I basically did your option 2, before I even heard of underfloor insulation. Overall it has worked pretty well. Before the drain-tile install I would get water leaking with every rain. After rain has not been a problem. That said I have also noticed some shifting of the remaining slab in the middle of the room. My guess is from unevenly draining from the soil that has been wet since the house was built. I figure at sometime later I will have to rip out the whole floor and make it level, reinforced, and insulated-like your option 1.
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