Heat-resilient design: the mapping and management of urban green roofs for cooler cities.

Abstract

Urbanization in cities has led to environmental challenges such as the UHI effect, air and noise pollution, and biodiversity loss. Green roofs have emerged as a promising multifunctional solution. This thesis aims to map and identify suitable locations for green roofs in Oslo using GIS analysis and to develop strategies to optimize their environmental benefits while considering local conditions and limitations. A comprehensive methodology was employed, combining a literature review, semi-structured interviews with local stakeholders, and GIS-based suitability analysis. The literature review identified key parameters and impacts of green roofs, with a special focus on Nordic climates. Interviews provided local insights, refining the parameters of the GIS mapping to the specific context of Oslo. The final GIS analysis revealed that 104 roofs (91 PRIOGRA and 13 PGRA) in Oslo were identified as the most suitable for green roof installations after applying all filters. These filters included roof surface area greater than 250 m², and dominating roof area and slope criteria, exclusion of cultural heritage buildings and existing green roofs, tree density per person deficit, and building age. These roofs should be prioritized for green roof implementation due to their high suitability. However, many additional roofs still hold potential for green roof installations, offering valuable environmental and social benefits despite not meeting all the stringent criteria used in this study. The GIS mapping identified approximately 2044 roofs as suitable before applying the building age criteria. These results highlight the primary candidates for green roof retrofitting, mainly residential buildings. The significant reduction in suitable roofs underscores the importance of considering individual roof load capacity when planning green roof implementations. The suitability analysis leveraged existing evidence to develop criteria for identifying suitable locations for green roof installations. This analysis indicated that, based on previous research, green roofs have the potential to significantly mitigate the UHI effect, improve air quality, enhance biodiversity, and manage stormwater effectively. However, this study did not directly verify these benefits but rather applied established criteria to assess the suitability of roofs for potential green roof implementation. These benefits are particularly valuable in densely populated urban areas with limited green spaces. Interviews with stakeholders highlighted practical challenges such as structural limitations, high installation and maintenance costs, and regulatory compliance issues. However, they also acknowledged the substantial environmental benefits that underscore the value of green roofs in urban sustainability strategies. Further research should focus on utilizing spatial data and available evidence regarding green roof suitability criteria to determine the best strategies for developing green roof infrastructure and mapping their potential spatial distribution. Investigating cost-effective installation and maintenance strategies, as well as financial incentives to overcome identified barriers, is crucial. Further inquiries, including interviews with local designers, planning officers, and engineers, should be conducted to explore practical solutions. Long-term studies should evaluate the impacts of green roofs on urban ecosystems and climate resilience, including their role in mitigating UHI effects, improving stormwater management, and enhancing urban biodiversity. In conclusion, the integration of green roofs into urban planning represents a promising avenue for enhancing urban sustainability and resilience. By addressing the practical challenges and leveraging the identified benefits, green roofs can play a vital role in creating healthier, more sustainable urban environments. The insights and recommendations from this study aim to guide future efforts in maximizing the potential of green roofs, ultimately contributing to the development of cooler, greener, and more resilient cities.