Insulating Floor Joists In Basement - Doe Building Foundations Section 2 2 Concrete Wall Interior Insulation / Install rim joist insulation using foam, caulk and fiberglass insulation to cut air infiltration and add r value around rim joist of basement. Insulating Floor Joists In Basement - Doe Building Foundations Section 2 2 Concrete Wall Interior Insulation / Install rim joist insula... Visit Site