Hi All,
I have a bathroom fan that is rated for use above the bathtub (wired to GFCI circuit). Due to the location of windows and doors it seems best to vent this through the roof but since it will be located so close to the exterior wall and the roof edge I am a bit confused. What is the general rule of thumb regarding roof vents and the edge of the roof?
Thanks.
Replies
Assuning you have an asphalt shingle roof, you could put it as close to the edge as the framing would allow. Make sure you seal down any small shingle pieces.
If you live in a heating climate, don't run the vent straight up. You'll get condensation dripping back out of the fan. Run it horizontally for a foot or so. If there's an option of running it through an exterior wall instead of the roof, take it.
Vent, or pipe, even the ac drain, don't look good breaking the roof line. I would step the vent away from the edge. I had torrential rain bouncing off the roof (3 1/2 pitch) shingles and leaking around the vent cover. I added more sheetmetal cover, but if you are near the wall, use the wall vent. Depending on the cfm of the fan, you may be allowed longer pipe, especially using metal duct with a straight run.
I should add that the bathroom has window (removing it is not an option right now) and there is a bedroom window on one side and the backdoor on the other so I do not have 3' span ( I believe this is required by IBC) along the wall from the fan's location in any direction for at least 8' but at that point the attic ends due to cathedral ceiling.