Heating, Ventilation and Air Conditioning Glossary of Terms

The terms below will help you better understand the HVAC installation and repair process and will allow you to better communicate with local HVAC companies.

air conditioner
A piece of home cooling equipment that controls indoor air temperature, humidity, air quality and movement of cool air. Air conditioning units can be portable air conditioners or central air conditioning systems that stand alone or are part of an integrated HVAC system.
Also known as: air conditioning, home air conditioner, residential air conditioner, air conditioning unit

air filter
An air filter is a device used to remove unwanted particles, dust, vapors and odors from indoor air. Air filters have two functions: protecting HVAC equipment from damage and improving indoor air quality.
Also known as: air filtration units, home air filters, air conditioner filters, furnace filters, HVAC filters

air handler
A piece of equipment that forces hot and cool air through ductwork and out the air vents.
Also known as: air handling system, air fan, HVAC air handler

BTU rating
BTU stands for British Thermal Units. BTUs measure the amount of heat needed to raise one pound of water one degree Fahrenheit. The higher an HVAC system’s BTU rating, the larger its heating capacity. Larger homes with more space to heat and cool require HVAC systems with higher BTU ratings.
Also known as: British Thermal Units, BTU ratings, heating capacity rating, cooling capacity rating

boiler
Boilers heat air using steam and hot water. Some boilers may be more efficient at providing even, draft-free heat than forced-air heaters.
Also known as: hot water steam boiler, boiler system, low pressure boilers, high pressure boilers, steam boiler, hot water boiler, steam system, gas system, oil system, boiler furnace

capacity
Capacity is defined as the ability of a heating and cooling system to heat or cool a space. When measured, the cooling capacity of an air conditioning system is generally stated in tons while heating capacity of furnaces and home heaters are measured in BTUs.
Also known as: heating ability, air conditioning ability, cooling ability, HVAC unit capacity

carbon monoxide
Carbon monoxide is a colorless, odorless, toxic gas that is produced when carbon fuels are burned. Carbon monoxide, also commonly called CO2, can leak into a home or business when furnaces or HVAC equipment become worn or leaky.
Also known as: CO, CO2

central air conditioning system
Systems that cool indoor air and dehumidify it in one central location and then deliver the cooler air via a system of ducts are known as central air conditioning systems.
Also known as: central air systems, central air conditioning units, central air conditioning

downflow furnace
Downflow furnaces take in cool air at the top of the furnace unit and blow warm air out the bottom of the unit.
Also known as: down flow furnace

ductwork
Metal duct pipes that form a system of ducts throughout a home or building are referred to as ductwork. Ductwork is used to transfer and circulate air from a heating, cooling and ventilation system throughout the building.
Also known as: ducts, duct system, ductwork system, stainless steel ducts

Energy Star
Energy Star is a government-sponsored branding program that tests and labels energy-efficient appliances and products.
Also known as: Energy Star rated HVAC units, Energy Star appliances, Energy Star heaters, Energy Star air conditioners, eco-friendly HVAC, Energy Star systems

forced air
Systems for heating, cooling, and ventilation that use fans and blowers to move air through the HVAC system and into the home or business are known as forced air systems.
Also known as: forced air system, forced air HVAC system, forced air HVAC unit

furnace
Self-contained heating units that heat air in homes and buildings are referred to as furnaces. Furnaces may be standalone heaters or can be part of a heating, cooling and ventilation system. Some furnaces provide central heating by heating air in one central location and then dispersing it through ducts to heat an entire home while other heaters are portable furnaces.
Also known as: heaters, home furnace, heater unit, home heating unit, HVAC system, gas furnace, electric furnace, free-standing furnace, central heating unit

HVAC
HVAC stands for heating, ventilation and air conditioning. It refers to air conditioning and heating systems in homes and other buildings. HVAC can also be used to describe the trade of installing, maintaining and servicing HVAC equipment.
Also known as: heating, cooling and ventilation; heating, cooling, ventilation; heating and cooling; heating and cooling systems; HVACR; heating, ventilation, air conditioning, refrigeration

heat pump
The heat pump is the unit that handles both heating and cooling. In some climates, a heat pump may handle your heating and cooling needs more efficiently than a furnace and air conditioner.
Also known as: heater pump, heating pump, home heat pump

horizontal flow furnace
Horizontal flow furnaces are installed on their sides, enabling them to draw in air from one side, heat the air and push it out the other side to heat the room.
Also known as: furnace, side furnace, horizontal furnace

heating seasonal performance factor
Heating seasonal performance factor measures the heating efficiency of heat pumps. The higher a heat pump’s HSPF, the more efficiently the heat pump works.
Also known as: HSPF

humidifier
Humidifiers add moisture to the air. Standalone humidifiers are portable and can be moved from room to room. Other humidifiers are available as permanent equipment additions to HVAC systems to add moisture to air as it comes out of the furnace to keep the air in a home or building from becoming too dry when the heater is running.
Also known as: home humidifier, air humidifier, humidifying system

load calculation
Load calculation is a way of computing the cooling and heating power an HVAC system must produce for indoor comfort. The load is influenced by many factors: climate, square footage of conditioned area, orientation and layout of the building, number of human occupants, room count and dimensions, window and door count and characteristics, insulation quantity and quality, and more.
Also known as: heat gain and loss calculation, heat loss calculation, heat gain calculation, load calculator, HVAC unit load calculation, heating & cooling load calculation, HVAC system load calculator

package system
An outdoor unit that houses heating and cooling blower and coil components, a package system provides heating and cooling for an entire building or home.
Also known as: packaged heat pump, package heat pump, packaged system, package air conditioner, packaged air conditioner, electric cooling package system, gas heating package system, electric heating package system

refrigerant
As used in an air conditioner or air conditioning component of an HVAC system, any chemical used to cool the air is referred to as refrigerant.
Also known as: air conditioning, home cooling, chemical refrigeration, refrigeration, chemical refrigerant

seasonal energy efficiency rating
SEER measures an air conditioner or HVAC unit’s cooling efficiency. The higher the SEER number, the greater the efficiency of the unit.
Also known as: SEER

thermostat
A thermostat is a device that monitors and controls the temperature inside a home or building. Thermostats may be manually set or can be programmable thermostats that are preset to heat and cool buildings at a certain time.
Also known as: programmable thermostats, wireless thermostats, touch screen thermostats, home thermostats, HVAC thermostats, heating and cooling thermostats, digital thermostat, home  comfort control

upflow furnace
An upflow furnace draws cool air from the bottom of the unit and blows warmed air from the top.
Also known as: forced air furnace

ventilation system
Home ventilation systems exchange stale indoor air with fresh air from outside the home. Ventilation systems often filter the incoming air. Ventilation components are often a standard part of home heating and cooling systems.
Also known as: home ventilators, HVAC system, home ventilation system

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