Insulation

[Mtsoxfan]

If you are talking about fiberglass, then yes, squishing it reduces its R value. Air in insulation is the factor.

Rigid insulation is an addition of listed R factor when you add rigid to rigid. 10+10=20

 

[Williy]

I have seen a lot of metal buildings with the spray foam
in the ceiling and gaping holes where it let loose

willy