How Is The Internal Foundation Wall Adhered To By Stiff Insulation?

Rigid foam insulation is a popular choice for insulating interior concrete walls due to its high R-value, which can reduce heat loss and make basements more energy-efficient and comfortable. It can be applied on either side of the foundation wall, with the code permitting both continuous insulation (like rigid foam) and cavity insulation (such as fiberglass placed in a stud wall on the inside). The most suitable product for this application is Halo’s Interra or Interra FR.

To reduce thermal bridging through studs, two main ways are to build a double-stud wall or install a continuous layer of rigid insulation on one side of the wall. Polyisocyanurate or extruded polystyrene (XPS) rigid foam board is recommended due to its low permeance to water and high insulation value per inch.

Rigid insulation placed on the exterior surface of a concrete or masonry basement wall has advantages over interior placement, such as providing continuous insulation with no thermal bridges and protecting against moisture buildup or leaks. A standard 4-ft. frost wall with 2 in. of rigid insulation on the inside of the wall is poured with a 6-in.-deep notch to accommodate 4 in. of sub-slab insulation and 2 in. of slab edge.

When used for the interior or exterior of foundation walls or below-grade basements, rigid foam insulation can improve insulation while avoiding moisture buildup or leaks. Foam board made from rigid foam can be adhered to concrete with foam-compatible adhesive or attached with special fasteners like Hilti IDP or Rodenhouse Plasti-Grip PMF anchors.

Drilling through the foam panels first, then placing it on the wall, drilling into the concrete, and inserting plastic anchors ensures that the walls are as smooth as possible for proper adhering.

In summary, rigid foam insulation is a popular choice for insulating interior concrete walls due to its high R-value, ability to reduce heat loss, and its ability to be installed on the interior side of exterior walls.