Abstract: A portable type spa is insulated by a sequence of steps involving initially the preparation of an insulation blanket having a metal foil heat reflective surface on one side with orthogonal dimensions of the blanket sized larger than the orthogonal dimensions of the spa shell. The spa shell is placed on top of the insulation blanket in a preferred method, with the metal foil heat reflective surface facing the exterior of the spa shell. The spa shell foot well is leveled by shims placed between the bottom of the spa shell and the underlying support surface such as a floor. The periphery of the insulation blanket is preferably sandwiched between the underside of a spa rim and a top edge of wood skirt panels surrounding the exterior of the spa shell. The insulation blanket forms a loose bag about the exterior of the spa shell and about plumbing connections on the exterior of the spa shell including warm water circulating tubing projecting outwardly of the spa shell exterior surface.