Experience with KFW55 solid + gas + 5 sqm solar

Good day everyone,

I wanted to share my experiences with my Kfw55 new build from 2013/2014.

We live at just under 300m altitude and built with solid construction.
The house is rather simple in shape.
Normal gable roof without dormer or skylight (one window per room upstairs on the gable side)

Styrofoam was not an option for various reasons, hence the rather expensive monolithic plan blocks with Lambda 0.08.

Size: 111 sqm living space.
Exterior wall: 36.5 cm Ytong // Lambda 0.2 W/m²K
Floor slab insulated with XPS // 0.21 W/m²K
Ceiling in the upper floor slant with 24 cm // Ceiling insulated with 34 cm mineral wool // 0.12 W/m²K
The door + windows are triple glazed and gas filled // overall including frame 1.05 W/m²K

Heat generator:
Gas condensing boiler: Viessmann Vitodens 300
System control: Vitotronic 200
Solar 5 sqm: Vitosol 200-F
Solar storage: Vitocell 100-W 300 liters

The solar system is only for hot water (without heating support)
Our gas boiler is turned off for heating from May to September and uses about 100 kWh over the summer.
In winter, the solar system hardly manages to heat the hot water (2 people), so it mostly runs on gas.

Ventilation runs via decentralized Lunos e² with 90% heat recovery.

In 12 months we had a consumption of 8000 kWh gas.
That is currently about €28 heating costs for the house.
We have set 23°C throughout the entire house
(By the way, electricity costs are €39)

Overall we are very satisfied. Of course, the energy certificate shows a lower consumption than we actually have.
There is no nighttime shutdown and otherwise nothing ever switches off or reduces itself.

Maybe someone has had similar experiences?
In any case, I can relax regarding heating costs, even if energy prices rise, paying double would still be less than I used to pay in my smaller 80 sqm apartment built in 1990.

Your message makes me very happy, as we are building something similar. That gives hope for gas consumption. Karsten

Thank you very very very much for the contribution. I also want to build like that. But I didn't know how to plan the heating costs. However, we want 160sqm of living space. But otherwise a comparable system. Can you say something about the decentralized ventilation? Noise level? Control options?

There is at least a 20-page thread with many impressions about the system here in the forum. You can form your own opinion there. We now have it in the apartment, and I definitely did not want it in the house.

There is at least a 20-page thread here in the forum about the system with many impressions. You can form your own opinion there. We now have it in the apartment and I definitely did not want it in the house.

Yes. I have already read that. Unfortunately, it doesn’t help much.

There is at least a 20-page thread here in the forum about the system with many impressions. You can form your own opinion there. We now have it in the apartment and I definitely did not want it in the house.

Hi. You are talking about the e2. I found and read the thread. But it’s as always: differing opinions. Ok. There are other models, of course. But the fundamental question is central or decentralized, isn’t it?

Well, pretty much all the advantages and disadvantages of these systems are mentioned in it. You have to weigh that for yourself. Perceptions also vary greatly; a colleague has the system and thinks it's great. We don't like the "hole in the wall" acoustics and the system noises. There really isn't one truth when it comes to construction.