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exhaust fan vent to attic or outside?

Posted by dixieinmotorcity (My Page) on
Thu, Aug 25, 11 at 14:35

We are having a new bathroom added to an existing room in our home. The contractor put the exhaust fan in but it is only venting to the attic. He says that is what he usually does and it's good enough. He went on to say when they are vented to the outside it is only run to the soffet which is designed to draw air into the attic pulling the moisture right back in anyway.

Any advice on code or the "right" way to vent the bathroom exhaust fan? It just doesn't feel right to be blowing on the moist air into my attic.


Follow-Up Postings:

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RE: exhaust fan vent to attic or outside?

Get a new contractor.

Also, get permits. I assume he hasn't done that because his work certainly won't pass inspection. All bathroom fans must be vented outside. If he is cutting such a simple, cheap, and obvious corner, I wouldn't trust any work he did.


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RE: exhaust fan vent to attic or outside?

Every vent fan should be vented to the outside. If I have learned anything from watching renovation shows on t.v. and from my own renovations is that fans should always vent outside.


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RE: exhaust fan vent to attic or outside?

He's a bum. Get rid of him.


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RE: exhaust fan vent to attic or outside?

Like everyone else said, they should vent outside. When ours was installed somewhere between 1971-2001 it was not vented outside. We plan to fix that once we redo our master-bath room that doesn't even have one.

NKBA guidelines
Bathroom Planning Guideline 26: Ventilation
Recommendation: Plan a mechanical exhaust system, vented to the outside, for each enclosed area.

Code Requirement: Minimum ventilation for the bathroom is to be a window of at least 3 square feet of which 50 percent is operable or a mechanical ventilation system of at least 50 cubic feet per minute (CFM) ducted to the outside.

Here is a link that might be useful: Rest of guidlines


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RE: exhaust fan vent to attic or outside?

How big is your attic and does it have plenty of ventilation to the outside?

Ours is very large and has quite a few vents to the outside, both on the roof and under the eaves.

When it was time to change our fan, we replaced the old duct with what the fan manufacturer required and did not vent it to the outside. Our thinking was that 1-It's very open and vented up there and 2-there were ZERO signs of any damage from the old fan being used for 15+ years.

If your attic is small and not well ventilated, the fan should definitely be vented outside.


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RE: exhaust fan vent to attic or outside?

When we bought our house, we had to replace all the plywood roof decking because excess humidity had caused it to delaminate.

You don't want to muck around with humidity in the attic. The fan exhaust doesn't go through the soffits; it goes through the roof. Your contractor is lazy and either ignorant or a liar.


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RE: exhaust fan vent to attic or outside?

thanks for the input everyone. it just didn't sit right with us. we will be standing our ground about venting it to the outside and away from the soffit. i would say the attic area is not very large. the upstairs was the attic, but it has now been finished. all the ceilings slope on the second floor. the attic is just enough room for the duct work to pass. i can't really say how well ventilated it is.

we actually aren't required to get any permits for this work. i was in disbelief too, but i checked myself. also, the room does have windows so we technically meet code without even having the exhaust fan.


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