

Select a letter to navigate through the glossary:





Opaque portion of the building envelope.


Increase in space temperature to occupied set point after a period of shutdown or setback.

Water Economizer


Water Heater

Vessel in which water is heated and is withdrawn for use external to the system.

Water Heating

The process or system used to heat service water.




The terms "fenestration", "window", and "glazing" are often used interchangeably. However, window actually describes a system of several components. Window is the term given to an entire assembly comprised of the sash, glazing, and frame.

Window Projection Factor

A measure of the portion of glazing that is shaded by an eave or overhang.

Window-Wall Ratio

The window-wall ratio is the percentage that results from dividing the total glazed area of the building by the total wall area.