Omit the single room rule? Controlled residential ventilation + gas heating, new construction

At that time, I was unaware of the exemption regulations, and therefore the ERR were initially installed by me. However, I have mostly deactivated them afterward. An exception is, for example, the guest room. It is heated at a low level by default but should also be able to be turned up when it is used. This should also be done without manual adjustment in the HK distributor. However, we also do not have controlled residential ventilation.

But the purchase price is also 5000€ higher and the electricity price is unknown, gas is still so established in Germany, even in many public institutions, they don’t quickly turn the price screw extremely, at least in my opinion.[...]

Where does the myth of the higher purchase price come from? Gas+solar thermal would have been significantly more expensive than our air-water heat pump.

My personal opinion: This is the same discussion as SAT yes/no, only that you have to obtain an additional approval for this. And from my point of view, it also aligns with SAT-no. You don't need it, but if you want to sell the house, you'll get weird looks. You know what I mean? My first and only house viewing had no ERR, as a layman you think oh man what a botch. No one assumes they will want/have to sell their house in 10-15 years. But I personally think it is also like SAT-no, depreciating to build without ERR. Why don’t you combine heating circuits on one ERR? You surely have an open living space! I come up with 8 controllers including the basement, even though I know that due to inertia I only fiddle with it 2-3 times a year. There are also changeover switch and ERR combinations where it doesn’t stand out directly. The extra cost of about €40 per switch was really too much for me, but the separate ERR doesn’t bother me either. Here, among other things, the heating distribution box on the ground floor is "hidden" behind a sideboard, moving it 2-3 times a year is annoying.

Yes, that is indeed a point. But you can also sell it as a technical highlight "self-regulating heating, you don't have to worry about anything." In the greatest emergency, it can be retrofitted quickly as well.

Flat roof and photovoltaics work great (as long as there is no shading). The edge around the roof a bit higher, a mounted 10kWp east-west system on it and you have electricity without changing the architecture. Priority on self-consumption (battery), feed excess production into the grid. If the liquidity is there, it's a "no-brainer".

It was about whether controlled residential ventilation is sufficient as a replacement for ST regarding the roof shape.
It has nothing to do with the roof shape at first, only gable roofs tend to be inexpensive to insulate, depends though.

Photovoltaics of course make sense. Battery storage is not yet economical.

How about pulling empty conduit instead of installing it? If necessary, it can be retrofitted at any time.