Budget planning for second house construction - experiences

Oh, in the area there are spots without internet and cell phone reception. Very good for the soul. The square meter doesn't cost that much there...

Basically, we are aiming for something between kfw40 and Passive House. It is supposed to be an age-appropriate + child-friendly house.
KfW loans or similar are rather uninteresting.
Unless there are corresponding child allowances and Baukindergeld combined up to a possible construction....

The floor plan should have clear structures (no bay windows / no dormers).

Back in 2008, we were told that the heating costs + hot water with about 500€ were excellent, and better insulation made no sense. Today, due to increased electricity prices (because of the air heat pump), we pay a good 1000€ per year. So I see the whole thing long-term.
But clearly: It makes no sense to spend 20,000€ more to ultimately save 100 euros in energy costs.

Land prices between 80 - 150€ are still possible here, without giving up the internet...

As for construction supervision by an architect, we don’t yet know if it makes sense. We tend towards TÜV supervision for certain trades (waterproofing/window installation/insulation/plaster). I think you can save a bit there. Especially since I have heard from a builder that their architect did not really fulfill the construction supervision properly (except for timely invoicing).

Since some acquaintances are currently building with local companies, we have current practical references.

Actually a ground source heat pump, because I want the best possible energy costs. The really good inexpensive air heat pumps (Panasonic / Nibe) nobody installs in our region.

Photovoltaics because I already have experience with it. Good purchasing options and contrary to popular belief, it pays off (apart from the hassle with the tax office - but I already have practice with that).
Questions:
Are there any experiences whether a flat pent roof (7° pitch e.g. with special roof tiles) is actually still cheaper than a flat roof with a slight roof pitch?

Can aluminum windows be priced between plastic and wood/aluminum?

Is it safe to assume that fixed glazing is cheaper than openable windows?

Are there concrete price comparisons/experiences between SOLID WOOD in Kfw40 / passive house range and SOLID STONE?

How much does an architect’s draft plan cost roughly, with which you can obtain offers from companies (once a plot of land is reserved)?

Attic with flat roof / shed roof?

Can aluminum windows be priced between plastic and wood/aluminum?

No, aluminum is significantly more expensive than wood-aluminum.

Can it be assumed that fixed glazing is cheaper than operable windows?

Yep

What does a draft plan from an architect roughly cost, with which you can obtain quotes from companies (once a plot is reserved)?

That would include approval planning phases 1-4. Roughly 14-18K€. It depends on the building value.

Attic with flat roof / shed roof?

No, aluminum is quite a bit more expensive than wood-aluminum.

Yep

That would be with permit planning phases 1-4. Roughly 14-18k€. Depends on the building value.

Thanks for the information. I like to get a rough idea in advance before entering into any discussions to choose a cheaper option beforehand.

Attic?
An attic would not be bad (but it doesn’t have to be 2 meters high).
Of course, it also depends on the maximum building height allowed in the respective development area.
Due to the maximum partial basement of, for example, the garage, a bit of storage space is needed.

Regarding the topic of solid wood vs. solid stone, I was interested in experiences concerning costs when both variants are brought to the same insulation level. So KfW40 or better towards passive house. The new KfW40 is already almost towards passive house as far as I have understood so far. Only the calculation according to passive house standard includes -from practice collected- values. Monolithic construction in the solid stone area is probably quite difficult to realistically achieve the values. For example, Poroton T8 0.15. Therefore, insulation makes more sense. U-value: Roof approx. 0.11 W/(m²K), Windows 0.60 - 0.80 W/(m²K), Exterior wall 0.10-0.12 W/(m²K), Basement wall ? W/(m²K), Floor slab ? W/(m²K)

Can aluminum windows be priced between plastic and wood/aluminum?

Do you mean windows made entirely of aluminum? We have plastic windows with an aluminum outer shell. It cost us just over €2000 more for 16 windows. Four of them are floor-to-ceiling. An exterior foil would have cost us about €1000. It was a local provider, Illerplastic. I'm also from the area. Wood-aluminum windows are of course something different. I imagine windows made entirely of aluminum are complex because of the thermal break, as is done with aluminum front doors. But I don't know how common aluminum windows are.