Abstract: A method for insulating a pier and beam foundation on a structure, wherein the pier and beam foundation includes at least one floor joist, at least one pier, at least one beam, a side skirt, flooring, and plumbing including at least one pipe, may include applying a synthetic underlayment to the at least one floor joist and to a bottom surface of the flooring; laying a radiant insulation board end-to-end across the at least one floor joist, over the synthetic underlayment, and along the side skirt; and applying a tape to adjacent radiant insulation boards to seal joints there between. The method may also include wrapping the at least one pipe with spray foam, a foam pipe insulator, and duct tape.