Experiences Single-Family House KfW55 - Assigning Tradesmen Yourself?

You have to calculate differently. Costs of the heating system, plus additional effort kfw divided by 120, due to 10 years of relatively low-maintenance use, plus monthly amount for consumption added gives comparable monthly costs. If you do this for a gas boiler plus gas, for an air-water heat pump plus electricity, etc. pp, you will find that kfw is not worthwhile, and the unpopular gas boiler is quite far ahead. Always remember, the heating engineers want to sell, not save your money. Karsten

Another generalization. Of course, we have calculated everything including investment. Our trench collector + brine/water heat pump investment is practically not higher than a gas system including the required gas connection, chimney, and solar thermal (probably the biggest nonsense) .... The trench collector costs us <3,000€ with a BAFA subsidy of 4,500€ ... and additionally significantly lower monthly costs... and also KFW funding... It is not only positive over a 10 or 20 year period, it practically pays off from the first minute....

But as I said, this is our individual case! Anyone who wants to build nowadays without controlled residential ventilation, I do feel sorry for them, but of course they save 10,000€ right away. This is accordingly not included in our investment since it is mandatory for us anyway, regardless of the KFW standard.

Almost everyone wants to sell condensing gas boilers... sure, here you can hardly make any mistakes in the design. For every heating technician it is probably the easiest option, even TGA planners love this possibility... if it is poorly designed, you simply raise the flow temperature arbitrarily... who cares about efficiency anyway

We consciously decided against the KFW-55 option during the planning phase. We are also building with a basement and solid construction. Execution according to reference values is usually nonsense and leads to high additional effort. When calculating all thermal bridges, it is mainly the energy consultant who profits. The additional costs then have to be financed, and interest is paid on them for 20 years.

Our tip would still be to pay attention to good execution; although it is then not an official KFW-55/40, it is energetically equivalent.

With [Kontrollierte-Wohnraumlüftung], new airtight windows, and no gross nonsense in the execution, heating costs should remain within limits.