I am installing a exhaust fan in a bathroom and the only way out for
the vent is through the roof. Can you point me to a resource that
describes how to do that? I assume it's more complicated than putting
some caulk around the edge... My roof is asphalt shingles.
Many thanks in advance!
On Mon, 26 May 2008 23:24:15 -0700 (PDT), Aaron Fude
Buy a vent cap type of assembly. They will have a door to keep wind
from blowing back in on windy days, and a big flange you weave under
your shingles. Once installed, you seal it down with roofing cement.
You can usually find such kits with the vent hose included.
When I had my roof re-done a few years ago the roofers took out the dryer
vent (which went straight up from the center of the house), decked over the
spot and put down shingles. I didn't realize the dryer was venting into the
attic until some time later.
Anyway, I was faced with the same conundrum as you and was reluctant to put
another hole in the roof.
I opted for about 30' of 6" PVC to run the vent to the closest soffit.
Here's a trick: Go UP into the attic about two or three feet, then a
continuous slope downward to the soffit. That way, most of the fumes that
condense will drain downhill.
If, that is, you can even get their. I must have one of the few
houses in the world that doesn't have four inches of clearance between
the top of the wall and the roof deck. The hole in the roof isn't a
big deal; this is roofing, not rocket science.
Here are a couple reasons you don't want to do this.
For more, do a search on "attic dryer vent" and maybe add mold.
There is a reason that venting the dryer, bathroom, or anything else
directly into the attic is a code violation.
Worst case, you could lose your roof--and I've read of it happening in
only a few years.
Most roof leaks are indeed caused by roofs :-)
Yea I know what you mean though. I've never had anything leak so far that
I've done - stacks, vents, plywood replacement, chimney flashing, wall
flashing, and an entire 26sq roof with combos of everythig including
valleys. With someone not too familiar with roofs, improper vent install
(aka this outta be good enuf, or I didn't know that) is always a
possibility. Also, just walking on a roof not knowing to look for nail
pops, especially where you are stepping, can cause leaks.
Running out a gable can be much safer. But they still have to be aware of
things like maximum code length, bends subtract from OA length, length
reduces airflow, make sure there are no sags to collect moisture,
insulating the hose may be necessary, and so on.
As soon as that hot, humid air is chilled by the cold in the attic, it
become condensate and return to the fan.
I say take flexible line almost immediately toward the nearest eave,
and after making the angle, transition to 4" Schedule 40, with a
bit of slope, and then at the eave, change back to flexible to go
And put a 2x4 under the Schedule 40, propped up to maintain the
or the PVC will sag from attic heat in the summertime.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.