The following is a compilation of building energy-code related terms and acronyms used on the Building Energy Codes website and throughout the building construction industry.

Select a letter to navigate through the glossary:


A (23) B (23) C (41) D (27) E (28) F (15) G (12) H (21) I (20) K (5) L (11) M (16) N (15) O (11) P (21) R (22) S (37) T (14) U (12) V (11) W (10)



The perimeter heat loss factor for slab-on-grade floors, expressed in Btu/h x F.

Facade Area

Area of the facade, including overhanging soffits, cornices, and protruding columns, measured in elevation in a vertical plane parallel to the plane of the face of the building. Non-horizontal roof surfaces shall be included in the calculation of vertical facade area by measuring the area in a plane parallel to the surface.

Fan Coil

A fan-coil terminal is essentially a small air-handling unit that serves a single space without a ducted distribution system. One or more independent terminals are typically located in each room connected to a supply of hot and/or chilled water. At each terminal, a fan in the unit draws room air (sometimes mixed with outside air) through a filter and blows it across a coil of hot water or chilled water and back into the room.

Fan System Energy Demand

The sum of the nominal power demand (nameplate horsepower) of motors of all fans that are required to operate at design conditions to supply air from the heating or cooling source to the conditioned space(s) and return it to the source or exhaust it to the outdoors.

Feeder Conductors

The wires that connect the service equipment to the branch circuit breaker panels.


All areas (including the frames) in the building envelope that let in light, including windows, plastic panels, clerestories, skylights, glass doors that are more than one-half glass, and glass block walls. A skylight is a fenestration surface having a slope of less than 60 degrees from the horizontal plane. Other fenestration, even if mounted on the roof of a building, is considered vertical fenestration.

Fenestration Area

Total area of the fenestration measured using the rough opening and including the glazing, sash, and frame. For doors where the glazed vision area is less than 50% of the door area, the fenestration area is the glazed vision area. For all other doors, the fenestration area is the door area.


The component of a luminaire that houses the lamp or lamps, positions the lamp, shields it from view, and distributes the light. The fixture also provides for connection to the power supply, which may require the use of a ballast.


A horizontal exterior partition, or a horizontal demising partition, under conditioned space that separates conditioned space from unconditioned space.

Flue Damper

A device in the flue outlet or in the inlet of or upstream of the draft control device of an individual, automatically operated, and fossil-fuel-fired appliance that is designed to automatically open the flue outlet during appliance operation and to automatically close the flue outlet when the appliance is in a standby condition.

Fluorescent Lamps

A light source consisting of a tube filled with argon, along with krypton or other inert gas. When electrical current is applied, the resulting arc emits ultraviolet radiation that excites the phosphors inside the lamp wall, causing them to radiate visible light.

Fossil Fuel

Fuel derived from a hydrocarbon deposit such as petroleum, coal, or natural gas derived from living matter of a previous geologic time.


A material that may be used to produce heat or generate power by combustion.

Fuel Fired Furnace

A self-contained, indirect-fired furnace that supplies heated air through ducts to spaces that require it.