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I want to add a gable fan in my garage to help cool it and help to let out the humidity in the winter. My garage doesn't have a high peak, so there is about 24" of height at the peak on the gable and about 12" between the 2x4 vertical supports. It would seem that I would need to cut out a support in order to fit in a fan. Is this correct and what is the proper way to support the roof if a 2x4 needs to be removed in order to fit in the fan? Would it make more sense to do a roof mounted fan instead?

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    You probably really only need a gable vent. Let normal convection do the work. – Tyson Jul 12 '18 at 0:51
  • You should not consider cutting supports to mount an exhaust fan. A fan intended for winter use would be small enough to exhaust between two of the supports. Is an exhaust fan for winter use in a garage commonly installed where you live? Where is this -- state and city or county? – Jim Stewart Jul 12 '18 at 1:23
  • If there is direct sun on the roof of this garage, then in summer it would have a high heat gain. A modern house under construction in my neighborhood has an open cell foam insulation sprayed on the underside of the roof decking. This allows any roof leaks to dry to the inside. The builder told me it gives R-30. – Jim Stewart Jul 12 '18 at 3:00
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I hate adding anything to the roof, it just gives a place to leak.

That truss you need to cut is non-structural. It’s made similar to a truss, so it will match the pitch, etc. Often carpenters will build a wall to match the pitch.

Therefore, yes, you can cut into that wall, cut through the middle 2x4 web (flat stud) and install a vent. (Make sure you don’t cut the roof joists.) However, I’d add a 2x4 around the opening to stiffen the area where the vent will be installed.

However, I’d verify that that side of your house is not the windward side. (I’d prefer the leeward side.) Wind driven rain could push through the vent causing multiple problems.

  • I live in Denver. So in the winter we have snow and then next day it is sunny and warm. Snow melts off the cars in the garage and creates a lot of moisture. That is why I would like a vent or fan to help pull some of that out in the winter and reduce some heat in the summer. If I would install a vent to allow normal convection work, it seems like I should install a fan too since they aren’t very expensive. I still would crack my garage entry door across from the vent/fan to help move the air. Does this sound right? This is a detached garage too. – junta Jul 12 '18 at 15:54
  • @junta Hmmm...not sure how that would work. remember the same amount of air you remove will be brought into the garage too AND it will be the outside air temperature. If it’s freezing outside, it could freeze the moisture indoors...before the snow turns to liquid and then turns to vapor. – Lee Sam Jul 12 '18 at 16:10
  • In the summer, it would most likely be hotter inside a closed garage than the air temp outside. So wouldn’t that thought work for hot temps? For winter, wouldn’t it be the same concept as someone who runs an attic fan with soffit vents to remove moisture? Thanks for helping me think this through. – junta Jul 12 '18 at 18:02
  • @junta We don’t have snow where I live, so don’t rely on me much for winter conditions. To remove hot air, yes the plan seems sound, unless you live in Phoenix and you’re bring in 105 degree air, which might still be cooler then the trapped air in the attic. – Lee Sam Jul 12 '18 at 18:51

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