04/10/2021 · R-value denotes the capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power. It is normally noted (for example) “6.5 per inch“, which means applying one inch thickness of the material will provide 6.5 R-value; applying two inches will provide 13.0 R-value; and so on.R-value takes into account all three heat transfer