If your hot tub is installed outside, you'll probably need to cover it up to keep in some of the heat when you’re not relaxing in your outdoor spa. Since the cover helps to keep the heat inside, it will help to reduce your home energy costs, too. You'll also save a little on the cost of chemicals, since the chlorine and bromine in the water can't evaporate into the air as easily with a cover, and it will also help to keep out leaves, dirt and other debris, making each dip in the outdoor spa tub a cleaner experience.
1 Measure the length and width of the inner walls of your hot tub with a measuring tape.
2 Use the measuring tape and a straightedge to draw the measurements on the insulated floating pool cover. If your hot tub is round, oval or oblong shape, it can be more difficult to obtain adequate measurements to draw the outline. Instead, lay the pool cover on top of your hot tub and outline around the inner edge with a marker. You might need an assistant to help hold the pool cover steady for an accurate outline.
3 Lay out the pool cover on the lawn or a large working space and cut along the marker line to cut out the shape for the floating insulation blanket.
4 Place the insulation cover back in the hot tub and use the marker to note any edges that need to be trimmed off in order for it to fit within the hot tub properly. The edges of the blanket should sit about 1/8 inch away from the inner walls. Cut off any excess, and then place the blanket back in the hot tub.