What is the meaning of “HVAC”?

Technical fields often use lots of acronyms, and the first step to understanding them is taking a look at what these acronyms stand for. HVAC stands for heating, ventilation and air conditioning. This highly skilled discipline is responsible for the comfortable, clean air in our homes, workplaces, factories and indoor leisure spaces. Well-functioning HVAC technology is a cornerstone of our modern way of life, and experienced HVAC technicians and contractors are needed wherever people live and work. Let’s take a closer look at each word of the acronym and what it means in the industry.

Search HVACR Certified Technician Programs

Get information on HVACR Certified Technician programs by entering your zip code and request enrollment information.

Sponsored Listings


Heating is the first component of an HVAC system.

In historic times, fire generated by burning wood, coal, peat or even dung was the main source of heat. Today, modern buildings are most often warmed by central heating, in which a furnace, boiler or heat pump is connected with a system that transmits throughout the building. This can be done via warmed air forced through ductwork, pipes carrying steam or water circulating through systems of pipes.

A heat pump is a device that transfers heat energy from a source of heat, such as a domestic furnace, to what is called a thermal reservoir. Heat pumps do the opposite of refrigeration or air conditioning system by moving thermal energy in the opposite direction of spontaneous heat transfer, by capturing heat from a cold space and pumping it into to a warmer one.

Generally, the heat is created through the burning of fossil fuels such as natural gas or oil in a boiler or furnace. Residential systems and smaller buildings used to use coal for these purposes, and there were coal stores built into most homes. After World War II, coal was used mostly for larger buildings.

Heating systems powered by electricity are generally more expensive and tend to occur in areas with low-cost electricity or with hydroelectric power available. Other ways of generating heat include electricity from solar panels and district heating, in which a factory or other industrial facility that generates a lot of heat can heat water, which is piped to buildings in the area to use in radiators.


Ventilation represents the “V” in HVAC systems.

Ancient humans built dwellings that were small enough to use natural ventilation from smoke holes, windows and doorways. It is far more challenging to ventilate, for example, a 12-story building, but proper ventilation is one of the most important factors in determining air quality within the structure. The intentional delivery of outside fresh air to the interior space is the focus of modern ventilation.

Fans are key to ventilation. Even the humble ceiling fan plays a role, circulating warm air in winter. Mechanical exhausts—basically powered fans in vented boxes—appear in places where there are smells or smoke to let out, like kitchens and bathrooms.

For larger-scale buildings, an air handling unit, which combines fans, sound dampeners and heating and cooling units can be installed in or on a building to deliver multiple changes of air per hour via ductwork. Air exchange and filtration, heating and air conditioning are often combined in these systems in order to improve space, cost and energy efficiency.

In areas with a great deal of air pollution, filtration of particles and odors is a crucial role for ventilation systems. Adequate ventilation also reduces the transmission of airborne disease.

Air Conditioning

Air Conditioning is the “AC” in an HVAC system.

People refer to turning the air conditioning on when they want to cool the air down, but alongside cooling, air conditioning also involves managing the humidity level of the air. Air that is too dry or too humid isn’t good for people, plants, pets or furnishings.

Heat can be removed through radiation, convection or conduction. This can take a lot of energy. One of the most common methods used is the refrigeration of air, which uses a similar method to a household refrigerator, called the refrigeration cycle. In short, a refrigerant fluid in a closed HVAC system is allowed to condense and evaporate in a way that gives it an opportunity to absorb heat from the outside air passing through the unit. There are many ways to accomplish this process including mechanical heat exchangers, and the refrigerant fluid is continuously reclaimed and reused by HVAC systems.

A split system of air conditioning consists of an outdoor and an indoor unit. The outdoor unit is installed on or near the exterior wall of the space you wish to cool. It houses the compressor, condenser coil and the expansion coil or capillary tubing. The indoor unit contains the cooling coil, a long blower and an air filter.

Dehumidification, which is almost always required in air conditioning—the need for humidification is much rarer—is accomplished as part of the refrigeration cycle, because the chilly evaporator that is working on condensing the refrigerant fluid allows the outside air circulating past it to get cool enough that dew condenses on the evaporator coil tubes.

The close relationship between refrigeration, dehumidification and air conditioning means that HVAC system work is often referred to as HVACR, with an R for refrigeration added to the end of the acronym.

The requirements for climate control – heating and cooling, and controlling indoor air quality and humidity – in any building will vary widely according to the climate, the nature of occupancy of the building, the cost of electricity in the area, and what the client can afford. An HVAC contractor needs a good command of the mechanical skills and physics of the processes involved, as well as an understanding of the computer technology required to regulate temperature according to client demand. As an HVAC technician your brain and hands will both get a workout as you work to build these complex heating, ventilation and air conditioning systems that make modern living a reality.