Bathroom fan vent through roof --straight up?

domh · 10-04-2012, 11:41 PM

I have a bathroom fan that needs to be vented through a hip roof. I am using rigid vent. I have the opportunity to pretty much go straight up to get through the roof, and it would be less than a 36" run.

Is it best to just go straight up?

Or should I run horizontally for a bit and then go straight up?

Thanks for any tips!

Fairview · 10-05-2012, 12:12 AM

Air exhausted from a bath can have relatively high dew point temperatures so if possible it's better if you can run it horizontal to the soffit with some down slope so the condensation in the pipe can drain to the outdoors in colder months.

federer · 10-05-2012, 01:26 AM

we ran ours straight up through roof but our run is only about 14inches

joecaption · 10-05-2012, 07:05 AM

For that short a distance as long as you insulate the pipe it will be fine.
I use PVC as the vent pipe so there's no rusting.

Fairview · 10-05-2012, 07:27 AM

In this application insulation is of little value without a heat source. We can look at the bath mirror condense at 75°F and have a good idea what a pipe in the attic at say 45° is going to do. Immediate water draining back unless the fan is way better than the ones I've seen.

JohnC20 · 10-05-2012, 08:22 AM

Quote:

Originally Posted by Fairview

Air exhausted from a bath can have relatively high dew point temperatures so if possible it's better if you can run it horizontal to the soffit with some down slope so the condensation in the pipe can drain to the outdoors in colder months.

This is interesting. I didn't think of this. I have the same issue as the op of this thread and is an upcoming project.

Thanks!