KFW55 in unheated existing property

Hello,
we bought a plot of land with an old fieldstone building.
It is a former granary. It was built around 1900 and is completely dry. The floor area is 450 sqm over 3 floors, a total of about 1350 sqm.
The wall thickness is about 80 cm fieldstone masonry up to the roof. Not just the base.
We would now like to build two apartments on the second floor of about 350 sqm.
The second apartment is for my parents.
The ground floor is intended to be used as a garage and workshop, and the third floor only as an attic.

We would also like to use the KfW153 funding and achieve the KfW55 standard. Is this even possible with such an old building, and can only one floor of a building be used energy-efficiently?

The alternative would be to build a completely new building next door, but this old building has much more charm and I would like to preserve it.

We do not yet have concrete plans. If a new building were cheaper, I would rather build new.

With a new building, I roughly know what to expect regarding thermal insulation, heating, etc., but with an existing property, I would be interested to know what kind of thermal insulation would still have to be done from the inside with 80 cm fieldstone walls.

Best regards

Hi,
something like that sounds exciting! :-) Technically it is probably possible, but only at a high price. Building new will almost certainly be cheaper. Building inside the grain storage will mean preserving the outer walls and building a house inside. Someone did that in my hometown, the result is beautiful, but it was apparently significantly (!!) more expensive than just tearing down and rebuilding.
Also, the 80 cm wall thickness will spoil your view out of the window. You’d have to cut in huge windows to let in any light at all.
It can absolutely turn out great, but definitely not cheap!

Best regards,

Andreas

That would be my question, is it necessary to build a house within the house or would it be sufficient to install an [WDVS] from the inside, or to build without [KfW] funding at the bank's worse financing rate.

There are a total of 14 windows per floor and currently one door per side each. The doors were previously used to have access from outside with the conveyor belt and are quite large. They are well suited for floor-to-ceiling windows and the windows are also sufficiently large. Nothing should be changed regarding the statics. I would leave 3 large floor-to-ceiling windows and 9 small windows. I did not want to change the lintels etc. nor the size. It is bright enough.

What would be the minimum requirements for thermal insulation in order to reclassify the building as a residential building at all? Leaving the interior construction completely out for the time being. Purely the shell construction costs for 4 walls + ceiling + floor + heating.
I can obtain the costs for the interior construction separately from various companies, as I know enough people in the different trades from electricians to plumbers to drywall installers.

The intermediate ceilings are designed to hold tons of grain. I did not want to gut the building.

However, I lack the information or the requirements for the shell construction and what is necessary there.

KfW 153 is only available for new buildings. Energy renovations can be found in program 151 and the other programs that can be combined with it. In addition, depending on the federal state, there are often subsidies for conversions to residential use.

What you are planning is a change of use requiring a building permit, which is only possible through the application by an architect. In addition, you need a structural engineer for the building application statics and the thermal protection certificate. For KfW funding, a building energy consultation (calculated proof of energetic renovation) and the support + documentation of the implementation by a qualified energy consultant are necessary.

What you first need to clarify in advance - in the form of a building inquiry - is whether you are even allowed to carry out a change of use at this location according to building and planning law. If the grain storage is located in the so-called "Außenbereich" [outer area] - outside built-up localities - relatively strict requirements apply to changes of use and structural alterations according to §35 of the Building Code. This also applies to your new construction project.

I recommend, for all further considerations, immediate collaboration or consultation with an architect experienced in renovations. Expertise is also a prerequisite for (energetic) renovation planning in order to avoid construction damage. Own work should also be planned in advance.

Whether the conversion is financially worthwhile for you can be shown by the architect at the end of performance phase 2 (preliminary planning) in a cost estimate. Generally, in such contexts, a conversion is always significantly more expensive when carried out properly = with architect/structural engineer.

Basically, the KFW raised interest rates significantly again last week. Currently, you can sometimes get significantly better conditions on the market than with the KFW. The effort is only worth it to achieve a KFW standard in that case.

For me, the question is more about the time horizon, as this can change again. At the moment, I would advise everyone to talk to their bank! We are signing tomorrow and are getting a better interest rate than with the KFW, along with a 10 years longer (30 years) fixed interest period :-)