in stark contrast to the material they are replacing.

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.

Shading Coefficient: The ratio of solar heat gain through a glazing system to the solar heat gain through a single layer of clear glass.

Sick Building Syndrome: A phenomenon in which building occupants experience acute health and/or comfort effects that appear to be linked to time spent in a particular building.

Smart Grid: A two-way power distribution system where electricity between suppliers and consumers utilizes digital technology to control appliances at consumers' homes or commercial buildings to save energy, reduce cost and increase reliability and transparency. It overlays the electricity distribution grid with an information and net metering system.

Smart House: A home that consists of programmable electronic controls and sensors that can regulate heating, cooling, ventilation, lighting, and equipment operation in an energy conserving and climatically responsible manner.

Smart Meter: An advanced meter (usually an electrical meter) that identifies consumption in more detail than a conventional meter; and optionally, but generally, communicates that information via some network back to the local utility for monitoring and billing purposes. A smart grid includes an intelligent monitoring system that keeps track of all electricity flowing in the system. It also incorporates the use of superconductive transmission lines for less power loss, as well as the capability of integrating renewable electricity such as solar and wind. When power is least expensive the user can allow the smart grid to turn on selected home appliances such as washing machines or factory processes that can run at arbitrary hours. At peak times it could turn off selected appliances to reduce demand.

Soil Carbon: A major component of the terrestrial biosphere pool in the carbon cycle. The amount of carbon in the soil is a function of the historical vegetative cover and productivity, which in turn is dependent in part upon climatic variables.
Solar CollectorAny 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 Panels: General term for an assembly of photovoltaic modules. 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.

Solar Renewable Energy Certificates (SRE): A form of REC or Green Tag that is available in states where a Renewable Portfolio Standard (RPS) exists with a specific allocation of solar energy. REC programs provide a means for SRECs to be created on behalf of a solar panel owner and sold to state electric suppliers to meet the solar RPS requirement. Electric suppliers are required to use the SREC program to show compliance with this part of the State’s Renewable Portfolio Standard. In order to produce SRECs, a solar system must first be certified by state regulatory agencies, usually public service commissions or public utility commissions, and then registered with the registry authorized by the state to create and track SRECs.
StagingThe 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.

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.
SunshadesDevices for blocking unwanted solar gain.

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.

Sustainability: The concept of sustainability can be traced back to President Theodore Roosevelt who stated in 1910, “ I recognize the right and duty of this generation to develop and use the natural resources of our land; but I do not recognize the right to waste them, or to rob, by wasteful use, the generations that come after us. ” In 1987 the United Nations World Commission on Environment and Development (The Brundtland Commission) defined a sustainable development as one that “meets the needs of the present without compromising the ability of future generations to meet their own needs”. Sustainability has three interdependent dimensions relating to the environment, economics and society—often referred to as the triple bottom line.

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 Energy Storage: Technologies used for storing energy in a thermal reservoir for later use. For cooling, ice is produced at night to provide daytime cooling, thereby reducing peak daytime electricity demands. For heating, solar collectors are most commonly used to gather heat, which is then stored for later use. 

Triple Bottom Line: According to the World Business Council for Sustainable Development, “Sustainable development involves the simultaneous pursuit of economic prosperity, environmental quality and social equity. Companies aiming for sustainability need to perform not against a single, financial bottom line, but against [this] triple bottom line.”

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.

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.

Upcycling: The process of recycling in such a way that new products are of higher economic value.


USGBC (United States Green Building Council): A non-profit organization committed to expanding sustainable building practices. The USGBC is composed of more than 12,000 organizations from across the building industry that are working to advance structures that are environmentally sustainable, profitable, and healthy places to live and work. Members includes building owners, real estate developers, facility managers, architects, designers, engineers, general contractors, subcontractors, product and building system manufacturers, government agencies, and nonprofit organizations.

Value Engineering: An organized activity in which building systems, equipment, design features and materials are analyzed in order to attain the lowest building life cycle cost while maintaining the stated functional and performance goals including quality, reliability, and safety.

Vampire Energy: A term used to describe the energy that is used by household appliances and electronics when they are not in use or powered-down into 'standby' mode. This energy is easily conserved by unplugging appliances and electronics from electric outlets when not in use. The process whereby worms feed on slowly decomposing materials (e.g., vegetable scraps) in a controlled environment to produce nutrient-rich soil.

Ventilated Façade: A special type of curtain wall that consists of two glazed facades separated by a gap through which ambient air is allowed to flow.

VOCs (Volatile Organic Compounds): Compounds that evaporate from many housekeeping, maintenance and building products made with organic chemicals. These compounds may be released from the products both in use, and in storage. In sufficient quantities, VOCs can cause irritation and some are carcinogenic and are suspected of causing or exacerbating acute and chronic diseases. The health effects of VOCs at levels found typically in commercial indoor environments are still not completely known and continue to be a point for further study.

Volatile Organic Compound (VOC): Any organic compound that evaporates at room temperatures and is hazardous to human health, causing poor indoor air quality. Many VOCs found in homes, such as paint strippers and wood preservatives, contribute to sick building syndrome because of their high vapor pressure. VOCs are often used in paint, carpet backing, plastics, and cosmetics. The United States Environmental Protection Agency (EPA) has found concentrations of VOCs in indoor air to be, on average, two to five times greater than in outdoor air. During certain activities, indoor levels of VOCs may reach 1,000 times that of the outside air.

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.
Water-Source Heat PumpHeat pump that uses wells or heat exchangers to transfer heat from water to the inside of a building. Most such units use ground water.

Waterless Urinal: Urinals that use 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.

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.

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: A device that converts the kinetic energy of the wind into mechanical energy that can be used to drive equipment such as pumps. The addition of a generator allows the wind’s kinetic energy to be converted into electricity. There are two types of wind turbines, namely: horizontal axis turbines - blades rotate about a horizontal axis; and vertical axis turbines - blades rotate about a vertical axis.

Xeriscaping: Landscaping design for conserving water that uses drought-resistant or drought-tolerant plants.