I live in an ICF house that I am renting. It is pretty awesome, but I am building a SIPS house now. One thing I have found (we are in the country) is that rodents get into the styrofoam and can/will burrow all though it. So make sure you have a real rodent barrier (those mice can get almost anywhere) and stay on top of them. I have dogs, so poison baits aren't an option. Also had carpenter ants that found there way in though pest control guy said it was probably a small leak in the roof that attracted them.

So why SIPS? It is cheaper and does essentially the same thing. Plus the SIP has something to adhere to on the inside for sheetrock and other things mounted to walls and is faster to build.

On the radiant heat. I am planning on putting the PEX into my insullated slab for someday as I see it as a fantastic option for heating. I just can't get past the huge expense of the heater (seems like any hot water heater would work with enough capacity) and pump (what is up with that??). So for now, I will have a heat pump (they work here maybe not there) as I will have AC too and the ducts will be there even with the radiant heat.

The house I am currently building is ICF, and I love it. I considered SIP's, especially steel SIP's, but it wouldn't have been feasible for one old man (me) working alone. I went with a conventional wood floor structure and roof trusses. I did build everything to FL wind standards, even though I am in upstate SC. If money were no object, I would have still used ICF, due to the structural strength, but I would have done a suspended concrete floor, and used light steel framing for the roof, with steel SIP's for the roof.

Not only rodents, but termites have been shown to tunnel through the foam for considerable distances. Either critter can get through a conventional OSB SIP, and of course, ICF, although they can't get through the concrete in the ICF to actually get inside.

The reason for all of the steel and concrete is that it doesn't rot, burn, or get eaten by anything. Also, wood quality these days is dismal. It took me a LONG time to strap and shim my ceilings to get them flat. I used steel framing for the interior walls to get them straight and flat. The inside of the ICF was already perfectly flat. BTW- there are fastening points every 8" with ICF, so attaching drywall and other items to the wall is as easy, or easier than wood framing.

I used concrete over metal deck and K joists (open web steel) for the floors and roof of my concrete house.

You might want to ck out this web site. greenbuildingtalk.com

They have an ICF forum.