The temperature of a medium, such as gas or liquid, which comes into contact with or surrounds an apparatus or building element.

A measure of the heating requirements of a building expressed in Btu per degree-day.

Energy available as a result of motion that varies directly in proportion to an object's mass and the square of its velocity.

A type of electrical current, the direction of which is reversed at regular intervals or cycles; in the U.S. the standard is 120 reversals or 60 cycles per second; typically abbreviated as AC.

That portion of supply air that is drawn from outside, plus any recirculated air that has been treated to maintain a desired air quality.

The angular position of the sun at solar noon with respect to the plane of the equator.

In reference to solar energy systems, the angle that a solar collector is positioned above horizontal.

A category of electric power producer established under the Public Utility Regulatory Policy Act (PURPA) of 1978, that includes small-power producers (SPP) who use renewable sources of energy such as biomass, geothermal, hydroelectricity, solar (thermal a ...

The amount of heat energy that may be converted into useful energy from a fuel.

The transparent or opaque sphere in an electric light that the electric light transmits through.

An insulation product composed of loose fibers or fiber pellets that are blown into building cavities or attics using special pneumatic equipment.

The pressure corresponding to the outlet velocity of a fan; the kinetic energy per unit volume of flowing air.

A device used by energy auditors to pressurize a building to locate places of air leakage and energy loss.

The weight of a material per unit of volume compared to the weight of the same volume of water.

Energy terms

A type of combustion heating appliance in which the combustion gases are vented to the outside, either with a fan (forced) or by natural convection.

An air distribution outlet, typically located in the ceiling, which mixes conditioned air with room air.

A device used to simulate the angle of the sun for assessing shading potentials of building structures or landscape features.

An agency of the U.S. Dept. of Agriculture that makes loans to states and territories in the U.S. for rural electrification and the furnishing of electric energy to persons in rural areas who do not receive central station service. It also furnishes and i ...

The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit; equal to 252 calories.