Basement & Rim Joist Insulation

The rim joist — the band of wood framing that sits directly on top of the foundation wall, running around the perimeter of the basement — is often the least-insulated part of the whole house, regardless of the home's age. It's a common source of cold floors upstairs and drafts in the basement.

Spray foam is the standard fix because it both insulates and air-seals in one step, which matters more here than in almost any other part of the house given how much air can leak through gaps in older rim joist framing.

This pairs well with basement wall insulation for homeowners planning to finish the space, since insulating before finishing avoids having to redo drywall later.