Welcome to our forum.
heh heh heh....... ok, so maybe I didn't read your whole question.. been a long day.Arctic uses a "cast core" foam, as opposed to EPS. I"m not exactly sure what "cast core" is, but I believe it's similar to extruded polystyrene. Most all spa covers are expanded polystyrene.The R value of expanded polystyrene, based on 1 of thickness, varying densities;1.0# R-3.851.25# R-4.01.5# R-4.172.0# R-4.35I'd have to look up extruded, but my recollection is R-5 per inchWhy you guys come to me for this stuff? You think I can just spit out something like, R-14 stops about 90% of heat loss, and R-20 about 95%?
Since we're not starting a new thread, here's a question to ponder;At what point does R Value become redundant in the case of a spa cover's thickness and then instead, become a feature for added strength? Steve