Stupid question, but could someone explain what the difference is between an insulated/passive slab foundation and a regular slab foundations?

The former sits on and is surrounded by a thick layer of insulation, expanded polystyrene in the case of my build.  The difference to the building is greatly reduced loss of heat through the floor.

Thanks.

 

I can't see many local companies offering insulated slabs, not sure if general builders are suitable or not?

The builders should build to your spec , I would imagine most builders know about insulated slabs now 

all slabs should be insulated to meet regs. however, a pasive slab will have a greater amount of insulation below as well as to the sides to avoid cold bridging

Both have insulation under the concrete slab. The main difference is how they deal with the cold bridge formed where the inner leaf of the outside walls reaches the ground. For example in many houses this leaf is block and rests on the foundations - so it penetrates through the floor insulation. There are many ways around the problem. One is to extend the insulation under the inner leaf and build the inner leaf resting on the slab rather than the foundations. That way the insulation under the floor joins u with insulation in the walls.

 

https://images.app.goo.gl/fqbHMhnXRw9P4YwL7

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Edited January 26, 20206 yr by Temp