Attic insulation should generally be 10 to 14 inches thick, depending on the R-Value needed for your region.
The thickness of R38 batt insulation is usually about 12 inches. This substantial thickness helps to provide excellent thermal resistance, making it a popular choice for insulating attics and other areas where maintaining a high level of energy efficiency is crucial.
Spray foam insulation is made from polyurethane, which expands and hardens to form an insulating barrier.