Can You Vent a Bathroom Exhaust Fan into the Garage?

When homeowners consider how complicated it is to vent a bathroom fan in an already existing building, many are tempted to find an easy route. One location in the house that usually pops up when it comes to bathroom venting is the garage. But is it a good idea to vent the bathroom fan into the garage? Here is what I found out after hours of research

Venting your bathroom fan into the garage is not only against the International Residential Code, but moisture from the bathroom will also enhance mold growth in the garage and contribute to the rusting of equipment in the garage.

In detail, let’s take a look at why it’s a bad idea to vent the bathroom exhaust fan into the garage. After that, I will walk you through the safer ways of venting your bathroom exhaust fans and some helpful tips.

Reasons not to vent a bathroom vent into a garage.

1. It’s against the International Residential Code

The International Residential Code is a set of regulations made to protect homeowners and their families. It offers the best practices building contractors need to follow to ensure a safe environment and home for people to live in.

Most contractors are well aware of the codes off the top of their head because they constantly reference it to make sure they don’t violate it. DIY’ers are, however, the ones who usually breach these codes. That’s because most are not aware that there are codes that exist for these projects.

What’s the point I’m trying to make? According to Section M1507.2 of the IRCExhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space, or other areas of the building.

In simple terms, it is against the code to vent exhaust air from the bathroom and toilet rooms to any other room in the house, and that includes the garage. 

Going contrary to the residential code can result in a fine when caught. And the worst-case scenario, you will have to redo the entire project. Meaning you have to undo the work you have already done, and then do it the proper way. You certainly don’t want this to happen because it can add up to a hefty amount.

2. It will enhance mold growth.

Let’s assume there is no regulation against venting into the garage. All the moisture and bad smell from your bathroom into the garage will make the garage a breeding ground for molds and bugs.

We are well aware that the garage is not considered a well-ventilated area. It’s usually not part of our home’s HVAC system. And a lot of garages have no windows or vents. An unvented room full of moisture is the perfect breeding place for mold and mold growth.

Over time, these molds will start growing on your garage walls and turn into mildew. And in no time, this will lead to a musty smell in the garage.

The process of mold removal is not pleasant for a lot of people. That’s because of how gross it looks and how bad they smell. For this reason, most homeowners resort to hiring mold remediation experts, and that can be expensive depending on how bad the situation is.

3. It will contribute to the rusting of equipment in the garage.

As we all know, the garage isn’t just a place where we keep our vehicles anymore. It has turned into a storage facility where we keep rarely used equipment such as tools, lawnmowers, portable generators, and more. 

These are all items that need to be kept in a dry place. That’s because most of their parts are made of metal. Metals are materials which are susceptible to moisture. Exposing metals to moisture will lead to rusting.

However, that is what you do when you vent the bathroom exhaust fan into the garage. All the moisture from your bathroom will be discharged into the garage. After a while, all that moisture will condense on this equipment, and this is a recipe for disaster.

This will cause the equipment in the garage to rust, and it can lead to serious damages beyond repair. Electrical and electronic components stored in the garage are at high risk. Plug-in sockets installed in the garage may begin to electrocute, and some devices may not function anymore. 

I wouldn’t want to put my expensive tools and equipment at risk, and I’m sure you don’t want that either. So, venting the bathroom into the garage is definitely not the way to go. There are better options.

Where to vent bathroom exhaust fans

Now that we have established that the garage is not an option, what are the safest places to vent the bathroom exhaust fan?

According to the code, the exhaust air from the bathroom and toilet room must be vented outside. Here are three ways to vent your bathroom exhaust fan outside.

1. Through the roof

Most homeowners don’t prefer venting through the roof. That’s because it involves a lot of work, running a sheet metal ductwork or PVC pipe from the bathroom ceiling, through the attic, and out through the roof. This is the reason why they look for simpler options.  

However, it has been proven to be the best way to vent a bathroom fan. By discharging the humid air from the bathroom through the roof, there is a low probability of it blowing back into your home.

To make the ventilation more effective, a vent hood is installed on the roof-end of the pipe. It has a cover that only opens when the exhaust fan is working, allowing the warm, humid air from your bathroom out into the atmosphere. When the fan stops, it closes to prevent outside air from entering the bathroom. 

Also, it’s crucial to use an insulated duct system inside the attic. That’s because in the winter, the attic will be very cold, and this can condense the moisture running through the pipes. You don’t want that to happen because the water will run down the pipe back into the bathroom.

An insulated duct system inside the attic will prevent water condensation, allowing the bathroom steam to be discharged through the roof without any problem.

2. Through the gable wall

Another place you can discharge the warm waste air from the bathroom is through the gable wall. This is similar to the roof. Pipes are run from the bathroom ceiling, through the attic, and then to the gable wall. A hole is then drilled inside the gable wall. Similarly, a vent hood will be installed on the pipe outside the gable wall to prevent air from flowing through the pipe to the bathroom.

3. Through the soffit

The roof soffit is also an excellent place to vent the bathroom exhaust. The installation process is similar to the ones already discussed.

Bathroom Exhaust Fan Venting Tips and Best Practices

  1. Never vent the bathroom into the attic. It is against the residential code and will lead to mold growth in the attic.
  2. Run the vent pipes to the nearest discharge place to keep the pipes as short as possible. This will make it easy to fix when it blocks
  3. Use more straight pipes if possible, instead of flexible ductwork. This will make it easy for the fan to blow the warm, humid air outside.
  4. Regularly clean dust accumulated in the fan vents. This will allow easy airflow

Also: Can I Run a Generator in my Garage? Everything you need to know

Does a Garage Attic Need to be Vented?

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