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I've asked this question before but would like to ask it again, as I'm now more certain of what I'm up against. Also, let me preface this post with "wall mounted fans are not a viable option."

I need to install a ceiling bath fan in each bathroom. The reason I'm selecting a fan-only model is because I want to keep ample light in each bathroom. I'm probably going to purchase 2 of the NuTone Ultra Silent™ 110 CFM Bath Fans from Home Depot. Their exhaust port is 4" round. I would use a dryer elbow directly on the fan, then run rigid 4" vent pipe straight up through the ceiling. What type of flashing should I use on the roof and how do I fasten it to the roof? Most importantly, how do I make sure it is waterproof? Should I use caulk and no screws or caulk with screws, then kool-seal the area? All inputs appreciated!

Thanks, Keith.

A buddy and myself installed a Panasonic Whisper Ceiling Bathroom Fan FV-11VQ5 in each bathroom ceiling and vented through the roof. The total for both was $265.70. These are extremely quiet and pull LOTS of air. Outstanding investment on my part.

1. Cut out bathroom ceiling area of about 2' x 4' to allow plenty of room for installation
2. Drilled a hole in 3/4" plywood (approximately 18" x 23") for duct to pass through and then mounted this 3/4" plywood underneath roof skin between rafters
3. We built braces made of wood and secured the fan
4. We wired them so that the fans comes on and goes off with the light fixture.
5. Installed dryer vents on roof using Geo-Cell 2300 caulking; (the screws passed through the plywood in step 2)
6. Covered bathroom ceiling with white shiny tile board from Lowe's.

Keith

Those NuTone/Broan Ultra Silent models are very good units. They have spreader bars that make attaching to trusses easy. That part is self explanatory. But I would do a lot of the install from the roof, after cutting the appropriate hole in the ceiling. I would look at the direction that the fan exhaust is coming off of, and center my roof hole to the vent. On top, I would be using a 14" x 14" passive vent, basically just a large square cap. I will cut a 12" square to reach through and do my electrical connections, attach the spreader bars and attach the elbow and flex or solid pipe (whatever you decide to use). Then I will make some type of cross member from 2x2 to go from the top of one truss to the other and attach the top of the vent pipe to that, to keep it stable. I will have the pipe extend 1/2" above the roof. I will then close off the 12" hole around the vent pipe with flashing aluminum, or some type of galv metal. On this piece, you will want to use bugle head screws to keep as flat of a profile as possible. Then when installing the vent cap, you want to use something between the vent and the roof to keep the metals from touching. Eternabond double stick roof tape is ideal, because it is very aggressive adhesive, water proof and will insulate the two metals from each other. Lot's of polyurethane or butyl rubber caulk can do this too. It can be as simple as a 13" square of 30lb roof felt. Just something to keep the electro-chemical reaction of the two different metals from happening. I say 13" because you really don't want the paper sticking out from under the vent and you want a little roof for sealant. Fasten the vent to the metal roof with hex head screws, 3" o.c. I use 1/4" head #8 x 1/2" screws on an original install to allow for moving up to the 5/16" #10 heads in a future repair. I'll put a bead of caulk around the under side edge of the vent cap and a heavy amount of caulk on the top over the screws and the edge of the vent cap. I use Tremco Vulkem 116 one part polyurethane sealant and highly recommend it. But anything from PL or OSI in a roof/flashing sealant should work well also.

Sometimes you might want to add small pieces of plywood to the trusses to get the spreader bars more wood to fasten to. Depends on the type of spreader bars the fan comes with.

That's how I do it anyways

JD