Traditionally, spa manufacturers have used blown in foam to insulate their spas. While this technique is billed as the ultimate in insulation, it is primarily used for structure to hold the cabinet to the spa and is prone to pick up moisture eliminating its insulating capacity and making servicing the plumbing components difficult as well as very costly. With the Black Rhino Steel frame on all Stonewood models, the need for additional structure from our insulating was not necessary and therefore eliminated. Stonewood Spas thermal retention system consists of several layers of insulating material. The first being a 20mm Styrofoam slab around the entire perimeter of the spa bonded to the spa panels, retaining any heat created by the operation of the pumps. Next, layers of sealed bags of thick Roxul insulation are overlapped around the entire core providing a blanket of insulation with a higher R-value than blown in foam. This reduces noise and is easily removed if interior access is required.