Historic renovations in Aachen – or how to reach the right balance between monument and energy conservation

Joseph-von-Görres-Strasse_After_Façade

Some buildings maintain decades of history inside them, survive wars and bombings, but fail to keep their inhabitants and visitors warm in hard winter times. In Aachen, at the border of Germany and at the heart of past European conflicts, several historical buildings from the early twenties suffer from insufficient insulation and do not comply with current energy efficiency standards. In the framework of the EU-GUGLE Smart City Initiative, the municipality, owner of the buildings, has decided to include two of these building blocks in the city’s renovation programme to offer their inhabitants increased comfort and reduced energy bills.

From officers to refugees: Aachen’s social housing buildings throughout times

Located in the Eastern part of the city, mainly developed as from the 19th century, the two building blocks selected for renovation were erected in the early twenties, according to the designs of the architects Joseph Catzen and Fritz Toussaint. Following the destructions resulting from the First World War and due to the arrival of Belgian troops with their families, and persons displaced by the conflict, the city of Aachen was facing a shortage of apartments in that period. To be able to provide a roof to its new inhabitants, the municipality undertook an ambitious construction and extension programme in the Eastern part of the city.

After being the homes of soldiers, the buildings became a shelter for low-income populations, including craftsmen and teachers, offering rooms as from 10 Reichsmark per month. Each of the building blocks integrates an inner courtyard for laundry as well as playgrounds for children. Their general architectural style follows the German Heimatstil, with some characteristics of the “new objectivity” (Neue Sachlichkeit) movement from the twenties. The building blocks retrofitted in this area as part of the EU-GUGLE project are located in Joseph-von-Görres-Straße, and between Reimanstraße and Sigmundstraße in the Rehmviertel, and include respectively 19 and 14 buildings. They are now used as social housing, hosting asylum seekers and other deprived households.

Making energy-efficient renovation rime with heritage conservation

Some parts of the buildings were severely damaged during the Second World War, meaning that renovations had been already carried out before to restore the residential estates in a makeshift manner. The two locations are now protected as listed buildings and their refurbishment is thus partly restricted in order to preserve their original design. Looking for ways to improve the comfort of their present inhabitants, the municipality of Aachen engaged dialogue with the monument protection authorities to discuss possible options to increase the buildings’ energy efficiency. As this is very often the case for historic buildings, the façades could not be insulated, and no solar panels could be installed on the roof due to monumental restrictions. But if there is one thing the municipal team of Aachen is good at, it is compromise. To compensate thermal bridges from the front façade, additional insultation was added in cellar ceilings and attics – and when this was not even possible, as in the case of the Reimanstraße building, insulation was installed under the screed of the ground floor. As for the windows, their choice reflects the perfect balance between energy efficiency and monument preservation: while their frame is made of wood to adapt to the buildings’ architectural style, their panes are triple-glazed to ensure maximal protection against the cold during winters.

“In historic buildings, you have to find tailor-made solutions to balance energy efficiency and heritage conservation” says Dr. Maria Vankann, Climate protection Manager at the Municipality of Aachen, “very often, it is just a matter of ensuring close dialogue between monument conservation authorities and technical experts”. In the course of the revision of the Energy Performance of Buildings Directive, the European Commission committed to meet nearly zero energy standards in the building sector by 2050. If historic buildings are not expected to reach the best energy performances, their contribution will be essential to reach this target and move towards a decarbonised European building stock.