Cold air comes in thru bathroom fan - why?


  #1  
Old 11-08-08, 07:19 PM
tucats's Avatar
Member
Thread Starter
Join Date: Dec 2003
Location: Halifax NS CAN
Posts: 59
Received 0 Votes on 0 Posts
Cold air comes in thru bathroom fan - why?

I am asking this question because my son is asking for help again and you guys have made me look smart before!
He has live in his house for about 5 years and every winter his upstairs bathroom is freezing (under certain conditions, cold, wind direction etc). Up to now they have just lived with it, but they have a new baby and that changes things.
Today I went over to have a look-see. The fan is a pretty decent one (Broan 90CFM) and is in the centre of a narrow bathroom about 4 feet from an outside wall (in 2 directions). From outside we cannot see a vent for the fan, and there is no roof vent. I suspect it is being vented into the soffit/roof overhang area which would be a short run of ducting. (4.5 ft at best)
Here are my questions:
1. Should there be a directional flapper at the end of the ducting (outside vent) to stop cold air from coming in when the fan is off?
2. Is there a fan made with the flapper at the fan housing end.
3. Do you think just changing the fan to a newer/better model will change anything as far as a cold draft goes on the next cold windy day?

P.S. I don't mind a cold draft once in a while... Beer 4U2
Thanks for any and all comments - Mike
 
  #2  
Old 11-08-08, 07:30 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
Flapper (damper) should be built into the fan.
 
  #3  
Old 11-09-08, 07:32 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
Hi tucats, As airman said fans most often have a flapper built in. But the flappers in the fan or outside as part of a vent hood never work very well. When you have a through the wall vent, they make better devices. But with yours just venting into the soffit it is probably just an open flex duct.
The best solution is to run the vent to the outside. Venting into the soffit results in most of the warm moist air going back up into the attic, which is not good, moisture, condensation. You can probably look closely at the bottom of the roof above the area where the vent is and see some discoloration, often the wood is black.
If you can get it to vent through an outside wall, there are ball or can type covers that allow the air out, but close tight when not in use. Running the vent to an outside wall can require some important details, so check back if that's an option.
GL
Bud
 
  #4  
Old 11-09-08, 10:16 AM
tucats's Avatar
Member
Thread Starter
Join Date: Dec 2003
Location: Halifax NS CAN
Posts: 59
Received 0 Votes on 0 Posts
Ok, thanks guys. I will look into it a bit more to see exactly what's going on up in his attic and where it's venting to. Will get back to you later on this. Cheers.
 
  #5  
Old 11-09-08, 09:56 PM
M
Member
Join Date: Jan 2008
Location: Tennessee
Posts: 479
Received 0 Votes on 0 Posts
fan problems

If the fan is working you might want to remove and clean the backdraft damper to get it to seal again. As to why you have that much air coming in you obviously have negative pressure in your home, a little bit is not too bad, if you have a lot of negative pressure it can cause indoor air quality problems. This can be caused by something as simple as a fireplace with a tall chimney with an open damper or improper soffit venting.
 
  #6  
Old 06-04-09, 04:35 PM
B
Member
Join Date: Jun 2009
Posts: 1
Received 0 Votes on 0 Posts
Question hope you're monitoring this thread....

Originally Posted by Bud9051 View Post
Hi tucats, As airman said fans most often have a flapper built in. But the flappers in the fan or outside as part of a vent hood never work very well............................
If you can get it to vent through an outside wall, there are ball or can type covers that allow the air out, but close tight when not in use. Running the vent to an outside wall can require some important details, so check back if that's an option.
GL
Bud

Hi Bud - if you see this reply, or if anybody else that knows does, could you point me to a web page that has these type covers ? I googled ball and can covers but didn't find anything that was relevant and have no idea what they are to begin with. Thanks, Brian
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: