Energy Efficiency Definitions

A

Audit
The analysis of a specific building's envelope, equipment or processes to determine the potential to conserve energy.

B

British Thermal Unit (Btu)
The quantity of heat needed to raise the temperature of 1 pound of water by 1 degree Fahrenheit at or near 39.2 degrees Fahrenheit.

Building Envelope
The assembly of exterior partitions of a building that enclose conditioned spaces, through which energy may be transferred to or from the exterior, unconditioned spaces, or the ground.

C

CFM
Cubic feet per minute.

Chiller
Device to cool water which will be used for cooling purposes.

Condensation
The process of changing a vapor into a liquid. Condensate often forms on cold

Conduction
The transfer of heat by direct contact or traveling through a material. This is one of the ways in which heat moves from its source. The other two are convection and radiation.

Convection
The process of heat transfer by movement of fluid (air). Natural convection is due to the difference in density and the action of gravity. Force convection is produced by mechanical means.

D

Design Temperature Difference
The difference between inside and outside temperatures expressed in degrees Celsius.

E

Efficiency
The ratio of the useful energy delivered by a dynamic system (such as machine, engine, or motor) to the energy supplied to it over the same period or cycle of operation. The ratio is usually determined under specific test conditions.

Energy
The capacity to do work. Forms of energy include thermal, mechanical, electrical, and chemical. Energy may be transformed from one form into another.

Energy Efficiency
Increases in energy efficiency take place when either energy inputs are reduced for a given level of service or there are increased or enhanced services for a given amount of energy inputs. Energy efficiency is the relative thrift or extravagance with which energy inputs are used to provide goods or services.

Energy Efficiency Rating
A certification of a home's energy efficiency or a relative indication of its energy efficiency on a graduated scale.

Energy Efficiency Ratio (EER)
The ratio of the cooling capacity of an air conditioner, in Btu per hour, to the total electrical input in watts under test conditions.

Exfiltration
Air flow outward through a wall, building envelope, window, etc.

H

Heat Loss
A decrease in the amount of heat contained in a space, resulting from heat flow through walls, windows, and other building surfaces and from exfiltration of warm air.

Heat Pump
An air-conditioning unit capable of heating by refrigeration, transferring heat from one (often cooler) medium to another (often warmer) medium, and that may or may not include a capability for cooling.

Heating, Ventilating, and Air Conditioning System (HVAC)
A system that provides heating, ventilating, and/or cooling for a building.

I

Infiltration
The uncontrolled inward leakage of air through cracks and gaps in the building envelope, especially around windows and doors.

L

Low Emissivity (low-e) Coatings
Low-emissivity coatings are put on window panes to reduce the amount of heat they give off through radiation. In hot climates, where the outside of the window will typically be hotter than the inside, low-e coatings work best on the interior of the outside window pane. In cold climates, where the inside of the window is typically hotter than the outside, the low-e coatings work best on the inside window pane, on the side that faces toward the outside.

O

Outside Design Temperature
The average extreme outdoor temperature that can be normally expected for a given locality.

P

Passive Solar Technologies
Technologies that combine architecture to benefit from solar radiation incidence on buildings for heating, cooling, and lighting, with good conservation techniques for the building envelope and energy-efficient equipment and controls. Passive solar technologies are typically sunspaces, direct gain systems and thermal storage walls.

R

R-Value
A unit of thermal resistance used for comparing insulating values of different materials. The higher the R-Value of a material, the greater its insulating properties and the slower the heat flows through it.

S

Setback Thermostat
A device containing a clock mechanism, which can automatically change the inside temperature maintained by the heating, ventilating and air conditioning (HVAC) system according too a preset schedule. The heating or cooling requirements can be reduced when a building is not occupied or when occupants are asleep.

T

Thermal Envelope
The building's exterior shell - walls, foundation, floors, ceiling, windows, doors and roof.

V

Vapor Barrier
Also called a vapor retarder, this is a material that retards the movement of water vapor through a building element (such as walls, floors, and ceilings) and prevents metals from corroding and insulation and structural wood from becoming damp.

W

Weatherization
Retrofitting a buildings envelope with basic energy efficiency measures, such as weather-stripping, caulking, and insulation.