I’ve built lots of hives out of foam. Started with 2” thick, then 1.5” thick and I may go down to 1” thick for some next winter. I really like the 1.5” thick stuff; it’s probably the easier and safest to cut (less binding), has good rigidity in a box shape, and has a nice high R value for Michigan. However it’s 66% more cost here than the 1” stuff.
I have yet to do a layout for a 4’x8’ sheet of foam because there are numerous ways a person can construct foam boxes and numerous little issues you may want to design around. Keep in mind that bees, ants, and wax moths can drill through foam if they desire! I’m still trying to come up with a perfect design, so I don’t have a layout yet. I just get sheets of 4x8’ foam, build something that would seem logical in my mind and later discover some unforeseen problem. Then go back to the drawing board and repeat the process all over again. I think they used to call that the product design cycle: Imagine it, design it, build it, test it and find out you screwed up, and repeat ad infinitum
