A type of insulation material with fine, closed cells, containing a mixture of air and refrigerant gas. This insulation has a high R-value, good moisture resistance, and high structural strength compared to other rigid insulation materials.

The process of moving air (changing) into and out of an interior space either by natural or mechanically induced (forced) means.

A method for making sheets of polycrystalline silicon in which silicon dendrites are slowly withdrawn from a melt of silicon whereupon a web of silicon forms between the dendrites and solidifies as it rises from the melt and cools.

The production of an electric current in a conductor by the variation of a magnetic field in its vicinity.

The amount of energy service or useful energy delivered per unit of energy input. Often used in reference to lighting systems, where the visible light output of a luminary is relative to power input; expressed in lumens per Watt; the higher the efficacy v ...

A two step process where in the first step natural gas is exposed to a high-temperature steam to produce hydrogen, carbon monoxide, and carbon dioxide. The second step is to convert the carbon monoxide with steam to produce additional hydrogen and carbon ...

Ratio of useful energy output of a device to the energy input, averaged over an entire heating season.

A type of heat pump that uses sealed horizontal or vertical pipes, buried in the ground, as heat exchangers through which a fluid is circulated to transfer heat.

A large number of thermocouples connected in series.

A non-crystalline semiconductor material that has no long-range order.

A total life cycle cost divided into equal amounts.

An abbreviation for one thousand cubic feet of natural gas with a heat content of 1,000,000 Btus, or 10 therms.

A tube in which combustion gases from a combustion appliance are vented out of the appliance to the outdoors.

The maximum possible voltage across a photovoltaic cell; the voltage across the cell in sunlight when no current is flowing.

Any light source designed specifically to direct light a task or work performed by a person or machine.

The housing around a motor that supports the active parts and protects them. They come in different varieties (open, protected) depending on the degree of protection required.

A device that measures the intensity of direct beam solar radiation.

To heat a gaseous mixture to the temperature at which combustion takes place.

Generation of energy at the location where all or most of it will be used.

Those elements of building used to control the interior climate.