kfw40plus monolithic solid - tips/experience?

Hello everyone,
we are planning a house in the Allgäu. Since it is not exactly small and includes 3 residential units, we would like to use the kfw40plus subsidy. The photovoltaic system is already planned extensively (the entire roof), so that is already decided. In addition, a water-guided wood stove.

Now I definitely want to build solidly and do not like external insulation. My favorite is a purely monolithic stone like aerated concrete or expanded clay (so also without the filled stones like Cariso).

The house is being built on a hillside, the basement is open on one side and is used as living space. Therefore, I would like to use a masonry basement if it is not counterproductive to achieving the kfw40+ target.

I have now received several opinions from construction companies and architects (including passive house planners). I have the impression that everyone wants to "sell" me what they have their experience with.
How can I calculate whether, for example, a 42.5 cm Ytong wall meets the kfw40+ standard and which accompanying measures I need to implement (windows, roof, basement floor, other energetic measures...)
Possibly one can adjust a few other factors so that the masonry is as thin as possible (possibly even 36.5 + plaster)? Of course, the whole thing should not cost more than the subsidy and the heating cost savings bring!

Some say the 0.07 Ytong or Poroton is so delicate that it breaks in your hands... I should rather go for 0.08 and make the wall thicker... there are so many opinions.

Is there anyone here who has truly built purely monolithic massive and achieved the kfw40+ standard?
Who has tips?

Greetings from Munich.

Can no one here really give any tips? The kfw40+ issue is surely also relevant for other builders and thus for architects and construction companies!?

I would suspect that an independent energy consultant with proper training can help. Alternatively, an architect – but no one will do it for free; after all, it is a planning service. Alternatively, you follow the regulars' table or educate yourself. Your specialist planner will then surely also question the technologies you have "set" once again – in terms of sensibility and economic viability -> photovoltaics over 10 kWp; the residential unit with the stove goes on vacation, etc.

The purpose of photovoltaics becomes clear in the relocation of an existing system, in the operation of electric cars, and a public charging station. The surplus electricity is sufficient to heat all residential units. The wood stove is intended for the ambiance and possibly as an adjustment to meet the funding requirements. As a double backup for heating/domestic hot water, I am open to further measures, e.g., pellets, heat pump... or simply a gas condensing boiler.

As mentioned, I consulted several specialist planners, energy consultants, and architects. Everyone tries to talk me out of kfw40plus or persuade me to choose a timber frame construction or external thermal insulation composite system (ETICS). Apparently, nobody likes to tread untrodden paths... maybe there is no possibility? That may be. But here in the forum, I read that builders have even achieved a KfW40 standard with a monolithic Liapor exterior wall of 42.5 cm. Somehow it has to be possible – KfW would hardly try to steer builders away from solid construction, especially since there are energy-saving potentials in the production of exterior walls, not to mention recycling!?

Who can show me which wall constructions are possible monolithically? With which measures a weaker wall structure can possibly be compensated for?

Hello,

Photovoltaics are already well planned anyway (the entire roof), so that is already set. Additionally, a water-guided wood stove.

I understand photovoltaics - but not the type of stove. You should urgently talk to an MEP planner about this.

How can I calculate whether I can meet the kfw40+ standard with, for example, a 42.5 Ytong wall and which accompanying measures I need to take (windows, roof, basement floor, other energetic measures...)

You can't, there are people who have learned this and constantly update their knowledge.

Maybe you can turn a few adjustment screws elsewhere so that the masonry is as thin as possible (possibly even 36.5 + plaster)? Of course, the whole thing should not cost more in additional expenses than the funding and heating cost savings bring!?

Some say the 0.07 Ytong or Poroton is so delicate that it breaks in your hands.. I should rather go for 0.08 and make the wall thicker.... there are so many opinions.

Is there anyone here who has really built purely monolithically massive and achieved the kfw40+ standard? Who has tips?

Kfw 40 and KfW 40+ are absolutely no problem monolithically. But you will very likely have to give up trying to achieve this with a 36.5 stone. Since you initially speak of 3 residential units, the little "loss" of floor area due to the 42.5 stone should not be a problem.

You will need an independent energy consultant to accompany the construction project anyway. It would therefore be advisable to seek early talks with him so that all components - residential basement + 2 residential units - can be lived in at the end of the day without any loss of comfort. The same obviously applies inversely to possible oversizing. At the very least, a salesperson who has already built houses of this kind and knows the subject matter.

I have a slight feeling that you are getting lost in planning without knowing _exactly_ what is coming your way. Is there already a planning and a price overview?

Rhenish greetings

Hello construction expert,
Thank you for the information. I have already answered some questions in my post sent at the same time.

Sure, there is a completed and approved submission plan. Financing is also secured. I am only looking for a contractor and/or architect to implement it.
Contractors all only give me offers for kfw55. I would have to sign this offer and then enter the calculation phase... only then would I know the additional cost that achieving kfw40+ entails. This is unsatisfactory. There are suggestions that it will only be feasible with great effort and with 50 cm walls and will cost more than the repayment subsidies (3x €15,000 + €18,000).
An energy consultant and passive house planner I found, who seems competent and open enough to me, on the other hand, indicates feasibility but does not give me a price for the house construction. This requires extensive planning for which he wants to charge me about €4,000 initially. Only then will I know a price at all and may then find out that this is outside the budget or that kfw55 would be the more economical alternative anyway!?