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)
Balancing, Air

Adjusting air flow rates through air distribution system devices, such as fans and diffusers, by manually adjusting the position of dampers, splitter vanes, extractors, etc., or by using automatic control devices, such as constant air volume or variable air volume boxes.

Balancing, Hydronic

Adjusting water flow rates through hydronic distribution system devices, such as pumps and coils, by manually adjusting the position valves, or by using automatic control devices, such as automatic flow control valves.


A device used in conjunction with an electric-discharge lamp to cause the lamp to start and operate under the proper circuit conditions of voltage, current, wave form, electrode heat, etc.

Basement Wall

Basement walls that enclose heated spaces are part of the building envelope. Basement wall refers to the opaque portion of the wall (excluding windows and doors). To be considered a basement wall, at least 50% of the wall's total wall area (including openings) must be below grade. Treat walls on each side of the basement individually when determining if they are above-grade or basement walls. For any individual wall less than 50% below grade, include the entire opaque wall area of that individual wall as part of the above-grade walls.

Below-Grade Wall

That portion of a wall in the building envelope that is entirely below the finish grade and in contact with the ground.

Below-Grade Walls

Basement or first-story walls (Section 802.2.8) associated with the exterior of the building that are at least 85% below grade.


Building Officials and Code Administrators International, Inc.


A pressurized system in which water is vaporized to steam by heat transferred from a source of higher temperature, usually the products of combustion from burning fuels. Steam thus generated may be used directly as a heating medium or as the working fluid in a prime mover to convert thermal energy to mechanical work, which in turn may be converted to electrical energy.

Boiler, Packaged

A boiler that is shipped complete with heating equipment, mechanical draft equipment, and automatic controls; usually shipped in one or more sections. A packaged boiler includes factory-built boilers manufactured as a unit or system, disassembled for shipment, and reassembled at the site.

Branch Circuit

The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s); the final wiring run to the load.


Board of Standards Review.

BTO Peer Reviews

A space or group of spaces within a building with any combination of heating, cooling, or lighting requirements sufficiently similar so that desired conditions can be maintained throughout by a single controlling device.


British thermal unit, which is the quantity of heat required to raise the temperature of 1 pound (0.454 kg) of water 1°F.

Budget Building Design

A computer representation of a hypothetical design based on the actual proposed building design. This representation is used as the basis for calculating the energy cost budget.


A structure wholly or partially enclosed within exterior walls, or within exterior and partial walls, and a roof, affording shelter to persons, animals, or property.

Building Entrance

Any doorway, set of doors, turnstiles, or other form of portal that is ordinarily used to gain access to the building by its users and occupants.

Building Envelope

A building envelope includes all components of a building that enclose conditioned space. Building envelope components separate conditioned spaces from unconditioned spaces or from outside air. For example, walls and doors between an unheated garage and a living area are part of the building envelope; walls separating an unheated garage from the outside are not. Although floors of conditioned basements and conditioned crawlspaces are technically part of the building envelope, the code does not specify insulation requirements for these components.

Building Envelope Interior

The elements of a building that separate conditioned space from unconditioned space or that enclose semiheated spaces through which thermal energy may be transferred to or from the exterior, unconditioned spaces, or conditioned spaces.

Building Exit

Any doorway, set of doors, or other form of portal that is ordinarily used only for emergency egress or convenience exit.

Building Grounds Lighting

Lighting provided through building's electrical service for parking lot, site, roadway, pedestrian pathway, loading dock, and security applications.

Building Information Model (BIM)

A digital representation of the building process. The BIM facilitates exchange and interoperability of information in digital format.

Building Materials

Any element (other than air films and insulation) of the building envelope through which heat flows and that is included in the component U-factor calculations.

Building Official

The officer or other designated representative authorized to act on behalf of the authority having jurisdiction.