ᐅ Retrofitting an air conditioning system – will that affect KfW funding?

Reltaw2021 schrieb:

Would the situation look different if, instead of using thicker windows, more photovoltaic panels were installed on the roof? At least then there would be some benefit throughout all seasons, and the surplus in summer could be used effectively, right?

I don’t think so. As far as I know, photovoltaic systems can only be partially accounted for. But the energy consultant can quickly clarify that.

I have had individual split air conditioning units in the bedrooms for years, costing from 300 euros and branded inverters from 600 euros. The best investment I have ever made, and the KFW does not care either.

Grundaus schrieb:

I have had individual split air conditioning units in the bedrooms for years, costs starting at 300.-- and brand inverter models from 600.--€. The best investment I ever made, and KFW doesn’t care either.

Could you explain in more detail how you installed them?
Which units did you use? How were they installed?
Do you have any pictures?

Helado schrieb:

Currently, the indoor temperature in individual rooms is between 26°C and 28°C (79°F and 82°F), even though it is just as warm outside. We can only lower the temperature by opening the windows at night.

This is a "tricky" aspect of insulation: it simply doesn't let any heat escape. That's a benefit in winter, but less so in summer. Using air conditioning to compensate improves living comfort but also highlights some absurdity regarding energy-saving goals.
Shading helps by preventing heat from entering the house in the first place. A fan directed at a chair with a damp towel provides quick, effective, and fairly inexpensive cooling. Evaporation makes a difference.

I wouldn’t let the KFW issue confuse you. The real question is how to implement it technically. The only viable and professional solution is a split system or multiple units.
You need to answer the following questions:
- How many indoor units are necessary?
- Where will the outdoor unit(s) be placed?
- How can the indoor and outdoor units be connected (each requires two refrigerant lines)?
- Where will the power supply come from (the circuit should be separately protected)?
- Where will the condensate from the indoor unit drain?

We have a single indoor unit, which can be directed from the bedroom into an open space, effectively cooling the entire house. The sleeping area is well covered, and temperatures in the rest of the house have never exceeded 22°C (72°F). The construction is very open, it’s a solid concrete house, and on really hot days the air conditioning runs all day (we turn it off at night, but even then the interior stays cool enough to prevent temperatures rising above 22°C (72°F)).

We installed everything from the start (despite KFW 55 standards – nobody ever asked about it) and were able to run all the lines through a shaft into the basement, where the condensate drains into the wastewater system and the lines run outside to the outdoor unit.

Is it possible for you to run lines through an attic or position the indoor and outdoor units close together? Is there maybe an accessible service shaft or a garage directly next to the house? If you like, you can upload floor plans.

The installer has already complained that no openings were planned for the various pipes. I believe that if everything is installed completely afterwards, the effort will be even greater than in a partially prepared shell construction.