Found this about the insulation. They use some kind of foam as well as the panels. Sounds smart. Hope it works!
At Trévi, all spas are created keeping in mind Quebecers’ tastes and winter harsh conditions. The insulation of a spa should not be neglected. Some spas are insulated with urethan. With time, urethan hardens and may crack. When this happens, there is no possible insulation and if there is a leak, urethan has to be broken. This is why Trévi prefers two different types of insulation. The first is an insulating foam that always goes back to its original shape. It has air cells that provide an excellent insulation. Should a leak happen, the foam will absorb the water and allow us to locate the leak area, to slightly scratch the foam and to repair the leak. The other insulant is the MAX panel surrounding the spa. Should a problem arise, the spa skirt and the panels are removed, the problem repaired and everything put back in place. The panel is seven times more efficient than urethan. The foam provides 50% more insulation than any other material commonly used.