This is a gable roof with two pitches, the bottom pitch being steeper than the top. The term gambrel is also used to describe the hing leg of a horse, with a angle at the joint that looks like a gambrel roof, or much more likely, the other way around.

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Hot water or steam extracted from reservoirs beneath the Earth's surface; can be used for heat pumps, water heating, or electricity generation. The term may also mean the use of near-constant underground temperatures by ground-source heat pumps to provide heating and cooling.

When referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill.

Gallons per flush. Measurement of water use in toilets. Since 1992, toilets sold in the United States have been restricted to 1.6 gpf or less. The standard for high-efficiency toilets (HETs) is 1.28 gpf.

Gallons per minute. Measure of liquid (usually water) flow.

Wastewater from a building that does not include flush-water from toilets and (as most commonly defined) water from kitchen sinks or dishwashers. In some places, graywater can be collected and used for subsurface irrigation.

Electricity generated from renewable energy sources, such as photovoltaics (solar power), wind power, biomass, and small-scale hydropower. (Large, conventional hydropower sources usually are not included in definitions of green electricity.)

Green mortgage
Type of mortgage in which the lending institution raises the allowable loan amount for an applicant's earnings level because the applicant's green home has lower monthly operating costs and may even reduce the applicant's transportation costs. See energy efficient mortgage.

Roof system in which living plants are maintained in a growing medium using a membrane and drainage system. Green roofs can reduce storm-water runoff, moderate temperatures in and around the building (by providing insulation and reducing heat island effect), as well as provide a habitat for wildlife and recreational space for humans. When properly constructed, green roofs can increase roof durability because the roof assembly’s air and water barriers are buffered from temperature fluctuations and UV exposure.

Independent, nonprofit organization that certifies a variety of products as environmentally responsible based on established criteria. Certified products include coffee filters, air chillers, paints and coatings, papers and newsprint, various cleaning products and services, windows and doors, and lodging properties.

Third-party certification program that identifies building products and materials which produce relatively low levels of emissions. GreenGuard is administered by the nonprofit GreenGuard Environmental Institute (GEI). Other GEI programs include the Children & Schools standard, which addresses emission standards for educational facilities, and the GreenGuard for Building Construction Program, a mold risk-reduction program that certifies the design, construction, and ongoing operations of new multifamily and commercial properties.

Dissemination of misleading or false information designed to make an organization or product appear more environmentally friendly than it actually is.

Home heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger. The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures.

Building renovation in which all interior walls and ceilings are removed, leaving framing and exterior sheathing or structural brick or block.

Often referred to as drywall or Sheetrock. Flat sheet of the mineral gypsum, usually faced with paper, that is used as a building material for interior (and sometimes exterior) walls and ceilings.