Drafty Bathroom Fan

[Dragster Racer]

Okay. Not a garage question really. But here it goes.
Just had a new home built. R19 with wrap on walls and R38 ceiling blow in fiberglass. I'm having a heck of a time with drafts though. First, the master bath has a closet for the toilet with a fan, and then a fan outside of the shower. That shower fan has cold air falling from it like crazy. Of course it has been around 0F here for a couple days. It is making the bathroom pretty cool though. Now the closet doesn't have a duct, so it can get cool with a window in there.
If the garage door is open and you open the door to the house, it seems like the door just blows in hard. I just hate drafts, and I have to start somewhere getting them tied down. The bathroom fan has a flapper at the fan, and the wall outlet outside has flappers also. They tend to make noise when the wind is out of the right direction. The duct seems to be covered by the blown in insulation in the attic. Where do I start here? I can go to the contractor, but I would like to be a bit educated before going there.

 

[tomroblee]

There are several possibilities:

The flappers could be missing

The flappers could be installed in the wrong direction so that the outside wind pushes them open and the fan pushes them closed.

It's possible that the duct isn't properly attached to either the fan or the wall flapper--or that it leaks.

It's possible that your house is too tight and there isn't a sufficient source of make-up air. If you have a gas or oil furnace or water heater they are all venting to the outside. You may also have multiple fans venting air outside (two in the bath that you described plus more in other bathrooms or the kitchen). Make-up air has to come from somewhere, and your bath fans may be the source with the least resistance.

If all else fails, a piece of duct tape can seal off the fan during really cold weather. You could probably use some of the humidity from your shower in the house this time of year anyway. No comments about the toilet closet.

 

[KINGY2]

i had the same problem and i am in a very wind location .
new house i tried everything finally i closed off the vents permanently and disconnected
the fans at the switch .....no more noise or draft and the moisture is removed with
the air exchanger .
those 2 bath vents i had were like having a window open in the winter .
an enormus loss of heat .

 

[Dragster Racer]

Flappers present. One is visible and correct. The other I thought I checked when I installed. But I would bet the inside one is stuck/frozen.
The house should be tight. The gas water heater and furnace do have outside air supplies, as does the fireplace.
I really could see some cross talk with the bathroom fans. I may very well seal them during the winter. Hopefully not too much humidity in the toilet closet!
Thanks for the reply tom.

 

[nate379]

No vent in teh bathroom is a bad idea. Just asking for mold.

 

[tdkkart]

A couple weeks ago I was doing my business in our master bath. It's cool in the upstairs of our house anyway, and always has been especially cool in this bathroom, which I attributed to it being on an the outside NE corner of the house. This particular day it seemed excessively cool.
After I finished up I started investigating and found cold air pouring out of the ceiling vent fan?? Of course, there was a strong NE wind blowing, and this fan is vented out the east wall, 3 or 4" PVC pipe with a downward facing elbow on the end.
A square of "press-n-seal" plastic wrap over the fan grill, and the bathroom is much warmer. It is dry in the in house in the winter anyway, so I'm not terribly concerned about a moisture problem.

 

[Scotto]

This type of insulation will work the best to keep the cold air out of your ducting:

Also, what kind of flapper do you have on the outside of your house? The 3 or 4 flap type don't seal very well at all. There's a few others that seal a ton better.

 

[Falcon67]

The back bath has a fan with the cheap plastic 3 flap seal. The vent faces north, under an eve. Have not noticed any problem with back drafting in that fan. I wonder if your problem isn't still some kind of negative pressure issue. Our house has additional insulation, but it is way far from anything called "tight". They didn't build tight in 1926.

 

[Dragster Racer]

Thanks for the replys all! I could believe that the flappers outside don't work that well the way they blow in the breeze! Must be something better.
What all can cause negative pressure? The lp appliances have thier own outside air source, so that should be it should it? Fireplace has outside air source and chimney, and the problem exists when the flue is closed. Even with good insulation and wrap and vapor barrier, I do get some cold air coming if from outlets. I can seal those with foam and the pads, but what the heck?

 

[Falcon67]

That's a good question, given the notes that all your air burners are fed from outside.

You might think about going to a roof jack that hugs close to the roof with an internal damper. Or maybe a better set of flappers (??). Maybe a deflector of some kind installed in front of the exit to ward off direct wind blasts.

This is our forecast for tomorrow - I'll check the back bath fan and see how much air is coming in. It uses maybe 3' of uninsulated duct and the outlet faces due north. My wife keeps it cold in the house, so whadda I know from air leaks

"Wednesday Night: Areas of freezing drizzle. Mostly cloudy, with a low around 21. Wind chill values as low as 7. Blustery, with a north northwest wind 10 to 15 mph increasing to between 20 and 25 mph. Winds could gust as high as 40 mph."
"Thursday: Partly sunny and cold, with a high near 26. Wind chill values as low as 5. North wind between 15 and 20 mph, with gusts as high as 35 mph."

All our systems are fixing to get tested.

Note - In my daughter's new expensive custom home, the builder used the lowest grade fans in the bath and didn't even bother to duct the exhaust outside the attic.

 

[Dragster Racer]

It is a wall exit, not roof. And I think that possibly the protector would do a great deal of good. I need to see if they make them in our house color, and if not, find some spray paint!

 

[Falcon67]

Late followup - never had any issue with drafts in the back bath fan.

 

[sillyhillbilly]

Flappers present. One is visible and correct. The other I thought I checked when I installed. But I would bet the inside one is stuck/frozen.
The house should be tight. The gas water heater and furnace do have outside air supplies, as does the fireplace.
I really could see some cross talk with the bathroom fans. I may very well seal them during the winter. Hopefully not too much humidity in the toilet closet!
Thanks for the reply tom.

in winter the air is dry anyway, so a little humidity will be good