ᐅ Is a gas condensing boiler without solar thermal system sufficient for a KfW 70 standard?

Dear forum community,

I have already posted some information and read a lot about heat pumps and related topics. We are planning to build (with solid construction) and have signed the contract with our developer. The plans are completed, and the application for the KfW loan has been prepared (the loan has already been approved, but I still need to provide the proof).

The architect calculated a yearly primary energy demand of 36.2 kWh/(m²a) (11.5 kBtu/(ft²·yr)).
We want to use a heat pump for heating and hot water (IWS, ground-source heat pump, including controlled ventilation with heat recovery up to 90% (90 percent)).
The windows are double-glazed, and the exterior walls, including the bricks, insulation, and cladding, are about 44 cm (17 inches) thick in total.

The architect included a solar thermal system for hot water preparation in the calculations. However, we do not want this system, and he said: Then KfW 70 will not be achieved! 😕 🙁

He argued that the heat pump consumes electricity, which is negative.
If we were to install a gas condensing boiler (but no solar thermal system), KfW 70 would be reached.
I actually expected that with the heat pump, ventilation, heat recovery, and overall insulation, we would at least meet KfW 70, possibly even KfW 55.

I am quite frustrated about this right now...
🙁

I should probably mention: We have electric roller shutters and are considering possibly installing a photovoltaic system on the roof (however, this is not yet certain).

I would have the same doubts as you.
We achieve KFW 70 by installing a heat pump instead of a gas condensing boiler and solar panels.
Why should it be different for you?

The only thing that caught my attention in your entire list is the double-glazed windows.
You invest a lot of money in the building envelope, heating system, and mechanical ventilation with heat recovery, and then save on the windows?

Hello,

James schrieb:
...and we have signed the contract with our general contractor, ...

A general contractor (GC) or main contractor, not a developer! The legal differences should actually be known!

James schrieb:
....The architect also included a solar thermal system for domestic hot water preparation. But we don’t want that – and he said: Then KfW 70 won’t be achieved! 😕 🙁

With a ground-source heat pump usually the issue is not qp´´ but rather Ht´. How exactly a solar thermal system would solve or improve this is probably only known to that architect! ;-) I would part ways with such a blind spot!

James schrieb:
....He said the heat pump consumes electricity and that’s bad.

Nothing is free of charge, basically! ;-)

James schrieb:
...If we installed a gas condensing boiler (but no solar thermal), KfW 70 would be reached.

How should that work without additional thermal insulation (15% rule) according to the Renewable Energy Heat Act (EEWG)? ;-) Does he really know what he is talking about?

James schrieb:
....I had rather expected that with a heat pump, ventilation with heat recovery, and standard insulation we would achieve at least KfW 70, perhaps even KfW 55.

With a heat pump as the main heat source, usually not qp´´ but rather Ht´ is the challenge to reach, for example, KfW 55. Achieving KfW 70 is generally not a problem!

James schrieb:
....I’m quite frustrated right now...

Maybe better ask a specialist (beforehand) ;-)

Best regards

James schrieb:
The architect has been working for our general contractor for many years and they are very satisfied with him.

That might be an advantage for the two of them, but is it really beneficial for you...?

We are currently working on a KfW 70 house. We don’t have solar panels or photovoltaic systems, but we do have an air-to-water heat pump and triple-glazed windows. Unfortunately, I don’t know the exact name of the building material we’re using, but it’s not Ytong. The insulation thickness will be calculated later to ensure we meet the KfW 70 standard.

Our architect said that triple glazing is already standard these days. He also pointed out that you need to make sure the insulation thickness matches the windows properly to prevent condensation.