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Insulating garage ceiling/first floor

I have a colonial style house with an attached family room in northern Massachusetts. I have a two car garage under the family room, the kitchen, and dining room. The gargae is 24 x 26 feet, and the first floor joists are 2x10's 16 inches on center. Had some issues with a couple of rodents which have been resolved. I am getting ready to re-insulate the garage ceiling/first floor floor joists with all new insulation. I have two options, I could use 9 inch faced batts insulation, or a combination of 3 1/2 faced and 6 inch unfaced insulation. I have three questions

1. Which way should the faced side of the insualtion be installed, faced side of the insulation be placed up against the first floor sub flooring, or faced side of the insulation be down so you can see the insulation face(kraft paper) when standing in the garage looking up?

2. Shoud I add a sheet of plastic as a vapor barrier before I strap and put up firecode drywall/sheetrock?

3. How many "mils" should the plastic vapor barrier be?


Timothy Miller
Re: Insulating garage ceiling/first floor

Howdy consider having a sealer coat of foam insullation sprayed on to the framing members this seals the cavity- keeping auto off gasing out- and then non faced bat r/22 into the cavity the foam is a moisture and vapor barrier depending on which type of foam you use.

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