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)

A duct and damper arrangement and automatic control system that allow a cooling supply fan system to supply outdoor air to reduce or eliminate the need for mechanical refrigeration during mild or cold weather.


See Energy Efficient Ratio.


A metric used to compare light output to energy consumption. Efficacy is measured in lumens per watt. Efficacy is similar to efficiency but is expressed in dissimilar units. For example, if a 100-watt source produces 9000 lumens, then the efficacy is 90 lumens per watt.


Performance at specified rating conditions.

Efficiency Exchange 2015

Architectural Aluminum Manufacturers Association.

Electric Meter

A mechanical/electrical device that can measure electric power.

Electric Resistance

The property of an electric circuit or of any object used as part of an electric circuit that determines for a given circuit the rate at which electric energy is converted into heat or radiant energy and that has a value such that the product of the resistance and the square of the current gives the rate of conversion of energy.

Electric Supplier

An agency that sells and/or distributes electric power.

Electronic High Frequency Ballasts

Electronic ballasts improve fluorescent system efficacy by converting the standard 60 Hz input frequency to a higher frequency, usually 25,000 to 40,000 Hz. Lights operating on these frequencies produce about the same amount of light while consuming up to 30% less power than a standard magnetic ballast.

Emergency Power System (EPS)

A system that is required by codes or other laws to automatically supply illumination or power or both in the event of failure of the normal supply or in the event of accidents to such systems. Such systems may also include standby loads incidental to system operations but shall not include systems for optional standby loads only.


The ratio of the radiant heat flux emitted by a specimen to that emitted by a blackbody at the same temperature and under the same conditions.

Enclosed Space

A volume substantially surrounded by solid surfaces such as walls, floors, roofs, and openable devices such as doors and operable windows. Spaces not meeting these criteria for enclosure are considered to be exterior to the building for purposes of determining envelope requirements. For example, most parking garages do not qualify as enclosed space.


The case or housing of an apparatus, or the fence or walls surrounding an installation, designed to prevent personnel from accidentally contacting energized parts and to protect equipment from physical damage.


The capacity for doing work. It takes a number of forms that may be transformed from one into another such as thermal (heat), mechanical (work), electrical, and chemical. Customary measurement units are British thermal units (Btu).

Energy Cost Budget

The annual energy cost budgeted for the building.

Energy Efficient Ratio (EER)

The ratio of net equipment cooling capacity in Btu/h to total rate of electric input in watts under designated operating conditions. When consistent units are used, this ratio becomes equal to the coefficient of performance.

Energy Factor (EF)

A measure of water heater overall efficiency.

Energy Performance Rating

The energy use of the proposed building under actual operating conditions. Projected energy use targets can be used for buildings in the design or construction process. Examples include kBtu/sf/yr, $/sf/yr, $/gross sales, Energy Performance Rating Score (US EPA), or like expressions of energy performance.

Envelope Components

The building assemblies that provide a barrier between conditioned space and unconditioned space. This includes the floors, walls, and ceiling/roof assemblies of the building.

Envelope Floor

That lower portion of the building envelope, including opaque area and fenestration, that has conditioned or semiheated space above and is horizontal or tilted at an angle of less than 60 degrees from horizontal but excluding slab-on-grade floors. It is needed to determine building envelope requirements.


Devices for comfort conditioning, electric power, lighting, transportation, or service water heating including, but not limited to, furnaces, boilers, air conditioners, heat pumps, chillers, water heaters, lamps, luminaires, ballasts, elevators, escalators, or other devices or installations.

Equipment Efficiency

The energy efficiency of equipment. The measure of equipment efficiency varies with the equipment type.


Uncontrolled outward air leakage from inside a building, including leakage through cracks and interstices around windows and doors and through any other exterior partition or penetration.

Existing Building

A building or portion thereof that was previously occupied or approved for occupancy by the authority having jurisdiction.

Existing Equipment

Equipment previously installed in an existing building.

Existing System

A system or systems previously installed in an existing building.

Exterior Lighting Power Allowance

The maximum lighting power in watts allowed for the exterior of a building.

Exterior Wall

An above-grade wall enclosing conditioned space. Includes between-floor spandrels, peripheral edges of floors, roof and basement knee walls, dormer walls, gable end walls, walls enclosing a mansard roof, and basement walls with an average below-grade wall area that is less than 50% of the total opaque and non-opaque area of that enclosing side.