Lignon gets a facelift
© 2012 EPFL
The facades of this massive Geneva architectural complex, home to 6,500 people, will undergo the beginning of a lengthy renovation process today. EPFL conducted studies that gave property owners a choice in how they updated the complex’s energy efficiency.
From above, it almost looks like part of the Great Wall of China. Lignon, a massive architectural complex built between 1963 and 1972, is now part of Geneva’s cultural heritage. The longest building in Europe – 1.5 km – today houses some 6,500 people.
But the entire architectural design, audacious at the time, no longer meets current energy consumption standards. The 100,000 square meters of thin exterior “curtain walls” have no structural role; they only protect apartments from climatic extremes, but at a level that is now considered substandard. Because they are a fundamental element of the building’s character, however, it was unthinkable to change their outward appearance when it became necessary to update the buildings’ insulation.
The government of Geneva and the Lignon property owners’ group thus approached EPFL to study options that would improve the buildings’ energy consumption while still preserving its unique character.
Two variants
Franz Graf, head of EPFL’s Laboratory of Techniques and Preservation of Modern Architecture (TSAM), led this extensive research project, which began in May 2008. “We were lucky to be able to do this in a very systematic and in-depth manner, to reunite all the stakeholders around the same table, and to outline various scenarios,” he explains.
Of the four options initially considered – from simple maintenance work to complete replacement of the curtain walls – two were seen as feasible: overhauling the existing facades while increasing the level of insulation and replacing windows, for energy savings of about 33%; or their complete renovation, which would involve installing brand new insulation on the opaque panels, for energy savings of 38-40%.
© Creative commons / Esteban@flickr
These results, delivered in mid-2011 and compiled in an impressive book*, allowed the property owners to make an informed decision about the way they chose to renovate. Above all, since the work had to be done from inside the buildings, they were able to plan the work in the way they saw fit. Over the next six months, 23 apartments will be renovated.
Communal areas – hallways and entrances – will also undergo a facelift. And the installation of solar collectors on the roofs will enable the complex to reach a level of energy efficiency compatible with the Minergie standard, as well as reducing CO2 emissions by thousands of tons. Graf hopes that this undertaking will “serve as a model for renovating other buildings like this.”
* La cité du Lignon, 1963-1971. Etude architecturale et stratégies d’intervention, sous la direction de Franz Graf, hors-série de « Patrimoine et architecture », janvier 2012.