- AFUE
- Annual fuel utilization efficiency, a seasonal test measure used for fuel-burning furnace efficiency.
- Air handler
- The indoor cabinet that contains a blower and, often, heating or cooling coils.
- Balance point
- An outdoor condition at which a heat pump’s capacity or operating-cost relationship may trigger supplemental heat, depending on system design.
- BTU/h
- A rate of heat transfer commonly used in equipment capacity. One BTU/h is not an amount used over a whole season.
- Combustion air
- Air supplied so a fuel-burning appliance can burn safely.
- Condensate
- Water produced by condensing equipment or removed from indoor air during cooling.
- Direct vent
- A sealed or dedicated vent arrangement that typically draws combustion air from outdoors and exhausts outdoors.
- Heat loss
- The rate at which a building loses heat under specified indoor and outdoor conditions.
- HSPF
- A seasonal efficiency metric for heat pumps; rating versions and test regions matter when comparing models.
- MERV
- A filter-performance rating. Higher particle capture can also increase resistance depending on filter design.
- SEER
- A seasonal cooling-efficiency metric. Confirm which rating version is being quoted.
- Temperature rise
- The difference between return-air and supply-air temperatures across heating equipment under specified conditions.
Home Comfort Glossary
Plain-language definitions for common furnace, heat-pump, air-conditioning and water-heating terms.