Crawl space versus slab, which is better?
I am in the early stages of planning a new home build. Am I correct in assuming that slab on grade constuction with passive floor heating would rule out the use of a heat pump. Also I would question your depiction of crawl spaces as damp and moldy. In a previous house I built with ICF walls the crawlspace was warm and dry. My main reason for considering a crawl space is I would like everything on one level.
Yes you can use a heat pump with under floor radiant heating. Most radiant heated floors in new constructio are done with hydronic heating (liquid), so you can have an air to water heat pump feed water into a boiler to bring it up to temperature. Here are a few relevant pages :
All about radiant under floor heating
Ground source heat pump vs air source heat pump, which is better?
Slab on grade, basement or crawl space - a comparison
As for a dry crawlspace, yes they exist, but usually after repair. There are no doubt homes where crawl spaces have been buit very well and efficiently, but that is far from the norm.
Building a basement with ICF walls is a far better way than the mold-inviting normal practice of trapping moisture in basement walls with a vapor barrier. A crawl space is a just a short basement, so if you did it with ICF then kudos to you for a good design, but in general we find the very notion of a crawl space a bad building concept. In almost all cases, we would prefer a slab on grade or a basement, not a crawl space that is basicaly a basement you have to hunch over or crawl through.