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Bathroom fan heat loss


Northern Mike's Avatar
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04-09-12, 10:52 AM   #1  
Bathroom fan heat loss

After doing a little bit of investigating and testing, I have nailed down a major heat loss on my second floor to be the bathroom exhaust vents.
I have two full baths on my second floor that go straight up into the attic, join together, then exit out a dryer vent on the side of one of the attic dormers. I noticed this weekend when working on some eaves that the dryer vent has missing blades so it's a perfectly straight up and out path for the warm air.

So now I'm looking for a solution to solve the warm air (while the fan is not in use) from excaping straight out.

I am thinking something like this may be an option, any thoughts or other suggestions?

 
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Pilot Dane's Avatar
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04-09-12, 01:18 PM   #2  
Most vent fans have a damper to allow air to exit but stop wind & drafts from blowing in. They help but don't seal tight so there is always some air leaking by and any air movement from the fan or drafts can open it. If the house is quiet on a gusty day you may be able to hear it clanking open & closed, basically meaning that it's opening when it shouldn't and letting your warm air out.

 
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04-10-12, 05:06 AM   #3  
I had taken some pictures of the setup (attic and outside venting) but didn't get a chance to pull them off the camera before heading into work this morning.
The two bathrooms use what appears to be 4" plastic dryer tubing, goes to an aluminum HVAC tee, then out a 4" dryer vent (which is missing most of the fins).

I picked up one of those draft traps (pictured in my previous post) just to see how it works on the dryer. It cost me less then a Starbucks coffee, so if it helps at all, it was worth it.
Now that I know that the vents are 4" as well, I might toss one on each bathroom just to see.

I'll try to post the pictures tonight. Might not get to it as my 2yrs old is having surgery today, so things might be a bit crazy around the house.
Hopefully the pics might identify other areas of improvement.


Last edited by stickshift; 04-11-12 at 10:04 AM. Reason: removed quoting of entire post
 
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04-10-12, 06:01 AM   #4  
I hope all goes well with your 2yr old.

 
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04-11-12, 03:51 AM   #5  
Didn't get to post the pictures last night. Was tied up with working on the water softener, installing the new dash cam in the car, and watching top gear with my 2yrs old (everything went good with the surgery).
Will get the pictures posted tonight for sure.

 
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04-11-12, 04:10 PM   #6  
Here are the pictures as promised.

This picture is where the exit vent is located (third floor/attic)


Close up (300mm telephoto lens sure helps)


Here is the inside tee and pipe work from the two vents. One from the master bathroom is well insulated, and the other main bathroom is not. Both are 4" plastic dryer lines.


This attic is huge btw. so lots of surrounding cold air.

 
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04-11-12, 04:35 PM   #7  
During winter I bet you get some condensation in those lines. Is the water staying inside the tubing or did you notice any evidence of dripping while you were in the attic?

 
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04-11-12, 04:50 PM   #8  
I did not notice any water or condensation in the attic during the winter. I was also not really looking for it or at this system. We moved in to this house at the end of this past December and because of it's size, have been playing discovery ever since.

 
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04-12-12, 04:38 PM   #9  
If you turn on one fan do you get blow back into the other fan? I am under the impression that each bath fan should have it own vent.

I strongly suggest replacing the white vent (or both) with 4" insulated flexible vent. With your cold winters you will get condensation inside there. Also, it will not last in the attic. I replace my BiL's which was almost dissolved to nothing.

I'm sure you already know, you need to replace the outside vent. It's broken.


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04-12-12, 05:38 PM   #10  
Each fan should have it's own vent to the outside. Get insulated lines a ssuggested. That will help with heat loss too. Even if you have a good baffle installed in the line, if it isn't insulated, the cold will transfer through the side of the duct.

 
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02-18-13, 10:48 AM   #11  
Just as a question. Is it possible or would it be too much resistance to install some sort heat trap in the ducting (like from a hot water heater)? Would this cause condensation to pool? How high and low do I need to go if I did?

My 1/2 bath on 1st floor only has an exhaust fan for venting (all interior walls) and currently no heat source. Currently 15F degrees outside and that bathroom is cold. You can feel the cold dropping from the fan. Fan is only 4 months old (panasonic) and the plastic draft door is working fine. Duct goes to uninsulated attic and up to hooded roof vent.

I need to install 2 fans in upstairs bathrooms but I'm trying to draft seal all the air leaks and heat loss areas not add to them. They are heated so maybe not as noticeable but again trying to prevent when I install.

Any suggestions on good, quiet high CFM fans? the other 4 members in house prefer very steamy showers and I need to vent that out. Do separate or one attic mounted unit with 2 ducts?

 
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