I don't know why nobody has commented. A concrete slab big enough for a house generally will crack some, although not fatally so. When we put new flooring in our FL home, there were several cracks, but they don't seem to be going anywhere. The subsoil can have a big impact on how well the slab will hold up, as well as proper site prep , reinforcement, and installation. When building a subdivision, a lot of dirt is moved around, and you really want undisturbed dirt as much as you can for a slab. Build it on soft fluffy dirt, and it will crack.

I'm looking at SIP's myself. I'm going to use metal SIP's. They don't burn or rot, and termites won't eat them. There are no splines to conduct heat, and they are weather-proof as is. In fact, they are used for commercial buildings without any further siding. The place I'm using also carries a full line of steel framing, so my whole structure may be steel. The only wood would be the flooring and cabinetry.

flgargoyle- Thank you for your comment. I will have several inches of soil removed and back fill with gravel. I'm just not sure if I want to risk the pipes for the floor heat. They could help keep the slab from separating even though it cracks. But concrete could also make short work of PEX tubing.

I went to a SIPschool class in Mississippi last weekend. It was very helpful. I highly recommend it if you have a chance to attend one.