A

Air Handler (AHU)

A device used to condition and circulate air as part of an HVAC system, typically consisting of a blower, heating and/or cooling elements, filter racks, and dampers.

ASHRAE

American Society of Heating, Refrigerating and Air-Conditioning Engineers. A global organization that sets standards for HVAC systems.

Air Balancing

The process of adjusting an HVAC system to ensure that air is evenly distributed throughout a building.

B

BTU (British Thermal Unit)

A unit of heat energy; it is the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

C

CFM (Cubic Feet per Minute)

A measurement of air flow volume, indicating how many cubic feet of air pass by a stationary point in one minute.

Chiller

A machine that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. This cooled liquid is then circulated through a heat exchanger to cool equipment or another process stream (like air or process water).

Condenser

A component of the HVAC system that condenses a substance from its gaseous to its liquid state, by cooling it. In so doing, the latent heat is given up by the substance and transferred to the surrounding environment.

D

Ductwork

The system of ducts used for the delivery and removal of air necessary for ventilation, heating, and air conditioning.

E

ERV (Energy Recovery Ventilator)

A system that exchanges the energy contained in normally exhausted building or space air and uses it to treat (precondition) the incoming outdoor ventilation air in residential and commercial HVAC systems.

F

Filter

A device that removes particles from the air passing through it to improve indoor air quality.

Freon

A trademarked term commonly used to refer to refrigerants used in air conditioning systems, though it’s being phased out due to its ozone-depleting properties.

G

Grilles

Covers for HVAC ducts that allow air to enter or exit a space.

H

Heat Pump

A device that transfers heat from a cooler space to a warmer space, making the cool space cooler and the warm space warmer.

Humidifier

A device that adds moisture to the air to prevent dryness that can cause irritation in many parts of the body.

I

IAQ (Indoor Air Quality)

The quality of the air within and around buildings and structures, especially as it relates to the health and comfort of building occupants.

L

Load Calculation

The process of determining the heating or cooling needs of a space based on various factors like size, orientation, and type of occupancy.

M

Make-up Air Unit (MAU)

A device that brings in fresh, outside air to replace existing air that cannot be recirculated within a given space.

R

Refrigerant

A substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. It absorbs heat at low temperature and pressure and releases it at higher temperature and pressure.

RTU (Rooftop Unit)

A type of HVAC system that is located on the roof of a building. It is commonly used in commercial buildings for air conditioning larger spaces.

S

SEER (Seasonal Energy Efficiency Ratio)

A measure of the cooling output of an air conditioner or heat pump over a typical cooling season, divided by the energy it consumed in Watt-Hours.

Split System

A type of HVAC system that has components divided between an inside and outside unit, typically involving a furnace and air conditioner or a heat pump.

T

Thermostat

A device that regulates the temperature of a system so that the system’s temperature is maintained near a desired setpoint.

Ton

A unit of measure used in air conditioning to describe the cooling capacity of a system. One ton is equivalent to the ability to cool 12,000 BTUs (British Thermal Units) per hour.

V

VAV (Variable Air Volume)

A type of heating, ventilating, and/or air-conditioning system that allows the volume of air delivered to space to vary according to the demand.

Z

Zone

An area or space in a building that has its temperature controlled separately from other areas.