Hopefully this is my last question regarding insulation for my basement project. I touched on this this before but wanted to see about a specific answer or recommendation.
Im looking at putting insulation in the roof joists of the basement. But im uncertain as to which option would be best.
I already have the roll faced insulation. (it was a discount if you buy enough. And enough just happened to be the amount it would take for all the walls, and the roof. And i needed to save money.)
Picture of one section of the roof in the basement. As you can see, many areas have a lot of nails coming down. It was that way when i got this place.
The roof joists are about 7-1/4" deep. And the insulation is 3.5" thick.
As far as i see atm, i have three main options with what i have.
1. put the insulation in and staple the face to the bottom of the joists. (Just like doing it in a 2x4 stud wall.) And have a large pocket of air/open space above it.
2. Push it all the way to the top. Seems like a bad idea since that many nails would likely compress the insulation.
3. Push it up to the nails but not into it, so it doesnt compress. Leaving a small bit of air/open space above it.; and also leaving a little bit of room below it so it wouldnt need stapled into the joists.
(#2 and 3 would be held up with insulation supports)
Im guessing #2 or 3 would be the better option. But im not sure how that pocket of air would, small or large, would impact the insulation value. Also not sure if i want to cover the joist with face or not.