In the present day, the image of towering skyscrapers, dense urban cities and constant construction is synonymous with the modern Asian City. Estimated to have 111 of the world’s 140 new large or big cities post 1990 and a population growth of 1.25billion by 2025 (half of which will live in cities), the Asian region is highly dependent on the skyscraper to house as many individuals as possible. Unfortunately for the environment, such rapid development and intensive use of land via the stacking and crowding of living and work spaces has meant an unsustainable leap in energy consumption and an abandonment of ecological conservation. Add in the impact of air conditioning that allows for all large buildings and high-rises to be consistently comfortable in the tropical heat, it is apparent that changes need to occur to ensure a more sustainable urban future. The introduction of the skyscraper to the Asian region began to take hold at the beginning of the 20th Century. Initially appearing in China, ideas from Europe and America encouraged engineers to incorporate the import and use of metal, concrete, steel and glass. Visiting engineers and architects accelerated the speed and scale of industrialised urbanism, creating a landscape of reinforced concrete and expanses of glass that soon rippled through the rest of the continents cities.
From the 1960s onwards, the adoption of HVAC and domestic air conditioning units became rather common in commercial and domestic buildings across South and Southeast Asia. For the first time, the ability to chill and dry the air of an entire enclosed interior meant bodies were able to dwell in and move about spaces of evenly distributed, non directional thermal regulation. Furthermore, the use of AC meant that high-rise towers could now glaze their facades in glass and remove open windows as interiors provided even more precise climatic regulation than the outside world. Fast-forward forty years and more and more daily activities are moving indoors to the interior of the skyscraper, a space perceived as safer, more hygienic, more convenient and of course more comfortable than the outdoors. As air conditioning pioneer Walter Fleisher pointed out in the 1950s; today we have become so accustomed to luxury that we consider it our inalienable right to have every type of comfort that our creative technology has developed and among these is artificial cooling” – a factor, despite the environmental impact, that has not changed much in over sixty years. The internalising of society in the region as a result of such interior comfort has spurred the rate of urban development, and along with it the negative impact of energy consumption, carbon emissions, the heat island effect and ecological degradation. Whilst high-rises and air conditioning are now a necessity for such urbanised cities, there is still the potential to prevent such long-term damage.
The more recent mode of introducing passive cooling into high-rise development is one such approach that can reduce energy consumption and reduce dependence on artificial air. By implementing features that have evolved from vernacular design, such as ventilation, shade, natural heat sinks and specific facades, the tropical heat level is minimised in the interior space, human thermal comfort is maintained and the overall structure is far more energy efficient. Ken Yeang is one such architect who has built upon these ideals and developed the concept of the bioclimatic skyscraper. As he states in his own words, a bioclimatic building is “a tall building whose built form is configured by design using passive low energy techniques to relate to the site’s climate and meteorological data, resulting in a tall building that is environmentally interactive, low energy in embodiment and operations and high quality in performance.” With greater investment and research into ‘green’ skyscrapers and the benefits they offer, sustainable high-rises in the tropics can very much become a reality in the urban centres of developing Asian Cities. The compromise of environmentally responsive design with mechanical cooling ultimately promises better results in energy efficiency and an overall more sustainable society.
In 2010, on a global level, as well as in Asia, the building sector (construction through to operation to deconstruction) accounted for 30% of energy related carbon emissions and 51% of total global electricity consumption. With long periods of hot and humid weather in tropical Asia, air conditioning accounts for almost half of that energy consumption – a statistic that is steadily growing with the expansion of mechanical cooling across the region. To compensate for such a spike in energy consumption, a new variety of skyscraper has emerged that incorporates a number of passive cooling elements as a means to conserving energy. Passive cooling systems work either by removing heat from the building to a natural heat sink or alternatively by preventing heat from entering the interior from external heat sources. The selection of the appropriate passive strategies is very much dependent on the local climatic condition of the site, in particular the air temperature and relative humidity. In the tropics specifically, the aim is to avoid excessive solar radiation and allow for moisture evaporation by maximum ventilation. To attain such objectives, the following elements have been utilised in various buildings in the tropics and have subsequently changed the artificial cooled environment to one that is partially natural.
Natural Ventilation is the integral element to keeping high-rise buildings cool in the tropics, especially in those places that are particularly humid as ventilation acts as a form of evaporative cooling. To optimise cooling, a building must be orientated to maximise exposure to main wind directions, designed with a relatively narrow plan form across the prevailing wind direction to channel air through the building, locate wall openings to facilitate the passage of air through the building and use vegetation to modify the external wind direction and enhance ventilation. Large windows that have adjustable openings should be implemented through out the building as a means of encouraging cross ventilation and a way to control the channelling of airflow, dependent on the wind direction. Many strategies have been tried and tested in achieving optimum thermal comfort via natural ventilation, including the use of wing walls (capture a wider angle of incident wind and accelerate it through the narrowing gap into the building) and skycourts (deep set garden balconies that attract airflow and cool interior space via evaporative cooling).
For tall buildings in the tropics, main openings and windows should be installed on a north-south axis to minimise solar intake and thus air conditioning loads. If windows must be on the east and west sides, some form of shading is advised to reduce heat absorption and glare.
Shading is used as means of blocking and reflecting solar radiation which in turn inhibits heat absorption into the interior of the building. Coming in a wide variety of items like landscaping, roof overhangs, shade screens, photovoltaic cladding, fins and adjacent buildings, the appropriate selection of shading depends on the orientation of the building and the latitude of the location. Architects and engineers employ computer simulation tools to analyse the performance of shading devices and to track solar intensity and angles. Some buildings can even be designed to be self-shading – a study on hemispherical roofs in the tropical regions established that they received 25-35% less daily average solar radiation than flat roofs (dependent on latitude, day of the year and time of the day). Additionally, many shade devices these days are able to block solar radiation and heat gain but still allow natural lighting, minimising the need for artificial lighting.
The roof and walls of high-rise building should be constructed from low-thermal capacity materials with reflective outside surfaces (unless shaded) and a layer of high quality thermal insulation is recommended to minimise heat absorption. The more the surface material reflects and distributes heat (sometimes minimised simply through using lighter colours), as opposed to slowly absorbing radiation, the lower the temperature will be inside the building – again reducing the need for mechanical ventilation. Some buildings also incorporate a second façade, external to the glass, that allows for shading, natural ventilation and cross ventilation, minimal impact of rain and high winds without the loss of external air, noise reduction and prevention of the stack effect from transferring hot, stale air from lower floors to upper floors.
The implementation of passive cooling techniques in tropical high-rise buildings has provided a natural means to creating a comfortable environment while simultaneously reducing heat gain and air conditioning loading. Through the use of specific climate responsive design, each building utilising passive cooling measures has evolved to suit its context and over time changed user behaviour to engage more with the natural world for thermal comfort and less with the artificial cooling of air conditioning. Further benefits, besides the obvious energy usage reductions, include longer life span of the building, less need for upgrades to mechanical ventilation, less contribution to the urban heat island effect, greater interaction with the outside world by occupants and in turn a better understanding of environmental motives and even health benefits as natural air dilutes air borne pollutants. Such benefits do not eradicate the need for air conditioning altogether, the dependence on thermal comfort expectations are far too great and the initial start up costs far too high to completely overhaul the current system. However, the fusion of passive and mechanical cooling techniques in sky rise buildings is a step towards a far greater sustainable built environment.
The evolution of the sky-scraper in Asia has also seen the gradual uptake of more sustainable built forms of high-rises – in particular what is known as the bioclimatic skyscraper. Developed by Malaysian architect, Ken Yeang, the bioclimatic skyscraper is highly responsive to its climate and locality and must utilise passive-mode and low energy strategies. In addition to incorporating multiple passive cooling features, the bioclimatic high-rise is built as an system within the natural environment. Comprising of four principles, Yeang’s eco-masterplan outlines a coherent system that integrates; green infrastructure – natural corridors and networks that link open spaces and habitats for fauna and flora; grey infrastructure – sustainable engineering systems such as roads, sewages and utilities; blue infrastructure – hydrological management, sustainable drainage, retention ponds and storm water management; and red infrastructure – the built environment, enclosures and human social, economic and political systems. According to Yeang, planning in response to these four principles holistically encompasses eco-design, allowing for the integration of the artificial built environment with the organic ecosystem, ultimately taking advantage of the natural sites offerings (climate included), minimising negative outcomes and producing more energy efficient buildings. One way Yeang has implemented such theory is through the use of sky-rise greening.
Via the planting of vertical landscaping and roof gardens on skyscrapers, organic matter has been introduced into a small space of highly concentrated inorganic mass and subsequently has recreated some form of natural environment. Including aesthetic, ecological and energy conservation benefits, the practical act of planting on skyscrapers provides shade to internal spaces and external walls, minimises external heat reflection and glare, effectively cools the building façade via plant evapotranspiration, absorbs solar radiation and ultimately allows for the reduction of mechanical cooling. The Singapore Government has even set up a Skyrise Greenery Incentive Scheme which funds 50% of installation costs in a bid to bring about environmental benefits – a factor that is encouraging more skyscrapers to integrate bioclimatic design principles. Overall, research suggests that bioclimatic buildings may use up to five or six times less energy than conventional buildings over their lifetime. The additional advantages of cooler buildings, reduced waste emissions, less demand on cooling load and healthier occupants have encouraged architects and engineers to design high-rises that interact with their ecological environment, their geographical climate and with the city around it.
Skyscrapers that encompass both passive and bioclimatic features are slowly emerging throughout Asian Cities and are garnering attention as a way to produce more energy efficient urban spaces. Architects have designed buildings for both residential and work purposes that tend to include a hybrid of passive and mechanical cooling techniques. The following three case studies outline some of the strategies employed to create an ideal sense of thermal comfort and take advantage of the geographical and climatic conditions for cooling in the tropics.
Goodwood Residence – Singapore - WOHA
Goodwood Residence is a two 12-storey interlocked L shaped building, comprising of 210 units and bordering the Goodwood Hill tree conservation area – a green space in the middle of downtown urban Singapore. Broken into three green squares, the complex is submerged in greenery, providing shade, privacy and cool communal areas for all residents. A thin cross-section of the exterior covering remains permeable to enhance cross-ventilation throughout the entire building, making air conditioning use minimal; water features provide evaporative cooling; and the sustainable design of the building from the outset will lead to an estimated 20% reduction on the cost of monthly utilities. The dominant feature of the site is the fine aluminium fins that cover the majority of the façade. Inspired by the patterns of traditional Asian woven textiles and the roll up bamboo chicks of colonial houses in the area, and angled at 45 degrees to north-south, the fins can be independently altered to block sun but maintain optimal ventilation. The pent house apartments, whilst not having the fins to regulate sun impact, have Euro Grey tinted glass to reduce heat intake and stabilise thermal performance of the building. The final feature of the Goodwood Residence’s façade is the 1,700sqm of vertical landscaping that provides additional shading and contributes to regulating the buildings core temperature.
Pearl River Tower – Guangzhou City, China – Skidmore, Owings and Merrill
Marked as the 59th tallest building in the world, the Pearl River Tower (PRT) stands at 71 floors high in Guangzhou’s business district. Designed initially to be a net zero energy building, until technical regulations inhibited such goals, the PRT is only one of a few to attain LEED Platinum certification and is estimated to use 44% less energy than a similar tower without sustainability measures in place. The 309 meter high office tower, orientated to attain southerly winds, has a sculpted façade (some compare to a smart phone) that directs wind to four openings at its mechanical floors and subsequently is drawn through the tower’s ventilation system as well as into a series of turbines that generate electricity for the building. Mechanised blinds have been installed on the northern and southern walls whilst the eastern and western walls have been triply glazed to block solar absorption and reduce the cooling load. The building’s interior climate is controlled by a set of integrated technologies, including a raised floor displacement ventilation system, a double wall façade that draws in cool air but blocks solar gain and a network of copper tubes in the ceiling panels that circulate chilled water throughout the building. Simultaneously the building saves energy and maintains optimal temperature and humidity levels for occupants.
Menara Mesiniaga – Malaysia – Ken Yeang
At 15 storeys high, Menara Mesiniaga was constructed in 1992 and is deemed Ken Yeang’s first bioclimatic high-rise tower. Built for Software Company IBM the tower is circular in plan, and constructed of concrete, steel and glass. It’s most well known feature is a series of landscaped skycourts on varying levels, positioned on the ‘hot’ side of the building, as well as a sloping natural ramp that connects the exterior environment to the interior of the building. The use of greenery provides shade to the interior of the building, absorbs solar radiation before it enters the building and allows workers to engage with the aesthetic beauty of the natural environment. Rather than a sealed façade, the building instead has a series of windows, louvers and shutters, all positioned in relation to the sun’s path and the predominant wind direction, to maximise cross ventilation and deter heat gain. Acknowledging the heat building services, such as elevators, cooling units and data storage can create, Yeang situated all these services into a single core on the east side of the building – a formula that minimised artificially created heat entering the office space and also acted as a thermal buffer for external solar radiation. To ensure thermal comfort is maintained, air conditioning systems were installed but their energy consumption is regulated by automation systems - combined with passive cooling measures, up to $13590 is saved annually on air conditioning costs (1993 statistic). These days Menara Mesiniaga is recognised as an icon in bioclimatic high-rise design and as a symbol of what is achievable in the tropics.
The evolution of the skyscraper has both helped, hindered and dramatically altered all aspects of the urban centre in tropical cities. On the one hand the development of such a sky-rise city has allowed for social and economic growth, better opportunities for the public and a condensing of space to enhance the movement and lives of people in a more functional way. On the other hand however, the negative impacts are becoming more obvious – higher energy consumption, increase of the urban heat island effect, dependence on artificial cooling and even a growing anxiety towards the outdoors. As Heschong quotes, “…what we lose is “sensual delight” as we perfect our control of built environments. We have used our heating and cooling systems… to homogenize and erase culturally linked responses to seasonality, in food, clothing, activities, festivals and building design. Our systems are mundane, functional, convenient and perhaps worst of all, unchallenging.” Recognising that such problems to exist, mainly as a result of high density skyscraper complexes, has spurred on a small number of architects, engineers and designers to turn towards the passive and the natural environment as a means of reducing the sky rocketing air conditioner energy usage levels and allowing people to reconnect with their external environment. Applying climate responsive design features to skyscrapers that have long being used in tropical vernacular design, such as natural ventilation, shading and façade materials, has enabled high rise structures to utilise environmental resources and in return lower the mechanical cooling load and ultimately create happier and healthier workers and residents. Air conditioning is always going to be a requirement for thermal comfort in cities in the tropics – the dependence has come too far and the expectation too embedded in social norms. However, the creation of hybrid skyscrapers that use both passive and artificial cooling methods provides an alternative that is less harmful to the environment, ensures a longer lifespan of a building and promotes a more holistic understanding and connection to the unique climate and landscape around us.