What Is an HVAC System?

There are many systems and components in a home or building that we tend to take for granted, like roofing, plumbing, and electricity. Possibly chief among the underappreciated systems is HVAC: the sprawling heating and cooling systems powered by a tiny thermostat. 

What is HVAC? 

HVAC is an acronym that stands for Heating, Ventilation, and Air Conditioning, which refers to the system in a home or building that produces safe, clean, comfortable air within the space. 

  • Heating: The “H” in HVAC stands for heating, and as one might guess, this system warms the air within a home. Generally speaking, this could involve heating the space with forced hot air from a furnace or radiant heat from a boiler within a home. In a commercial building, heat might come from a boiler, heat exchanger, and coil within an air handler.
  • Ventilation: The “V” in HVAC stands for ventilation, and it’s all about exchanging old, stale air and carbon monoxide for fresh air to improve indoor air quality. Manual ventilation would involve opening windows and doors. Mechanical ventilation (which HVAC is concerned with) often involves a heating or air conditioning unit that can draw fresh air into the system. The system cleans the air via filters, adjusts its temperature and humidity, and exchanges it for the stale air. 
  • Air Conditioning: Just as important as the other two components of HVAC, air conditioning is all about comfort and humidity control. The air conditioning component of HVAC takes warm, moist air from within a space and cools it. At the same time, it removes the moisture from the air to control the humidity. 

How does an HVAC system work?

All three of the HVAC components work together as a system, with different components performing certain functions. 

In the case of a home HVAC system, there is typically a central heating unit known as a furnace. The furnace has a supply side to push air throughout the home through the ductwork, as well as a return side to pull the house air back into the system. When the system pulls the house air in through the return, the air then passes through the furnace, over the coil where it’s heated, and back into the home by the blower. 

HVAC systems also contain air conditioning, typically in the form of an outdoor unit placed just outside the home. This air conditioner unit contains a compressor that condenses a refrigerant gas into a liquid and then pumps it through a system known as a line set. The line set travels to a coil within the home’s existing ductwork to cool the moving air. This system still relies on the furnace’s blower to pull the air through the return and push it through the ductwork. 

When it comes to ventilation, these systems work in a few ways. Some have a simple set of louvers that the homeowner can open and shut. Others might have advanced components known as HRV (heat recovery ventilation) systems. These systems draw in fresh air while allowing outgoing air to warm or cool the fresh air. At any rate, ventilation is about improving indoor air quality.

What is the difference between HVAC and air conditioning?

Despite the two being so closely related, there is a slight difference between HVAC and air conditioning. Air conditioning is simply about cooling a space and controlling the humidity. HVAC entails much more.

All HVAC systems contain an air conditioning component, but not all air conditioning systems can be considered HVAC. If an air conditioning system doesn’t entail heating and ventilation, it is simply air conditioning. However, if there is a furnace and a method of ventilation, it becomes an HVAC system. 

Think of it this way: Air conditioning is just one piece of the HVAC pie, with heating and ventilation being equally as important. 

HVAC systems come in many shapes and sizes. Other systems might include energy-efficient heat pumps, ductless split units, humidifiers and dehumidifiers, and more. If your next home improvement project involves HVAC work, be sure to do some research in order to choose the right home HVAC system for your needs. 

MT Copeland offers video-based online classes that give you a foundation in construction fundamentals with real-world applications. Classes include professionally produced videos taught by practicing craftspeople, and supplementary downloads like quizzes, blueprints, and other materials to help you master the skills.

Avatar Photo of JEFF DEMASSARI

Featured Instructor


Jeffrey DeMassari is a lead HVAC technician for a small company based out of Metuchen, NJ. His father got him a job as a parts runner for the company, and after just a week, he was thrown head first into the field as an apprentice. That’s where Jeff first discovered his passion for the trade, which he’s now been advancing in for 9 years. During the onset of the pandemic, he started an Instagram to showcase his work and found quite the community of fellow trade-smiths there. When he isn’t installing and making custom metal work onsite, you can find him chasing around his three kids.

Explore Classes

Build Smarter

Get the latest updates about new courses, special trainings, resources, and more.