A MgO SIP house went up near here. Looks to be primarily light steel construction with the MgO sips as infill. I got a sample and soaking it in water had no effect. The roof is not made of SIPs and I assume that they will insulate it in some other way. I can't say that I understand using 5" of foam and then having so much thermal bridging. The SIPs will be covered with mesh + stucco/plaster.

Very interesting! Looks like they built the first floor and then the second, because the panels don't line up. And I assume there must be splines between the panels?

This is in the US? Where is it?

There are two C channel studs welded together in each joint. This is in Central America (ie, loose regs).

Are they in a track at the bottom?