Surcharge KfW 70

Hello everyone,

We are close to deciding whether provider A or provider B should build our house.
The planning for both houses is exactly the same except that House A is equipped with a Dimplex air-to-water heat pump installed indoors and achieves Kfw 70.
House B has a Viessmann split air-to-water heat pump and does not reach Kfw 70. My advisor told me that the extra cost to reach the 70 standard would be about €7,500.
How do you assess this? Both houses are built solid with 36.5 cm Poroton bricks.
Thanks in advance for your answers!

Regards

Hello,

from my inquiry experience, I want to tell you that KFW70 is actually standard. Without extra charge.

What kind of Poroton bricks?
36 cm bricks are not equal to 36 cm bricks.

With T12 or T14 bricks you will not reach Kfw 70. With T9 or T8 you will. If a supplier usually only uses T12 bricks, then the surcharge for T9 is already realistic.

We build with 36 cm T9 Poroton bricks and also get an air-water heat pump as a split unit and easily achieve KFW 70.

from my inquiry experience, KFW 70 is not standard, but must sometimes be requested or mentioned right away.

Oh, my mistake.
Provider A: aerated concrete blocks with 0.09W/mK
Provider B: aerated concrete blocks with 0.27W/mK

Supplier A: aerated concrete blocks with 0.09W/mK

What kind of stone is that supposed to be?
The standard offer from our supplier was also without KFW70; only a 30 cm Ytong was installed here with, I believe, 0.32 W/m2k.
However, our extended KFW70 offer includes far more than just a different stone. The KFW70 planning contains a 36 cm Ytong with 0.23 W/m2k, as well as additional insulation for the floor slab, roof, windows, and doors. The additional costs amount to just over 5500 euros for us.
Both offers, however, are planned with a gas condensing boiler and residential ventilation with heat recovery. I don't know if the air-to-water heat pump plays such a strong role in the calculation that only a different stone is sufficient for you, especially since the efficiency of an air-to-water heat pump strongly depends on the insulation.

All in all, I find the 7500 quite realistic, depending on the size and type of the house.

Hello,

Oh mistake on my part.
Provider A: aerated concrete blocks with 0.09W/mK
Provider B: aerated concrete blocks with 0.27W/mK

Something else must still be wrong here. In the original post you write about Poroton and now about aerated concrete...

Rhenish greetings