This floating Thermal Blanket is one of the best little investments you can make. Using a thermal blanket under your hard cover will drastically increase the insulation value specially in a cold Canadian weather. By using spa cover and thermal blanket in conjunction, you will maximize heat retention. The hard cover keeps the cold air out and the thermal blanket keeps the heat in the water. It works on the same concept as a double pane window.
Tips: You cut the blanket to the same size and shape as the water surface of your spa hot tub.