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Microclimatic Effects of Retrofitting a Green Roof Beneath an East–West PV Array: A Two-Year Field Study in Austria

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  • Leonie Möslinger

    (Research Unit of Ecological Building Technologies, Institute of Material Technology, Building Physics and Building Ecology, Faculty of Civil- and Environmental Engineering, Vienna University of Technology, Karlsplatz 13/207-3, 1040 Vienna, Austria)

  • Erich Streit

    (Research Unit of Ecological Building Technologies, Institute of Material Technology, Building Physics and Building Ecology, Faculty of Civil- and Environmental Engineering, Vienna University of Technology, Karlsplatz 13/207-3, 1040 Vienna, Austria)

  • Azra Korjenic

    (Research Unit of Ecological Building Technologies, Institute of Material Technology, Building Physics and Building Ecology, Faculty of Civil- and Environmental Engineering, Vienna University of Technology, Karlsplatz 13/207-3, 1040 Vienna, Austria)

  • Abdulah Sulejmanoski

    (Research Unit of Ecological Building Technologies, Institute of Material Technology, Building Physics and Building Ecology, Faculty of Civil- and Environmental Engineering, Vienna University of Technology, Karlsplatz 13/207-3, 1040 Vienna, Austria)

Abstract

Integrating photovoltaic (PV) systems with green roofs presents a synergistic approach to urban sustainability. Many existing flat-roof PV installations, often east–west oriented with limited elevation, present integration challenges for green roofs and are therefore understudied. This study addresses this by investigating the microclimatic effects of retrofitting an extensive green roof beneath such an existing PV array. Over a two-year period, continuous measurements of sub-panel air temperature, relative humidity, and module surface temperature were conducted. Results show that the green roof reduced average midday sub-panel air temperatures by 1.7–2.2 °C, with peak reductions up to 8 °C during summer, while nighttime temperatures were higher above the green roof. Relative humidity increased by up to 8.1 percentage points and module surface temperatures beneath the green roof were lowered by 0.4–1.5 °C, though with greater variability. Computational fluid dynamics simulations confirmed that evaporative cooling was spatially confined beneath the panels and highlighted the influence of structural features on airflow and convective cooling. Despite limited vegetation beneath the panels, the green roof retained moisture longer than the gravel roof, resulting in particularly strong cooling effects in the days following rainfall. The study highlights the retrofitting potential for improving rooftop climates, while showing key design recommendations for enhanced system performance.

Suggested Citation

  • Leonie Möslinger & Erich Streit & Azra Korjenic & Abdulah Sulejmanoski, 2025. "Microclimatic Effects of Retrofitting a Green Roof Beneath an East–West PV Array: A Two-Year Field Study in Austria," Sustainability, MDPI, vol. 17(16), pages 1-23, August.
    • Handle: RePEc:gam:jsusta:v:17:y:2025:i:16:p:7495-:d:1727810
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    References listed on IDEAS

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    1. Maurizio Detommaso & Antonio Gagliano & Luigi Marletta & Francesco Nocera, 2021. "Sustainable Urban Greening and Cooling Strategies for Thermal Comfort at Pedestrian Level," Sustainability, MDPI, vol. 13(6), pages 1-23, March.
    2. Mohammed J. Alshayeb & Jae D. Chang, 2018. "Variations of PV Panel Performance Installed over a Vegetated Roof and a Conventional Black Roof," Energies, MDPI, vol. 11(5), pages 1-14, May.
    3. Lamnatou, Chr. & Chemisana, D., 2015. "A critical analysis of factors affecting photovoltaic-green roof performance," Renewable and Sustainable Energy Reviews, Elsevier, vol. 43(C), pages 264-280.
    4. Alexander Pichlhöfer & Azra Korjenic & Abdulah Sulejmanovski & Erich Streit, 2023. "Influence of Facade Greening with Ivy on Thermal Performance of Masonry Walls," Sustainability, MDPI, vol. 15(12), pages 1-17, June.
    5. Jaffal, Issa & Ouldboukhitine, Salah-Eddine & Belarbi, Rafik, 2012. "A comprehensive study of the impact of green roofs on building energy performance," Renewable Energy, Elsevier, vol. 43(C), pages 157-164.
    6. Smith, Sarah E. & Viggiano, Bianca & Ali, Naseem & Silverman, Timothy J & Obligado, Martín & Calaf, Marc & Cal, Raúl Bayoán, 2022. "Increased panel height enhances cooling for photovoltaic solar farms," Applied Energy, Elsevier, vol. 325(C).
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