KFW 55 - Insulation under the floor slab

Logically, thermal bridges are relevant, also according to the Energy Saving Ordinance 2013, furthermore, they must be individually proven for the KFW house as well, even if generally optimized thermal bridges are assumed.

Where should the problem be if you want to have a heated basement?
One can also work with exterior and interior insulation.

Why gamble here when the experts are on site,...

When you mention the heated basement, it is not common to heat the basement if the floor slab is insulated. It does not have to be 21°. Are your basements cold? Our basement is not meant to be a living basement, only for technical equipment, utility room, and workshop.

U-values: Roof 0.15 Exterior wall 0.20 (42.5 T9) Basement wall 0.24 Floor slab 0.25 Thermal bridge surcharge ??? Brine-water heat pump (trench collector) with controlled residential ventilation with heat recovery.

We don’t have a basement, but that would actually make it even better. As I said, it strongly depends on the details, but your basement walls will be insulated from the outside, right? For comparison: We also have 42.5 T9 Roof however 0.13 and floor slab 0.19. Air-water heat pump and controlled residential ventilation with heat recovery By the way, we simply calculated with a thermal bridge flat rate since it didn’t matter (no KFW subsidy claimed). What heating load do you come up with? Want to have it calculated? KFW 55 shouldn’t be a problem with those specifications. Windows surely also 0.8?

It is the Iko Enertherm PIR Aluminium WLS 023.

Where did you buy the insulation? I need 10cm insulation -> 60 and 40mm and I'm currently looking for where I can get the insulation cheapest.

I bought 2 x 5 cm at the local hardware store for €9.71 including VAT. It was even slightly cheaper than online, but much more importantly – it was available on site, so I could return the leftover remainder. If you do it yourself and order online: don’t count on 10% waste. You hardly have to throw anything away. Leftovers can always be fitted in somewhere. We had maybe 1% waste... we cut both sides with the utility knife and then simply snapped it off as usual.

I bought 2 x 5 cm at the local hardware store for €9.71 including VAT. It was even slightly cheaper than on the internet, but much more importantly - it was available on site, so I could return the leftover piece. If you do it yourself and order online: don’t count on 10% waste. You hardly have to throw anything away. You can always puzzle the leftovers somewhere. We had maybe 1% waste ... we cut both sides with the utility knife and then just broke it normally.

Was that possibly a hardware store chain? I somehow can't get the insulation for under €12. Your price is really amazing. We have already laid the insulation and screed ourselves in the technical room. Although here it's only 9cm PUR, but in that room it doesn't really matter.