I am remodeling a one car garage in an old house. As part of the remodeling, I am taking all the insulation out (in the walls that have insulation). It is a combination of faced and unfaced fiberglass insulation and rigid insulation. The fiberglass insulation is all jambed into place (not sure if it is as an artifact of time or the installation was not done right). The wall shared with the house has no insulation!
I'm leaving intact the vapor barrier (tar paper) between the 2x4 studs and the exterior walls that have siding. The studs are a variety of distances ranging from 13"-18" apart. Most of the studs are a non-standard 18" apart center to center (but even those are not exact). The house is in Central Texas.
I am thinking of buying 24" faced fiberglass insulation (pink one) and cutting it to be 1/2" bigger than the opening (whatever the opening is in the bay I am working on). Installing the faced side towards the inside of the garage. Is this the right thing to do around all the exterior walls? So that I don't have too many wasted strips can I tape (what type of tape do I need?) two pieces together and keep the integrity of the vapor barrier and insulation?
Also, I see that Owens Corning has a FastBatt product that doesn't have flanges. This is supposed to be held between the studs by friction against the studs and not by staples through the flanges. Any opinions on this product? I would like to use this in the shared wall with the house. Given that my access to the wall is from the "outside" of the house, I won't have the ability to stable the flanges to the interior of the 2x4 studs. Hence, I was thinking of installing this type of insulation with the faced part towards the house sheetrock and let friction keep it in place. Then, install some type of vapor barrier on the side of the studs facing the garage. Then, install the fireproof 5/8" drywall.
Thoughts on both the exterior walls and the shared wall are appreciated.