Learning Center
HVAC Glossary
The HVAC terms you'll hear from a technician — explained in plain English.
- AFUE
- Annual Fuel Utilization Efficiency — the percentage of a furnace's fuel converted to usable heat. Learn more →
- Air Handler
- The indoor unit that moves conditioned air through your ducts; it houses the blower and (in cooling systems) the evaporator coil.
- BTU
- British Thermal Unit — a unit of heat energy used to rate heating and cooling capacity.
- Compressor
- The heart of an AC/heat pump that pressurizes refrigerant to move heat. Learn more →
- Condenser
- The outdoor coil that releases heat from the refrigerant.
- Dual-Fuel
- A hybrid system that pairs a heat pump with a gas furnace, switching to gas on the coldest days. Learn more →
- Ductless Mini-Split
- A ducts-free system with indoor heads for room-by-room heating and cooling. Learn more →
- EPA 608
- Federal certification required to handle refrigerant — every qualified tech holds it.
- ERV / HRV
- Energy/Heat Recovery Ventilators that bring in fresh air while recovering energy.
- Evaporator Coil
- The indoor coil that absorbs heat from your home's air.
- Heat Pump
- A system that heats and cools by moving heat rather than burning fuel. Learn more →
- HEPA
- High-Efficiency Particulate Air — a filter standard that captures 99.97% of fine particles.
- HSPF2
- Heating Seasonal Performance Factor 2 — the heating-mode efficiency rating for heat pumps.
- HVAC
- Heating, Ventilation, and Air Conditioning — the combined systems that heat, cool, and circulate air in your home.
- Indoor Air Quality (IAQ)
- How clean and healthy the air inside your home is — shaped by filtration, humidity control, and fresh-air ventilation. Learn more →
- Load Calculation (Manual J)
- The industry-standard method for sizing equipment to a home's actual heat gain and loss. Learn more →
- MERV
- Minimum Efficiency Reporting Value — rates how well an air filter captures particles (1–16 residential). Learn more →
- NATE
- North American Technician Excellence — the HVAC industry's leading technician certification.
- R-410A
- The refrigerant being phased down in favor of lower-GWP R-454B. Learn more →
- R-454B
- The lower global-warming-potential refrigerant used in new systems as of 2025. Learn more →
- Refrigerant
- The fluid that absorbs and releases heat as it cycles through the system. Learn more →
- SEER2
- Seasonal Energy Efficiency Ratio 2 — a measure of cooling efficiency over a season. Higher is cheaper to run. Learn more →
- Static Pressure
- The resistance to airflow in your ductwork — high static pressure hurts comfort and efficiency.
- Thermostat (Smart / Programmable)
- The control that sets and schedules your home's temperature. Smart and programmable models add remote access, learning, and multi-stage control.
- Ton
- A unit of AC capacity equal to 12,000 BTU/hour. Home systems are typically 1.5–5 tons.
- Zoning
- Dividing a home into independently controlled comfort areas using dampers and thermostats. Learn more →