Insulating heated slab where foundation is raised in parts

Discussion about insulating slabs and slab edges

Insulating heated slab where foundation is raised in parts

Postby jmarshallnz » Thu Jun 27, 2019 12:07 pm

Hi there,

First off, excellent set of tools and great to read through the forum - it's been most useful for learning how things work!

We're planning a build at the moment on a hilly site. It'll have garage/entrance underneath and concrete slab on top, partially suspended over garage. At the end that's not over the garage, the distance from top of slab to ground is about 1.8m at extreme where the hill starts falling away. Rest of it is mostly around 300mm above ground level. The slab will be heated, walls 140mm timber, located on Kapiti coast.

My question is how do we best insulate the slab? Underneath is easy enough - can go with probably 100mm EPS given it's heated (soil is sandy, so probably pretty dry). Perimeter insulation we were considering something like insulfound (66mm XPS), which goes to heights of 1.2m, replacing boxing. Presumably it'd be worth insulating the entire external face of foundations, which I guess we could do with extending the insulfound down to bottom of foundation using E/XPS? Would it also be worth insulating the interior face of foundation? e.g. using something like ICF for the foundation walls, with insulfound or similar perimeter insulation up to the wall framing?

Thanks for any and all input! :)

Jonathan
jmarshallnz
 
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