A device used to control temperatures; used to control the operation of heating and cooling devices by turning the device on or off when a specified temperature is reached.

The ability of a building construction assembly (partition, wall, floor, etc.) to resist the passage of fire. The rating is expressed in hours.

A unit or measure of electricity supply or consumption of 1,000 Watts over the period of one hour; equivalent to 3,412 Btu.

The arithmetic wind speed over a specified time period and height above the ground (the majority of U.S. National Weather Service anemometers are at 20 feet (6.1 meters).

A house built into the ground or slope of a hill, or which has most or all exterior surfaces covered with earth.

Energy supplied during periods of relatively high system demands as specified by the supplier.

The process of breaking down organic material; reduction of the net energy level and change in physical and chemical composition of organic material.

The ratio of the radiant energy (heat) leaving (being emitted by) a surface to that of a black body at the same temperature and with the same area; expressed as a number between 0 and 1.

A system capable of rotating about one axis.

A room heat delivery (or exchanger) component of a hydronic (hot water or steam) heating system; hot water or steam is delivered to it by natural convection or by a pump from a boiler.

The force that pulls a wind turbine blade, as opposed to drag.

The total diffuse and direct insolation on a horizontal surface, averaged over a specified period of time.

A form of thermal energy resulting from combustion, chemical reaction, friction, or movement of electricity. As a thermodynamic condition, heat, at a constant pressure, is equal to internal or intrinsic energy plus pressure times volume.

An electrochemical battery that uses lead and lead oxide for electrodes and sulfuric acid for the electrolyte.

States that energy cannot be created or destroyed, but only changed from one form to another. First Law efficiency measures the fraction of energy supplied to a device or process that it delivers in its output. Also called the law of conservation of energ ...

The trapping of light inside a semiconductor material by refracting and reflecting the light at critical angles; trapped light will travel further in the material, greatly increasing the probability of absorption and hence of producing charge carriers.

An air heater in which air is blown over electric resistance heating coils.

The wind speed with 50 percent probability of occurring.

The energy developed through the use of heat energy.

A gas that does not react with other substances; e.g. argon or krypton; sealed between two sheets of glazing to decrease the U-value (increase the R-Value) of windows.