Exterior Insulation for Existing Foundation Walls Description Guide describing how to insulate a new foundation wall or an existing foundation wall by adding rigid insulation to the exterior side.
Rigid Foam Board Interior Insulation for Existing Foundation Walls Description Guide describing how to insulate closed crawlspace walls and band joist areas with rigid foam board insulation.
Spray Foam Interior Insulation for Existing Foundation Walls Description Guide describing how to insulate an existing foundation wall by adding spray foam insulation to the interior side of the wall.