ᐅ Does this turn a KfW 70 house into a KfW 55 house?

Hello everyone,

So far, our house design has been officially certified by the architect as KfW 70 standard.

However, there are now some changes: a ground source heat pump instead of a gas/solar system, a controlled ventilation system with heat recovery (previously none was planned), and 0.5 glazing instead of 0.7 glazing.

Could these changes affect the KfW rating? Since the architect is currently on vacation for three weeks, I’m unable to ask him =(

Best regards

Hello,
everything is possible.
We have planned a KfW 70 house (with ground source heat pump, controlled mechanical ventilation with heat recovery, good insulation). Due to the building services technology, we could even choose simple glazing – the overall window U-value only needs to be 1.2 W/m²K (0.21 Btu/h·ft²·°F)!!!
We have now also decided on a small photovoltaic system because, with our large family (constantly running appliances like washing machine/dryer/dishwasher), a lot of electricity can be used on site. This allows us to meet the requirements for a KfW 55 house.
Therefore, the answer for your house can only come from the person who prepares the energy performance certificate.

KFW55 is possible, but the entire process needs to be recalculated from scratch. We are currently going through this process (from KFW70 to KFW55). As a layperson, I didn’t realize there are so many additional forms and requirements that all have to be submitted for KFW55. Especially the confirmations during the construction phase make it somewhat more complicated. So, in general: it is possible, but definitely not guaranteed.

nordanney schrieb:

We have now decided to install a small photovoltaic system because, with our large family (constantly running appliances like the washing machine, dryer, dishwasher), we can use a lot of the electricity ourselves. This way, we achieve the values required for a KfW 55 house.

Hmm, then something must be wrong?! Electricity used for the household cannot be included at all in the KfW calculation if there is a separate meter for the heat pump! We fell for that as well; the KfW or the energy consultant corrected us. (As I said, with two separate meters for the heat pump and the household, and the photovoltaic system tied to the household, it does not count at all for the KfW calculation – it is explicitly excluded.)

Hello Wastl,
there will be no separate meters. The heat pump has a direct connection for the electricity from the photovoltaic system, and the energy certificate specifies KfW 55.
These are the details we have, and this is also how the KfW application looks.

nordanney schrieb:
Hello Wastl,
there will be no separate meters. The heat pump has a direct connection for electricity from the photovoltaic system, and the energy certificate requires KfW 55.
These are the details we have, and the KfW application looks the same.

Then that’s correct – only the electricity from the photovoltaic system used for the heating system (possibly a controlled ventilation system with heat recovery?) qualifies for KfW 55. I just wanted to clarify your original post: electricity for the washing machine, dryer, PC, etc., does not qualify for KfW funding. With your setup, you will need to calculate (or estimate) exactly how much electricity actually goes to the heat pump and what does not. But the energy planner has probably already done that.