Does this not count the R-value twice, effectively doubling the insulation value of the partition between the two zones?
Install insulation with the proper R-value, a factor that describes the material's ability to resist heat.
Pay attention to R-values: All insulation is rated with an R-Value.
The R-value is the measure of the insulation's ability to stop the flow of heat.
Insulation with a higher R-value will offer you greater protection against heat loss.