Bathroom Vent Question

[molo]

Hello All,

I want to install a bathroom ceiling vent. The distance from the ceiling to the roof is only about 3'.

1. Is this far enough distance (I've heard there are minimums for distance from the vent to the outlet).

2. I live in a heavy snow area, is it a problem to outlet the vent out the roof?

3. I'm concerned about cold air entering the room through the vent. Are there some vents that are better than others at preventing cold air from entering the home?

Thanks for any help,
Molo

[Randyj]

Might need to check with local codes or local recommendations. I do know that all vents should be significantly higher than snow depth that is a normal high for your area.... in Alabama a typical vent is about 12" above the roofing.

[Gencon]

The closer to the roof, the better. Roof caps are available that have backdraft dampers in them. Most fans have them as well. This will prevent the outside air from getting in.
With fans, you get what you pay for. A $20-$30 fan will be noisy, get worse and do a poor job.
Install something around the 110CFM area, with a 4" duct. Use ridgid duct, tape all the seams and insulate the duct, sealing everything up tight. vapor barrier over the fan to bring it into the building envelope.
The short distance and the insulated duct will allow some air flow out of the house, past the backdraft dampers. These are both gravity controlled dampers so there isn't much of a seal. This minor air flow keeps the snow away from the opening. When the fan is on, you will notice a large swath of bare roof directly below it.

[molo]

Thanks for the responses,

I want a very powerful vent that doesn't leave any moisture in this bathroom. Any ideas how to tell how powerful a vent is?

TIA,
Molo

[gsfromc]

I know my local Home Depot has a display of fans. Each one is labeled in CFM (cubice feet per minute) of air flow as well as decibel (noise) level. Plus you can actually turn each on to get a listen of the actual noise level. You can really listen to how much quieter the more expensive squirel cage fans are. I spent about $Cdn 150 for one I put into my kids bathroom reno and it is very quiet.

Other retailers may have similar.

[jadnashua]

Most people don't leave the fan on long enough. Leaving it on too long wastes energy. The ideal way to control one is to use a hygrometer controlled switch - i.e., one that monitors the relative humidity, and turns itself off (and on) when needed.