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Bathroom Exhaust Fan Venting


CuriousGeorge2's Avatar
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Join Date: Aug 2006
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08-22-06, 09:36 AM   #1 (permalink)  
Bathroom Exhaust Fan Venting

I am in the process of having my bathroom remodeled. I am having a Panasonic Whisper Lite exhaust fan installed.

I am being told that the fan can vent directly into the attic, not out of the house via a vent in the roof or wall. I think this is incorrect. Can someone let me know if I am crazy or if the contractor is?

Additional info: I live in north eastern Illinois and it can get really cold in the winter. It is an second(top) floor bathroom.

Thanks for your help.

 
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Doug Aleshire's Avatar
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08-22-06, 10:34 AM   #2 (permalink)  
CuriousGeorge2,

What you were told is wrong - any exhaust vent cannot vent directly into an attic, particularily a bathroom vent as the moisture would create problems to insulation, wood and drywall.

I think this will help....

http://www.shopfnc.com/bathfan1.htm

http://www.doityourself.com/electric...exhaustfan.htm

http://www.lowes.com/lkn?action=howT...c=howToLibrary (it shows soffit vent option)


1. Exhaust airflow must take the air all the way to the outside of the building -NOT INTO AN ATTIC SPACE. This does not apply to kitchen hood vents that are considered "ventless".
2. Duct runs should be short and as straight as possible.
3. Use smooth, rigid ducting whenever possible.
4. Slope ducting to the outside to allow any condensation to weep to the
outside of the building.
5. Ducting running through unheated spaces must be insulated.
6. Exhaust vents - roof or soffit must prevent birds or animals from entering.

Hope this helps!

 
mattison's Avatar
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08-22-06, 01:38 PM   #3 (permalink)  
Doug is 100% correct.

If they vent that thing into the attic, in the summer you'll grow mold and in the winter you'll have icecicles up there.

 
Joe.Carrick's Avatar
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08-22-06, 02:29 PM   #4 (permalink)  
Doug is correct except for:

5. Ducting running through unheated spaces must be insulated.

When it's an exhaust duct, no insulation is required. Likewise for combustion supply air for gas appliances such as Water Heaters, FAU's and Fireplaces.

Supply and Return Air ducts in a Heating/Cooling system must be insulated so they do not have too large a heat transfer to the unconditioned space. The air in those ducts is returned to the conditioned space. Exhaust Air and Combustion Air go directly to the exterior so those ducts do not need insulation.

-Joe

 
CuriousGeorge2's Avatar
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08-23-06, 07:30 AM   #5 (permalink)  
Thanks. More info.

I spoke with him today and he said he will now be venting it to an existing roof vent. He mentioned a trap will be added to deal with any condensation.

I am assuming this will be accomplished with a felxible duct. Is this acceptable? What happens to the condensation in the trap?

Thanks again for all of your help.

 
Doug Aleshire's Avatar
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08-23-06, 01:47 PM   #6 (permalink)  
CuriousGeorge2,

I am thinking that your contractor is not experienced or just lazy, IMHO in regards to this simple exhaust fan roof cap install. Please refer to the link below and click the installation instructions. You will see that there are 2 ways of venting these to the OUTSIDE. You do not run the duct just to the underside of an EXISTING ROOF VENT. That is not venting to the outside.

The NEW roof cap has a damper which is closed when the fan is not in operation but has a screen to prevent birds from entering.

http://www.nutone.com/product-detail.asp?ProductID=11024

Hope this helps!


Joe,

Your concern about condensation forming inside the pipe is valid. It can and does happen to thousands of people because the installer failed to insulate the pipe. This is the most common mistake and overlooked issue on bathroom venting.

Even though the kits do not usually have insulated pipe doesn't mean that it is the right way. Insulation is best for those in the colder climates when talking about bathroom exhaust fans. You are correct in the areas on HVAC issues.

 
jbutsler's Avatar
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10-16-06, 05:58 PM   #7 (permalink)  
Related to this question if I am not getting moisture through my exhaust fan now that the weather is getting colder and my furnace is running, is that an indication that my duct work is not insulated, thus I am getting condensation?

 
Doug Aleshire's Avatar
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10-16-06, 06:35 PM   #8 (permalink)  
Jbutsler,

Unsure what you mean by "if I am not getting moisture through my exhaust fan now"??

 
David Kantor's Avatar
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01-12-11, 11:14 AM   #9 (permalink)  
Bath fan exhaust direct to attic (best soluiton in N.W. U.S.

I've used this method for customers (in Seattle area) and it works just fine. Not enough moisture to really affect attic (which has soffitt vents or gable vents anyway on most homes). Most vents through wall or roof are lousy installs resulting in rain entering unit or bugs getting into the attic. A little moisture is better in my opinion and has less chance of clogging rather than having long flex tubes running all over the attic and getting smashed by people pulling maintenance or just doing stuff in the attic.

 
Wayne Mitchell's Avatar
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01-12-11, 01:37 PM   #10 (permalink)  
A four year old thread David and I think most would disagree with your position.

I know the installation instructions for NuTone say that "ducted fans must be ventilated to the outside". If a contractor can't install a roof vent without it leaking he should find other work.

 
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