Using EPS flooring for ICF extension instead of PIR

[damocoleman]

So I have an ICF extension to an old stone cottage.

In the old stone cottage I am putting in a standard limecrete floor, however for the ICF part, I am torn as to whether I really need PIR in there.

I'm looking at putting in either 50 or 75mm EPS given the insulation of the ICF.

 

I will be using standard rads in the ICF, not UFH btw

 

Any thoughts greatly appreciated!

[Dave Jones]

75mm of eps is basically nothing. you need roughly double the thickness of eps to achieve same as celotex.

[saveasteading]

17 hours ago, damocoleman said:

an old stone cottage

This will probably have very shallow footings that must not be undermined.

Limiting the insulation to 75mm adjacent might be wise. But pir will double the insulation and the extra cost will be recovered very quickly. It may reduce heat loss from the existing house a bit too.

There's no reason you can't then increase the thickness away from the wall.

Ask your merchant if they've got any damaged pir. It's going to be buried.