There is a little understood part about insulation that needs to be covered. There is a substantial difference between insulation for temperature control and insulation for heat loss control. For instance, the graph (below) shows the heat loss control of the spray-in-place urethane foam insulation. Any insulation will have a similar graph but with thicker amounts of insulation. This graph points out that more insulation is not necessarily cost effective. There is a point where more insulation is pointless from a total heat loss perspective.
This graph illustrates the reduction in heat loss from a building when it is insulated with various thicknesses of spray-in-place urethane foam. Note: the insulation benefit tops off very quickly above three inches. The graph is not exact, but it shows in general what happens as additional insulation is added to the surface temperature. In other words, by super-insulating , the surface temperature of the inside of the exterior walls comes very close to the room temperature. This prevents condensation, which prevents the growth of mold.
The graph shows that 70% of heat loss from conductance is stopped by a one inch thickness of spray-in-place urethane foam. Remember we are going to stop nearly 100% of the heat loss from air infiltration with the first one-fourth of an inch of urethane foam. The second inch of spray-in-place urethane stops about 90% of the heat loss and the third inch 95% and so forth.