Foundations
HVAC Glossary
The vocabulary your next quote will be written in — defined in plain English for North Bay homeowners. Terms link to the Learning Center guide where they matter most.
- AFUE
- Annual Fuel Utilization Efficiency measures how efficiently a furnace turns fuel into heat over a season — a 96% AFUE furnace delivers about 96 cents of heat per dollar of gas. Higher is better, and it applies only to combustion heating, not heat pumps. Learn more about AFUE →
- BTU
- A British Thermal Unit is the basic measure of heating and cooling energy. HVAC capacity is given in BTUs per hour (one 'ton' equals 12,000 BTU/hr). Matching BTUs to your home through a load calculation matters far more than simply buying the biggest unit. Learn more about BTU →
- CSLB
- The California Contractors State License Board licenses and regulates contractors statewide. Enviro Heating & Air Conditioning holds CSLB license #928565 — always verify any HVAC contractor's license before hiring.
- Diamond Certified
- An independent rating awarded to local companies that pass an in-depth quality and customer-satisfaction evaluation and score highly with verified customers. Enviro is Diamond Certified, a recognition focused on Bay Area service quality.
- Dual-fuel (hybrid) system
- A system that pairs an electric heat pump with a gas furnace. The heat pump handles efficient heating and cooling most of the year; the furnace takes over on the coldest days — a practical middle ground for many North Bay homes. Learn more about Dual-fuel (hybrid) system →
- Ductwork
- The network of channels that distributes conditioned air through a home. Leaky, undersized, or poorly designed ducts waste energy and undercut even the best equipment — one reason ductless mini-splits suit older homes without good ducts. Learn more about Ductwork →
- ERV / HRV
- Energy- and heat-recovery ventilators bring filtered fresh outdoor air into a tight home while recovering energy from the air being exhausted — so you ventilate without throwing away heating or cooling. Useful for indoor air quality during wildfire smoke season. Learn more about ERV / HRV →
- HEPA
- High-Efficiency Particulate Air filtration captures 99.97% of particles at 0.3 microns. True HEPA usually needs a dedicated or bypass unit rather than a standard furnace slot, but it's the highest level of particle filtration for smoke and allergens. Learn more about HEPA →
- Heat pump
- An all-electric system that heats and cools by moving heat rather than burning fuel — pulling warmth indoors in winter and pushing it out in summer. Because it moves heat, it can deliver several units of heating per unit of electricity, which suits the mild North Bay climate. Learn more about Heat pump →
- HSPF2
- Heating Seasonal Performance Factor 2 is the current efficiency rating for a heat pump's heating mode. Higher HSPF2 means more heat per unit of electricity, and rebate programs often require a minimum HSPF2 to qualify. Learn more about HSPF2 →
- IAQ (indoor air quality)
- Indoor air quality describes how clean and healthy the air inside your home is. HVAC filtration, ventilation, and humidity control all affect IAQ — which matters most during North Bay wildfire smoke events. Learn more about IAQ (indoor air quality) →
- Load calculation (Manual J)
- The industry-standard method for sizing HVAC equipment to a specific home, accounting for insulation, windows, orientation, and air leakage rather than just square footage. A proper Manual J is the foundation of a comfortable, efficient system. Learn more about Load calculation (Manual J) →
- MERV
- Minimum Efficiency Reporting Value rates how well an air filter captures particles. MERV 13 captures much of wildfire smoke's fine PM2.5 — but only use what your system can move air through, since too dense a filter chokes airflow. Learn more about MERV →
- Mini-split (ductless)
- A heat pump that conditions rooms through small indoor 'heads' connected to an outdoor unit by refrigerant lines, with no ductwork. Ideal for older Sonoma County homes, additions, and zoning specific rooms. Learn more about Mini-split (ductless) →
- NATE
- North American Technician Excellence is the leading independent certification for HVAC technicians. NATE-certified techs have proven their knowledge through rigorous testing — Enviro's technicians are NATE-certified.
- Refrigerant (R-454B / R-32 transition)
- The HVAC industry is shifting from older high-GWP refrigerants like R-410A to lower-impact blends such as R-454B and R-32. The transition affects new equipment and the cost of servicing older systems — worth weighing when deciding whether to repair or replace. Learn more about Refrigerant (R-454B / R-32 transition) →
- SEER2
- Seasonal Energy Efficiency Ratio 2 is the current rating for cooling efficiency. Higher SEER2 means more cooling per unit of electricity, and rebate programs frequently set a minimum SEER2 to qualify for their larger incentives. Learn more about SEER2 →
- Static pressure
- The resistance to airflow inside a duct system — like blood pressure for your HVAC. Too-high static pressure, from undersized ducts or an over-dense filter, reduces airflow, strains the blower, and hurts efficiency. Technicians check it during maintenance. Learn more about Static pressure →