Short answer
Thirty-two terms, grouped by trade. These 32 terms are the ones that most often appear on a Vermont plumbing or HVAC proposal without explanation, grouped by trade: plumbing and drainage, heating equipment and hydronic distribution, heat pumps and air conditioning, ventilation and indoor air, and the language of the proposal itself: allowance, change order, commissioning, exclusion. None of them is a guarantee by itself.
A high AFUE or SEER2 rating describes the equipment under a standardized test, not the building's actual fuel or electric bill, and an AHRI certificate matters only for the exact indoor-and-outdoor model pair named on the proposal, not the product family. The purpose of knowing these terms is not to sound technical. It is to notice when a proposal uses one loosely, substitutes a broad category for a specific model, or states an efficiency figure without the equipment behind it, which is one of the more common ways a bid looks more complete than it is.
Efficiency ratings at a glance
Four ratings appear on almost every heating and cooling proposal. Each measures the equipment under a standardized test, not a guarantee of your actual bill.
| Rating | Equipment | What it measures |
|---|---|---|
| AFUE | Furnaces, boilers | Annual Fuel Utilization Efficiency: seasonal fuel-to-heat conversion |
| HSPF2 | Heat pumps (heating) | Seasonal heating efficiency under a defined test procedure |
| SEER2 | Heat pumps, A/C (cooling) | Seasonal cooling efficiency under a defined test procedure |
| MERV | Filters | Particle-removal rating; higher is not automatically compatible with every system |
Plumbing, drains and water
Terms commonly used in plumbing repair, water-heater work and drainage.
- Backflow preventer
- A device intended to stop water from reversing into the potable supply. The type and testing requirements depend on the hazard and local rules.
- Cleanout
- A capped access point used to inspect or clear a drain or sewer line.
- Drain-waste-vent (DWV)
- The piping system that carries wastewater and admits air so traps and drains can work correctly.
- Fixture shutoff
- A valve that isolates one toilet, faucet or appliance without shutting water to the entire property.
- Hydro jetting
- Controlled high-pressure water cleaning used on suitable drain or sewer piping to remove broad buildup.
- Pressure-reducing valve (PRV)
- A valve that lowers incoming water pressure to a controlled downstream pressure.
- Sewer lateral
- The pipe connecting a building drain to a public sewer main. Ownership boundaries vary by municipality.
- Temperature-and-pressure relief valve (T&P)
- A water-heater safety valve designed to discharge under specified excessive temperature or pressure conditions. Its outlet must not be capped.
Heating equipment and distribution
Terms used for boilers, furnaces, hydronic systems and controls.
- AFUE
- Annual Fuel Utilization Efficiency, a standardized seasonal efficiency measure for fuel-burning heating equipment. It does not predict the entire building’s fuel use.
- Aquastat
- A boiler control that responds to water temperature and may manage burner, circulator or limit functions.
- Combustion analysis
- Instrument testing of applicable fuel-burning equipment to evaluate flue conditions and support safe setup or diagnosis.
- Condensing boiler
- A boiler designed to recover additional heat by condensing water vapor from combustion gases under suitable return-water and operating conditions.
- Expansion tank
- A tank that absorbs water-volume change as a closed hydronic system heats and cools.
- Heat-loss calculation
- A room-by-room estimate of how much heat a building loses at an outdoor design condition, used to size heating equipment and distribution.
- Hydronic heating
- A system that moves heated water through baseboard, radiators, fan coils or radiant tubing.
- Short cycling
- Equipment starting and stopping more frequently or running for less time than intended, often as a symptom instead of a complete diagnosis.
Heat pumps and air conditioning
Terms used in cooling, mini-split and cold-climate heat-pump proposals.
- AHRI certificate
- A matched-system performance record in the AHRI directory. The exact indoor and outdoor model combination matters.
- Balance point
- The outdoor condition at which a heat pump’s available output and the building’s heating load are equal under the stated assumptions.
- BTU/h
- British thermal units per hour, a rate of heating or cooling capacity. Twelve thousand BTU/h is commonly called one ton of nominal cooling capacity.
- Cold-climate heat pump
- A heat pump designed and tested to provide useful low-temperature heating performance. Exact capacity data matter more than the label alone.
- Defrost cycle
- A temporary operating mode that melts frost from an outdoor heat-pump coil during heating operation.
- Ductless mini-split
- A heat-pump or air-conditioning system with one or more indoor units connected by refrigerant lines, not central supply ducts.
- HSPF2
- A standardized seasonal heating-efficiency rating for heat pumps under a defined test procedure. Climate, sizing and installation affect actual use.
- SEER2
- A standardized seasonal cooling-efficiency rating under a defined test procedure. It is not a guarantee of a home’s electric bill.
Airflow, ventilation and indoor air
Terms used in duct, humidity and ventilation work.
- CFM
- Cubic feet per minute, a measure of airflow.
- ERV
- An energy-recovery ventilator that exchanges indoor and outdoor air while transferring heat and some moisture between separate airstreams.
- HRV
- A heat-recovery ventilator that exchanges indoor and outdoor air while primarily transferring sensible heat between separate airstreams.
- MERV
- Minimum Efficiency Reporting Value, a filter rating for removal of particles in defined size ranges. Higher is not automatically suitable for every system.
Proposals and project completion
Terms that should be clear before work is authorized.
- Allowance
- A budget amount for an item or condition not fully selected or known when the proposal is written.
- Change order
- A written revision to authorized scope, price or schedule.
- Commissioning
- A documented process of checking installation, setup, controls and operation against the design and manufacturer’s requirements.
- Exclusion
- Work, material or responsibility specifically not included in the quoted scope.
Common questions
Does a higher efficiency rating guarantee lower bills?
No. Weather, utility rates, building load, sizing, controls, installation and occupant use all affect actual energy cost.
Is a ton a unit of equipment weight?
No, not in HVAC sizing. A ton refers to nominal cooling capacity of about 12,000 BTU per hour.