Exhaust fan placed in the floor?

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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Since "hot air" rises, the practicality will depend upon your ability to create a relatively closed system, like the dryer.

    Bookmark   July 17, 2014 at 8:32PM
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Sophie Wheeler

How on earth did it pass inspection? Rooms without windows are required to have mechanical ventilation. Through the roof, or through the wall up high. Not the floor.

    Bookmark   July 17, 2014 at 8:58PM
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hollysprings - this is a good question. It's a 100year old house and I suspect a lot of renovations were done by prior owners without pulling a permit - and this halfbath was one of them, I'm sure.

So you are sure that it would be against code to vent through the floor?

    Bookmark   July 18, 2014 at 8:11AM
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snoonyb - hot air rises, yes. but what about stinky air? That's the one I want to get rig of :)
(heat is taken care of by a supply air vent in the ceiling...)

    Bookmark   July 18, 2014 at 8:13AM
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Methane is lighter than oxygen;

Methane, CH4,16.044

Oxygen, O2 31.9988

So, you would need the supply to operate the length of time, your olfactory senses are "assaulted," winter and summer.

    Bookmark   July 18, 2014 at 9:05AM
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Can you put a powered vent through a wall into another room just to disperse the concentrated fouled air in the bathroom?

If you got supply air in, then I don't see why you couldn't put an exhaust out the floor, it would force an exchange of air beyond the exchange from just the supply in.

    Bookmark   July 18, 2014 at 1:27PM
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Put the vent opening high on the wall or in the ceiling and then route the exhaust pipe down and out underneath to the outside wall. You may need to use a bigger fan to overcome the resistance of multiple bends and increased length-- doing as much of the run as possible in smooth rigid pipe will help. There are tables online to tell you how much to de-rate the fan for a longer run.

    Bookmark   July 18, 2014 at 2:27PM
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Hi. I have seen units with the same problem. These were
3 plexes 2 story with the problem bath down stairs in the middle of the unit. The units were built about in 1990. In construction they installed a re circulator fan that filtered the air through a charcol filter. This was new constructiun public housing in Ca that was inspected. I did not live in the units so I can't say how well they worked. If you go this route make sure you can get replacement filters for it.
Good Luck Woodbutcher

    Bookmark   July 18, 2014 at 4:16PM
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