What does HVAC mean?

In recent years, we often hear people using the term “HVAC” to refer to air conditioning.
HVAC is an abbreviation for ‘Heating, Ventilation and Air Conditioning’. The term refers not only to air conditioning but also to concepts related to air conditioning, such as systems and technologies. HVAC is a terminology used to refer to an entire system that adjusts the temperature and humidity to deliver comfort, achieves efficient use of energy and improves air quality.

An HVAC system includes a system that takes in fresh air from the outside through a filter and maintains a clean and refreshing air environment, as well as a system that provides a suitable humidity environment. The main functions of an HVAC system are described below.


“Cooling” generally refers to the reduction of room temperature to a comfortable level by using an air conditioner. When liquid changes to vapor, it absorbs heat from the surrounding environment. This heat is called heat of evaporation. Air conditioners use the above phenomenon to cool rooms. An air conditioner uses a liquid that evaporates easily at a low temperature, and this liquid is called a refrigerant. When an air conditioner operates in cooling mode, the air sucked in through the upper section of the indoor unit is cooled by the heat exchanger inside the indoor unit, and then the cooled air is discharged from the indoor unit. This process continues and reduces the room temperature. The heat exchanger is a component that absorbs and releases heat. The heat exchanger absorbs heat from the air sucked in through the upper section of the indoor unit and uses that heat energy to cool the air. The cool air is discharged into the room and the warm air is discharged from the outdoor unit. That’s why the air that blows out from the outdoor unit is warm. The indoor unit and outdoor unit are connected by two tubes: one for inflow and the other for outflow. These two tubes circulate the refrigerant. The heat absorbed by the heat exchanger is carried by the refrigerant gas.


“Heating” refers to warming the inside of a room. Heating is achieved by a process opposite to the cooling process. When an air conditioner is in heating mode, the outdoor unit takes in outside air and compresses it to generate heat. That heat is carried to the indoor unit, and the indoor unit uses it to warm the air and discharges the warm air into the room. The component that performs this process is called a heat pump.



“Ventilation” is a process of exchanging room air with fresh outside air. Since residences and buildings are becoming increasingly airtight in recent years, it is necessary to formulate a detailed air conditioning plan to optimize the air intake and exhaustion during air conditioning.


“Dehumidification” is a process of removing moisture from stagnant humid room air. Generally, dehumidification is achieved by operating equipment such as an air conditioner, dehumidifier or ventilation fan, or by using chemicals such as a dehumidifying agent. If too much moisture continues to remain in the room, it leads to dew condensation and promotes fungus growth, rotting of wood materials in the house and other adverse effects.


“Humidification” refers to a process of adding appropriate humidity to a very dry room. If the humidity in a room falls below 40%, people in the room feel uncomfortable dryness of nasal passages, throat and skin. What’s more, such room environments can vitalize viruses such as influenza in some cases. A humidifier is usually used to add an appropriate amount of moisture to the room air. Placing house plants, wet towels or wet laundry in the room also provides some humidifying effect.

Various types of HVAC

A relatively small space such as a living room can be cooled/heated by one air conditioner and ventilated by one ventilation fan. In the case of a large building, however, it is necessary to install a HVAC system designed by a dedicated engineer. The following introduces various types of HVAC.

Heat pump

The heat pump is a technology to collect heat from the ambient air or the like and utilize the collected heat as a large amount of thermal energy. This technology is used in many products around us, such as air conditioners and refrigerators. Since a heat pump provides more heat energy than the amount of energy used, it enables the effective use of valuable energy. Use of heat pumps significantly reduces CO2 emissions and contributes to the conservation of the global environment.

Air handling unit

An air handling unit is an air conditioning unit with a relatively large capacity, which is comprised of a hot/cold water coil, humidifier, drain pan, blower fans and air filter. Since each air handling unit can be configured with the most suitable components according to the required condition of discharge air, air handling units are used when strict control of the temperature and humidity is demanded.

Packaged air conditioner

The major difference between a packaged air conditioner (PAC) and residential air conditioner is the cooling/heating capacity. Packaged air conditioners can be roughly divided into two groups: “Air conditioners for offices and stores” which are designed for medium-size spaces such as offices and stores and “Multi-split air conditioners for buildings” designed for buildings and large facilities. Since the packaged air conditioner to be installed must be selected in consideration of the room size, ceiling height and usage, various types of indoor units are available in the market.