[stevehull]

Let's all recall that we are in vastly different climates with code (or rational engineering) being different in Ireland vs Oklahoma where I live.

In general, the further north toward the respective pole (north or south) you go, means that a thicker underconcrete foam layer is needed and has a quick return on investment.

In Oklahoma, our deep soil temp, which become the underslap temp, is about 60 F, whereas Ireland is likely some 20 degrees less.

Even here in Oklahoma, I would put in some subslab insulation, especially if I do the labor (which is minimal. But maybe only 1 inch - ~ 25 mm. But guess, what - code here does not even address subslab insulation.

I tip my hat to the Irish, with their colder soil temperatures, for insisting (code) on at least 150 mm subslab insulation. Not only does this save money, but the slab floor is just SO much more comfortable!


Steve