How Does an HVAC System Work?

What is HVAC?

HVAC stands for heating, ventilation, air conditioning system. It provides thermal comfort and improvement in air quality. This system is one of the most important parts of a building, it includes the exchange of air to the outside and supplies the circulation within the building. Supply ventilation systems allow for better control of the air that enters the house. It removes pollen, dust and dehumidifies to provide humidity control.

What is the difference between supply vents and air returns?

Supply vents blow air outwards into a room. They are usually smaller and have slats behind the vent covers. Air returns suck the air out of the room into your ducts, and back into the furnace. 

Where does my HVAC system filter the air?

If your furnace is in the basement, more than likely this is where you will find the removable air filter that keeps your air clean. If you don’t have a basement, then most likely your furnace is in the attic. It would be very inconvenient to go to switch the filter in the attic, that’s why these homes will filter the air in the air returns located on the walls and ceilings. This makes the filters easier to access and replace! 

How often should I replace my air filter?

Typically air filters for HVAC systems should be changed at least twice a year. A good trick to keep on track is to replace the filters when you switch your clocks for daylight savings time. Change the clocks, change the filters. That way you never forget! 

If your home is more prone to dust, or pollutants, than you may want to change it more than twice a year. 

The overall ventilation process 


The most important part of a HVAC system is the thermostat. The thermostat triggers the entire system to start cooling or heating.  It is normally centrally located in your home and programmed based on your preferences. 

Furnace &  Heat Exchanger

The furnace heats the air that moves through the system with natural gas. Within the furnace is a heat exchanger, which is responsible for heating up the air to the right temperature. You’ll typically find the furnace in the attic, basement, or a specially designed closet space.

Air Conditioner

The air conditioner cools the air and is found outside of the building. It uses electricity and coolant liquid to reduce the temperature of the air, while sending hot air outside and cold air inside.


Ducts are a very important part of the HVAC system! They help move air efficiently throughout the home. It is a channel of connected tubes that are built behind the walls. Ducts are responsible for delivering and balancing the air flow through the rooms of your house. Ducts connect to the air vents that you see on your floors, walls and ceilings.

Air Vents

Vents are the final part of this system. There are two types of vents - supply vents and air returns:

Supply vents, supply air to the room.

Air returns remove the air from the room and suck it back into the system to be recycled and reconditioned by the furnace.

Shop Air Vents & Air Returns