HVAC Terms and Technical Definitions
Heating, Cooling & Indoor Air Quality Products
This comprehensive HVAC glossary explains common heating, cooling, and indoor air quality terms to help homeowners understand furnaces, air conditioners, heat pumps, thermostats, and energy efficiency ratings.
A
AFUE (Annualized Fuel Utilization Efficiency)
AFUE measures a furnace’s heating efficiency. A higher AFUE percentage means greater efficiency. The U.S. Department of Energy (DOE) requires a minimum AFUE rating of 78%.
Airflow
The movement or distribution of air through HVAC ductwork and ventilation systems.
Air-Conditioning and Refrigeration Institute (ARI)
ARI is an industry trade association that establishes standards for HVAC performance testing and certification, including sound-level guidelines.
Air Handler / Coil Blower
The indoor HVAC component that circulates heated or cooled air throughout your home via ductwork.
B
Bioaerosols
Microscopic airborne organisms that thrive in warm, humid environments and can impact indoor air quality.
BTU (British Thermal Unit)
A unit of heat energy. One BTU equals the amount of heat needed to raise one pound of water by one degree Fahrenheit.
BTUH
British Thermal Units per hour, commonly used to measure heating and cooling capacity.
C
CAE (Combined Annual Efficiency)
Measures how much heat is produced per dollar of fuel used for space heating and water heating.
Carbon Monoxide
A colorless, odorless, poisonous gas produced by incomplete combustion. Proper ventilation and detectors are critical for safety.
Central Air Conditioning System
A system that cools air at a central unit and distributes it through ductwork using fans.
CFM (Cubic Feet per Minute)
Measures airflow volume. Higher CFM indicates greater air movement through HVAC ducts.
Compressor
The outdoor HVAC component that compresses refrigerant and enables heat transfer.
Condenser Coil
Located outdoors, this coil releases or absorbs heat depending on heating or cooling mode.
D
Damper
A movable plate inside ductwork used to regulate airflow, often used in zoning systems.
Decibel (dB)
A unit of measurement for sound intensity.
DOE (Department of Energy)
A federal agency that sets HVAC efficiency standards and regulates energy consumption.
Dual Fuel System
A system that combines an electric heat pump with a gas furnace for optimal energy efficiency.
Ductwork
The network of channels that distributes conditioned air throughout a home.
E
Electronic Air Cleaner
Filters airborne particles, allergens, and bioaerosols to improve indoor air quality.
ENERGY STAR®
An EPA-backed certification for HVAC systems that exceed standard efficiency requirements.
Evaporator Coil
An indoor coil that absorbs heat from indoor air during cooling operation.
G–H
Heat Exchanger
A furnace component that transfers heat to air circulated through the home.
Heat Pump
An HVAC system that heats and cools by transferring heat rather than generating it.
HSPF (Heating Seasonal Performance Factor)
Measures heat pump heating efficiency. Higher ratings indicate better performance.
Humidifier
Adds moisture to indoor air to improve comfort and air quality.
HVAC
Stands for Heating, Ventilation, and Air Conditioning.
I–M
Indoor Coil
Another term for an evaporator coil.
ISO 9000
International quality management standards.
MERV Rating
Indicates a filter’s efficiency in trapping airborne particles. Higher MERV = better filtration.
Micron
A unit of measurement equal to one-millionth of a meter.
N–P
Net Metering
Allows homeowners to receive credit for excess electricity generated by solar systems.
Programmable Thermostat
Allows scheduled temperature adjustments to improve comfort and energy efficiency.
R–S
R-410A Refrigerant
An environmentally friendly refrigerant that meets current EPA standards.
Refrigerant
A chemical used in HVAC systems to absorb and release heat.
SEER (Seasonal Energy Efficiency Ratio)
Measures air conditioner cooling efficiency. Higher SEER ratings reduce energy costs.
Split System
An HVAC system with indoor and outdoor components.
T–Z
Thermostat
Controls indoor temperature by regulating HVAC operation.
Ton
A measurement of cooling capacity. One ton equals 12,000 BTUH.
Variable Speed Motor
Adjusts airflow automatically for improved comfort and efficiency.
Ventilator
Brings fresh outdoor air inside while removing stale indoor air.
Zoning
Divides a home into multiple climate zones for personalized comfort and energy savings.