Planning of heating and ventilation technology for KfW 40-Plus single-family house

The heating engineer must know which one fits best.

I am just experiencing that some (many?) heating engineers actually don’t know exactly. They prefer to play it safe with oversizing. I just received a rejection for my tender. Due to BAFA, the requirements are too high...

Then be glad that he is so honest. ;)

That is also true again.

At first glance, that seems very cheap to me. So that’s a total of 39.5 kEUR for ventilation + heating + rough installation minus approx. 11.0 kEUR BAfA funding.
For the sanitary equipment, we have budgeted another 18 kEUR including installation.

I can answer that question myself. The heating engineer got back to me and said that there is "a worm in the offer" for the heating - presumably the labor costs are still missing.

The uniSTOR is only intended for hot water, that’s fine, but I am surprised by the heating capacity of the offered heat generators or the fact that two devices with different outputs are offered. The heating engineer must know which one fits best.

I would also plan for an external current anode for the storage tank. Costs little, but you’ll have peace of mind forever.

That was also my thought. I will definitely have an independent engineering office carry out a heating load calculation.

The thing with the external current anode (as corrosion protection, right?) is noted. Thanks.

There is still a compact buffer storage listed under the heat pump/Unistor sets and not as an alternative item...

And what does that mean?

It referred to the statement by that the Unistor is only for hot water. That is true, but there is also this compact buffer tank specified, and I don't know what it is for. However, I have since read that buffer tanks are not good for efficient operation of heat pumps with standard underfloor heating and heated screed without additional heat sources. Therefore, I would ask what it is for and whether it is absolutely necessary.

But be careful, I have driven away my general contractor's heating engineer with too many questions!

The thing with the impressed current anode (as corrosion protection, right?) is noted. Thanks.

Yes, exactly, as corrosion protection. The hot water tanks from Vaillant are still "classic" (i.e. not stainless steel) and therefore need a sacrificial anode, which must be replaced every few years – depending on the water quality – or alternatively an impressed current anode, which then lasts forever and protects the tank.