While finishing my attic, I added 1" extruded polystyrene to the backs of the 2x4 knee walls. However, when doing this, I noticed the builder placed R-19 in the 2x4 knee walls. From a chart I found online, the compressed R-19 will provide R-13 insulation value. Therefore, I am considering leaving the R-19 in place since it proved the same R-value as replacing it with R-13. Any suggestions or comments?