The Telli Area in the Swiss town of Aarau is a high-rise complex with space for about 2,500 residents. It was built between 1973 and 1985. Two of the four blocks, or about 24 buildings, underwent energy renovation between 2020 and 2023. This involved upgrading the stairwells, elevators, underground parking lots, entrances, and the building envelope, including, roofs, windows, and ventilation systems.  

The tenants only had to leave their homes for two weeks while the renovation took place. To ensure that it worked, the project team employed a high degree of prefabrication, modular construction, and lean construction management.   

The planning consortium of Drees & Sommer Switzerland and the architecture firm Meili Peter & Partner were commissioned to plan the energy renovation. Drees & Sommer Switzerland then became the general planner for the overall project management of construction for the major project.