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Are Vents Required in Garages in California

Garage ventilation can be a tricky thing. It can be difficult to determine what regulations say about garage spaces since they aren’t mentioned in international codes. Yet the idea of car exhaust being able to build up in the garage makes you think that they are crucial.

When looking at a specific state, you always have to look beyond the international building codes to the local codes, which are adapted for the climate and circumstances of that region.

In California, garage ventilation is not required by code, but it is recommended by the EPA, and there are many benefits to it. Air movement keeps heat levels down, making garages more comfortable. It also helps keep AC costs down for homes with attached garages. Vents improve air quality.

California Ventilation Governed by CMC

The International Residential Code (IRC) doesn’t regulate garage ventilation. While the IRC is applicable in California, adaptations and additions have been made to certain regulations. In this case, the California Mechanical Code (CMC) supersedes the IRC to determine statewide building ventilation standards.  

The CMC, Chapter 4: Ventilation Air, determines the general requirements for many aspects of ventilation, such as air rate, air class, and ventilation efficiency within different types of spaces, including businesses, health care facilities, and homes.

CMC Doesn’t Regulate Garage Vents

While the CMC covers a wide variety of spaces, there is no section dedicated to the ventilation of garages in residential homes. California garages, therefore, do not have any specific ventilation requirements they need to meet.

garages in California

Should Vents Be Installed?

I always like to ask “should you” to questions like this. No, you don’t have to install vents in your garage, but surely there are a whole bunch of reasons why it would be a good idea. When researching garage ventilation, I certainly found these reasons, and they are not only applicable in California.

Even though garage ventilation is not legally required, it is recommended by the Environmental Protection Agency (EPA).

In the EPA’s report on Building Codes and Indoor Air Quality, on Page 17, the agency recommends attached garages be ventilated with a 100 CFM ducted or an 80 CFM un-ducted exhaust fan.

This fan should be designed for continuous operation or run on an automated system so that it turns on when the garage is occupied and stays on for an hour after it is vacated.

Additionally, the fan should be exhausted outside, not to any indoor areas of the home.

Benefits of Vents

There are several benefits to ventilating your garage in California.

Having an exhaust fan will help cool off the inside of the garage. In California’s heat and humidity, this is especially important for creating a comfortable space and lowering the cost of air conditioning, since the heat from an attached garage can permeate to the rest of the house.

You may also choose to find an exhaust fan with two-way movement so that air circulation can continuously cool the garage.

Ventilation promotes higher quality air that creates healthier living conditions. It is important to prevent the build-up of any toxic fumes coming from substances stored in the garage. Paint, cleaning agents, and pesticides are all commonly stored in garages and produce unhealthy fumes.

In addition to these hazards, carbon monoxide from vehicle exhausts can potentially permeate the walls of an attached garage without the proper ventilation. This gas is very poisonous and has low enough density to seep through gypsum board, a common type of drywall used to separate an attached garage from the home.

If you purchased a how with a ventilated garage, then these benefits may have been the reason why the previous owners installed the vents. However, if you do not think that the benefits are worthwhile, you can always seal the vents up.


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