Our bathroom extractor fans are vented into the attic of our ~70yr old house in Philadelphia. According to our home energy auditor this is pretty common here. We want to vent these to the outside before we proceed with insulation which might involve spray foam spray foam bringing the attic into the envelope of the house.
The best solutions seem to be infeasible:
- Go straight up through the roof. We have a slate roof and I have concerns about the aesthetics, cost, and impact on an older roof.
- Go out through the soffit. We have minimal soffit space to install any vent, so we'd have to go through the stone wall. Doesn't sound like fun.
We have a whole house fan on one gable of the house which is not stone. This seems like the only easy place to get to the outside.
Unfortunately this is a pretty long run (25 ft plus). Assuming we use rigid and insulated pipe, how far can we run a vent pipe?
Best Answer
In rooms with no shower or bath, 25' should be no problem. Just run the smooth wall pipe and go with 4" diameter.
For the rooms with showers and baths it should not be a problem if you can get it go vertical into the attic, then slope down towards the exit. Even at 25' it should not be a problem. You could even possibly use ABS pipe for the sloped run because moisture will condense in the pipe and create water. This water, however, should drain and evaporate and not cause a problem.