Northern Exposure® is the ultimate hot tub insulation system. The unique thermal barrier technology recycles the free heat energy got more efficient heating and lower energy costs. All four sides of the spa, plus the floor and cover are lined with reflective copper material to reflect radiant heat energy generated from the pumps back into the spa. Heat is absorbed back into the plumbing helping raise and maintain water temperature. Finally the entire exterior of the hot tub is wrapped in 3M™ Thinsulate™ Insulation, the same incredible material utilized in winter clothing. This three layer patented system ensures energy created by the spa stays in the spa.