a bit of context:-
My shed is 30m^2 in area and about 100m^3 in volume. The walls and roof have
5" of PU foam in the SIPS and the floor has 100mm of EPS under 8" of concrete. At the moment in the UK the average temperature is about 4-6 C with highs of 11 and lows of 2. The temperature in the shed has varied between 15-19 C in the last two weeks according to my thermo-humidigraph. There is no heating at all. There are two computers, a box of disk drives and a sump pump. When I'm in the shed there are 450W of fluorescent lights, plus whatever machines I'm running, plus me.Last summer, I had to run air conditioning to control the temperature and the UK doesn't have hot summers. This summer I hope to have the ventilation system sorted. At the moment there is no deliberate ventilation and there is only about one air change every 5 hours from leakage with the door shut (I _like_ SIPs :-)
Four sheets of plywood. maybe 3/4" doubled up if the soil is a bit dubious. Then four container jacks. Lift the whole lot up in the air, machines and all. Then slide the insulation under it.
Infra-red is good, so long as your hands don't stick to the hand wheels on the tools :-0
I wish I had known more about building a cellar 3' below the water table before I did it...
Regards Mark Rand