Styrofoam and polystyrene

[Javier_Pacer]

I saw blue Styrofoam 1/2 inch r value 3.
Polystyrene white stuff with foil backing 1 inch 2.85 R value.
Which has better integrity and how much is insulation overkill when doubling insulation does not give much R value?

Thanks

[Javier_Pacer]

This would go into a CT cavity to 1 3/4 .

[Javier_Pacer]

Thanks

[Javier_Pacer]

[Lgboro]

I planed my blue insulation to 3/4" and glued up two pieces to fill my 1 1/2" walls. It is very, very quiet inside and heats and cools very easily. Well worth the effort and expense in my opinion.

[Bogo]

I saw blue Styrofoam 1/2 inch r value 3.
Polystyrene white stuff with foil backing 1 inch 2.85 R value.
Which has better integrity and how much is insulation overkill when doubling insulation does not give much R value?

Thanks

If you want the foil layer, it needs a tiny bit of air space to work. For one project I used 1/8" beads of construction adhesive every 6" in a diamond pattern to hold the foam in place, and keep it slightly away from the surface it was glued to. That gave the foil face a small area to reflect across. Also, most foams are a moisture barrier form the standpoint of a house so the foil being a moisture barrier isn't an issue. You can get foil faced craft paper if the foam you choose doesn't have a foil face and you want one.