How to Calculate Whole-Wall U-Factors
Figure 1. The illustration shows a sample wall assembly
in which insulated siding helps meet or exceed the
2009 IECC for climate zones 1 through 8 with a U-factor
of .057. This illustration depicts a wood-framed wall
assembly with R-3.0 insulated siding, R-1.5 foam
sheathing, and R-15 cavity insulation.