Insulation and R-value go together like hard work and sweat. R-value is, of course, the resistance to heat flow. We’ve been taught to think more is better, which is true to a point. I’m changing the insulation in the wall of my home from R-7, originally installed in 1952, to R-15, and I’m excited to see how much more comfortable my home becomes. There is an argument that at a certain level, more insulation will cost dollars to save pennies. At what point do we reach diminishing returns?