A seal used to prevent the leakage of fluids, and also maintain the pressure in an enclosure.

One thousand kilowatts, or 1 million watts; standard measure of electric power plant generating capacity.

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.

This designates the resistance of a material to heat conduction. The greater the R-value the larger the number.

A configuration of an electrical circuit in which the voltage is the same across the terminals. The positive reference direction for each resistor current is down through the resistor with the same voltage across each resistor.

These lights use an electrically heated filament to produce light in a vacuum or inert gas-filled bulb.

A type of water heater that has no storage tank thus eliminating storage tank standby losses. Cold water travels through a pipe into the unit, and either a gas burner or an electric element heats the water only when needed.

The ratio of the percentage change in the quantity of a good or service demanded to the percentage change in the price.

A house built using passive solar design techniques.

A type of water heater that circulates water through a heat exchanger in a boiler. The heated water then flows into an insulated storage tank.

A valve used to mix heated water with cold in a heating system to provide a desired water temperature for end use.

A mainly flat surface for transmitting radiant energy.

A building energy auditing technique for locating areas of low insulation in a building envelope by means of a thermographic scanner.

Any device (or plant) that follows the sun's apparent movement across the sky.

A salt, sodium sulfate decahydrate, that melts at 90 degrees Fahrenheit; a component of eutetic salts that can be used for storing heat.

A hydrocarbon gas obtained from underground sources, often in association with petroleum and coal deposits. It generally contains a high percentage of methane, varying amounts of ethane, and inert gases; used as a heating fuel.

An instrument for measuring solar radiation.

A measure of the amount of energy lost during the generation, transmission, and distribution of electricity.

The area of glass that fits in the window frame.

The minimum temperature at which combustion of a solid or fluid can occur.