I have a small (7’x10′) upstairs bathroom. The bathroom has a dormer and I was thinking about installing a fan in the ceiling of the dormer and have it vent out through the gable-end of the dormer. Are there any code issues with this? I live near Boston, MA.
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I just did that on my sisters house. Replaced the ceiling because of mold, and while I had it down I put in a fan and vented it straight out to the front of the dormer. This way It was able to run between the 2x6 roof beams. I cut a dryer vent into the front just under the roof and used metal flex pipe. One word of caution; the fan was too tall to fit inside the 5 1/2" allowed by the 2x6 beams so I moved the fan back beyond that area where the flat ceiling was nailed to joists and there was room for the fan. It wasn't a large bathroom (about 8 or 9' long) so the fan centered about 1 foot from the toilet and 3 feet from the tub which was on the outer wall. I also wired it to the light so whenever the light was turned on the fan went on. No mold since. Also used a mold resistant paint by Zinncer (?)
I can't see any reason why it wouldn't be up to code - not that I asked.
In general, the codes don't allow soffit exhausting of bathroom fans due to the issue of humid air being re-introduced into the house, via any soffit venting, and causing moisture problems in the rafter bays.
So, if your dormer has any vents, it might be a bad idea.
I should say that I haven't read the actual code regarding this, so a closer look is in order if there are any doubts.
Jake Gulick
[email protected]
CarriageHouse Design
Black Rock, CT