ᐅ Experience with KfW55 solid construction + gas heating + 5 sqm solar panels

Hello everyone,

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

We live at just under 300 meters (985 feet) above sea level and built with solid construction.
The house has a rather simple shape.
A standard gable roof without dormers or skylights (upstairs there is one window per room on the gable side).

Styrofoam was not an option for various reasons, so we chose the rather expensive monolithic plan blocks with a lambda value of 0.08.

Size: 111 sqm (1195 sq ft) living space.
Exterior wall: 36.5 cm (14 inches) Ytong blocks // Lambda 0.2 W/m²K
Floor slab insulated with XPS // 0.21 W/m²K
Ceiling on the upper floor has a sloping roof with 24 cm (9.5 inches) // ceiling insulated with 34 cm (13.5 inches) mineral wool // 0.12 W/m²K
Doors and windows are triple-glazed and gas-filled // overall including frames 1.05 W/m²K

Heat generator:
Gas condensing boiler: Viessmann Vitodens 300
System control: Vitotronic 200
Solar thermal system 5 sqm (54 sq ft): Vitosol 200-F
Solar storage tank: Vitocell 100-W 300 liters (79 gallons)

The solar system is used only for domestic hot water (no heating support).
Our gas boiler is switched off from May to September for heating and still consumes about 100 kWh of gas over the summer.
In winter, the solar system barely manages to heat the hot water (2 people), so it usually runs on gas.

Ventilation is handled by decentralized Lunos e² units with 90% heat recovery.

Over 12 months, we had a gas consumption of 8000 kWh.
That currently corresponds to heating costs of about €28 for the house.
We have the temperature set to 23°C (73°F) throughout the house.
(Electricity costs are about €39.)

Overall, we are very satisfied. Of course, the energy certificate shows lower consumption than we actually have.
There is no night setback, and nothing ever switches off or regulates down.

Maybe someone has had similar experiences?
Personally, I’m relaxed about heating costs; even if energy prices rise, paying twice as much would still be less than I used to pay in my smaller 80 sqm (860 sq ft) apartment built in 1990.

I’m very pleased to receive your message, as we are building something similar. That gives hope regarding gas consumption. Karsten

Thank you very, very much for the post. I am planning to build something similar. However, I wasn’t sure how to account for the heating costs. We want about 160m² (1,722 sq ft) of living space, but otherwise a comparable system. Could you also say something about the decentralized ventilation? Noise level? Control options?

@Abbrummbaer There is a thread in this forum about the system that is at least 20 pages long, with many impressions. You can form your own opinion there. We now have it in the apartment, and I definitely wouldn’t want it in the house.

ares83 schrieb:
@Abbrummbaer There is a thread in this forum about the system that is at least 20 pages long with many impressions. You can form your own opinion there. We have it in the apartment now and I definitely wouldn’t want it in the house.

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

ares83 schrieb:
@Abbrummbaer There is a thread in this forum about the system that is at least 20 pages long with many impressions. You can form your own opinion there. We have it in the apartment now and I definitely wouldn’t want it in the house.

Hi. You’re talking about the e2. I found and read the thread. But, as always, opinions are mixed. Okay. There are other models, of course. But the fundamental question is whether the system is centralized or decentralized.

Well, pretty much all the pros and cons of these systems are mentioned in there. You have to weigh them up for yourself. Perceptions vary a lot; a colleague has the system and thinks it’s great. We don’t like the “hole in the wall” acoustics and the operational noise. There really isn’t a single truth when it comes to construction.