KfW from 57 to 55 - Calculation and Certification, Expert

Hello,

We had planned so far with KfW70.

Some information is still missing; but as I read it, you will also only get a KfW 70 efficiency house. More is not possible with your house design - as described in the post.

For me, it is not primarily about the KfW55 certification, but rather about possibly achieving higher comfort without additional costs.

Then stick with KfW 70; this is currently the most economically sensible choice. The next step towards 55 definitely requires about €10,000 (and depending on the provider, significantly more), an external expert must oversee the construction, and at the end of the day you might save just €100.00/150.00 annually on energy costs. Now you can calculate yourself how long it takes to amortize the additional investment.

Rhenish regards

Hello,
I just spoke again with the expert office.
The problem is indeed the H'T value, meaning the heat loss through the building envelope. A ventilation system doesn’t help with that either.
To get this value below 70%, bigger measures (thicker stone or insulation) would be necessary, which alone would exceed the 2,500 € significantly.

Therefore, I will stick to the planned KfW 70 efficiency house and keep in mind that at least on paper I have good values.

Thanks also for your hints and contributions!

Good that you recognize the issue with the paper. A previously somewhat more active co-writer here, whose name rhymes with a widely used European currency, would have probably explained to you very explicitly that the paper format can differ significantly from reality (keyword: heating costs), especially for air-to-water heat pumps.

VG

K1300S