KFW40(plus) standard multifamily house cannot be achieved

double-shell masonry with a thickness of 49cm, structure 17.5 Ytong, 12cm PUR insulation, 0.24 air layer and 11.5cm facing brickwork

8cm air layer? Please check again.

You have 49cm thickness with 24cm blocks, 12cm core insulation, 1.5cm finger gap and clinker. If you have 17.5cm blocks then the wall is 42-43cm with 12cm insulation. With better insulation maybe 2-4cm more. The expensive PUR insulation seems unnecessary for KfW 40. PUR behind clinker? Sure?

You are trying to compensate for weaknesses of your energy consultants through the forum. Based on your information one can only guess where the problem with the calculation lies.

Where is this supposed to lead? It certainly will not be the only problem. What else do the energy consultants do for you?

My suggestion: It is a large project. Find someone who fits your plans. Now is exactly the right time. Wrong planning may possibly cost more than the emergency brake.

I read a lot of inconsistencies there. The house is supposed to measure seven by twenty meters in floor area. That is already an unfavorable dimensional ratio in terms of exterior wall area to building volume – one is glad to comply economically with the Energy Saving Ordinance and does not aim to exceed the standard. Especially for a multi-family house, especially since 74 sqm in the attic and 2x 2x 50 sqm sound like zero self-used residential units. I would not call it a five-family house but rather a house for one family apartment and four apartments. That alone already sounds, to put it mildly, like a greenhorn as an investor. And a plot of land that is supposed to be so disadvantageously usable on the other hand allows five residential units (by the way, usually equivalent to eight parking spaces)?

My spontaneous impression is, with due respect, someone fell for the "multiplying borrowed money made easy" sayings from real estate salespeople, something like "with subsidy money, it pays for itself." I imagine a plot that is awkwardly cut with too much area to be interesting for a single-family house buyer: you then sell it to someone who is told that with the right advisors you can fill it up to the eaves height with yield.

These are the calculated values.
Annual primary energy demand QP / QP,Anf 2.7 kWh/(m²a)
Transmission heat loss H'T 0.192 W/(m²K)

I see a lot of inconsistencies there. The house is supposed to measure seven by twenty meters in ground area. That alone is already an unfavorable ratio in terms of exterior wall area to building volume – you’re glad to economically comply with the energy saving ordinance and are not aiming for over-fulfillment of the standard. Especially in the case of a multi-family house, as 74 sqm in the attic and 2x 2x 50 sqm sound like self-used residential units of zero occupancy. I wouldn’t call that a five-family house either, but rather a house for one family apartment and four apartments. That alone already sounds like, to say the least, a greenhorn as an investor. And a plot that is supposedly so unfavorably utilizable still allows five residential units (by the way usually equivalent to eight parking spaces)?

My spontaneous impression is, with due respect, that someone fell for the "multiplying borrowed money easily" sayings of real estate salespeople, like "with subsidy money it pays for itself." I imagine a plot that is awkwardly shaped with too much area to be interesting for a single-family home builder: you then sell it to someone who is told that with the right consultants you can fill it up to the eaves height with yield.

Unfortunately, you are mistaken, the plot is a double plot and is already built with a house from the 1950s and already in my possession, next to it is space of the indicated size, since there is no development plan, the new buildings have to adapt their size according to the existing buildings according to the building authority.

8cm air layer? Please check again.

You have 49cm thickness with 24cm bricks, 12cm core insulation, 1.5cm finger gap, and clinker. If you have 17.5cm bricks, then the wall is 42-43cm with 12cm insulation. With better insulation maybe 2-4cm more. The expensive PUR insulation seems unnecessary for KfW 40. PUR behind clinker? Are you sure?

You are trying to compensate for weaknesses of your energy consultants through the forum. Based on your information, one can only guess where the problem in the calculation lies.

Where is this supposed to lead? It will certainly not be the only problem. What else do the energy consultants do for you?

My suggestion: It is a big project. Take someone who fits your plans. Now is exactly the right time. Wrong planning may cost more than the emergency brake.

The energy consultants otherwise do nothing for me, only the calculations for the KfW. PUR behind clinkers only came into play to improve the thermal values, not a good idea?

The energy consultant otherwise does nothing for me, only the calculations for the KfW PUR behind brick slips was only applied to improve the thermal values, not a good idea?

That's what I thought. Nevertheless, this attempt apparently did not help. With the 49cm wall thickness, that is completely unnecessary, unusual, and expensive. I doubt the wall thickness or your information about it – see my post above – please calculate it yourself, there must be an error somewhere. But the wall does not seem to be your problem. Where the consultant can get information has been written by .