What Does HVAC Mean?

Some people just say, "H-V-A-C." Others use the term "H-Vac." It all means the same thing, "heating, ventilation and air conditioning." HVAC is a catchall term that covers regulating the interior environment - temperature, humidity and air exchange in buildings.

Technically speaking, HVAC design is a mechanical engineering discipline based on thermodynamics, fluid mechanics and heat transfer. Occasionally, you'll come across the term HVACR or HVAC&R, which stands for heating, ventilation, air conditioning and refrigeration. But for now, we'll just stick with HVAC.

HVAC came into its own beginning in the industrial revolution, so it has been around for a couple of hundred years. You could argue that it started much earlier than that, dating back to ancient Rome, where builders included cooling systems using water in the construction of some buildings.

Today, we talk about HVAC systems because the various HVAC functions tend to be integrated. For example, central heating and air conditioning are often not thought of as separate functions, although they are. They're frequently designed to work together to keep indoor temperatures comfortable and the air quality high.

Most homes in cooler climates have central heating. The system is made up of a boiler or furnace. The heat itself derives from water, steam or air that is warmed in one place and then distributed throughout the structure. Such a system requires ductwork, or piping and radiators, for heat distribution.

Water and steam heating systems are clearly separate from central air conditioning. Forced-air heating systems might not be. The reason is that a forced-air furnace and a central air conditioner can use the same ductwork for air distribution. The air conditioner will most likely run on electricity and the furnace on gas, but the shared ductwork makes them seem to be one system.

Ventilation refers to the process of exchanging air to help manage temperature, remove moisture and control contaminants, such as pathogens and particulates that might cause health problems. The air can be exchanged with air from the outside or from elsewhere in the structure.

There are two basic types of ventilation: mechanical/forced and natural. Mechanical/forced ventilation controls the air quality inside the building. It removes humidity, odors and contaminants by diluting them with outside air. This type of ventilation system requires a fan to move the air.

Natural ventilation uses outside air without a fan or other mechanical method to move the air. It can be achieved by an action as simple as opening a window or providing vents. Natural ventilation can be quite effective in moderate climates, but it might not do the job when the weather becomes too warm. Understanding the elements of HVAC systems helps owners discover ways to improve the energy efficiency of their homes.