Reference
HVAC Glossary
The heating and cooling terms you'll run into, defined in plain English — no jargon.
- AFUE
- Annual Fuel Utilization Efficiency — a furnace's efficiency as a percentage of fuel converted to usable heat.
- AHJ (Authority Having Jurisdiction)
- The local office (city or county building department) that adopts codes, issues permits, and performs inspections.
- Compressor
- The pump at the heart of the system that circulates refrigerant; the most expensive component to replace.
- Condenser
- The outdoor coil/unit that releases the heat collected indoors to the outside air.
- Evaporator Coil
- The indoor coil where refrigerant absorbs heat from your home's air. Often where ice forms when something's wrong.
- Furnace
- A heating system that burns gas (or uses electric elements) and pushes warm air through ducts.
- Ground Loop
- The buried piping a geothermal system uses to exchange heat with the stable temperature of the earth.
- Heat Exchanger
- The furnace part that transfers combustion heat to your home's air while keeping exhaust gases separate. A crack is a carbon-monoxide safety risk.
- Heat Pump
- A reversible system that both heats and cools by moving heat rather than burning fuel; highly efficient in moderate climates.
- HSPF2
- Heating Seasonal Performance Factor 2 — the current standard rating for heat-pump heating efficiency.
- Humidity Control
- Managing indoor moisture (whole-home humidifiers/dehumidifiers). Ideal indoor humidity is roughly 30–50%.
- Load Calculation (Manual J)
- An engineering calculation of a home's actual heating/cooling needs, used to size equipment correctly instead of guessing.
- MERV
- Minimum Efficiency Reporting Value — how well an air filter captures particles. Higher captures more, but too high can restrict airflow.
- Permit
- Local building-department authorization that work meets adopted safety codes, verified by inspection.
- Refrigerant
- The fluid that absorbs and releases heat as it cycles through an AC or heat pump, enabling heat to be moved out of (or into) your home.
- SEER2
- Seasonal Energy Efficiency Ratio 2 — the current standard rating for cooling efficiency. Higher is more efficient.
- Ventilation
- Controlled exchange of stale indoor air for fresh outdoor air, important in tightly sealed homes.
- Zoning
- Conditioning different areas of a home independently, each with its own temperature control.