A combustion heating appliance that vents the combustion by-products directly into the heated space. The latest models have oxygen-sensors that shut off the unit when the oxygen level in the room falls below a safe level.

Heat stored above room temperature (in a solar heating system).

The deposition of thin films of semiconductor material by the evaporation of elemental sources in a vacuum.

The highest energy band in a semiconductor that can be filled with electrons.

A material that retards the movement of water vapor through a building element (walls, ceilings) and prevents insulation and structural wood from becoming damp and metals from corroding. Often applied to insulation batts or separately in the form of treat ...

Turbines in which the rotor speed increases and decreases with changing wind speed, producing electricity with a variable frequency.

A component of a heating or ventilation appliance used to conduct fresh air into, or waste air or combustion gases out of, an appliance or interior space.

A device mounted in the vent connector that closes the vent when the heating unit is not firing. This traps heat inside the heating system and house rather than letting it draft up and out the vent system.

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

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.

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

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

A type of wind turbine in which the axis of rotation is perpendicular to the wind stream and the ground.

The amount of visible light that passes through the glazing material of a window, expressed as a percentage.

The visible portion of the electromagnetic spectrum with wavelengths from 0.4 to 0.76 microns

A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm.

A unit of electrical measurement equal to the product of a volt and an ampere.

The amount of electromotive force, measured in volts, that exists between two points.

A thin sheet of semiconductor (photovoltaic material) made by cutting it from a single crystal or ingot.

A vertical structural element that holds up a roof, encloses part or all of a room, or stands by itself to hold back soil.