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Green roofs for reduced runoff in a subarctic climate?

Published: 25 October 2022

How well do green roofs work to reduce runoff in subarctic climates? This is the question that Dag Schéele, student in Master Programme in Architectural Engineering at LTU, investigated in his master thesis project "Rainwater management with green roofs in subarctic climate".

By analyzing data from green roofs in Kiruna and Umeå, the retention could be quantified. Even in a subarctic climate, the various roofs could reduce runoff by 60 to 70 percent on an annual basis. A model was also built for the roof in Umeå to further study which design factors were important for the roof's hydrological performance. It was found that the depth of the roof substrate has a large effect on the retention capacity of the roof, while the slope of the roof or the length of the flow path over the roof was of less importance. This indicates that you have quite a lot of freedom to design the roof based on for example aesthetic considerations without negatively affecting the function of the roof.

The measurements in Umeå was carried out in collaboration with VAKIN and in Kiruna in collaboration with Tekniska verken and NCC. Ico Broekhuizen and Joel Lönnqvist have been the supervisors for the degree work and Godecke Blecken the examiner.