The potential for vertical gardens as evaporative coolers: An adaptation of the ‘Penman Monteith Equation’

Abstract

This research paper investigates the use of vertical gardens as evaporative coolers. Vertical gardens play a key role in tackling the increasing challenges cities face, due to a rapidly growing urban environment with associated reductions in vegetation and an increase in the urban heat island effect. This paper aims to develop a mathematical model based on the FAO-56 Penman Monteith Equation that quantifies the effects of vertical gardens for evaporative cooling. The theoretical results are then compared with empirical findings for the experimental setup undertaken by Davis & Ramirez [1], which involved passing air behind the vertical garden (between the substrate and the surface). Correlation is observed when the computed value is at the lowest humidity (35%) of the three test runs (35%, 40%, and 45%). This either indicates that the vertical garden performs better than predicted by the mathematical model, or the relative humidity at the time when the measurements were made was in the region of 35% instead of the predicted 40%. This research indicates the potential for the FAO-56 Penman Monteith Equation to be integrated into a future design tool that facilitates the application of vertical gardens as evaporative coolers in building designs.