Financing / Equity / Granny Flat - Fundamental Thoughts

The heating system consists of a brine heat pump and surface heating/cooling ceiling. Photovoltaics/storage are of course primarily intended to cap energy costs.

I am not an expert in innovative heating technology, I only know a few examples where what was once innovative is now a burden.

In order to deduct everything from taxes without limitation, the rent must be 66% of the local customary amount. But even then, there are design options (garden work). The rest is regulated through Christmas gifts; without me wanting to encourage tax fraud here

It's all double-edged. Low rent = good for taxes. Low rent = low income at the bank and no loan ;).

It's similar to "I sell my house and the kitchen, furniture, garden tools, etc. separately to save real estate transfer tax." And then being annoyed that the bank values the house low, you get a worse interest rate, and over the next 30 years pay a multiple of the "saved" real estate transfer tax through the higher interest rate.

The heating technology consists of a brine heat pump and surface heating/cooling ceiling. Photovoltaics/storage are of course primarily intended to cap energy costs.

I am not an expert in innovative heating technology, I only know a few examples where what was once innovative is now a burden

However, I am an expert in innovative heating technology. In the future, the cooling load will be more decisive than the heating load. The Energy Saving Ordinance forces builders to implement massive insulation measures and controlled residential ventilation. This greatly reduces energy consumption for heating but, combined with large windows, results in a high cooling load. The houses warm up and the heat is nicely stored inside. However, an air conditioner or a reversible air heat pump operates on electricity, i.e., the cooling compressor, which leads to very high energy consumption. At the same time, too much cooling of the building components carries the risk of condensation due to dew point undershoot.

The combination of brine pump and cooling ceiling provides a) energy-efficient cooling (for example, only a 40-watt pump runs, passive cooling with ground probes, no compressor cooling, no Carnot principle) and the cooling ceiling ensures better "heat transfer," so the component temperature does not have to be lowered as much, hence the risk of dew point undershoot does not exist.

There are such pilot houses from BayWa, built in Bavaria. Highly efficient, basically simple systems. The funding is of course also lucrative.

explain to the experts who back then recommended night storage heaters, large water masses heated overnight, or the first heat pumps. Even the first intelligent controls are now just a burden, just like the mistakes made in insulation back then. If you want, you can build your house according to the latest technological achievements, but you should not expect it to be worth more in 20-30 years compared to a "normal" house

Interesting. What does such a cooling ceiling look like in practice? I only know it from office buildings, but that’s not really something for the living room. So what does it look like in the single-family house sector? Why not use controlled residential ventilation for air conditioning?

Storage batteries are not really cost-effective yet. Do you get them so cheaply that it still works out? Also keep in mind that you might not receive funding if the installation is not carried out by a professional company. Material for self-performed work is no longer subsidized, right?

Also note that you might not receive any funding if the execution is not carried out by a professional company. Materials for self-performed work are no longer funded, right?

No, everything must be done through professional companies.