Sep 30, 2011 · If you want to use the rigid foam sheathing as your WRB, you can. However, you still need to address the challenge of flashing each window opening so that the rough window opening has a sill pan under the window. This sill pan (or site-built sill flashing) must direct water to the WRB -- that is, the exterior of your rigid foam.
Johns Manville (Common: 1-in x 4-ft x 8-ft; Actual: 1-in x 4-ft x 8-ft) AP Foil R- 6 Faced Polyisocyanurate Foam Board Insulation at Lowe's. Johns Manville AP™ Foil-Faced Foam Sheathing board is rigid polyisocynurate foam sheathing that provides exceptional heat, moisture and air control