Step 5 · Install Insulation (Optional but Recommended)

If desired for further energy efficiency, insulate the crawl space walls and rim joist. Rigid foam boards (like XPS or polyiso) can be directly adhered to the foundation walls and rim joist. Alternatively, fiberglass or mineral wool batts can be friction-fit between studs if there's a framed crawl space wall. Ensure insulation is fitted snugly without compressing it.