Bathroom exhaust fan installed in the floor, anyone?

DinahVJuly 17, 2014

We have a half-bath without any exhaust fan (it has supply air vent only). So it stinks on occasion. We'd like to install an exhaust fan, but the half-bath is located in the middle of the first floor, and there is absolutely no way to vent it outside through the ceiling (long to explain why but really, no way)
The house is pier-and-beam though, and it would be very easy to install the exhaust fain in the floor and vent outside of the house by running the duct vent through the crawl space under the house (this is how our dryer is vented, it's located in the room next to the half-bath).

Do you know of any code such floor-installed exhaust fan might violate? Have you ever done or seen a floor-installed exhaust fan?

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Don't know about code, but I doubt it would work. Hot air rises, the steamy warm moisture ridden air you you want to remove will not be where you are removing air.

If it's not otherwise possible, you could put the vent intake in the ceiling and then run it down an interior wall and then out as you describe, using a remote fan unit.

    Bookmark   July 18, 2014 at 2:04PM
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It violates the code of common sense.

In addition to not being very effective, think about all the crap that is going to fall down into it and bugger up the blades and motor.

Does this bathroom have an exterior wall ?

    Bookmark   July 18, 2014 at 8:47PM
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Babka NorCal 9b

You mean there is NO space between the ceiling and the floor above? Could you run the ducting up thru a closet or whatever is up on the next floor?

The fixtures in the bathroom must be vented, so there IS a way up, even is it is only 3.5" wide.


    Bookmark   July 18, 2014 at 9:30PM
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Babka: ha. they (fixtures) are vented to the space above, (which is under the stairs), not to the outside - which is against the code, I know that much. I guess they (whoever added this bath) ran into the same problem with venting fixtures as we are facing trying to figure how to vent the exhaust fan. and maybe that's why there is no exhaust fan to start with.
The bathroom is under the staircase whichi s in the middle of the house, and there is space directly above it because the ceiling is short. But then the ceiling height changes as you go to any neighboring room (the rest of the house around has much higher ceilings). Basically, you can put the duct vertically through the ceiling above the bathroom, but then as you turn it 90 degrees towards in the direction of any outside wall, it would have to come out through the wall of any room around, not in the ceiling above the rooms. And if you try to go higher with the duct so that the turn is at the level of the over-the-ceiling space for these rooms, then the duct would have to come out through the staircase! Hard to explain, but I hope you go the picture.
Also, even if we could somehow get the duct to the space over the ceiling of any adjacent wall, then we still can't open up that high ceiling to run the duct further because it has some fancy beams and moldings (house is over 100years old) so we cannot touch the ceiling. That's why I wrote "absolutely no way" for the ceiling route

Unless, as somebody above suggested, we place the fan in the ceiling, but run the duct through the wall down to under the house (actually through the under-the-stailrcase part as the stairs go down). But as far as I understand that comment, we will have to install some inline fans in the duct to keep the air moving down...

    Bookmark   July 19, 2014 at 12:27AM
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xedos: unfortunately not, it's dang in the middle of the house, under the staircase. If it did, we would use a through-the-wall exhaust fan like we did in the upstairs bathroom (which didn't originally have exhaust fan either - I suppose previous owners liked the smell of their crap, lol).

pprioroh: "remote fan" - do you mean one of those in-line duct fans, to help keep air moving down?

    Bookmark   July 19, 2014 at 12:33AM
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Yes - an inline fan so the fan itself can be remote mounted elsewhere and all you need to do is run the ductwork in the interior wall and over ceiling to the vent

    Bookmark   July 19, 2014 at 11:34AM
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Babka NorCal 9b

Ah, now I understand your dilemma. We had a similar situation with a basement toilet/sink under the stairs when I was growing up. No fresh air from anywhere down there. But with a family of 5 and only one bathroom, that second toilet was a godsend, odors and all.

Lots of potpourri? Air freshener with a cute little fan? Or a "no pooping" sign? Sorry I cannot be more helpful.

You are in a very unusual situation there aren't you. ;-)


    Bookmark   July 19, 2014 at 2:56PM
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My sister has a similar problem on her main bath, although a different set of construction circumstances. I recently suggested a non ducted recirculating fan for her, would this be better than nothing? I am only familiar with Broan, although there may be other manufacturers. HTH

Here is a link that might be useful: Recirculating fan

    Bookmark   July 30, 2014 at 2:38AM
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suburbanjuls: Oh, thanks! I think it would work - if they actually take the odors out. I had no idea that such fans exist for the bathroom to start with! There was a thread somewhere on this forum where a person was asking about "downdraft fan equivalent" for the bathroom - nobody there told him it exists!

    Bookmark   July 31, 2014 at 1:17PM
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Hi DinahV,

I believe it operates on the same principle as recirculating vent hoods that use a charcoal filter to pass the air through, thereby removing odors. Yes, you would have to replace the filters, but if it were my hall bath I would seriously look into this type rather than do all this complicated construction. I suppose only you can determine which way is better suited to your home and needs but I would have a hard time justifying an expensive solution for a hall bath, even if it is the most used one.

    Bookmark   July 31, 2014 at 1:31PM
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no, totally - at the price of this fan it is definitely worth the try before attempting anything more elaborate.

    Bookmark   July 31, 2014 at 1:58PM
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DinahV, we lived in a condo once that had a very unusual set up. In each bathroom, there was an exhaust fan in the wall next to the toilet slightly above (maybe 6") the level of the toilet seat. It was right next to where it was needed most, if you get my drift. It seemed to work very efficiently.

Could you put a fan in the wall as I described above and run the ductwork down to wherever you would have run it if you had put the fan in the floor? I believe there is rectangular ductwork that will fit between the studs but ask an HVAC professional.

    Bookmark   July 31, 2014 at 2:08PM
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