Best way to vent a bathroom fan using insulated flex duct
MM1973
| Posted in General Discussion on
Venting a bathroom fan to the roof, I am reading conflicting opinions on how to prevent condensation.
1. We are installing Panasonic fans, good quality
2. Using flex duct, insulated
3. Venting to the roof
4. Bathroom is at the front of the house, vent is just over the back roof about 15’ away from the fan
Should the line be hung in as straight a path to the roof vent as possible OR with bends to keep any condensation from running back to the fan?
Replies
There are several good articles on the topic on this site, including this one: https://www.finehomebuilding.com/2018/03/01/bath-fan-venting-cold-climates
The short answer is to duct the fan in as straight a path as possible, but there's more to know.
Provide as straight a run as possible.
Best if you can use rigid duct.
Make sure the bathroom door is undercut properly. This is for the replacement air supply. If there's not enough replacement air, the fan draw will be limited and too weak to eject the humidity. Then the condensation will pool wherever it can. FYI - 1/2" undercut is NOT enough. 3/4" is a lot better.
Frankie
In addition, I install a back draft damper In the run, as most unit flappers are just that.....flappers. There are dampers available this application.
Put the fan on a timer and run 15 to 30 mins after showering.