Garage Insulation

[adammuelta]

Hi,

I am installing 2 new insulated garage doors. While i'm at it, I want to make the whole garage as tight as possible.

I have an attached 2-car garage. It has a flat ceiling and there are 2 bedrooms above. The ceiling has 2x10 joists. The house is 50+ years old.

I have the following questions:
Should there be an air gap between the ceiling insulation and the subfloor immediately above? (I don't think so.)
Should I consider a vapor barrier? (I think so.)
I was looking at one site that recommended caulking any openings in the sheetrock / wall studs to prevent an exhaust fumes from entering the living quarters. What do you think?

I was surprised that I couldn't find any applicable websites/youtube videos. I looked all over too. What do you all think?

Thanks!

 

[Jeffgage]

U don't need any insulation or vapor barrier if the space above is a heated area as well. Unless u find that those bedrooms are unusually cold. If u want the garage to look finished u could add some drywall and seal the joints.

 

[DC73]

I have the following questions:
Should there be an air gap between the ceiling insulation and the subfloor immediately above? (I don't think so.)
Should I consider a vapor barrier? (I think so.)
I was looking at one site that recommended caulking any openings in the sheetrock / wall studs to prevent an exhaust fumes from entering the living quarters. What do you think?

You don't need an air gap.

Vapor barriers are highly climate dependent. Most building scientists are getting away from recommending a true vapor barrier like poly plastic sheeting but instead prefer a smart membrane to function as a vapor retarder.
Even then, they are not always necessary and can function to trap moisture if installed incorrectly. Check out GreenBuildingAdvisor.com and in particular take a look at their Q&A forum. There are building science gurus who hang out there who can help with this question. Be sure and tell them your location as their advice will be climate specific.

Air sealing between the garage and the living quarters is a great idea and should be done as it will help with the air quality in the home.

One thing I'd bet you can do but it might be a pricey option is to have someone spray closed cell spray foam. The closed cell foam will be a great insulation and an air barrier and a vapor barrier.

Good luck,

DC

 

[ItsNemo]

R32 closed cell spray foam is the way to go.

It's code to seal the garage air space from all living areas.

 

[fourbyford]

...most jurisdictions require 5/8" "fire rated" rock on each wall or ceiling adjoining living space... taped & mudded...
This is not only intended to help prevent a fire in the garage from entering the living space, but to also help prevent carbon monoxide entering as well...
D

 

[fourbyford]

...I'll add that, if it were me, I'd definitely add insulation under the floor of those rooms. Dont think I'd worry about installing a vapor barrier, per se, but, once the rock is taped/mudded on the garage ceiling, a couple good coats of latex paint will perform a similar function...
D

 

[machsnell]

Yes. You dont want exhaust fumes to get into house so you need to seal.

Also you dont want the bedroom (floor) to not be insulated from outside air which is what you have when it's connected in what seems to be not a conditioned garage.



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