Floor construction height: KfW55, ventilation ducts, underfloor heating 150 mm

For our new building KfW55, the general contractor proposes a floor construction of 190mm. An independent architect confirmed to us that he has planned and built his floor construction in the past with 150-160mm. His calculation is as follows:

In any case, it is your "calculation without the host" if you let your second-opinion architect meddle in the construction recipe of your planning and site management architect - too many cooks spoil the broth! This obviously applies equally to the floor construction and the roof drainage. If you have doubts about the abilities of your construction contractor architect, you should discuss with your contractor that you want to shift the lead role to the second-opinion architect. But do they have a well-practiced way of working together? Because of the difference between 270 and 266 cm clear room height, I wouldn't do that, those are peanuts. You will never notice on your sofa whether you are sitting 4 cm lower relative to sea level - that does not make a relevant air pressure difference, not even for those with heart-lung damage.

In all floors we even have 25 cm of floor construction, so I do not consider 19 unrealistic.