The Frugal Farm Living life deliberately

Here's a shot of the insulation board on the outside (over) the osb. The insulation board adds an R4 (over and above whatever your get in the wall cavity - typically r13. Initially the extra R4 may seem like an extra 33%, but since it is continuous, the effect should be much greater. The average wall is composed of 25% studs. Meaning in a 12' long wall, you likely have 3' of solid studs. This is an average and takes into account jacks and criples next to windows, ... At any rate, that 25% only gets an R-value of 1.5 (wood is .5 per inch). so even if the cavity gets R13, 25% is only R1.5, which averages closer to R10 - which makes adding R4 to the outside an extra 40%. And this doesn't even take into the account the advantages of breaking the thermal bridging caused by studs (notice the frost lines on roofs where you can see the outline of trusses and bays on a frosty morning). At any rate, for ~$350, and a bunch of my labor, it should pay off in a season or two of heating and cooling.