As the IBA Project Thuringia, a prefabricated housing estate from GDR times has been undergoing renovation since 2020. The Ossietzky courtyard in Nordhausen with the houses "Franzi", "Ludwig" and "Sophia" is exemplary for the preservation of the building fabric - the buildings were carefully developed and given a new architectural quality with the smallest possible interventions. In the case of "Ludwig", the architectural firm Hütten & Paläste succeeded in doing this in particular with an additive component: it expands the living space, serves as a balcony, loggia, and wintergarden at the same time, and contributes to energy generation as a climate buffer.

In its architectural concepts, the architectural firm Hütten & Paläste generally considers the entire life cycle of a building. With such a sustainable approach, they impressed in 2018 in the realization competition "Multitalent gesucht" for the prefabricated housing district Nordhausen-Nord, organized by the municipal housing association in cooperation with the city of Nordhausen. The search was on for smart ideas that achieve the greatest possible effect with the smallest possible interventions.

The building names "Franzi", "Ludwig" and "Sophia" also come from the competition phase, which are intended to underline the change from uniform prefabricated buildings to individual living. Today, they are connected to each other by a common terrace zone, which enables barrier-free access. The terrace creates an intimate green interior that doubles as a rainwater buffer reservoir.

In the end, "Franzi" had to make way for an energy-plus house in timber construction due to excessively high pollution levels. Among other things, "Sophia" was modernized with maisonettes and a wide arcade to create a "flexible value-added panel" and upgraded to KfW Standard 85. The planners envisaged the fewest interventions for the "Ludwig A+B" building sections, which were renovated while they were inhabited: The adjacent five-story prefabricated buildings from 1980 were retained in their basic structure and now comply with KfW Standard 100 through a few but targeted measures.

"Glass completely or half open, sun protection lowered or not – in the added wintergardens, residents can control the climate and atmosphere of their open space themselves," says Frank Schönert, summarizing the advantages of the additive component. He sees another positive effect in the fact that these are visible on the façade as individual actions of the residents, thus picking up on the basic idea of the design concept."

In the ground floor flats, the conservatory glazing from the Proline T system by Solarlux was chosen to be floor-to-ceiling, creating a seamless transition into the gardens. On the upper floors, they are mounted on the parapets, a deliberate decision made in consultation with the building physicist to avoid excessive heat gain on sunny days. However, if it gets too warm or more fresh air is required, the glazing elements can be pushed aside by the residents and rotated by 90 degrees. They are parked as unobtrusive glass packages on the balcony partition walls. A narrow ventilation gap of just 3 mm between the vertically frameless elements ensures the necessary air exchange when closed.

The energy concept was planned across all buildings and demonstrates the possibilities of climate-friendly neighbourhood development: Up to 44 percent of the energy required for heating and hot water will be generated on site in future. Photovoltaic systems were installed on the roofs of ‘Ludwig’ and ‘Sophia’ to supply the building services. ‘Ludwig’ is therefore heated with a mix of district heating and local renewable energy sources, while “Sophia” is heated with exhaust air heat pumps, with district heating only being switched on at peak times. The new ‘Ludwig’ conservatories also contribute to local energy generation. ‘Heat recovery via the climate buffers, geothermal energy and the large solar panels generate surplus energy. This has reduced the ancillary energy costs to around 70 percent,’ says Frank Schönert from Hütten & Paläste, explaining the benefits for the residents, who will be significantly less dependent on fluctuating energy prices in future.