HVAC Glossary

Understanding HVAC terminology is essential for homeowners and professionals alike. This comprehensive glossary covers common terms, acronyms, and definitions used in heating, ventilation, and air conditioning systems.

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A

AFUE

Annual Fuel Utilization Efficiency - A rating that measures furnace heating efficiency over an entire year.

Air Handler

The indoor portion of a central air conditioning or heating system that circulates conditioned air through ductwork.

Airflow

The volume of air moved through an HVAC system, measured in cubic feet per minute (CFM).

B

Blower Motor

The fan that circulates air through the ductwork and throughout the home.

BTU

British Thermal Unit - A measurement of heat energy, used to rate heating and cooling capacity.

Building Envelope

The physical separator between the conditioned and unconditioned environment of a building.

C

Capacitor

An electrical component that stores energy and helps start motors in HVAC equipment.

CFM

Cubic Feet per Minute - The measurement of airflow volume in HVAC systems.

Compressor

The heart of an air conditioning system that circulates refrigerant and provides cooling.

Condenser

The outdoor unit of an air conditioner that releases heat to the outside air.

Condenser Coil

The coil in the outdoor unit where refrigerant releases heat to the outside air.

D

Ductwork

The network of tubes that distribute heated or cooled air throughout a building.

Ductless System

An HVAC system that doesn't use ductwork, typically mini-split systems.

E

EER

Energy Efficiency Ratio - A rating of air conditioner efficiency at peak load conditions.

Energy Recovery Ventilator

A device that exchanges heat between incoming and outgoing air streams.

Evaporator Coil

The indoor coil where refrigerant absorbs heat from indoor air.

F

Filter

A device that removes particles from air as it passes through the HVAC system.

Furnace

A heating unit that uses fuel combustion or electric resistance to generate heat.

G

Gas Valve

The component that controls natural gas flow to the furnace burners.

H

Heat Exchanger

A component that transfers heat between two fluids without mixing them.

Heat Pump

A reversible air conditioner that can provide both heating and cooling.

HSPF

Heating Seasonal Performance Factor - Efficiency rating for heat pump heating performance.

Humidity

The amount of water vapor in the air, expressed as a percentage.

HVAC

Heating, Ventilation, and Air Conditioning - The technology of indoor environmental comfort.

I

IAQ

Indoor Air Quality - The air quality within and around buildings and structures.

L

Load Calculation

A process to determine the heating and cooling requirements of a building.

M

MERV

Minimum Efficiency Reporting Value - A rating system for air filter efficiency.

Mini-Split

A type of ductless HVAC system with separate indoor and outdoor units.

P

Package Unit

An all-in-one HVAC system where all components are housed in a single cabinet.

Psychrometrics

The study of the physical and thermodynamic properties of gas-vapor mixtures.

R

Refrigerant

A substance used in air conditioning systems to absorb and release heat.

Return Air

Air that is drawn back into the HVAC system to be conditioned.

S

SEER

Seasonal Energy Efficiency Ratio - A rating of air conditioner efficiency over an entire season.

Split System

An HVAC system with separate indoor and outdoor units connected by refrigerant lines.

Supply Air

Conditioned air that is delivered to the living spaces through ductwork.

T

Thermostat

A device that senses temperature and controls HVAC system operation.

Tonnage

A measure of air conditioning capacity, where 1 ton = 12,000 BTU/hour.

V

Ventilation

The process of supplying fresh outdoor air and removing stale indoor air.

Ventilator

A device that controls the exchange of indoor and outdoor air.

Z

Zoning

The division of a building into separate areas with independent temperature control.

Common HVAC Terms

Additional important terms used in HVAC industry.

System Types

• Central Air: A system that conditions air in a central location and distributes it through ducts
• Heat Pump: A reversible air conditioner that provides both heating and cooling
• Furnace: A heating unit that generates heat through combustion or electrical resistance
• Boiler: A system that heats water for distribution through radiators or radiant floors

Efficiency Ratings

• AFUE: Annual Fuel Utilization Efficiency for furnaces
• SEER: Seasonal Energy Efficiency Ratio for cooling
• HSPF: Heating Seasonal Performance Factor for heat pumps
• EER: Energy Efficiency Ratio for peak load cooling

Air Quality Terms

• HEPA: High Efficiency Particulate Air filter
• MERV: Minimum Efficiency Reporting Value
• VOC: Volatile Organic Compounds
• PM2.5: Particulate matter 2.5 microns or smaller

Portland-Specific Terms

Local terminology and considerations.

• Willamette Valley: The region known for high humidity and mild temperatures
• Urban Heat Island: Phenomenon where urban areas are significantly warmer than surrounding areas
• Wildfire Smoke: Air pollution from regional forest fires
• Utility Rebates: Incentives from Pacific Power and PGE for energy-efficient upgrades