Bathrooms are undoubtedly the wettest parts of our home, and as a result, obviously, need an efficient ventilation system. While bathroom exhaust fans are commonplace, a lot of older homes discharge these vents into their attics. 

This practice has now been deemed illegal by Section 1504.3 of the International Residential Code, which states that the air removed by a mechanical exhaust system has to be discharged to the outdoors, and not into an attic, ridge vent, soffit, or crawl space. 

As a result, all building codes in the country have now made it mandatory for all bathroom vents to be discharged outside the home. If you want to find out why you should not vent the bathroom into the attic, as well as more about discharging bathroom vents, this short and informative blog is just what you need. 

Why you can’t vent your bathroom into the attic

bathroom ventilation

You already know your bathrooms are among the most humid and moist places in your home. And the attic space is one indoor space in most houses that do not have temperature control.

If you have your bathroom fan venting into the attic, that warm and moist air will come into contact with the cold air in the attic. This will result in condensation forming and cause water droplets to settle on the ceiling and floor joists, attic insulation, roof sheathing, and rafters.

All of this will eventually lead to mold and mildew spreading on these surfaces, which, as you all know, can lead to severe respiratory diseases and other illnesses. In addition to leading to mold issues, this excess moisture can also lead to wood rot, and degradation and could even cause your roof to collapse if left untreated.

Then, there is also the matter of energy efficiency to be considered. If the warm air from the bathroom remains indoors, it will make the home warmer, which means your home’s air conditioning system has to work harder to maintain the ideal indoor temperature.

Where should you vent your bathroom fan?

Virtually all building code in the USA now dictates that all bathroom vents should be discharged outside the home. If you are venting the bathroom exhaust through the attic, then it should terminate at the other side of the gable wall, to a soffit, or to the roof.

The only buildings that are exempt from these rules are older homes built in the 1960s and earlier, which will have a grandfathered-in status.

Not only should the vent be discharged directly outside, the vent should also have a vent hood cover installed.

In most cases, this exterior hood cover is a flap that remains closed when the vent is not in use but opens up when your exhaust fan is in use to let the air out. 

This flap serves two purposes. The first is that it allows air from the bathroom to exit, but prevents outside air from entering your home when the exhaust is not in use. It also prevents birds from nesting in the vents, because should that happen, your bathroom fan will be far less effective. 

Another thing to keep in mind is that these vent caps will not be effective if they are made of a flimsy material such as plastic. Code dictates that these should be made out of galvanized and powder-coated metal, which also makes them a little expensive.

How much will it cost to install a bathroom vent?

bathroom vent to attic

Let’s take a look at what you can expect to spend if you want to vent your bathroom exhaust outside through the attic. 

The least expensive part of the project is going to be the materials you need. A 25-foot exterior vent with a vent cover will cost you around $100 or even less. However, labor charges may cost you a minimum of $200 to a maximum of between $500 and $750. 

The amount you will need to spend on labor will depend on where you want the vent to discharge. For example, roof vents will cost more than a soffit ridge vent or a gable wall vent because it will involve paying for a roofer as well. 

The importance of bathroom exhaust fans and proper venting

Bathroom exhaust fans play a very important role in our homes. They make sure that all of the warm air and moisture that builds up in the bathroom does not settle on surfaces like walls, floors, and ceilings inside the bathroom, leading to the build-up of mold and mildew. They also rid the bathroom of unpleasant odors.

Now if these fans vent into our attics instead of outside the house, we will need to deal with mold issues in the attic, which could spread through the HVAC system and pose a health risk for your family. Then, there is the wood rot that is bound to set in with time, not to mention the burden the warm air will put on the HVAC system.

It is, therefore, always a good idea to consult specialists and find out the most efficient and affordable way to discharge these vents outside your home.

Can I vent my bathroom into the attic? was last modified: October 6th, 2022 by Narayan Shrouthy
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