Because exterior insulation places the foundation wall within the thermal envelope, this approach offers several advantages over insulation in the interior. To start, continuous exterior insulation avoids thermal bridges and protects and maintains the basement waterproofing. It also minimizes moisture condensation problems and, perhaps most importantly, does not reduce the interior basement floor area.
Despite the advantages, builders still prefer to place the insulation inside the basement walls. This location avoids the main downside of the exterior placement, namely, covering the foam to protect it from ultraviolet sun rays and whipping weed-eaters. As an advocate of exterior foam insulation, I have resorted to protecting above-grade foam with an aluminum coil, fiber-cement board, and parging with an EIFES finish coat. One problem with most of these finishes is that the manufacturers do not recommend them at or below grade. The other is labor. It takes time to add this special step to the construction process.
Warm basement walls
All exterior foundation insulation materials must be approved for below-grade use. Only three types qualify, including extruded polystyrene, expanded polystyrene, and rigid mineral fiber panels. The FoundationPRO, “one-piece insulated foundation finish system,” is made with Neopor, an expanded polystyrene insulation with added graphite. The manufacturer laminates this material with PVC, or a “thick polymeric shell,” affixed with a permanent polyurethane adhesive. The system includes color-coordinated aluminum channels to hold the top and bottom of each panel in place. Right now,…