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Background
Sustainability has been the impetus over the past few decades as global concerns regarding the impact of climate change increases. The United Nations Environment Programme (UNEP) (2009) reports that 30 per cent of total global greenhouse gas emission (GGE) is accounted from buildings while consuming up to 40 per cent of all energy worldwide. Moreover, rapid urbanization has contributed to the proliferation of high-rise, high-density buildings in cities leading to urban heat island (UHI) effect. Feng and Hewage (2014) reports that vertical greenery systems help mitigate UHI effects and contributes to the development of ecological cities (Kuang, 2013; Wang et al., 2014; Pérez-Urrestarazu et al., 2015). The “vertical greenery systems” (VGS) which refers to “green walls”, “vertical gardens”, or “vegetated walls” pertains to edifices where plants propagate on its vertical surface in a well-organized method through consistent up keeping (Wood et al., 2014). VGS application on buildings carry with it economic (i.e. better energy efficiency, building’s eco-refurbishing/retrofitting, urban rehabilitation, improved façade/building structure’s lifespan and higher property values); environmental (i.e. noise barrier provision, upgraded air quality and filtration to storm water management, better microclimate, reduce building’s ecological footprint and supports climate change adaptation, enhanced building’s aesthetic value and reduced temperature); and social benefits (i.e. user comfort, well-being, health and privacy provision, while encouraging community assimilation) as reported by various authors (Johnston, 1990; Peck et al., 1999; Johnston and Newton, 2004; Ottelé et al., 2011; Sheweka and Mohamed, 2012; Mazzali et al., 2013; Ottelé et al., 2014; Djedjig et al., 2015; Manso and Castro-Gomes, 2015). However, only few researches have reported about VGS issues, particularly in high-rise buildings in a tropical setting (Chew and Conejos, 2016).
VGS implementation is one of the widely accepted green building design strategies to help promote and achieve Singapore’s vision in promoting sustainable development through greening its built environment (Ministry of the Environment and Water Resources and Ministry of National Development, 2014). However, incorporating vertical greenery systems into innovative facades generates maintainability challenges. It is important to prevent the occurrences of defects specifically on VGS application on high-rise buildings which vary considerably in terms of building design as compared to a low-rise building (e.g. building systems design, environmental exposure and VGS requirements). High-rise...