Achieve a whole-wall R-value of 12 or greater

A wall's R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. is usually considerably less that the R-value of the insulation packed into it, due to the thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. of the framing. The problem is particularly acute with steel framed walls. Use whole-wall values when computing loads and energy usage.

A house with a whole-wall R-value of 12 or more can maintain comfort levels with much smaller and simpler heating and cooling  systems. It's even possible to eliminate heating and cooling distributions systems altogether in smaller, very well-insulated buildings.