Impact of 2050 tree shading strategies on building cooling demands

Abstract

As urban heatwaves become more severe, frequent and longer, cities seek adaptive building cooling measures. Although passive building design, energy-efficient materials and technologies and mechanical means are proven cooling methods, the potential of nature-based solutions (particularly trees as shading elements) has been understudied despite its significant opportunity. Using a new framework to explore this at the neighbourhood level, three future (2050) potential tree planting strategies are modelled for increasing tree volume and canopy cover and their impacts assessed for summer building-level solar radiation absorption (SRA) and building cooling energy demand (BCED) for a densifying neighbourhood in Vancouver, Canada. The boldest tree planting strategy, with 287% more trees than baseline and 16% canopy cover, reduced neighbourhood-scale total SRA (22%) and BCED (48%) over a no-trees scenario. BCED reductions of up to 64% for retrofitted/redeveloped buildings and 53–79% for low/medium-height buildings (mostly single-family residential) were associated with targeted south-side tree planting. Taller/larger buildings (predominantly mixed use) and buildings along north–south-oriented streets (mainly commercial and mixed use) encountered more tree shading challenges and would require more site-specific interventions. The methodology presented provides a framework to assess current and potential future shading and cooling energy benefits through various tree planting strategies. Practice relevance This research illustrates the tree shading and cooling potential to improve indoor liveability, reduce energy demand and reduce vulnerabilities amidst mounting extreme heat risks. This novel framework and method can be used by planners and urban designers to understand the potential cooling reduction and to develop tree planting and management strategies for effective shading and indoor cooling at the neighbourhood scale. Based on a case study neighbourhood in Vancouver for 2050 climate scenarios, this research shows increased tree volume and canopy cover can significantly reduce building SRA and BCED during the summer. The level of tree shading impact on buildings’ SRA and BCED was associated with the intensity and location of tree planting, but also the relative amount of lower height (and smaller) buildings. The boldest tree planting strategy yielded a 48% reduction in energy demand for cooling.