Gas condensing boiler & ST for KFW 55 in a single-family house

Hello to the experts,

please provide assessments for the above-mentioned topic:

Family 2 adults / 2 children, single-family house approx. 150 sqm living space, concrete slab, prefab house (wall Kfw40 standard), underfloor heating
Roof orientation south with 25 degree tilt.

We want to install a gas condensing boiler with solar thermal for domestic hot water (2 collectors BF 5.02 m2) + controlled residential ventilation and thus achieve KFW 55. Why no air-water heat pump - costs!?

Now the questions:
Would heating support possibly make sense?
Would photovoltaics for heating the water and for own power consumption possibly be more useful?
I have read various things about installing a hot water line for dishwasher and washing machine, I like the idea, do you have to provide anything on the appliances for this?

Thanks for the assessments.

Regards
Charly

Would a heating support possibly make sense?

IMHO no, you will use so little gas that additional investments "are not worth it."

Would photovoltaic for heating the water and for self-consumption possibly be more sensible?

If the air-to-water heat pump is too expensive, photovoltaic will hardly be possible. By the way, for us the air-to-water heat pump was cheaper than gas + solar thermal would have been (of course, your case may be different and the air-to-water heat pump undoubtedly has its disadvantages).

We want to install a gas condensing boiler with solar thermal for domestic hot water (2 collectors BF 5.02 m2) + controlled residential ventilation and thus achieve KfW 55.

To my knowledge, according to the current Energy Saving Ordinance, a solution with a gas condensing boiler is already difficult enough. How do you then manage to achieve KfW 55?

As far as I know, according to the current Energy Saving Ordinance, a solution with a gas condensing boiler is already difficult enough. How does one then still achieve KFW55?

Gas condensing boiler + solar + controlled residential ventilation with heat recovery achieves KFW 55. Only the Energy Saving Ordinance should also work without controlled residential ventilation.

That depends on the wall structure!

There are enough topics or answers for that here.

Yes, that's right, it depends on the wall construction. In our case, it is standard KfW40. We already have the KfW confirmation. Many thanks to BIeber0815, who at least answered my question.