ACTIVE SOLAR ENERGY -- Solar radiation used by special equipment to provide space heating, hot water or electricity.

ARRAY - A group of photovoltaic or solar electric modules connected together in a power system.

BRITISH THERMAL UNIT (BTU) - A measure of energy. It is the amount of heat necessary to raise one pound of water one degree Fahrenheit. Heat loss and gain can be measured in BTUs per hour and BTUs per year.

BUILT GREEN - official designation of homes registered in the program and meeting the criteria of Built Green Colorado.

COMFORT ZONE - The range of temperatures over which the majority of persons feel comfortable (neither too hot nor too cold).

DIRECT SOLAR GAIN - Solar energy collected from the sun (as heat) in a building through windows, walls, skylights, etc.-

ENERGY EFFICIENT MORTGAGES -

ENERGY STAR - government/industry partnership that offers businesses and consumers energy-efficient solutions, making it easy to save money while protecting the environment for future generations.

EPA - The Environmental Protection Agency. A federal agency charged with protecting the environment.

GLAZING - Layers of glass or plastic, used in windows and other solar devices for admitting light and trapped heat.

GRID -- The electric utility companies' transmission and distribution system that links power plants to customers through high power transmission line service.

HEAT GAIN - an increase in the amount of heat contained in a space, resulting from direct solar radiation, heat flow through walls, windows, and other building surfaces, and the heat given off by people, lights, equipment, and other sources.

INSULATION - any material used to reduce or "slow down" or "resist" the flow of energy.

INVERTER - An appliance used to convert DC power into standard household current.

LOW-E - A special coating that reduces the emissivity of a window assembly, thereby reducing the heat transfer through the assembly.

PASSIVE SOLAR SYSTEM - A solar heating or cooling system that uses no external mechanical power to move the collected solar heat.

PHOTOVOLTAIC CELL - Device consisting of an array which in the presence of sunlight is capable of generating usable electrical energy.

RENEWABLE ENERGY - Resources that constantly renew themselves or that are regarded as practically inexhaustible. These include solar, wind, geothermal, hydro and wood.

SHADING - Measures for blocking out unwanted sunlight that can overheat the house.

SOLAR COLLECTOR - A component of an active or passive solar system that absorbs solar radiation to heat a transfer medium which, in turn, supplies heat energy to the space or water heating system.

Sustainable Home Design - Energy Efficient: Fire Resistant: Sound Absorbent: Weather Resistant: Long Lasting

THERMAL MASS - A material used to store heat, thereby slowing the temperature variation within a space. Typical thermal mass materials include concrete, brick, masonry, tile and mortar, water, and rock or other materials with high heat capacity.

UNIVERSAL DESIGN- Design of products and environments to be usable to all people - young and old, tall or short, able bodied or challenged by disabity.

U-value or U-factor - A measure of how well heat is transferred by the entire window - the frame, sash and glass - either into or out of the building. U-value is the opposite of R-value. The lower the U-factor number, the better the window will keep heat inside a home on a cold day.