crawl space under extension

Our contractor is doing some work to our garden level (one story) extension. Currently, the floor is a slab of poured concrete directly on top of bare earth (we presume) and gets pretty cold in the winter, and is a good 8 inches above the floor level of the rest of the garden-level rental.

We would like to try to a) lower the extension floor to match the rest of the garden and b) put some better heating and/or insulation under the new floor.

Obviously this means jackhammering the existing floor. But our contractor has suggested two options:
1. pour a new slab floor at the appropriate height, with several layers of blueboard insulation underneath it and maybe some radiant floor heating tubes embedded in the concrete (no prob, since the rest of the house uses that)
2. dig deeper down, create a 2′ high crawl space accessible from the basement underneath this floor, run joists across, and put the same type of flooring over that (insulation, tubing, concrete).

He says that both are about the same cost. Any suggestions on which we should choose?

By PHfamily | 05/01/2009 12:58 PM