Work

Summer thermal consequences of EU retrofit Strategies: An integrated microclimate and indoor comfort study in Düsseldorf

Year: 2026

Type: article

Abstract: Building retrofits in temperate European climates primarily target winter heat losses, yet their dynamic implications for outdoor microclimate and indoor thermal safety under heatwaves remain poorly understood. This study investigates how winter-oriented retrofits modify both outdoor microclimate and indoor thermal conditions during July 2022 Central European heatwaves, using a one-way, offline integration of ENVI-met and CitySim. A dense residential neighborhood in Düsseldorf, Germany, was simulated under multiple retrofit and greening scenarios, incorporating realistic building data derived from the EU TABULA archetype database to ensure reliable façade–microclimate interactions. Methodologically, results show that using realistic archetypes alters simulated outdoor heat stress by up to 1.5 °C compared to generic defaults. In terms of mitigation, façade retrofits alone slightly reduce outdoor Universal Thermal Climate Index (UTCI) by up to 0.8 °C, while green infrastructure provides the strongest cooling, lowering local UTCI by up to 6 °C through shading and evapotranspiration. Typically, indoor simulations revealed a crossover effect, where retrofitted buildings remained cooler at night but became up to 3.8 °C warmer during daytime peaks, increasing short-term overheating risks in the absence of active cooling. These findings highlight a mitigation–adaptation trade-off in EU retrofit strategies: measures optimized for winter energy savings can exacerbate summer heat stress if not combined with greenery and summer-oriented design measures. The proposed framework offers a scalable workflow to support climate-resilient, human-centric retrofit planning in other TABULA-covered cities.

Source: Energy and Buildings

DOI: 10.1016/j.enbuild.2026.117163

Authors: Qinghua Yu, Gerald Mills, Gunnar Ketzler, Michael Leuchner

Institutions: RWTH Aachen University, University College Dublin

Language: English

Topic: Urban Heat Island Mitigation

Subfield: Environmental Engineering

Field: Environmental Science

Domain: Physical Sciences

SDGs: Sustainable cities and communities, Climate action

Open Access status: hybrid

Estimated APC paid: $4,260