Adding exhaust fan to 1st floor bath.....

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Chrisexv6

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Mods feel free to move this if its in the wrong forum.

Planning a remodel of our 1st floor bathroom (house is 2 floors, so above this bath is another finished bath). It currently has no exhaust fan and I wanted to add one during the remodel.

Im not sure how to vent it out though.

Do I put a 4" hole in each joist between the bathroom and outside, including the rim joist? That worries me in regards to structural integrity.

Do I convert to rectangular duct and go down the inside of an interior wall to my basement, and then out the back of the house? Might work, but Id have to worry about how long the run was.

Or do I just get a wall mounted fan and hang it off the side of my house? (least attractive option because the area it would hang is a breezeway and is right near the most used entry door, so it would be visible and not too great looking).

Opinions/other ideas would be appreciated.

Thanks.

-Chris
 

Jadnashua

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a 4+" hole in each joist is not a good idea!

There might be an option to go up, but it would entail tearing more walls apart, either through the roof, or an end wall.

How far away is it if you go along the joist runs? If there's no insulation between floors, it might be essentially clear until you hit an outside wall. You'd have to compare that to the max length run the fan supports.

The easiest is probably a wall mount. Note, some of these are very quiet, so other than the exhaust smell possible (now, how often is it really that bad - it most often just for moisture control), maybe unnoticeable. Panasonic has a really good rep for quality, quiet fans. Fantec is another company, but many of theirs are remote, not through-wall.
 
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Chrisexv6

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Yeah, my tiny amount of common sense says 4" holes in joists are bad :)

I havent taken a stud finder to the ceiling yet so I dont know which way the joists run. It would be the difference between a 8' straight shot to the rim joist vs. a 15' straight shot to the rim joist, but that has to go over another room with a finished ceiling so Id have drywall work to do there.

It *might* be possible to go straight up inside the wall cavity, but I then worry about cutting out a decent size chunk of the top plate of the 1st floor bath wall, along with the sill plate of the 2nd floor bath wall. At least if I went DOWN into the basement I would only be affecting the 1st floor bath. But Im not sure DOWN is acceptable based on the goal of getting rid of moisture (and the occasional funky smell).

Thanks for the tip on Panasonic fans. Ive seen them, just wasnt sure of the quality.
 

Jadnashua

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Down probably isn't a great idea...the air is likely to be hot and humid, so it will want to go up. Still, the fan could probably do it, but at decreased efficieny.

The distances you mention are likely within the limits of the fan, but you'd have to check their specs carefully. Except in the bathroom, you may not need to open up the ceiling in the other room if it isn't insulated. You'd need enough room in the bath to insert 5' sections of rigid duct and then just continue to push it along and add a new one until you reached the outer wall. Then, a big holesaw into the right bay. You should be able to then get it out and mount the louver on the end. Wiring or recessed lights could confound that effort as would insulation. I'd poke a hole in the ceiling of the bath (if you don't already have one, stick my head and a light up there and check out the lay of the land...
 

Chrisexv6

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It would be an unusual house if the upstairs joists ran a different direction from the downstairs ones.

Thats what I was thinking, and thats what I was worried about. That would make them in the wrong direction for the easiest install.

Its possible the other direction might work OK, I would just have to be very close when I make the hole for the exhaust vent, as I would be making it from the outside in. There shouldnt be insulation above the other room, and there is definitely no electrical there (house has no in-ceiling light fixtures except for where Ive added them in 2nd floor)

Further complicating it would be the fact that the 2nd floor is cantilevered over the 1st floor by about 2'. So I would probably be coming out somewhere in that cantilevered soffit area, then making a 90 to go straight down. Would look nicer but Im guessing harder to make an accurate hole.
 

Southern Man

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....

Further complicating it would be the fact that the 2nd floor is cantilevered over the 1st floor by about 2'. So I would probably be coming out somewhere in that cantilevered soffit area, then making a 90 to go straight down. Would look nicer but Im guessing harder to make an accurate hole.

You now know that the joists run: in the 2' direction of the cantilever. So you run your vent line in the joist cavity and out to the soffit. There should be solid blocking between the joists at the wall below, then a rim joist on the outboard end below the second floor wall. You can cut a 4" hole in the blocking and rim joist no problem, then exit out the bottom of the wall siding with a conventional flap vent.

You'll need to remove a soffit panel to get access to the blocking and rim.
 
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