“City apartments” for insects: UrbanInsects field trial

More than 40 percent of wild bee species in Baden-Württemberg are threatened with extinction. One of the reasons for this is the lack of habitat. As part of the “UrbanInsects” project, researchers at the University of Stuttgart are developing nesting aids for insects that are integrated directly into building facades. In doing so, they take a holistic approach, integrating nature conservation, environmental protection, societal needs, and technical requirements.

In March 2025, the researchers launched a field trial in downtown Stuttgart. They installed several so-called “facade-integrated habitat systems” on a residential building on Urbanstraße. After nearly a year and a half, the team is taking stock: How effective are the nesting aids? And how does this coexistence work in the “shared living arrangement” between humans and insects? 

Daniela Schätzel from the Institute for Acoustics and Building Physics (IABP) at the University of Stuttgart says, the findings point to a positive conclusion regarding the ecological effectiveness: “The nesting aids are particularly well received by wild bees and other stinging insects – and there are even a few endangered species among them.” Although the test buildings – and thus the facade-integrated nesting aids – are located in an inner-city area and are surrounded by limited food sources for wild bees and other stinging insects, five species were already identified during the first study period in 2025. Among them is the digger wasp species Passaloecus Pictus, which, as a heat-loving species, is very rare in Germany.

The research team emphasizes that while artificial habitats alone cannot compensate for the loss of natural habitats, they can serve as a useful supplementary measure to expand habitats in heavily urbanized (major) cities and thus preserve biodiversity. Ecologically valuable food resources, such as flowering native trees, shrubs, and perennials, are also indispensable.

In the field trial, the researchers are also investigating whether the facade-integrated habitat systems have any impact on the building: “Our data shows that the systems are biophysically safe for the building envelope and that its functions remain intact,” says Schätzel. In January 2026, measurements were taken of the surface temperatures on the exterior of the building’s wall and in the occupied interior space behind it to confirm the building’s structural safety. The measurements, as well as supplementary simulations, show that there is no risk of mold growth.

And how did people react to the nesting aids? During a discussion evening in November 2025, the residents of the test building expressed their overall satisfaction with the project. Throughout the entire trial period, the researchers did not receive any complaints. “That was a pleasant surprise for us. We know from numerous studies that insects are not always well-liked,” says sociologist Michael Ruddat of the Center for Interdisciplinary Risk and Innovation Studies (ZIRIUS) at the University of Stuttgart.

“However, people expressed a desire for more information and involvement before the actual installation,” Ruddat said. The sociologist and his colleague Yvonne Zahumensky, with their expertise in the field of citizen participation, can certainly understand this: “After all, the installation of these dwellings affects the immediate living environment of their human occupants. It is particularly important here to provide information about such measures early on, to communicate transparently, and to address people’s concerns through participatory processes.”

The project results provide important impetus for supporting the transition toward a sustainable city that promotes biodiversity. In order to continue studying the impact on insect populations, the project is now being extended.

About UrbanInsects
The UrbanInsects project (full title: Investigation of building physics aspects and public attitudes toward facade-integrated habitat systems for insects) is funded as part of the Federal Biodiversity Program by the Federal Agency for Nature Conservation (BfN) with funding from the Federal Ministry for the Environment, Climate Action, Nature Conservation, and Nuclear Safety (BMUKN). The “Urban Nature” funding focus within the Federal Biodiversity Program implements a key measure of the Urban Nature Master Plan, which the federal government adopted in 2019 as a program of measures for vibrant and attractive cities. The goal is to increase the proportion of near-natural, species-rich, and structurally diverse green spaces and open areas in urban areas through ecological green space management, and to improve the greening of cities and municipalities in a way that promotes biodiversity.