Serial renovation as a model for the future

In total, 16 buildings originally constructed in 1974 are being fully modernised. Their previous energy consumption was around 90 kWh/m²a, which corresponds to a “C” energy rating. The aim is to achieve the KfW55 Efficiency House standard and reduce the primary energy requirement to approx. 18 kWh/m²a. As part of the renovation, the external walls are being reinforced with pre-fabricated façade units using a timber frame construction method. These have already been fully thermally insulated, triple glazed, and fitted with window sills and sun shading. Thanks to the high level of pre-fabrication, it is possible to renovate over 2000 square metres of façade in around six weeks. The roofs are also being insulated, photovoltaic systems are being installed and the building services and lifts are being refurbished.

The apartments in the Corelli Quarter all have a loggia – a covered balcony that is integrated into the building floor plan. These loggias pose a challenge for serial renovations because, unlike the external walls, they cannot be reinforced with pre-fabricated units. However, it was not possible to renovate the loggias in the conventional way either. “The state subsidy programme for serial renovation stipulates that at least 80% of the non-thermally broken façade must be renovated in series using pre-fabricated units,” explains Jessica Böshagen, Technical Project Manager at Rheinwohnungsbau GmbH.

The solution was to use curtain wall façade units made of aluminium fitted with folding sliding systems, all from Schüco. They are prefabricated to exact specifications by the contractor Metallbau Helmut Pasternak GmbH & Co. KG, therefore ensuring the project's eligibility for serial renovation funding. They form the new thermal envelope of the building in the area of the loggias. In the spandrel area, the units consist of fixed glazing and, in the top area, of folding sliding windows. By using triple insulating glass with a U_g value of 0.5 W/m²K, a U_w value of 0.9 W/m²K can be achieved – outstanding thermal insulation, which transforms the former loggia into a pleasant living space that can be used all year round. By folding the window units and sliding them to one side, the space opens up across almost the entire width and can be used like a balcony, as before.

Installation of the façade units in the area of the loggias ran very smoothly. First of all, the spandrel cladding was removed and the balcony floors were renovated. The units, which were manufactured according to 3D measurements, were fitted with steel brackets for fixing by the metal fabricator at the factory. These were structurally calculated and bear the load of the units suspended in front of the wall. After installation, all of the attachments were insulated, with no thermal bridging, and clad with aluminium sheets or reinforced fibre cement panels. The units are fitted with vertical sun shading made from a textile fabric that can be controlled electrically, which provides the residents with both convenience and comfort. How the sunlight enters the building can be individually controlled, thereby preventing rooms from overheating.