10 HVAC Acronyms You Should Know

If you’re in the market for a new commercial HVAC unit, you’ve likely come across dozens of HVAC acronyms. Just like any other line of work, the HVAC industry uses hundreds of acronyms. And, sometimes this can make shopping for a new unit confusing. But, have no fear – we’re here to help decode 10 common HVAC acronyms.

1. ACH

Air changes per hour, or ACH, refers to the rate at which air enters and exits a room in one hour. To measure ACH, you take the air volume added to or removed from a space and divide by the volume of the space. So, the higher the value, the better the ventilation.

2. BTU

The British Thermal Unit, or BTU, is an international measure of energy. It specifies the amount of heat required to raise one pound of water by one degree Fahrenheit. And, in the HVAC industry, BTUs refer to the amount of heat the unit can add or remove from the air in one hour. In addition, being aware of the BTU requirements of a facility will ensure that the appropriate HVAC system is installed.

3. CAV

Constant air volume, or CAV, is a type of HVAC system. CAV systems are typically found in small commercial properties, as they are less expensive. In general, the supply airflow rate is constant, while the supply air temperature varies. All in all, the CAV system is an effective option in commercial spaces with single zones that have less variation in air temperature.

4. FCU

A fan coil unit, or FCU, is a simple device that utilizes a coil and fan to heat or cool a room. And, it can do this without any ductwork. In short, FCUs are available in ceiling, floor-mounted and freestanding designs to control the temperature in the space.

5. FAF

Fresh Air Fraction, or FAF, is a measure of economizer action. Specifically, it’s a ratio of the outdoor air intake and the total airflow supply rate.


Heating seasonal performance factor, or HSPF, describes the efficiency of a heat pump over a heating season. To get the rating, you take the total heat output. Then, you divide it by the total electric output during that same specific period. Overall, the higher the HSPF rating of a unit, the more energy efficient it is.

7. MAU

A makeup air unit, or MAU, is a large handler that provides a building with conditioned fresh air. In particular, it produces both heated and cooled air. Considering this, MAUs are typically used in applications that need high indoor air quality (IAQ).

8. RTU

A rooftop unit, or RTU, is a type of HVAC system often found in light and large commercial applications. Referred to as a package unit, it houses all the components needed to condition air without taking up any indoor space. The most common types of buildings that use this system are restaurants, stores, warehouses, and shopping centers.


The seasonal energy efficiency ratio, or SEER, is a rating used to describe the efficiency of an air conditioner. It’s based on a standard defined by the Air Conditioning, Heating, and Refrigeration Institute. In sum, the SEER rating takes the cooling output and divides it by the total electricity during a typical cooling season.

10. VAV

Variable Air Volume, or VAV, is a type of HVAC system. Unlike CAV systems, it varies the airflow at a constant temperature. In turn, VAV systems allow precise temperature control. Most importantly, they also help lower energy use and reduce fan noise.

Turn to The Severn Group

HVAC acronyms can be confusing. Even more, that’s just the tip of the iceberg. Needless to say, if you need an HVAC system replaced, it’s best to consult the experts. At The Severn Group, we offer complete HVAC system installations. Let our HVAC professionals design a system tailored to your facility. Just give us a call at 443-837-0828 to learn more.