Abstract
The assessment of the suitability of existing buildings for implementation of green roofs is an important research issue, especially in the context of Urban Heat Island (UHI), the negative impacts of which are locally exacerbated by the global warming. The studies carried out so far have covered a variety of buildings and have taken into account a range of different conditions. Relatively little attention has been paid to the possibilities of greening the roofs of prefabricated apartment blocks from the second half of the 20th century in the context of the potential climate effect. Yet, these buildings are found in many cities around the world, and seem in fact attractive for greening. In view of the above, we proposed a three-stage investigatory procedure to: (I) identify and classify buildings based on the number of floors and the rooftop available area; (II) select buildings by designating priority areas depending on the highest UHI intensity and roof density; (III) analyse the roof load capacity to develop retrofit scenarios. The procedure was applied to prefabricated housing estates built in the 1970s and 1980s in Wrocław, Poland. The research shows that there are 1962 buildings of different heights and roof area of 722405 m2, of which 480 buildings with a roof area of 122749.1 m2 were selected for greening within priority areas. The structure of the studied roofs was not designed to carry additional loads, which requires the application of complementary solutions. Scenario 1 assumes extensive greening provided that the existing ventilated roof is strengthened, scenario 2 –semi-intensive greening, which however requires the conversion of the ventilated roof to a non-ventilated one. The presented procedure can be applied in any other city with prefabricated apartment blocks and available UHI data, and serve to support the decision to implement green roofs to mitigate UHI.
Highlights
Planning and designing green roofs provide several environmental and social benefits and allows to achieve a more sustainable, resilient, healthy urban environment [1,2,3,4,5,6]
We proposed a procedure consisting in the identification and selection of buildings and the assessment of the possibility of greening their roofs as a way to mitigate the Urban Heat Island (UHI) effect
The annual cycle of UHI intensity depends on meteorological conditions and artificial heat release, so the most optimal conditions for UHI occur in the warm season, with the highest values recorded in Wroclaw in May and August due to increasing convective cloudiness in mid-summer (June, July)
Summary
Planning and designing green roofs provide several environmental and social benefits and allows to achieve a more sustainable, resilient, healthy urban environment [1,2,3,4,5,6]. Many countries are making strong initiatives to apply the green roofs at the newly erected as well as already existing buildings [6]. One of the main motivators for implementing green roofing systems is minimizing the UHI effect [7]. Covering the building with greenery, including replacing its roof with a green roof, is considered one of the ways of regulating the local climate, including the reduction of the UHI [10, 11]
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