How To Properly Seal A Gable Vent? - Roofing/Siding - DIY Home Improvement | DIYChatroom

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Old 08-05-2011, 12:39 PM   #1
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How to properly seal a gable vent?

So here's my dilemma. I recently purchased a gable fan with the intention of increasing airflow, thus keeping my attic temperature the same as the outside temperature (right now my attic is way too hot).
Currently there are 2 triangular gable vents on each side of the attic that measure 9.5" x 39.5". The fan I purchased is 15" in diameter and way to big to mount behind the vent. My plan is to seal one of the vents (south facing) and cut a new hole below the current vent for a larger vent that will accommodate the size of the fan.
My question is, what is the proper way to seal a gable vent from the inside? My first instinct is to cut a piece of Styrofoam to fill the vent and then plywood behind it but I'm guessing that's probably not the best way seal it properly.

I've attached a pic to give you a better idea. Any help is appreciated.


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Old 08-05-2011, 01:31 PM   #2
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I think I would get a smaller fan (actually i'd install proper ventilation cause attic fans pressurize your attic and push hot attic air into your house, or pull cool air out). If you are keen on blocking it off, add 2x4's to the trusses to give you a flat surface for plywood.


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Old 08-05-2011, 03:54 PM   #3
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The attic fan is a good idea to reduce the attic temperature. Install the fan as high on the gable peak as possible for the best airflow. You will probably need to remove the existing louvered vent and install plywood for mounting.
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Old 08-05-2011, 04:39 PM   #4
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You can also just cover up the interior of the gable vent with plastic sheating, such as visqueen and staple it to the perimeter framing.

If you wanted to do a more thorough job, then also caulk any voids along the perimeter and stick the plastic into it as a contact adhesive and then even more, spray a can or two of Great Stuff Expanding Foam over that entire area to encapsulate the plastic and add some insulating factor to that vented area.

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