Green roofs in the tropics: design considerations and vegetation dynamics

Abstract

Green roofs (GR) have been proposed as a possible solution for urban stressors that, integrated with other remediation and mitigation actions, can lead the way to a more sustainable society. Even when some aspects of green roof design are well established and known (i.e. depth arrangements, materials, structural components, etc.) there is a need for further development on ecological attributes. This study is a descriptive analysis of suitable plant species for their possible incorporation in green roof designs with tropical climate conditions. Green roof research has been mostly led by temperate climate countries and has neglected to address tropical areas; this study aims to move research towards this knowledge gap. The evaluation of the vegetation dynamics in these novel ecosystems was done through a case study in the renovated facilities of the International Institute of Tropical Forestry in Río Piedras, Puerto Rico, which incorporated a set of green roofs in their infrastructure. We also sampled an older green roof built in the Social Sciences Faculty at the University of Puerto Rico at Río Piedras. A three-dimensional approach, the Point-Intercept Method, was taken in the vegetation surveys to capture as much as possible the green infrastructure of the roofs. Most of the originally planted species did not appear in these surveys. On the contrary, mainly new species dominated the areas. Along with the findings of these surveys and those in other tropical countries, a list of suitable species for green roofs in Puerto Rico is suggested, and some general recommendations are made for the better management of green roofs in tropical zones.

What happens to nitrogen and phosphorus nutrient contributions from green roofs as they age? A review

“…1). The surviving vegetation is often colonised by other vegetation (e.g., Dunnett et al, 2008, Köhler & Poll, 2010, Rowe et al, 2012, Whittinghill et al, 2015, Catalano et al, 2016, Thuring & Dunnett, 2014, Aloisio et al, 2019, Jauni et al, 2020, Grullón-Penkova et al, 2020. For both extensive and intensive GRs installed in Puerto Rico, Grullón-Penkova (2020) reported that that only 6 species survived from the original 26 planted species (succulents, herbs, grasses, vines) over a 4-year monitoring period for young GRs that received minimal maintenance.…”

“…Even then, there is limited knowledge about how GRs develop over time in those climatic zones. There is now some work conducted in dry climates (e.g., Razzagamanesh et al, 2014, Beecham & Razzagamanesh, 2015, Savi et al, 2015, 2016 and the tropics (e.g., Vijayaraghavan et al, 2012, Demarco et al, 2020, Lim et al, 2021 that include old GRs (>20 yrs, Grullón et al, 2020, Arellano-Leyva et al 2021. Grullón et al ( 2020)'s study showed that the old GR in Puerto Rico experienced a reduction in the number of plant species and Arellano-Leyva et al (2021) found that rainfall retention was still high (approximately 60%).…”

Overview of Green Roof Technology as a Prospective Energy Preservation Technique in Arid Regions

“…Therefore, efforts are ongoing to conserve and maximize energy [15]. The reduction of the overall energy use in the course of buildings' life span through good use of the building envelope is one of the efforts employed [16]. A building envelope shields a building's interior environment from the outside hostile environment.…”

“…The primary goal is to reduce transmission of heat loads in order to save considerable amounts of energy. Authors in [16] looked into the impact of construction materials, thermal insulation, and envelope layer layout as solutions for lowering building energy usage. The heat resistance of a roof can be increased by 0.4m 2 K/W for every 10cm increase in thickness when the substrate layer is made of clay [18].…”

Unmanaged Vegetated Roofs Hydrological Performance in Subtropical Areas:An Investigation in São Paulo, Brazil

“…As of environmental influences of subtropical climates, the evapotranspiration rates and rainfall events are the main concerns regarding the water balance in VRs (Poë et al, 2015;Peng et al, 2019). Previous studies show that there has been very little VR water quantity performance investigation under tropical and subtropical climates (Blank et al, 2013;Grullón-Penkova et al, 2020) but it is an increasingly investigated topic (Liu et al, 2021). Geographical differences for the VR performance towards water management are relevant, as pointed out by Poë et al (2015).…”