Heat moves into and out of a building by three mechanisms: conduction, convection, and radiation. It has been standard practice to rate the performance of insulation products based on R-value. The problem is that R-Value measures performance of the insulation product via conduction only. Even then, tests are conducted under perfect laboratory conditions. Since the insulation in your home needs to control heat loss and gain through all three mechanisms of heat movement, and since you are building your home in the real world instead of a laboratory, we will need to look at more than just R-Value. R-Value is certainly an important measurement, but only one of many that will affect the performance of your home. The articles listed here provide excellent reasons to look beyond R-Value alone.