bath fan freezing issues

Nov 16, 2023 Last reply: 2 years ago 23 Replies

What are the issues with bath fan exhausts in cold regions?



February averages 20F and early February has several sub-Fahrenheit nights. Border between Endicott & Apalachin, in NY Appalachian Catskills. 1000ft elevation.


I would say the only issue is that they blow warm air out of your home that will be replaced by cold outside air, which you will have to pay to heat.

The only purposes of bathroom fans are aiui to remove high humidity after someone takes a hot shower or bath, and to remove odors.

Because of that occasional reason, bathrooms without windows aiui universally have fans that go on whenever the light is on, even when there is no humidity or odor. What a waste, plus the user has to listen to the noise of the fan.

When I bought this house only the bathroom off the main bedroom had a fan switch, so I installed a switch for another (mounted in the light fixture above the mirror. The wires were there already, wire-nutted at that location. I just put a switch in the middle.) and unplugged the third fan. Life has been much better since then.

At my mother's apartment, I couldn't make major changes but I put in a switch with a pull chain. Her life was much better since I did that.

Even without a fan, the water condensed on mirrors will evaporate soon, and by far, not every use of the toilet leaves bad odors to deal with. And the odor will dissipate soon even without a fan.

Once in a while, moisture from the air condenses in the unit or ducting, and drips back into the bathroom. Insulating the ductwork helps.

In my experience, bathrooms without windows have fans with manually actuated switches. I've seen one with no fan whatsoever. It's not up to code, of course, but the owner doesn't care.

I think the only issue in my area of central Nebraska would be that it lets some warm air out. The outside roof cover does a good job of keeping blowing snow and rain out if that's a worry. I don't remember any problem with the fan freezing up.

Yes, I missspoke here, alhtough I was correct later. The small bathroom off of my bedroom was built with a separate switch for the bathroom fan, maybe because it's right next to a bedroom and the noise would bother (not just someone in the bathroom but) people in the bedroom next door. An other bathroom opens to the hall and the powder room is across a hall from the kitchen

I hadn't thought about that. In my house, the only one I know much about, the output from the 2 fans on the 2nd floor go through the attic to 3 or 4 inches below the ridge rail, still inside the attic. I read here that this wasn't proper, but it saved them the problem of putting another hole or two in the roof and then having to cover it, and I don't care because I never use the fan anyhow.

Where the powder room fan expels its air I do not know. The fan is on the far side of the small powder room away from the stack, the empty area where heating ducts go up to the second floor, but I spent a lot of time in the attic looking at the stack when running 110v wire to the attic for a light and a roof fan, and I don't think I saw any little air duct from the powder room. The stack is open at the bottom, tbe basement ceiling, and at the top, what would be the attic floor if the attic had a floor, but it had a 1/2 inch or so layer of plywood between the first and second floors (part of the subfloor for the rest of the

2nd floor, I think).

No room to go down there (even if I had a way to get back up, so I lay on my belly with my 20" arm and 6" drill and a 6' drill bit and a 1' extension and tried to drill a hole through the plywood, while the flexible 6' drill bit bent and took much of the pressure off the tip** but eventually it went through. Then even though the romex came curled I was able to get though the hole and down to the basement.

**(Yes, I know you're not supposed to use pressure but you need some pressure, and drills (dull drills?) that aren't making progress often make a lot more progress with pressure.)

The total length of my arm, drill and drill bits adds up here to 8'8". What's the typical distance from the 2nd floor to the attic in modern houses? Eight feet plus the framing (6"?)? That comes out about right. (I guessed at the length of the electric drill.)

I also put in phone line, but I didn't put in speaker wire or doorbell wire; and we didn't have computers then so I didn't put in CAT-6, and now I'm too tired to do these things so in 3 or 4 cases I just ran the wires down the 2nd floor hall.

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My house has a windowless bathroom. The only fan in there is part of a heater. I've used the heater some times, although I've never wanted just a fan.

I've lived in NY, MA, OK, PA, CT and now in MD. All those homes had bathrooms without a window and none of those states required bathroom fan to be on whenever the light was on. We use the fans only when we need air conditioning. The rest of the year we welcome the additional humidity after a shower, especially in the winter.

But did others living with you wish you had used a fan?

That's a good point. For a while I was leaving the bathroom door open during a bath or shower, and I was cold after getting out. Now I shut it most of the way and open it in steps as I dry off.

(I decided years ago that towels only made a small difference in how long it took me to dry, that I still had to wait quite a while after using the towel, so now I don't use them at all. I just wait.)

If so, they never said anything. In any case, since moving here, we are enjoying the luxury of a "his" and "her" bathroom.

No pressure? I can't imagine not pushing on a drill. I didn't buy million dollar sets of bits though. Why is there such a thing as a drill press?

Big fan of Broan dehumidistats (variable - changes with temp)

If it's at the threshold, farting set them off

Maybe so. My mother liked hot, steamy baths. I don't. I like warm ones, 30-minute baths. There is some condensantion on the mirror when I'm done, with bath or shower, but it evaporates in 10 minutes. If they were hotter or the shower longer, or the house tighter, or all 3 at once, maybe there would be mold without a fan.

I find you need much less pressure if you check the drill is not in reverse before starting.

Or cold temperatures in the house.

I like a ripping-hot, 5-minute shower. I haven't willingly taken a bath since about 1970. Who wants to sit in their own effluvium? (Although I suppose it's better than someone else's effluvium.)

I typically leave the bathroom door open and the fan on when I shower, unless my husband is sleeping in the next room. The latter is the only circumstance in which the mirror steams up.

Not using fans when appropriate causes significantly increased water condensation on windows throughout the house all winter here, resulting in mold growth there.

I have hand cranked timers in both bathrooms. Crank then to 20 minutes or so as you enter, and they turn off after doing their job, whether for moisture or smells.

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