The Effects of Design Combinations of Surface Materials and Plants on Outdoor Thermal Conditions during Summer around a Single-Detached House: a Numerical Analysis

Abstract

Suburban areas with low-density buildings are subject to only limited shading from adjacent buildings. As a result, these areas have more surface area absorbing more radiation, which has the effect of increasing urban temperatures compared with built-up high-density areas. This study aims to assess the combinations of landscape design, namely the integration of wall-paint colors, used to influence the outdoor thermal conditions around a single house in a housing cluster in suburban Bangkok, Thailand. The investigation used the ENVI-met model to perform diurnal profiles of the air temperature (Ta), relative humidity (RH), direct and diffuse solar radiation, and wind speed (WS) in summer. The results show that only a single design element adversely affected the cooling effect, while other combinations of landscape design significantly improved outdoor thermal conditions. It was found that a combination of light wall-paint colors and trees planted near the house provided the maximum reduction in Ta of 0.7°C (1.6% from the base case), and a 2.7% reduction in the noon solar radiation. High-reflectance wall-paint was found to have a secondary influence of up to 0.2°C on the Ta, while the temperature reductions from changing the ground-cover materials had only a slight impact. Finally, landscape designs integrating wall-paint colors to promote a cooler outdoor environment are proposed.