A few questions:-

1/ why concrete.?
2/ is there a foil radiant barrier in place.?
3/ what insulation.?
4/ what level of air tightness.?
5/ is there a planned floor covering.?

oh, and why concrete.?

The first of (no doubt) many questions...

Owen

1. Why not ?
Yes, a wooden floor would be an option.

2. No. Don't they only work with an air gap, or are you talking about foil backed bubble stuff?

3. As described in the base case. Expanded polystyrene CO2 filled. See the intro.

4. The short bit of wall is only included to allow proper modelling of the edge. Air tightness = 100%.

5. I've used 10mm felt to roughly mimic carpet. Given how cold a tiled ensuite/bathroom gets in a typical NZ house I should do one with tiles.

In anticipation

No, I do not believe foamed glass is available in NZ yet, although I have seen plans for it.
And yes, it looks like a very good idea.

Ok, a foil back will improve the radiant results, and needs to be on the top surface of the 'foam' (insert any type here)with no air gap for maximum effectiveness.

Poly is quick and inexpensive, but... is an environmental nightmare. Much, much better is wool (no like there's lots of that in NZ)but you cant compress it.

Papercrete has a much better impact than pure concrete, and good insulation values - you just need a membrane below to stop further moisture ingress.

My fave is wood - the challenge is sealing it so that it is airtight. You can fill the void with pretty much any type of insulation, and foil back the ply top - it will exceed code. a real 'green' version would be sectioned to take strawbales. It has a negative environmental impact (ie allows new trees to grow, so sequestering carbon) is light, easy to move and doesnt consume the earth to make it... The engineered timbers now available are excellent.

Have fun

Owen

Owen,
Those are aspects of design, rather on my modelling research.
You should start a thread on your ideas for alternate designs/materials