a. R-values are minimums. U-Factors and solar heat gain coefficient (SHGC) are maximums. When insulation is installed in a cavity which is less than the label or design thickness of the insulation, the installed R-value of the insulation shall not be less than the R-value specified in the table.
b. The fenestration U-factor column excludes skylights. The solar heat gain coefficient (SHGC) column applies to all glazed fenestration.
c. The first R-value applied to continuous insulation, the second to framing cavity insulation; either insulation meets the requirements.
d. R-5 shall be added to the required slab edge R-values for heated slab.
g. Insulation sufficient to fill the framing cavity, R-19 minimum.
h. The first value is cavity insulation, the second value is continuous insulation, so "13+5" means R-13 cavity insulation plus R-5 continuous insulation.
i. The second R-value applies when more than half the insulation is on the interior of the mass wall.
j. For residential log home building thermal envelope construction requirements see R402.6.
k. The Ceiling R-Value in Climate Zone 5 may be reduced to R-38 when the Wood Frame Wall R-Value is increased to R-21 and the Fenestration U-Factor is reduced to 0.31.