Designers' guided site shading strategies: A simplified model for radiative cooling

Abstract

In the context of rising urban temperatures, the efficacy of cooling strategies, particularly shading installations, has garnered significant attention. However, prevalent issues in thermal radiation literature and assessment tools include challenging usability, insufficient guidance for design, and a lack of scientific data support. This study addresses these challenges by simplifying thermal radiation theory and integrating diverse assessment tools. The outcome unveils a site shading radiation cooling model, a user-friendly, design-guided, and scientifically supported approach for designers evaluating site shading.The research methodology involves conducting initial measurements on summer afternoons using ISO and Rayman to validate ENVI-met simulation accuracy. This study simplifies thermal radiation theory, creating a predictive model structure based on short- and long-wave radiation reception modes and translating scientific parameters into actionable design factors. Model parameters are derived from ENVI-met simulated Tmrt cooling benefits, followed by computations on numerous cases to verify and assess model applicability.Findings indicate a good match between the measured and simulated Tmrt data during summer afternoons. A common 1:1 width-to-height ratio colonnade in Taiwan contributes a 22 °C cooling effect in extremely hot afternoons, with an additional decrease of 5–8 °C if facing west. Each 10 % increase in the roof transmittance resulted in an approximately 3 °C Tmrt reduction benefit, with wood providing the best cooling effect and metal the least. Based on the obtained cooling data, a Site Shading Benefit (SSB) model was developed by incorporating area parameters, allowing for a simple calculation to assess the overall radiative heat reception of outdoor spaces on a site.