The chart shows requirements for Marine zone 4, Zone 5, Zone 6, and Zones 7 and 8 of the U.S. (zones displayed in next image). It then displays the code minimum R-Value and thickness of rigid foam sheathing for external insulation for both 2×4 walls and 2×6 walls. The right most column shows percentages of “the wall’s total R-value that needs to come from the rigid foam layer.”