Installing air conditioning --> KFW funding gone?

Would the situation look different if instead of thicker windows more photovoltaic panels were installed on the roof? At least then you would benefit from it in all seasons or could use the surplus sensibly in summer?

I don't think so. As far as I know, photovoltaic can only be taken into account to a limited extent. But the energy consultant can quickly determine that as well.

I have had individual split air conditioners in the bedrooms for years, costs from 300.-- and brand inverters from 600.--€. The best investment I have ever made and KFW is not interested either

I have had individual split air conditioners in the bedrooms for years, costing from 300.-- and brand inverters from 600.--€. The best investment I have ever made and KFW doesn't care either

Can you be more specific about how you did it? Which devices? How installed? Do you have pictures?

However, at the moment the indoor temperature in the individual rooms is between 26°C and 28°C, although it is equally warm outside. We can only lower the temperature by opening the windows at night.

This is a "nasty trick" of insulation: it simply doesn't let any heat escape. In winter it's a blessing, in summer less so. Compensating with an air conditioner makes sense for living comfort but also reveals a certain absurdity regarding energy-saving goals. Shading helps prevent the heat from entering the house in the first place. A fan directed at a chair with a damp towel quickly, effectively, and quite cheaply provides cooling. The evaporation helps.

So I wouldn’t let the KFW story throw you off. The question is more about how to implement it technically. The only usable and professional solution is a split system or several. You need to answer the following questions: - How many indoor units are necessary? - Where to place the outdoor unit? - How can indoor and outdoor units be connected (each with two refrigerant lines)? - Where does the power come from (the circuit should be separately fused)? - Where does the condensate water that forms at the indoor unit go?

We have a single indoor unit that can be directed from the bedroom into an airspace and thus basically cools the whole house. The sleeping area is provided for anyway and in the rest of the house the temperature has never been higher than 22 degrees. However, the construction is also very open, it is a solid house and on really hot days the air conditioning runs all day long (at night we turn it off, but even then everything inside is cooled down enough so that the temperature does not rise above 22 degrees).

We installed the whole thing from the start (despite KFW55 – no one ever asked about it) and were able to route all lines through a shaft into the basement, from where the condensate water goes into the sewage system and the lines are routed outside to the outdoor unit.

Can you possibly run lines over an attic or position indoor and outdoor units close to each other? Is there perhaps some kind of supply shaft that is easy to open or is there a garage right next to the house? If you like, you can upload floor plans.

The installer has already complained to us that no openings were planned for the various pipes. I think if this is installed completely afterwards, the effort will be even higher than in the only partially prepared shell construction.