What is HVAC?

What does HVAC stand for?

HVAC is an acronym for Heating, Ventilation, and Air Conditioning.

An “R” is sometimes added, HVAC-R. The “R” is for Refrigeration.

Your HVAC system is the combination and integration of HVAC equipment that control the temperature, humidity, and indoor air quality of your home or business. It promotes the comfort, health, and productivity of the inhabitants. Let’s take a look at each component of HVAC from a historical perspective.


Heating by burning of some type of fuel like wood or coal goes back to our earliest times and continues to now. Romans had elaborate heating systems using floor channels and firewood creating the first Central HVAC Systems. The use of wood, peat, and coal as a source of heating lasted for centuries. The method was very inefficient as most of the heat was drawn out the chimney. This brought about the invention of the metal or cast iron stove which is still used until this day. Fuel types and burners have continued to evolve over the years. New ways to harness and distribute electric, solar, and gas heat are constantly being created. These efforts have improved heating efficiency and reduced the carbon emissions. Heat pumps use the refrigeration process to create heat. The Geothermal HVAC system is being used more and more frequently. The heating field is often overlooked as "nothing new", "same old, same old." But the field is continuing to advance, finding new ways to heat homes and businesses. Technicians will need to be open to continued learning in order to keep up with changes in HVAC equipment.

HVAC - Gas Furnace burners heat exchanger


First uses of ventilation date back to the use of chimneys to remove smoke from homes. Ventilation is now commonly known as the use of ducting to distribute heat and cooling throughout your home or business. But that’s not all. It is also the means by which the air in your home is cleaned, humidity is reduced, and air quality is maintained. Controlling the humidity is an essential necessity in the comfort of your home. Think about outdoor temperatures. A seventy degree morning can by muggy in the middle of August, comfortable in October, and quite cool in March. Ventilation and airflow are critical subsystems in your overall HVAC system. It as important as the electrical or refrigeration systems. However, it is frequently overlooked and under appreciated by HVAC professionals and homeowners. Ventilation is one of the EPA's three strategies for controlling indoor air quality. In the COVID pandemic and the necessity to improve indoor air quality in public places, particularly in schools, has become a priority. Mechanical ventilation combined with high efficiency air filters to remove particulate as well as the use of natural ventilation to dilute impurities. It has also placed new emphasis on quality HVAC maintenance and HVAC repair.

HVAC - Ventilation ductwork in 3 ton home air conditioning system

Air Conditioning

Air Conditioning and cooling are often used interchangeably. Air Conditioning is a practice that dates back for centuries. Ancient Greece used large wet tapestries to cool air using evaporation. Business owners sprayed water in factories for air conditioning. Evaporative cooling systems are popular HVAC solutions that continue to be used today. Ice was used for many years to cool the air. It was used to palaces and hospitals. The US Capitol building had air conditioning by 1909. Ice was the coolant used. This is where “tons of air conditioning” was first coined referring to the amount of ice needed for cooling. The first in-home air conditioner was in 1914. The White House was equipped with air conditioning in 1930. In the 1950s, the air conditioner became very popular and requests exceeded supply. In 2015, more than 100 million homes had and HVAC system and that number continues to grow.

HVAC - Air Conditioner installed

Question: What is an HVAC ton?

HVAC cooling capacity is measured in tons. One ton is equivalent to the amount of heat that 2,000 lb of ice can absorb in one day. The amount of latent heat required to change 1 ton of ice into 1 ton of water is 288,000 BTU. If this amount is divided by 24 hr per day, the equivalent is 12,000 BTU/hr.

Standard Residential HVAC Tonnages

  • 2 Ton = 24,000 BTU/hr
  • 2.5 Ton = 30,000 BTU/hr
  • 3 Ton = 36,000 BTU/hr
  • 3.5 Ton = 42,000 BTU/hr
  • 4 Ton = 48,000 BTU/hr
  • 5 Ton = 60,000 BTU/hr

Up Next about HVAC

Find out some of the latest innovations in the HVAC industry. Energy efficient, personal comfort room to room is possible. Smart home products to zoning, get a snapshot in our next article, Modern HVAC.

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