KFW70 with gas-solar heating

We are building a timber frame house. It is insulated with cellulose. According to the architect/energy consultant, we will easily achieve Kfw55 and it will be quite "bio" thanks to renewable raw materials. A brick-and-mortar house builder we visited had already rolled his eyes when we mentioned KfW70. With wooden houses, good insulation may indeed be easier to achieve.

But always remember: Good insulation does not necessarily mean just a high insulation value. Especially in timber construction, the quality varies greatly here! Two cardboard covers with 20 cm of glass wool in between also have a great insulation value, but I wouldn’t want to live in that. Especially in timber construction, the necessary mass should also be considered. That does not exactly make quality timber construction inexpensive.

So after our appointment with the financial advisor yesterday, it currently looks like we do not want to build a KFW70 after all. The financial advantage is so small. I will still take the insulation that was intended for it, the underfloor heating that is laid closer together for the 35°C, and a ventilation system. The solar thermal system can also be added at some point if needed, and you can still have the KFW70 confirmed by an expert afterwards. Because the solar thermal system is probably not useful for anything else. Although our financial advisor looked strange when I said something about "around 30 years until it pays off." He said he had heard that it pays off after 10 years. I still have to check which one/what we were offered. And if it really is profitable (10 years), then we might take the solar thermal system after all, but no KFW70 expert. Because if we do not use the loan (with a 10-year fixed interest rate, the rest is tied up for 20 years for us), then why get the written confirmation that it is KFW70? What do you think?

Yes, that would also be nonsense

He probably means photovoltaics, which usually pay off after 10-14 years (depending on size, orientation, usage).

Hello,

we have only had the solar thermal system prepared, i.e. the corresponding pipes and empty conduits have been laid from the technical room in the basement to the attic.

Since we heat and produce hot water anyway with a [LWWP], we consider our photovoltaic system on the roof to be more important and sensible than a solar thermal module.

What kind of heating have you planned?

Best regards,

Dirk

A gas heating system. And the advisor also said that with his memories he probably had a system of over 7-9m² in mind, we only have 5.02m².