We have just received a quote from the general contractor. Our house is intended to meet the KfW55 standard. For this reason, they plan to insulate the foundation slab, among other things.
The foundation slab consists of 28 cm (11 inches) of waterproof concrete. The insulation is supposed to be 12 cm (5 inches) of EPS insulation beneath the foundation slab.
Now my question is: Is this okay? I tried to find some information online and keep seeing that XPS is usually installed under the foundation slab and EPS is used on top of the foundation slab. So, is this quote incorrect, or can EPS also be used beneath the foundation slab?
The foundation slab consists of 28 cm (11 inches) of waterproof concrete. The insulation is supposed to be 12 cm (5 inches) of EPS insulation beneath the foundation slab.
Now my question is: Is this okay? I tried to find some information online and keep seeing that XPS is usually installed under the foundation slab and EPS is used on top of the foundation slab. So, is this quote incorrect, or can EPS also be used beneath the foundation slab?
E
elVincent13 Sep 2016 18:41If I scale up linearly, my prices come to about €65/m² (approx. $65/sq ft) with 40cm (16 inches) GSS and a U-value of 0.28 W/m²K, or alternatively €46/m² (approx. $46/sq ft) with 14cm (5.5 inches) XPS and a U-value of 0.25 W/m²K. In this range, the price difference is quite noticeable; at 35-40mm (1.4-1.6 inches), GSS would have been cheaper.
I made a diagram showing total costs versus U-value
Edit: Diagram changed to unit price per m².
I made a diagram showing total costs versus U-value
Edit: Diagram changed to unit price per m².