At its most basic level, your home is a barrier between you and the elements. But it’s not a hermetically sealed container. Like you, it needs air to function well. In a sense, you could say your house needs to breathe — to have an exchange of air between the indoors and outdoors.
There are two types of air that work to make your home safe and comfortable: combustion air and ventilation air. They’re quite different in function and they need to meet very different codes to function correctly.
Three components are necessary to produce combustion: fuel, an ignition source, and air. Combustion air is simply the air (think oxygen) that’s needed to burn a fuel-powered appliance, such as your gas, oil, or wood-burning furnace. It’s important to have the correct amount of oxygen for a safe combustion process.
There are two types of combustion air:
- Dedicated combustion air, such as air piped directly into a furnace, is air supply just for that appliance. It’s sometimes called direct vent or sealed combustion.
- General combustion air is supplied for appliances that draw air from inside the home and may involve a single duct for several appliances.
Local codes and the appliance manufacturer mandate what rules an installer must follow to provide the correct amount of combustion air. While it may seem counter-intuitive — or even counter-productive — to have cold air filtering into your utility room when it's below zero outside, it’s there for your protection. Don’t block off that air inlet! Doing so could lead to damaged equipment and at worst, it could cause carbon monoxide build-up in your home.
Ventilation air is entirely different from combustion air. It’s also air that comes into your home, but for the purpose of refreshing the air that you and your family breathe.
Ventilation can be provided by the installation of a mechanical device such as a heat recovery ventilator (HRV), which brings in fresh air and exhausts stale air at the same time. It also exchanges heat from the incoming and outgoing air, which can save you on heating and cooling costs. More importantly, it maintains balanced ventilation. That means there’s an equal exchange of air so air pressure in your home remains neutral. (Both negative and positive air pressure can damage your home and cause other air quality issues.)
Codes and guidelines for mechanical ventilation can vary greatly depending on the type of ventilator being installed, the size of your home, how much air your home needs, and how it will be distributed throughout your home, as well as other factors. The International Energy Conservation Code (IECC) and International Code Council are good resources for researching the details.
Talk to the Pros
Whether adding to, upgrading, or replacing your HVAC equipment, it’s always advisable to consult with an experienced, reliable HVAC professional. You can find reputable dealers in your area using our convenient dealer locator.