Traveling_Carpenter t1_jaclpqd wrote on February 28, 2023 at 1:54 PM

You have to have a certain ratio of interior and exterior insulation in order to keep the sheathing above the dew point. The more insulation you stuff in the cavities, the more continuous insulation you have to add to the outside to compensate for the reduction in heat energy making it to the sheathing. There are tables in the IRC that should help. You can also use your search engine of choice to search for wall insulation ratios for your climate zone. https://codes.iccsafe.org/content/IRC2018/chapter-11-re-energy-efficiency

Thrawn89 t1_jacv6ha wrote on February 28, 2023 at 3:04 PM

The insulation values given in the prescriptive compliance path of the IRC are minimum values. Could you please help me find where the ratios are specified in the code?

Traveling_Carpenter t1_jad06em wrote on February 28, 2023 at 3:38 PM

The ratios are in the table at the bottom of this article from Building Science Corp. https://buildingscience.com/documents/building-science-insights-newsletters/bsi-100-hybrid-assemblies