Visit SIPS.org. It stands for Structural Insulated Panel.
From a much larger perspective, why don't you consider hiring an ASHI-Approved Home Inspector. Yes, you can hire one for NEW home construction. It's kinda like hiring a mini-contractor who's looking after YOUR interests. This would be the person who can answer your questions. Be sure to hire one that has experience in NEW home construction/inspection. Also, consider hiring your own Real Estate Attorney. Again, this is someone that would review ALL your paperwork with the Builder. You don't think that he hasn't had an Attorney 'approve' HIS paperwork, do you? And I will bet as much $$$ as you have that the Bank has an Attorney look at the financing paperwork on EVERY home they finance. And THEY write more contracts on new homes in 1 day than you'll do in a lifetime! They're always making sure their interests are looked after.
Ask the Inspector what they do for NEW home construction, THEN ask for the fee; NOT the other way around. And ask what else they can do for you for additional $$$. I would estimate his fee to be between $300 and $500. The same for the Attorney. Compare those costs to what your monthly mortgage will cost you over the life of the loan. It's a drop in the bucket for peace of mind, no?