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What is HVAC?

By Dan Blacharski
Updated Jan 22, 2024
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Climate control and comfort in modern buildings is a major design issue. Heating, ventilation and air conditioning (HVAC) systems help to control the climate and keep occupants comfortable by regulating the temperature and air flow. These systems are also important to occupants' health, because a well regulated and maintained system will keep a home free from mold and other harmful organisms. In some environments, such as museums, they are vitally important for the preservation of historic artifacts.

In choosing any type of HVAC system, finding one that is size-appropriate to the building is important in terms of achieving the best efficiency and comfort level. Beyond understanding the maintenance and installation of the systems themselves, sizing them appropriately is perhaps one of the most difficult tasks of an contractor. If a contractor recommends a heating system that is too big or too little for a home or business, the result will be an inefficient system that will cost more money in the long run. An oversized air conditioner will not efficiently dehumidify the air; an oversized furnace is likely to cause a large temperature swing and create an uncomfortable climate inside the target area.

Determining the size of HVAC systems only by square footage (square meters) is largely inaccurate, since it does not take into account the energy-efficiency or design of the building. Another common mistake made by many contractors is simply replacing an older unit with a newer one of the same capacity. This is not always the best strategy since older homes, for example, often had larger-than-necessary furnaces. An older home that has undergone significant renovation with new windows, weatherstripping, insulation, and caulking will be more energy-efficient, and may be better served by replacing the older, larger heating unit with a smaller one.

Gas and electric utility companies sometimes offer to perform a sizing calculation either for free or for a minimal charge. A good contractor will follow procedures set forth by trade organizations such as the Air Conditioning Contractors of America (ACCA) in regards to appropriate sizing, and may use software programs to assist in the calculation.

In larger, industrial systems, software is used to manage the HVAC system with respect to other areas such as scheduling, dispatch, billing, maintenance, inventory. Specialized software is also used by engineers to design ductwork and piping plans. These software programs usually integrate with computer aided design (CAD) software.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By anon958224 — On Jun 25, 2014

When the a/c is switched on, the fan outside doesn't come on. Why?

By anon351973 — On Oct 18, 2013

So is there someone I can call to fix both my heating and cooling? I'm trying to think what it could be that they're both broken.

By anon347994 — On Sep 12, 2013

I always wondered what the "V" stood for. Good to know. I also know I need to get help with our heating and air conditioning in Utah because it doesn't flow through the house very well.

By malik23 — On Jul 31, 2012

Proper HVAC systems in homes are important. This past few weeks my family was almost set ablaze because of the sweltering heat. Eventually, my grandfather called in a heating and cooling company who made the heat bearable. The heat slowly went away.

By anon34369 — On Jun 21, 2009

When a/c is switched on, the fan outside doesn't come on, why?

By anon795 — On May 04, 2007

what is the best method for cleaning kitchen canopy extract ductwork with heavy deposit of grease, by steam or degreaser or other?

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