Construction costs are currently skyrocketing

Slate floor would of course be better than slant floor.

Oh, by the way: My ventilation system ([Angebot 2020], now in operation but final invoice not yet issued):
approx. 7000 plus VAT. Designed for 151 m³/h volume flow

Sorry, but you can’t compare prices like that! None of you write what area or volume is supposed to be ventilated, nor anything else about the equipment. sergutsh even talks about a “surcharge” … surcharge based on what?

We have a fixed price with the general contractor for turnkey including painter’s fleece, painted. For ticking controlled residential ventilation, +7k. So without controlled residential ventilation, the total amount would be 7,000€ less. Without heat exchanger. I had written about the size.

...
What did you pay for your ventilation systems?

- a simple answer to an equally simple question

Existing houses are often individually designed, where an L-shape does not result. Many existing houses are quite charming because they are individually designed. Often I have the feeling that young people can't do anything with pearls because they are spoiled by L-space model houses.

I don't believe that this is due to the individual design. Fifty years ago, open-plan living simply wasn’t in fashion; you just had the kitchen, dining room, and living room separated. And conversely, with the individual architect-designed houses of today, you almost always have an open-plan living space because it’s modern. Just like floor-to-ceiling windows. In fifty years, we might have different floor plans. This is certainly also due to technical conditions (underfloor heating allows deep windows, windows are no longer weak points, separating rooms is no longer so important energetically, etc.). I wouldn’t make a young people bashing out of it either. Many existing houses are simply not in good condition, and as a potential buyer, you also have to critically question whether the offer and price match. And if you then have to make compromises with the floor plan in an unfavorable ratio...

I built my controlled residential ventilation system myself back then. It was a Helios Controlled Residential Ventilation EC 500 ET. It included 125mm spiral ducting (insulated with mineral wool and in problematic areas with Armaflex) with 125mm outlets and inlets including silencers and motorized dampers before each outlet and inlet. The costs were around 4k€ (because I could buy at equity prices, normally it would probably have been 6-7k€).

We are also getting the Q350TR - I don't know how much it costs individually, we said in the first conversation that we would like this one or an equivalent.