Attached garage air sealing
tjones1014
| Posted in General Questions on
Our siding contractor will be taping all exterior OSB seams with Siga Wigluv 60. Should we have him skip taping the seams on the garage and just do our air barrier between the garage and living space (on one wall only, no living spaces directly above)? Or should we do the air barrier on all of the exterior AND add an additional barrier between the garage and living spaces?
The garage will not be conditioned. Climate zone 3A/4A. 2001-built home reno.
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Replies
tjones,
If you are insulating the walls of the garage, then I would air seal them.
We had planned to have purple board on the garage walls since it gets so humid in GA for most of the year. I've seen mold growing on regular paper-faced drywall in people's garages here. Will the purple board trap moisture behind it if we insulate in there as well? Appreciate all suggestions for detailing that wall assembly!
tjones,
I shouldn’t give suggestions for managing moisture in walls in hot/humid climates like yours. I just don’t know enough about them. Hopefully someone with a better understanding will chime in.
The purple board is a lot less vapor open than "regular" drywall, meaning it won't allow moisture to migrate through it nearly as much. I don't think this property will affect mold growing on the surface of the material much though. I would use a mold resistant (usually called "mold killing") primer on the wall to deal with surface mold issues.
If the garage isn't going to be conditioned, humidity levels inside and outside the garage should be pretty similar, making the moisture permeance of the drywall not matter as much. There will be no moisture drive if the conditions on both sides of the wall are similar.
Bill
Thank you, Bill! We will not be conditioning the garage. Based on this, would you recommend air sealing the exterior OSB of the garage, insulating the inside, and installing paper-faced ("regular") drywall just like we are doing on the interior? Or should we approach this differently?
If it matters, we plan to air seal the wall that separates the garage and the living space and the ceiling of the garage. There is a bonus room in the upstairs portion of the home, though not directly above the garage.
Thank you!
Tiffany
I would air seal and insulate regardless, in case you ever want to condition the garage at all. It really doesn't take much to do the air sealing details at construction time.
I don't think you really gain much with moisture resistant drywall here. If you ware worried about mold, I think using mold killing primer on the walls will get you more bang for your buck.
Note that you do need to use 5/8" type X drywall for the garage, because it needs to be a fire rated assembly per code.
Bill
Can you please explain why we would need to air seal if we insulate? It's an unconditioned space. Trying to learn and understand, so I appreciate your help!
tjones,
Insulation relies on air-sealing for its effectiveness. If you aren't air-sealing, there isn't much point adding insulation.
Thank you! Is there any point air sealing & insulating the exterior walls if the garage door is leaky / not air-tight? Will that negate any of our efforts in that regard?