Ventilation Requirements and what it means for you
2015 IECC/IRC requires “continuous mechanical ventilation systems” in all residential homes. This is a fancy way of saying your home needs an HVAC system. The reason for this regulation is to provide residents with a continuous supply of fresh air that also cycles out stale air. Your HVAC system isn’t just for heating and cooling.
It also requires continuous operation to remain compliant, meaning it needs to cycle out air at least every four hours. An inspector will measure how well ventilated your home is by following a set of charts that accounts for the size of your home and the area it is in. Ventilation requirements can be satisfied in three ways: exhaust only, supply only, and balance/supply exhaust.
Exhaust Only
An Exhaust ventilation system is the most common and affordable option. It works by using one or more fans, such as bathroom or kitchen fan to depressurize the home so that it can draw fresh air through the leaks in your insulation. It does this by blowing air out of your home. Keep in mind that it is completely normal for homes to have air leaks, as long as they aren’t too big or pose risks to occupants of the home.
Supply only
The supply-only method is the opposite of the exhaust-only method. Instead of using fans to depressurize your home and draw fresh air in, it pressurizes your home to push stale air out. It can also pose some of the same issues with exhaust-only systems, such as humidity in your wall cavities. But there are some benefits to this approach.
A return can be added to your duct systems to produce the same effect. Exhaust-only systems are usually just fans on the roof of your home, and if you wanted to increase ventilation, you would have to add more fans. Using a return on your HVAC system using the supply-only method, you can use the fans already installed in your home.
But there is a catch. The return system only works when you need heating and cooling. Running your HVAC system for ventilation alone can be considered inefficient and can land you with unexpected energy bills.
Balanced ventilation
The balanced ventilation system brings together the best of both worlds. It works by using fans to draw air in and fans to push air out. This way, you avoid any potential problems with moisture in your wall cavities and have complete control over the heat exchanges. It can save you money on energy costs and repair costs.
A balanced ventilation system is typically the most expensive option and can be complicated to install for some homes. If you have the means, it is always recommended that you go this route because of its efficiency, control, and cost-saving features.