The house was built in the 1950’s and was owned for decades by a family that recently invested little in maintaining the building’s substance. The windows were fromthe 1980´s, the roof was not insulated and the facade was not in good condition. The balconies had to be renovated. The hallway, doors and backyard were in need of renovation. The building technology were also no longer state of the art.

Betzelsstr. is located in Mainz’s old town, vis-a-vis the State Theatre. The building was constructed after the war. It has two commercial units on the ground floor and a further 8 residential units spread over four floors. Five cars can be parked in the building’s backyard. The conversion work began in autumn 2021. The goal was to achieve the “KfW-eligible EE-55 house” standards. An energy consultant was hired for this purpose.

The roof was completely renovated and brought up to the state of the art. The new roof insulation and the PV system contributed significantly to achieving the energy standard. At the same time, the risers, downpipes and the entire electricity and heating supply were relaid in all flats, and a state-of-the-art hybrid system with heat pump and solar system was installed. All old windows were replaced with energy-efficient triple-glazed windows with a high standard of sound insulation. Meticulous care was taken to ensure that they were fitted with high-quality sealing strips. The bathrooms were extensively renovated and equipped with state-of-the-art technology. The old floor coverings were removed and replaced by modern parquet floors.

The facade was insulated with 18cm mineral wool. All balconies were energetically upgraded to avoid thermal bridges. Finally, the entire staircase was renovated and fitted with an interior banister running across all floors.

The reward for this detailed renovation is a final and primary energy consumption of 13 kWh/m2 per year.