Where Should I Put The Insulation?

[Mikes61]

My 920 sq ft wood construction, attached garage, is finally finished and signed off.

My wife and I insulated the walls and put up the drywall on the walls. The roof plywood has the aluminum foil on the inside ( can’t remember the name of it ). The ceiling is still open and from inside the garage I can look thru the ceiling joists to the underside of the roof joists.

My question is, should I put insulation between the roof joists or the ceiling joists? I live in So. California and it gets hot here in the summer. I’m probably not going to put any A/C in it and just rely of the shade from my trees and whatever insulation will do for me.

 

[Hank11]

Insulate the ceiling.

 

[The Cobbler]

between & above. you want a good bit of insulation up there to slow down radiant heating . biggest heat gain is thru the roof

 

[bluedog225]

The foil (radiant barrier) will not work unless it has an air gap between it and the insulation. See emissivity and reflectivity. I‘d put lots of blown cellulose on the ceiling. Can always add more.