I am designing a small cabin – about 750 sq. ft. – single level – in the pacific northwest (Vancouver Island). 

The cabin is on the beach, and will have to have a crawl space so that the floor joists can be above the local flood control level.

The client want’s hydronic in-floor heat, so we are planning to pour 1 1/2″ concrete topping over the 11 7/8″ engineered floor joists.

The crawl space below will end up being 4′-6″. The joists should obviously be well insulated, since they are supporting the heated floor.

Any ideas for details here? I am considering an un-heated vented crawlspace, with vapour barrier and concrete skim coat, and closed cell spray foam in between joists.

Or – conditioned crawlspace? What I don’t understand though, with a conditioned crawl, can you still insulate the floor joists above?

Any input greatly appreciated.