How do R-values combine in a wall?
A. Our walls are not homogeneous materials, but made up of many layers. An example of serial heat flow. The total r-value of an assembly will be the sum of all the individual R-values. To work out the overall R-value of the wall, we need to know the R-values of the wood studs, siding andsheathing and insulation – all of which make up the wall.