Plain-English Definitions
HVAC Glossary
Every heating and cooling term you'll hear from a contractor, in plain English — so you can make decisions with confidence.
Shopping for HVAC shouldn't require a degree. Here are the terms that matter most when you're comparing systems and quotes in Des Moines.
- AFUE
- Annual Fuel Utilization Efficiency — the percentage of fuel a furnace or boiler turns into usable heat over a year. A 95% AFUE furnace converts 95% of its fuel to heat; higher is more efficient.
- BTU
- British Thermal Unit — a measure of heat energy. Heating and cooling equipment is rated in BTUs per hour to describe how much it can heat or cool.
- Condenser
- The outdoor unit of an air conditioner or heat pump. It releases heat removed from your home and houses the compressor and condenser coil.
- Dual-Fuel System
- A setup that pairs an electric heat pump with a gas furnace. The heat pump handles efficient heating and cooling in milder weather; the furnace takes over in extreme cold — popular in Iowa.
- Ductless Mini-Split
- A heating and cooling system with an outdoor unit and one or more wall- or ceiling-mounted indoor heads, with no ductwork. Good for additions, older homes, and room-by-room zoning.
- Evaporator Coil
- The indoor coil (usually above the furnace) where refrigerant absorbs heat from your home's air to cool it.
- Heat Pump
- A system that both heats and cools by moving heat rather than burning fuel. Modern cold-climate heat pumps work efficiently well below freezing.
- HSPF2
- Heating Seasonal Performance Factor 2 — the current efficiency rating for a heat pump's heating mode. Higher numbers mean more heat per unit of electricity.
- Load Calculation (Manual J)
- An industry-standard calculation of exactly how much heating and cooling your home needs, based on size, insulation, windows, and climate — used to size equipment correctly instead of guessing by square footage.
- MERV Rating
- Minimum Efficiency Reporting Value — how well an air filter captures particles, from about 1 to 16. Higher MERV filters more, but must be matched to your system's airflow.
- Refrigerant
- The fluid in an AC or heat pump that absorbs and releases heat as it cycles between indoor and outdoor coils. Low refrigerant usually means a leak that needs a professional.
- SEER2
- Seasonal Energy Efficiency Ratio 2 — the current cooling-efficiency rating for air conditioners and heat pumps. Higher SEER2 means lower cooling energy use.
- Smart Thermostat
- A Wi-Fi thermostat that learns your schedule and can be controlled remotely, helping reduce energy use. Many may qualify for utility rebates.
- Tankless Water Heater
- A unit that heats water on demand instead of storing it in a tank, providing continuous hot water and saving space — though it requires proper sizing for your home's demand.
- Ton
- A unit of cooling capacity equal to 12,000 BTU per hour. A typical home needs roughly one ton per 500–700 square feet, confirmed by a load calculation.
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