What Insulation Is Best for a Basement?

Basements and below-grade walls don't follow the same playbook as attics. The big difference is moisture: foundation walls can wick dampness, so the wrong material or detailing can trap water and cause problems.

For basement walls, rigid foam board and closed-cell spray foam are popular because they resist moisture and provide both air sealing and R-value. Fiberglass batts against a bare foundation wall, by contrast, can trap condensation.

The rim joist — where the floor framing meets the foundation — is a major source of air leakage and a smart place to insulate and air seal.

The right approach depends on your foundation, moisture conditions, and how you use the space. We inspect first, then recommend a material and detail that keeps the basement comfortable and dry.