New building KfW55 with gas, solar, and controlled residential ventilation with heat recovery

Hello everyone!

We will start building next week. And we still have not planned any solar. The KfW application has long been approved and it will work without solar. I will check the exact data later. Just know that our exterior walls will be about 48cm thick. Double-shell masonry. Extra insulation in the base plate. And windows with a U value of 0.7.

Regards

With an air-to-water heat pump, KFW55 is not really a problem due to the better factor. The challenge here is the whole thing with gas.

That's how it is. Although controlled residential ventilation with heat recovery can replace solar thermal to represent the renewable share. However, the investment is likely greater than building solar thermal. On the other hand, you gain the benefit of controlled residential ventilation. Another alternative would be biogas, if available (which is probably rare).

Hi! I also have a question for the experienced ones:

Do the requirements to be met for the KfW55 loan correspond with the requirements for the heat demand calculation for the building application? In other words: can I meet the requirements for building my single-family house with gas and controlled residential ventilation, but without ST, and still not be eligible for the KfW loan? Regards does

Yes, you are allowed to build without meeting KfW55. The minimum requirements are regulated by the Energy Saving Ordinance.

and no, your described equipment does not automatically mean that the house also meets KFW 55. In addition to the technology, which essentially affects the primary energy demand, the insulation or transmission heat loss must also be correct.

Another update from us: We received confirmation today from the KfW consultant: KfW 55 according to the reference value method and system technology gas/ST & controlled residential ventilation with wall construction 3/4 clinker 1/4 plastered: bottom 17.5 calcium silicate brick + 16 cm insulation WLG 032 - 11.5 clinker - top 17.5 calcium silicate brick - 16 cm ETICS WLG 032 (possibly also 18 cm WLG 035, because we want mineral insulation) - 1 cm synthetic resin plaster)