Retrofitting Southern African cities : a call for appropriate rooftop greenhouse designs as climate adaptation strategy

Abstract

In response to the burgeoning building integrated agriculture (BIA) discourse and industry, and assumptions of this land use form as a climate change adaptation strategy, this study considers the impact of rooftop greenhouses (RTGs) on the thermal performance of the built environment in current and future climate conditions. Based on empirical evidence, the study simulates the thermal impact of completely retrofitting an existing building in a Southern African urban context with passively controlled, non-integrated RTGs under current and future climate change affected climatic conditions. The study concludes that the current greenhouse technologies used in South African rooftop farms provide limited thermal modulation capacity for farmers, as well as generally negatively affecting the thermal performance of the associated buildings. Simulating both highly and poorly insulated buildings reveal contrasting impacts on the indoor thermal environment, with a 0.73 °C decrease and 0.55 °C increase in mean temperatures, respectively. Conversely, the highly insulated simulation reveals an annual energy consumption increase of 3.5%, which progressively worsens under higher climate change induced temperatures. These findings, based on current practices in the BIA industry, hope to inform both the choice of technology, as well as the development of appropriate greenhouse technologies to maximise their performance and enable co-benefits as often assumed in the industry.