HVAC Terms You Need to Know

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HVAC Terms You Need to Know

HVAC Terms To Know - Superior Co-Op HVAC, Saratoga, NY

Curious about some of the terms and words you hear us use or see across our website? This helpful article from Angie’s list has some key terms and definitions for you.

HVAC Terms You Need to Know

Learn terms commonly used in heating and cooling projects.


The Annualized Fuel Utilization Efficiency (AFUE) measures how much natural gas or propane a furnace uses to heat your home and how much of it is wasted.

For example, a furnace with an AFUE rating of 95 converts 95% of the gas that you’re paying for to heat and the other 5% is lost out the flue (exhaust) pipe.

Air exchange rate

Air exchange rate is the rate at which air from outdoors replaces the air that exists inside a structure. Air exchange rate is measured in two ways.

Air changes per hour, or ACH, is defined as the number of times outside air replaces inside air within an hour. Cubic feet per minute, or CFM, measures the volume of outside air that replaces inside air.

Backup furnace

A backup furnace is installed as a secondary source of heat, usually in homes that rely upon geothermal systems or solar energy for primary heat sources.

British thermal unit

Most often referred to as BTU, the British thermal unit is a measurement of the amount of heat that is needed to raise the temperature of one pound of water one degree.

CFM/cubic feet per minute

A measurement of the volume of air that flows through any given space in one minute.

Combustion chamber

Combustion describes a series of chemical reactions that cause the release of heat. A combustion chamber in a furnace is an enclosed space where combustion takes place.

Condenser coil

The condenser coil is located within an air conditioner or heat pump. As the fan blows in air from the outside, the refrigerant circulates through the condenser coil.

Outside air is then either released or collected, depending upon the unit’s current function.

Cooling capacity

The term cooling capacity is used in reference to air conditioning systems. It is a measurement of the amount of heat that the AC unit can remove from a room in a one hour time frame.


Draft refers to the movement of heated air, or combustion air, through a chimney.

Energy Star

Created by the Environmental Protection Agency, the Energy Star Program rates energy efficient products that are used in homes, including heating and cooling systems.

Energy Star rating

Displayed as a comparative guide for purchasing new appliance, including heating and cooling devices, the Energy Star rating of a product is determined by how energy efficient that product is.

Rating guidelines vary from item to item. In order for a cooling system to be Energy Star qualified, it must be at least 10 percent more energy efficient than the minimum government standard.


The flue is the structure through which heated air, or combustion air, moves before they are released from indoors to outdoors.

Forced air system

A forced air system is a type of heating system. With a forced air system, rooms are heated by air that is blown with fans through ducts.


Freon is an organic compound that is used as a coolant in HVAC systems. The name Freon is a registered trademark of DuPont, but is often used interchangeably with coolants of the same type such hydrochlorofluorocarbons.

Fuel efficiency

Fuel efficiency refers to the ratio of amount of heat produced in regards to the amount of fuel that is used.

Heat exchanger

The heat exchanger is located inside a furnace. Its function is to transfer heat into the air, which is then pumped throughout the building structure.

Heat loss

Heat loss refers to the heat that leaks from the inside of a building to the outside, an important consideration when purchasing new HVAC equipment or making energy efficiency improvements.

Heat pump

A heat pump moves heat either into or outside of a building structure. To heat a home, a heat pump pulls air from outdoors, heats the air and moves it through rooms via ducts. To cool a home, air is removed from building structures and pushed outside.

Heating load

Heating load is a measurement, usually measured in BTUs, of the heat flow needed to keep a stable temperature indoors.

Click here to view the full list of terms on Angie’s List.