Passive house / KFW40 / KFW55 possible with gas condensing boiler?

Is it possible, with a gas condensing boiler and solar thermal system and

- sand-lime brick masonry with strong insulation
- controlled residential ventilation with heat recovery
- almost optimal south orientation (south-southwest)
- triple-glazed windows
- underfloor heating with very low supply temperature
- square floor plan without bay windows, projections, etc. / "city villa" with 2 full floors

to reach one of these standards? Is that economical as well?

(I mean, with the gas condensing boiler you have the lowest investment costs but the highest costs per kWh – so savings there should pay off the most, right?)

I haven’t given any thought to the slab on grade so far, I assume there are usual thicknesses and insulation here?

As always: It has to be calculated. It depends not only on the orientation but also on the type and number of windows. My experience: Kfw 70 is feasible, anything below that is only possible with considerable additional effort (if gas is used). ==> not economical within a finite observation period

Hello,

Is it possible, with a gas condensing boiler and a solar thermal system and

- sand-lime brick masonry with strong insulation

What does "strong insulation" mean?

- controlled residential ventilation with heat recovery
- almost optimal south orientation (south-south-west)
- triple-glazed windows
- underfloor heating with very low supply temperature
- square floor plan without bay windows, projections, etc. / "town villa" with 2 full floors

to achieve one of these standards? Is that also economical?

That is a question that depends on many factors and unfortunately cannot be answered through this forum. From experience with many construction projects, I would guess that you will "probably" achieve KfW 70 with this package, but certainly will not fall below that. It takes a bit more

Rhenish greetings