Sustainable in every sense: Telli renovation in Aarau

Sustainability played a key role from the outset in the renovation of the Telli development in Aarau. Alongside energy efficiency goals, social factors were also important.

We have all heard the saying that every problem is also an opportunity. Sometimes it rings true, other times not so much. In this story about real estate emissions, the former certainly applies. The problem is a familiar one: buildings account for a large share of greenhouse gas emissions around the world – Switzerland included.

The opportunity concerns reducing or even eliminating these emissions and thus making a substantial contribution to creating a carbon-neutral society. AXA owns a great deal of real estate, so it has a special responsibility in this respect. The refurbishment of the Telli housing estate in Aarau illustrates how it is addressing this in practical terms and why sustainability means more than just reducing CO₂ emissions. Building sections B and C, with their 581 apartments, are among the largest properties in AXA’s real estate portfolio.

Sustainability is about more than just reducing CO₂ emissions

Ground was broken on the Telli development in 1971. The four huge apartment blocks were designed by the architect Hans Marti and are listed as significant to the region's cultural heritage. Situated in an expansive park that serves as an important leisure space for the whole of the surrounding area, they currently house an eighth of the city's population. It would therefore not be socially acceptable to force all the affected tenants to move out during the renovation. This is one of the reasons for the decision to renovate the building while it is still occupied, making the Telli renovation one of the largest construction projects of its kind in Switzerland.

This information alone is an indication of the necessity, scale and complexity of this renovation. As the year of construction suggests, the development no longer met the standards that applied at the start of the renovation project, particularly in terms of energy efficiency. Its cultural significance demands a cautious approach. Its sheer size made social inclusion and political cushioning obvious. From this perspective, this project was a prime example of the practical application of a broader concept of sustainability that also took into account social aspects in addition to energy indicators and biodiversity targets and required transparent communication with all stakeholders.

A comprehensive, carefully thought-out renovation project

On the basis of these conditions and circumstances, a large-scale refurbishment project was drawn up which sought to upgrade the Telli in various areas without compromising its valuable character. From an ecological point of view, the focus was on two sub-projects. The first is a complete overhaul of the site's energy use that involves insulating the façade and installing a new district heating system as well as state-of-the-art ventilation. This will reduce CO₂ emissions by around 1,000 tons a year. On the other hand, the park was partly redesigned and upgraded with near-natural areas that provide habitat for different plants and animals. At the same time, the redesigned park landscape was intended to be a meeting place for all residents of the Telli. The landscape architect’s design explicitly addressed the wishes of the general public.

In the interests of social sustainability, meeting areas, friendlier outdoor areas, for example thanks to new lighting concepts, or even a neighborhood meeting point with common areas were created.

The key challenge of this project was to take the path towards carbon neutrality as a global society while preserving biodiversity. This was achieved only with broad local acceptance and support. The renovation of the Telli development is an example of how all aspects of sustainability, both environmental and social, can be addressed.