Do rooftop home gardens regulate temperature? Insights on indoor heat regulation and thermal comfort in Bangalore

Abstract Cities are warming rapidly and urban heat is already affecting liveability, labour productivity, and human health. Nature-based solutions (NbS) such as green roofs, increased urban tree cover, and demarcating space for urban parks are identified as promising strategies to adapt to increasing urban heat. However, the NbS literature pays relatively lower attention to examining how smaller urban green spaces, such as fragmented urban greens and rooftop home gardens, contribute to hyperlocal temperature regulation. We examine whether rooftop home gardens in Bangalore, India regulate indoor temperature and provide thermal comfort. We draw on perception-based data through a household survey and in-depth interviews, and modelled scenarios data to examine heat regulation potentials of different types of rooftop home gardens. Overall, people perceive rooftop farms/gardens providing thermal comfort in the rooms directly below, with reported air-conditioner use declining after starting rooftop gardening. The modelling analysis (using 7 scenarios from no green cover to complete green cover with a 100% soil bed on the roof) shows that heat reduction benefits from rooftop gardens range from 1.5°C to 14°C, depending on foliage type and density, and extent of green cover. Given most rooftops are used for multiple purposes, a more realistic temperature reduction is of 1.5°C to 3°C (scenario with 50% roof covered in dense foliage). The findings from Bangalore provide early insights into the role of urban home gardens in regulating urban heat and have relevance for national policies on retrofitting and planning for climate-resilient and liveable homes and cities.