I ran across an advertisement that says “Heavy Broken Hot Tub Covers Waste Tons of Energy”. Curiosity got me and I clicked on the website. Guess what they are selling? Rigid foam spa covers. How will this solve the problem of heavy hot tub covers when rigid foam spa covers typically end up heavy or broken in only two years? For me, this is like going around in circles. Like a shoe salesman telling you that your back problem is due to your old flat non-supportive shoe and offering a good deal on a new pair of the same non-supportive shoes.
Buying something that will solve your problem on a terminal basis is not solving the problem at all. Instead, you are just wasting your money by buying something that gets broken or heavy in just a matter of two years. Not a wise buy. Instead of buying the same old thing and going through the same process, why not buy quality Hot Tub Covers that will put an end to your misery?
Moisture trapped inside hot tub coves is what causes the foam to get heavy. Different types of insulation like freezer areas in supermarkets use rigid foam boards. Layers of foam board insulate cool storage areas while keeping the customer area comfortably warmer. This type of installation does not submit the foam to hot moist air. Insulation value is maximized as long as the foam remains dry. Once the moisture gets into the tiny air pockets of the foam, it will have no insulation value at all.
If you want to observe the saturation of rigid foam board, the perfect environment is to put it atop a warm, humid steam. In such setup, the rigid foam would saturate faster than being tied to the bottom of a swimming pool. It is because water molecules are bigger than steam molecules. The latter is able to penetrate much smaller spaces than the former can. Once the steam cools, it condenses back into water gradually displacing air in the foam.
Before you will come to notice it, moisture has replaced the air spaces in it. The insulation value of that cover goes down dramatically. The spa cover becomes comparable to a wet piece of plywood and is as heavy as it is.
A frozen, heavy and saturated foam cover has a shorter life, will cool the spa water much faster and will only drive power consumption sky high. Achieve freedom from these kinds of problem and look for SpaCap or Hot Tub Covers without rigid foam.