How much less do they cost? It's hard to believe they'd be less. Are you factoring everything in? I mean with sips, you can have all the chases precut, and sips are designed pre-engineered to reduce labor and increase speed. It looks like the two would have comparable materials, the raycore may even look a little more expensive with all the studs. There definitely seems to be more wood products in the raycore. Hmm, hopefully some with experience will chime in. How long is a foam like SIP Polyurethane good for? Is the raycore a similar urethane? I've heard that the R-value starts out high, but then drops down after a little while to a slightly lower value. Meaning it's not going to stay quite at that highest rated r value. I started a topic on Sips awhile back. I'll have to look for it and review some of the info we came up with.