Do I move a bathroom fan vent, or build around it?
I’m involved in an attic renovation and have noticed that the bathroom fan vent runs in a long, convoluted span that comes out at a wall before exiting the side of the house. I think it was likely run in this way in order to hide it from view.
I’m planning to close up all the attic walls, including this one, with closed-cell foam insulation, and then add drywall.
I imagine there may be issues with adding spray foam around this insulated vent tube, and I don’t think I can add drywall without crushing the tube. Would it be possible to sister 2x6s to the studs in order to deepen the wall cavity? Or should I just go ahead and try to create another exit for the vent? If creating another exit for the vent, any obvious do’s and don’ts in terms of where and how to place?
Thanks for any guidance here! Photos attached.
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Replies
My preference would be to move the vent, then "replumb" the duct using insulated rigid duct along a more direct route. You'll get better performance from the fan that way, and you'll also simplify your project.
Bill
Thanks Bill. From the looks of it, I can come up directly from the vent location in the bathroom to the roof, staying behind the knee wall and running rigid duct directly up from the vent location in a straight line to the roof, then attach my exhaust vent right there on the roof. It seems so obvious that it makes me wonder why on earth they did it the way they did, snaking the duct around to the dormer and out the side. Maybe worried about placing the exhaust vent on a steep roof and more exposed to the elements?
My guess is that they had easier access to cut the hole for the vent and make the connection from where they put it. It's often difficult to access attic spaces, so sometimes weird things get done to try to make the work easier.
In your case, I think going straight up to the roof is the best way to go. Do check if your fan is OK with a 90 fitting mounted right on the fan housing though -- some like to see a little bit of a straight section before the first bend. Be sure to insulate the duct too. I usually just use the insulating "sock" pulled off of some flex duct for this purpose: I slide the insulating sock onto the rigid duct. I tape all the ductwork with foil tape prior to insulating too. Tie the insulating sock off at the underside of the vent to make sure it doesn't slide down over time too.
Bill
Thanks! I'll try tackling this over the weekend. Hope you have a great 4th.
I have two packs of Costco bratwurst to grill. Love those things :-) We're supposed to have good weather too, so should be a good 4th.
Bill
I'm attaching three more photos as they show the various options for my new exhaust vent. I can come straight up from the fan and go out the roof, a distance of about three feet. I can go out to the gable wall, a distance of about four feet. Ideally, I'd like to just redirect the current insulated duct as it appears to be working just fine. Any recommendations on best route, all else being equal?