Thermal Regulation in Urban Surfaces: Evaluating 3D-Printed Porous Geometries for Wild Bee Nesting Aids

Urban surfaces play a central role in mediating microclimatic conditions, influencing not only human thermal comfort but also the viability of urban biodiversity. This study explores porous, geometry-driven design strategies for urban surfaces and evaluates their thermal performance as a preliminary step toward future building envelope systems that accommodate more-than-human inhabitants. With the nest microclimate of cavity-nesting wild bees as the target condition, three experimental setups were conducted using 3D-printed (3DP) porous nesting aids fabricated via Fused Deposition Modeling (FDM) from biobased polymers and compared to a conventional reed-based nesting aid. The samples were installed on a southeast-facing façade in Stuttgart, Germany, and internal nesting tube temperatures were monitored during August 2024. All 3DP samples maintained internal temperatures up to 1.6 K cooler on average than the conventional nesting aid and, critically, none exceeded the 40 °C threshold associated with high larval mortality. In contrast, the conventional nesting aid reached peak temperatures of 41.6 °C for over eight cumulative hours. While geometric and material variations produced only modest thermal differences among the 3DP configurations, the results demonstrate that porous geometries can reduce extreme heat exposure in sun-exposed urban contexts. These findings support further development of thermally responsive urban surface systems that integrate ecological performance criteria into building design.