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

A material used to seal areas of potential air leakage into or out of a building envelope.

An enzyme complex, produced by fungi and bacteria, capable of decomposing cellulose into small fragments, primarily glucose.

Energy terms

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

A long, underground metal or plastic pipe through which air is drawn. As air travels through the pipe it gives up some of its heat to the soil, and enters the house as cooler air.

To disconnect a transmission and/or distribution line; a power line that is not carrying a current; to open a circuit.

A type of heat pump that transfers heat from outdoor air to indoor air during the heating season, and works in reverse during the cooling season.

The downward facing structural element that is directly opposite the floor.

A generic term for a glazed opening that allows daylight to enter into a building and can be opened for ventilation.

The conversion of the complex carbohydrates in organic material into energy.

A type of impulse hydropower turbine where water passes through nozzles and strikes cups arranged on the periphery of a runner, or wheel, which causes the runner to rotate, producing mechanical energy. The runner is fixed on a shaft, and the rotational mo ...

The transformation on a compound or material into one or more substances by heat alone (without oxidation). Often called destructive distillation. Pyrolysis of biomass is the thermal degradation of the material in the absence of reacting gases, and occus ...

The overall rate of heat loss from a building by means of transmission plus infiltration, expressed in Btu per hour, per degree temperature difference between the inside and outside.

The mean wind speed over a specified period of time.

The heating capacity of a steam boiler; expressed in Btu per hour (Btu/h), or horsepower, or pounds of steam per hour.

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

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

A mound of dirt next to exterior walls to provide wind protection and insulation.

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