It has been known for sometime now that the benefit of greenery in city centres extends to many facets of public and private life. The more recent implementation of skyrise greening in the form of rooftop gardens and vertical greenery has highlighted even moreso the ways in which landscaping can become an integral part of urban development, ensuring communal interaction with the natural world. As one proponent of green spaces emphasised, “the integration of the living, organic systems characterised by green walls and green roofs, with the inorganic and lifeless structures that have come to dominate modern architecture, holds the promise of a new type of ‘living’ architecture." Not a new concept, vertical and rooftop gardens have long provided occupants with shade, aesthetically pleasing views, functional food productivity and greenery in confined spaces. With environmental issues gaining momentum in the 1970s in response to increased urban development, researchers began to investigate the ways in which plants on building facades could improve urban microclimates and decrease the carbon footprint of large scale structures.
Within the context of tropical Southeast Asia, the recent growth of skyrise greenery has been spurred on in response to ever increasing development and with it the effects of global warming, energy consumption and the urban heat island effect. The need to introduce passive cooling methods, especially in regards to skyscrapers – the most common form of new structure in Southeast Asia – has become a necessity. With proven results confirming improved interior thermal comfort, reduction of the urban heat island effect, removal of airborne toxins, reduced humidity, while all the while creating environments that promote social well being, the addition of vertical and rooftop gardens has become an vital design feature in contemporary sustainable construction. As a natural solution, vegetation in the form of green roofs and vertical gardens serves to reduce surface temperature through direct shading of hard surfaces, lower ambient air temperatures via consuming solar heat gain and lessen radiative temperatures in comparison to other hard surfaces with the same albedo. Green roofs can be defined as a roof that consists of vegetation and growing medium, is made up of several membranes (water proofing, root-barrier, drainage and filter membranes) onto which a substrate layer is placed to allow vegetation to grow and can either function as an ‘extensive roof’ (thin layer of vegetation) or an ‘intensive roof’ (heavier and can support small trees and shrubs). As a passive cooling method, the implementation of a green roof allows plants and the below layers of substrate to absorb large quantities of solar energy – in total, 27% is reflected, 60% is absorbed by the plants and soil and 13% is transmitted into the soil. As a result, the buildings surface and interior temperature remains low, air conditioning use is less due to the buildings consistent temperature, which in turn reduces energy consumption. Additionally, roof vegetation reduces the heat island phenomena via evapotranspiration from collected rainwater and the resulting humidification and air cooling. Vertical Gardens differ in design, but work to producing many similar outcomes to the rooftop garden.
Divided into two main categories – living walls and green facades – vertical gardens have been utilised in small residential homes all the way through to skyscrapers and large complexes. Green facades tend to consist of climbing plants or cascading groundcovers that are trained to cover specially designed supporting structures, whilst living walls are composed of pre-vegetated panels, vertical modules or planted blankets that are fixed vertically to a structural wall or frame. In terms of tall buildings, vertical gardens have the capacity to cover up to four or five times more area than the total area of the site, potentially lowering ambient temperatures of the building at street level by up to 5C. Additional passive cooling benefits include: promoting natural cooling processes, breaking vertical air flow which cools the air as it slows down, limiting movement of heat through thick vegetation mass and shading both buildings and people. Air conditioning use is substantially reduced as a result of the reduction of heat transfer, minimising energy consumption and in turn the urban heat island effect. Both rooftop gardens and vertical walls require careful selection of plants to produce the best cooling measures, initial large sum investment and can take some time until the plants fully mature, however the end results and various rewards received, especially in sustainable terms, justify the money, time and effort.
In the tropical regions of Asia, the use of greenery was always used traditionally as a means to cool the interior of buildings, be it through the shading of trees or using particular branches with insulating properties in roofs. It wasn’t until the 1970s however, that the realisation that greenery could be incorporated into more modern designs such as skyscrapers was reached. Charles Correa was one of the first designers to introduce tall building gardens as a means of passive cooling. The Kanchanjunga Apartments in Mumbai comprise of 32 luxury apartments, at a height of 84 metres. Small displacements of level on every floor allow for each apartment to have a deep set verandah and large open garden, creating a buffer to the effects of both the sun and the monsoon rains and promoting cooling breezes and lower temperatures to reach the interior of the apartment. Ken Yeang is another who has recognised the significance of skyrise greening, even producing a number of publications on the ‘bioclimatic skyscraper’. Incorporating some type of garden, rooftop or vertical or otherwise, into everyone of his designs, Yeang emphasises the importance of greenery in reflecting or absorbing radiation, creating shade, reducing active modes of cooling and encouraging plant species diversity that creates localised ecosystems (see fusionopolis article). Up and coming architects are also realising the benefit of green spaces and in response are devising even more interesting ways to immerse plant life within buildings for sustainability reasons.
Singapore based Chang Architects designed a house that is 40% made up of landscape elements. Placing trees, vertical gardens and natural water pools within the interior of the house has created a naturally cooled space that requires minimal technological cooling and lighting devices. It appears as though the popularity of vertical and rooftop gardens is only going to garner speed from here on in. Singapore in particular has embraced the idea of skyrise greening, claiming to have at least 61 hectares of rooftop green spaces in the city, all established within the last 5 years. National Parks Singapore, acknowledging the fact that the majority of future development will be in the form of high-rises, has established a Skyrise Greening section that provides subsidies for the installation of green walls and green rooftops, runs annual Skyrise Greening awards competitions, tests and monitors up to 8 vertical gardens within Hort Park and has set up the Centre for Urban Greening and Ecology (CUGE) to train landscape workers in the techniques of greening the city.
Multiple newly developed large scale buildings within Singapore have incorporated both roof gardens and vertical landscaping with the intention of passively cooling interiors and providing liveable natural spaces in densely built urban environments. The School of the Arts has covered the majority of their façade in vertical gardens to cut glare, reduce solar absorption and cool both outdoor and indoor spaces – making it a global attraction for visitors seeking to adopt similar models. Marina Bay Sands is another global attraction for which its cantilevered roof top garden is a focal point. Comprised of 250 trees and 650 plants (some up to eight metres tall), the SkyPark, in conjunction with other garden terraces throughout the building, absorbs and reduces heat entering the interior of the building, minimising the workload of the chillers, creates evapotranspiration via collected rainwater and provides continuous shade for visitors wanting to enjoy the green space. Lastly, Singapore has just claimed the largest vertical garden in the world, titled ‘Tree House’ and measuring 24,638.59 square feet on a 24 storey residential building. The sheer volume of green façade is set to dramatically cool the interior of the building and save the entire complex $500,000 in energy and water costs. The ability to incorporate such measures on some of the largest and tallest buildings in Singapore, indicates that the presence of vertical gardens and rooftop landscapes in Singapore is producing only constructive outcomes in the arena of rapidly urban development and environmentally responsive design.
Jason Pomeroy, architect, author of The Skycourt and Skygarden, and campaigner for skyrise greenery, summarised the concept of vertical landscapes and skygardens as “flexible and adaptable social spaces that adjust to a city’s idiosyncratic future expansions plans … they future-proof the design of our cities, and acknowledge the importance of a spatial sustainability to replenish the loss of social space through urbanisation.” Combined with the benefits of passive cooling, better energy efficiency and less consumption, improved social well being and a reduction of heat island effect, the urban environment with the inclusion of both, is a far more sustainable place to be. Although in need of further research and application in terms of cost effectiveness, life-cycle and selection of plants, water usage and long-term maintenance, cities worldwide appear to be embracing the idea, continuously looking towards the next futuristic design to implement. Future developments in tropical Asian regions will continue to expand, challenge and implement the growing concept of rooftop gardens and vertical landscapes, as a means of coupling development with green space, ultimately producing improved living conditions, continuous comfort, ecological sustenance and economic betterment.