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Attached Garage Insulation Project


I want to finally insulate my attached garage after 15 years. I will be heating it in the winter to about 50 degrees. I live in Minnesota. Question is do I put up a vapor barrier on the 2 exterior walls and ceiling?

One wall(back wall) is common to the house and has vapor barrier on the now warm side. This is also a tuck under with 10 feet of the ceiling which has the living room floor above.

I know that closed cell foam would be the best, but the cost is my consern.

I want to insulate with fiberglass bats. and then 5/8" drywall to fire code. So do I put up a vapor barrier on those outside walls and ceilings on the warm side?

I get 50/50 from local building inspectors. one says yes, and one says that's a tuff call because you don't want to trap moisture.

sorry for the long post, I just wanted to paint a complete picture of what I have.

thanks in advance.

Re: Attached Garage Insulation Project

I think I can understand the two opinions received by the different inspectors.

Since you will be introducing heat into this space this now becomes conditioned space.
With that because you will be heating this space and installing insulation you will be required to add a vapour barrier ( on the warm side of the insulation ) to all exterior wall and ceiling surfaces.

As for the ceiling --- the vapour barrier should only be on the portion that is directly adjoining the cold zone under the roof.

You don't want vapour barrier under the portion of the living room floor above.
This is what I suspect is the concern by one inspector for trapping moisture.

In that area you could install house wrap material instead which would breath and not allow moisture to be trapped as a result of any vapour issues.
Another reason for the house wrap is it becomes an air barrier to better assist with keeping the floor above being exposed to cold air from the opening of the garage doors.

Combined with the house wrap and the heating will provide enough temperature to maintain the moisture to be in it's gaseous state -- vapour --- and allow it to breath out.

Hopefully this makes sense and helps.:)

Re: Attached Garage Insulation Project

yes, makes sense and helps a lot.

Re: Attached Garage Insulation Project

I am insulating an attached garage. My plans are to use the garage ocassionally and heat only when in use (for projects). I have used a space heater, but I may as well be heating all of the out of doors. Thus the decision to insulate.
The walls are already finished with wallboard. I have access to the attic space and have run a course of R13 faced fiberglass between the rafters. The wall type of insulation fit neatly under the existing runways for electric and other obstacles.
Is the facing, on the insulation going to be enough to provide an adequate moisture barrier to the attic?
Do I need a moisture barrier?
My plans are to blow in insulation into the walls. Do I need a moisture barrier here, if so... How could a barrier be added?
I am open for ideas...

Re: Attached Garage Insulation Project

Hello Tomcatshass, I see a fellow neighbor. As you may be well aware we have been having a lot of mold/mildew issues both here in WI and there in MN. Be careful it what you do. Remember, a tight house/garage is not always best. They need to breath!! This has been a big issue and debate for years now. I have been part of some legal issues representing major window and door companies that have arrived up in your area just across the boarder with issues of who is to blame for the mold/mildew problem. 90% of the time, the homes were TOO air tight and not able to breath. Good Luck, do your home work, but remember in the end it is you who pays the price! ;)GregC

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