Houzz has an interesting discussion thread on building a foundation on bedrock that is just a few feet below the surface of the soil.
Ecohome has this post about it.
This article in the Toronto Star advocates ICF because it is easy to cut to match the bedrock.
The below from a thread on GreenBuilding Talk has some interesting thoughts to consider:
Backfilling several inches with river-rock with perf-drain for drainage and radon control, with a 10mil vapor retarder, and R10-R20EPS crawlspace floor insulation with a 1-2" rat slab ((or a full structural slab) on top of the insulation making it a conditioned crawlspace is a FAR superior solution than insulating between the joists. Joist insulation leaves the joist edge exposed to the humidity of the crawlspace, which may otherwise need to be ventilated to keep the radon levels low enough in a granite-bedrock situation. (Granite is a notoriously high radon emitter.)
Most of upstate NY has subsoil temps under 50F- coupling the house to the bedrock's thermal mass is far less useful than when the bedrock temp is 60F- it's a net heat loss, only useful during the cooling season, and a just a heat load most of the year. But if you need to move air under the slab to purge the radon as is likely, there's effectively ZERO benefit. Setting it up ahead of time to be able to actively move air through your perf-drain & bed of river-rock is a good idea. (Sometimes wind pressures alone will be sufficient, other times a bit of help from a whirlybird or venturi type stack turbine does it.) If you're building in heat recovery ventilation, venting the crawlspace as well as the rest of the house will also take the edge off the radon & moisture issues in a conditioned crawl.
Is Flowable Fill appropriate to put on the bedrock before adding insulation under the foundation? Maybe ask here.
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