R-Value is a measure of insulation’s ability to resist heat passing through it.
The higher the R-Value the better the thermal performance of the insulation. R-Value is a number given “per inch of thickness”. For example, an insulation type with an R-Value of 5 means “5 per inch of thickness”. Therefore, a 1” thick layer would have an R-Value of 5; a 2” thick layer an R-Value of 10 and so on. Thickness matters!