I'm under contract for a condo in a large building with drop ceilings in the bathroom and no vent fan. I am told that some units have external ventilation capabilities and some don't but I don't know about mine yet. If I'm not able to vent externally, is there any way I could reasonably still install a vent fan? Are there any designed for this situation perhaps? Is it possible that the electrical situation would be a limitation as well?

  • 3
    For a simple exhaust fan or exhaust fan + light (as opposed to heat + fan + light combo) power is a non-issue as the existing bathroom lighting circuit will have enough power. And drop ceiling means running the wires should be easy. But as the answer says, you must exhaust to the outdoors. Commented Feb 15 at 2:21
  • "not able to vent externally" : Need a 4" core bit or hole saw. That's how your neighbors got theirs.
    – Mazura
    Commented Feb 16 at 6:29
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    @Mazura: …and an exterior wall. If the OP's bathroom doesn't have one, that makes the project significantly more challenging. Commented Feb 16 at 23:58

3 Answers 3


You need to exhaust the bathroom via a duct in the ceiling void and through an outside wall. You can't just push bathroom air into the void ... it will cause mold up there and push humidity and bathroom smells into other rooms. To exhaust through an outside wall you'll need to talk to the building manager. You can't be the first one to want this!

Yes it will need power. It's not a limitation. It's just a thing you'll need to do, and you should talk to an electrician about that.

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    Yeah, living in a condo in the US should (in most cases) require a licensed electrician to do the work. You're allowed to burn down your own house with shoddy workmanship, but that right stops when other people live in the same building.
    – FreeMan
    Commented Feb 15 at 15:36
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    @FreeMan ya and let's hope this isn't in NYC. It's a $6000 project. Close your eyes and chant "assistant sidewalk flagman" 20 times. Then go buy a window fan. :)
    – jay613
    Commented Feb 15 at 16:04
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    @FreeMan that sounds good on paper but what's likely to happen is that shoddy workmanship will last until the shod moves out of the own house then the unsuspecting new owner gets hit by a surprise fireworks show. Commented Feb 15 at 17:25
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    A) That's the rules, I don't make 'em. B) that's what a home inspection is theoretically supposed to find before you buy. Then you negotiate repairs by the seller, or a lower price to cover the cost of repairs after purchase. Theoretically
    – FreeMan
    Commented Feb 15 at 17:56

The point of a bathroom exhaust fan is to pull humid air out of the bathroom. That humid air must go somewhere.

If that "somewhere" is another interior space, you're just moving the humidity problem from your bathroom to wherever the fan is venting into. If your fan vents into the ceiling space, for example, you'll have humidity and mold in the ceiling space instead of (or, more likely, in addition to) humidity and mold in your bathroom. And no, that will not be a good thing.

If you really cannot arrange external ventilation, your best (and basically only) alternative is to install a condensing dehumidifier instead. Instead of venting the humid air outside, these work by circulating the air through a system that pulls water vapor out of the air (by cooling it down and then reheating it) and then blows the now dry air back into the same space it was drawn from.

The main drawbacks of a dehumidifier compared to a ventilation fan are that:

  • a dehumidifier is more expensive to buy and install and consumes significantly more electricity than a simple fan, and also has more moving parts that can break down;
  • the dehumidifier may be noisier than a fan (although there certainly are both quiet dehumidifiers and noisy fans on the market);
  • the condensed water needs to be drained somewhere (not necessarily a big deal in a bathroom, where it can often just be piped down a drain, but more of an issue in other applications); and
  • unlike an exhaust fan, which also helps pull in fresh air through your apartment and into the bathroom, a dehumidifier just circulates the same air already present in your bathroom, making it less effective at getting rid of odors and keeping the air fresh (odor-absorbent filters can help here, if your dehumidifier can be fitted with one).

On the other hand, a dehumidifier has two major advantages over a ventilation fan:

  • a dehumidifier can dry the indoor air dryer than the air outdoors, making it attractive in places that experience a humid climate for at least part of the year; and
  • most importantly in your case, a dehumidifier can work even in spaces from which air cannot be easily vented outdoors.
  • The OP didn't specify half bath or full bath; I wouldn't think a half bath with a small hand sink would raise humidity enough to require a dehumidifier, but it might produce other odors that should be vented outside.
    – supercat
    Commented Feb 15 at 22:43
  • @supercat: Hmm, good point. If it's primarily an odor issue, an air purifier with an activated carbon filter could work. Those filters vary a lot in efficiency, though, so consulting reviews before buying is highly recommended. And the really effective ones can be awkwardly bulky and heavy (since more carbon = better filtration). The filters also do need to be replaced from time to time as they slowly lose their effectiveness. All in all, I'd much prefer an exhaust fan for odor removal if there's any way at all to arrange for it to vent outside. Commented Feb 16 at 7:45

Others already said you shouldn't dump humid air into your ceiling space or other rooms. As for what to do if you don't have a vent that goes outside...

There are duct free "exhaust fans" but they just run your air through a charcoal filter. That may or may not get rid of stank but it definitely won't help you get rid of humidity. For that you need a dehumidifier. I don't have real numbers on this and I've never tried to size a dehumidifier to get rid of shower steam in a bathroom but I would guess you need a pretty beefy dehumidifier to do as well as a moderately powerful exhaust fan.

If you have a window, put in a fan. If you have no way to vent that bathroom to the outside, I'd personally avoid that apartment, there's probably other stuff along the same lines you'll have to deal with. But I don't know if you have the freedom to make that kind of choice.

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