Cooling potential of greenery systems for a stand-alone retail building under semiarid and humid subtropical climates

Abstract

Recently, living walls and vegetative roofs have emerged as envelope technologies that can save energy owing to the cooling effects of the building envelope. However, simulation models are required as part of the design support tools available for sizing greenery systems according to architectural constraints and climate. In this study, a green roof heat and mass transfer (GRHMT) model was adapted to develop a novel pot-based living walls heat and mass transfer (LWHMT) model to assess the cooling potential of living walls. The LWHMT model is validated using climate data for Santiago (Chile), which demonstrated a close agreement between the experimental data and the simulated foliage and substrate temperatures and substrate volumetric water content. Along with a previously established GRHMT model, the proposed LWHMT model was coupled to EnergyPlus® through the MLE+® toolbox to simulate the heat transfer between a building and several vegetative surfaces simultaneously. Finally, a prototype retail building was simulated, using climatic conditions for Santiago, to evaluate the impact of wall and roof insulation on the performance of the greenery system, with additional simulations performed for three cities in the USA (Atlanta, GA; Tucson, AZ; Tampa, FL) using different greenery system configurations. The living walls show cooling load reductions of 19.7–24.9%, while the green roofs show much lower reductions of 9.6–15.1%. Moreover, the highest cooling load reductions were obtained by combining green roofs and living walls, achieving a maximum reduction of 36.8% compared with the base case building. In the future, the LWHMT model should be extended to continuous growing media such as pocket felts. In addition, GRHMT and LWHMT models should be integrated into building energy modelling software to develop the full potential of a parametric tool for greenery systems performance simulation.