Viessmann Gas Heating Vitodens 200-W as 26kw or 35kw version?

Hello. Our construction company suggests that we should get a gas heating system from Viessmann Vitodens 200-W in the 35kW version. I am a bit worried that the gas heating system might be oversized and not run economically, repeatedly turning on for short periods. The gas heating system is also available in 13kW, 19kW, and 26kW versions. According to the manufacturer, the 26kW or 35kW versions are recommended for single-family houses. 13kW and 19kW are only recommended for apartment units. We will build a two-story single-family house of about 185m2 with a ventilation system with heat recovery. 2 adults and 2 children want to shower and have it warm. ;) What do you think about it?

That is a big house. Take the 35 er. Having is better than needing.

What does the heating load calculation say, how is the hot water supply regulated? Heating load at standard conditions (-10 to -16°) should not be over 10kW for you! So what is a 35kW monster doing in there? Exception: hot water with the instantaneous water heater principle. But even then I consider 35kW to be.... That thing will short-cycle itself to death. Please have the heating technician justify it with the heating load calculation and not with "we've always done it this way"

Sorry , but in my opinion, this is the wrong approach...

A heating load calculation according to DIN EN 12831 should be carried out, on the basis of which the sizing of the boiler is done and the installation distances of the underfloor heating or the sizing of the radiators are determined.

Controlled residential ventilation with heat recovery (WRG) indicates a well-insulated house.

Example with us: 160 sqm, no basement, controlled residential ventilation with heat recovery, solar for hot water, KFW 55 => heating load 6.4 kW => 14 kW condensing boiler from Wolf. Our annual consumption is about 850 m³ of gas.

If the heating system is oversized, this mainly leads to frequent cycling and, in my opinion, is not exactly beneficial for durability.

just my two cents... ;-)

EDIT: 2 minutes too late... ;-)

The heating load for such a new building is somewhere around 6-8 kW, especially with [Kontrollierte-Wohnraumlüftung mit Wärmerückgewinnung], rather in the lower range. Anyone who wants to install a 26 kW heat generator there has missed their calling. It is simply sad how this industry works. The unit will cycle endlessly, which affects the device's lifespan. Even with the "small" 13 kW version, you get hot water like from a tankless water heater.