Quantitative approximation of shading-induced cooling by climber green wall based on multiple-iterative radiation pathways

Abstract

In hot, humid, subtropical climates, strong solar radiation imposes heat stress upon building users, who often resort to air conditioning in a bid to improve indoor thermal comfort. Green walls are a nature-based solution to this enormous cooling need. The foliage of climber vegetation can reduce the shortwave radiative penetration into the indoor space of windowed building envelopes. This chapter presents a revised radiation apportionment model (RAM*) for estimating the benefits of shading against shortwave radiation as a cooling-load reduction. Adhering to the principles of an improved radiative transfer model, field data harvested from net radiometers were input into a Microsoft Excel spreadsheet. The Solver function determined the radiative properties of various layers of windowed building envelopes featuring a climber green wall. The radiative transmissivity (t), reflectivity (p), and absorptivity (a) were 0.366, 0.079, and 0.555, respectively. Using objectively selected sunny days, daily reductions in electricity use, electricity tariff, and carbon dioxide emissions were 0.44 kWh, 0.07 USD, and 0.29 kg, respectively, for a square meter basis of the climber green wall featured in this study. Corresponding savings in a cloudy scenario were reduced to 0.25 kWh, 0.04 USD, and 0.16 kg. The RAM* features two major improvements, namely the reduction of bias due to manually input radiative properties of artificial building materials and the addition of iterative radiative transfer pathways. By approximating the potential shading-induced cooling, the RAM* fosters an evidence-based approach for practitioners in green building designs.