Climate change City of Zurich takes 40 measures to combat hot days

The city of Zurich has implemented or initiated around 40 measures to improve the city's climate in the first four years of "heat reduction planning": There are "forward-looking projects" in urban building and civil engineering projects, the city summarizes - now projects on non-urban areas are also to be promoted.

Heat reduction considerations are now firmly integrated into the day-to-day work of urban planning, Health and Environment Director Andreas Hauri (GLP) told the media on Monday. Corresponding measures are an "integral part" of road construction projects, said Simone Brander (SP), head of civil engineering, while André Odermatt (SP), head of building construction, spoke of "standard".

The tree as air conditioning

There will be more extreme temperatures and the number of hot days and nights will increase, Hauri noted. "We need to adapt our city to this." Trees that provide shade and noticeably reduce temperatures in the surrounding area through evaporation are the "best air conditioning systems".

According to Brander, trees are given better conditions for road projects. Instead of 12 cubic meters, 35 cubic meters are now available for their root zone. In addition, a specially developed granulate is used to promote growth in the urban environment.

In order to improve the urban climate, Odermatt also relies on additional trees in existing buildings. Artificially shading areas and unsealing built-up areas are also suitable for this purpose. "With these three measures, 90 percent of the possible heat reduction can be achieved."

Trees block the view

However, the "Status report on the 2020-2023 implementation period for heat reduction planning" also revealed that heat-reducing measures often compete with other requirements.

As part of the "Zurich West" pilot project, for example, the majority of areas that at first glance would have been suitable for heat-reducing redesigns could not be adapted at all. There were a number of reasons for this, Brander said on Monday.

Sometimes a new tree would have restricted visibility and endangered traffic safety. In other places, existing utility lines were in the way of the roots or the lanes were too narrow. In addition, not all asphalt surfaces could be torn up because they would no longer be obstacle-free to cross.

Gaining new insights

Even if not all measures could be implemented, the three members of the city council drew a positive balance from the first four years of "heat mitigation planning": many insights have been gained and more are to follow, they said on Monday.

The fog cloud installed on Turbinenplatz, for example, had a certain cooling effect on the surrounding area on hot days. However, the effect remained relatively small - partly due to the wind. The pilot project ended in 2023 and will not be continued.

Work continues elsewhere: On the Dreiecksplatz in Oerlikon, for example, which is a heat island as a gray asphalted parking lot, the effects of unsealing parking spaces are being investigated. Materials such as natural stone, concrete and lawn grids are being tested in various designs and in combination with different seed mixtures.

According to Brander, initial findings have already been published in information sheets. Two further series of measurements should confirm the effects in the coming years.

Promoting private conversions

According to the status report, the focus for the next period 2024-2027 will now be on completing the conceptual work and developing measures for areas in non-urban ownership.

One major instrument here is funding, such as that approved under the Urban Green Initiative. In April, the City Council approved an initial tranche of CHF 28.2 million to advise private property owners and support them in implementing heat-reducing measures.