Actually, I'm not sure that it would be nearly as effective. The wrapping for the foam blocks is a large bag with only one opening, which gets sealed. In my case, there is a bag over a bag, put on from opposite directions and then sealed. A "layer" would not really do as much to protect the blocks from absorbing moisture. It might help a little, though. Double wrapped from the factory seems to be the cheap, easy, and reliable fix for the problem. Not sure I'd want to have to deal with a seperate sheet of something everytime I opened or closed the spa. That sounds like an ongoing nuisance to me.