Vent those bath fans to the outside–NOT into the attic

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One of the things we look at in homes is the ventilation.  I’ll write more about that in the coming months.  The short version is that good ventilation is necessary to protect your health and your home.

Wait! You say.  Aren’t you making my home tighter with all that air-sealing?  But I need ventilation to bring air in? 

Yes, that’s exactly what we’re trying to do.  In my view, the perfect home would be perfectly tight, with no “natural” exchange of air—but allow you to determine both the rate of air-exchange, and where an how it comes from.  But we’ll save that for another day.  Right now, I’m going to focus on the bathroom—in part because GreenHomes Advisor John Scipione just found another doozy, this one in Fresno, CA.

Bathroom ventilation is particularly important to remove excess moisture (and heat in the summer).  Pulling out this moisture at its source helps prevent the mold and mildew from growing, and that a good thing.

Most of the bathrooms we see have poor ventilation, either no fans or cheap rattle traps which make a lot of noise but don’t move much air.  Adding a well-functioning exhaust is something I highly recommend.

I’ve talked before (maybe putting the cart before the horse?) about the Panasonic and Renewaire bath fans that I like.  Excellent choices.   And keep making good choices by exhausting the air directly to the outside via ducts, and not just into an attic or some other space in the house.  If your contractor says it’s OK to vent into the attic, the best solution may be to find a new contractor.   Dumping moist bathroom air into the attic can help rot your roof.  And remember those ice dams we’ve talked about?  In snow country, exhausting your bath fan into the attic—with all that warm air—is a recipe for ice dams (and more on ice dams).  Don’t do it!

Three bathroom fans exhausting into an attic

Please don't exhaust your bathroom fans into the attic!

Which brings me back to what John found in Fresno.  Exhausting one bath fan into the attic is bad enough.  How about three?  And if you’re going to do three, why not tie them together to concentrate the problem?  At least the installed helped with a well-organized bad practice.  Don’t do it!  Vent to the outside.

Thanks,
Mike

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5 Responses to “Vent those bath fans to the outside–NOT into the attic”

  1. James Says:

    Great article! Thanks for sharing

  2. Mike Says:

    I am pseudo new to the installation of bathroom fans and in regards to the bathroom ventilation. I am curious if you know if I have to use a use 3-wire cable to separate switches for the operation of the fan and light functions? The unit includes a heater and/or timer, is additional cable required? I am not replacing an existing fixture and do not require an independent switch operation for the fan and light.

  3. ninemsn Says:

    Great post.

  4. Irish Says:

    Howdy! I just would like to give you a huge thumbs up for the excellent information you’ve got right here on this post.

    I will be returning to your blog for more soon.

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