As a builder, I have value engineered projects to death. First I would plan open cell foam for both areas as a base no matter what you end up doing. The simplest route is a 2-zone gas split system. Since these areas will only be tempered sporadically, this justifies it's own system and...
Codes were also different when the original was installed. Based on bedroom count, usually. How many bedrooms are you planning over original count? ALso, they may require you extend the field. Do you have the lot footage if necessary? Most jurisdictions are on the buyers side in that the...
From what I have read, you are doing/have a pole building and putting a slab within this structure already built. Since you say the slab is only going to be 6-8". If this slab is independent from the pole structure (floating) then I wouldn't put footers in for a future loft. I would cut holes...
It does sere as a true thermal break, but because it's not continuously contacting the concrete surface (grid on the bottom) then they probably can't sell it as an insulated flooring tile.