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The Bioclimatic Tower of Singapore

Singapore, also known as Garden City is now rising up with a new inspirational green concept, 'Ecological Design In The Tropics' (EDITT) tower by Ar. Ken Yeang of TR Hamzah & Yeang Architects from Malaysia and sponsored by the National University of Singapore. It is a 26 storey building sited at the junction of Waterloo Road and Middle Road in Singapore, tropical climatic zone and rainforest vegetation zone.

The structure is considered as a 'loose fit' multi-use high rise building, initially conceived as an exhibition building incorporating exhibition spaces, auditorium, retail and office use, with the potential to metamorphosis later into a full office tower or apartment building. The site is a small 838 SQM and the project gross floor area is at a plot ratio of 7:1, giving a gross area 6,033 SQM. In its initial iteration, the tower will yield a net useable area 3,567 SQM (FSR 4.3:1) with an area of planting and vegetation of 3,841 SQM.

Design

The design concept brings together a range of issues that demonstrates the expanding domain of the architect for the new century. In urban context; vertical place making, high level linkages, ecological response to site, orientation, sun control, vertical landscaping, wind effects; deconstruction and recyclability, waste recycling, water collection and re-use, on-site energy production, embodied energy, energy in use, hybrid mixed mode services and more.

The architecture result is a visual stunning that marries some of the best plastic aspects of the early 20^th century modern movement with the 'bowellism' of the European 'high-tech' school (Pompidou and Lloyds) and adds Yeang's own now characteristic freedom of form and itinerary, underpinned by an attempt to present methods and measurable in terms of environmental and energy performance.

Ar. Yeang

Ar. Yeang is notable for 'Bioclimatic' architecture, 25 years of experience has established himself as a seminal contributor to think and practice to use his own taste of Bio-Architecture. His best Bioclimatic work are UMNO tower in Penang and Menara Mesiniaga in Selengor; both in Malaysia. His books include designing with nature: The Ecological Basis for Architecture Design (New York, McGrawHill, 1995) and The Skyscraper Bioclimatically considered: a Design Primer, (London, Academy Editions, 1996).

Site Occupancy and Hierarchy of Ecosystem

The treatise on the project provide by the architects elaborates the design process; a broad analysis of the site context, views, microclimate and non-existent flora and fauna described as a 'zeroculture' at the bottom of Yeang's hierarchy of ecosystems. A worthy evaluation of the vegetation patterns within 1.5 km radius of the site is used to plant on the project that is integrated with the site and structure in a vertical landscaping scheme of planted terraces and facades, using species selected to be compatible with indigenous species of the locality.

The strategy to confront the issue of spatial continuity, universally lacking in high-rise buildings due to physical compartmentalisation of floors also seems to be worth! The design creates 'vertical places', using a ramp system that allows pedestrian movement vertically through the tower along a vertical 'street' lined with exhibition and performance spaces, cafes, shops and offices with occasional sitting and gathering areas. There are bridge links as adjoin to buildings that reinforce the lower levels as public territory and planted terraces and sky-gardens continue up the full height of the structure.

Wind Wing Walls

A wind study of the proposed tower elaborates about the early Yeang studies of the impact of 'wind wing walls' in domestic buildings using a radical concept of inflatable air bags as wind fins strategically positioned on the outside of the tower to create vortices that improve the natural ventilation, it modify wind loads on the building and resulting perhaps in a lightening of the vertical structure. These studies also demonstrate the natural ventilation of toilet pods hung on the side of the structure.

Recycling and Energy Saving Methods

There is no reference to the use of recycled materials but considerable emphasis is given to the energy implications of the construction and structure which are designed to be capable of adaptation during use and 'deconstruction' at the end of use. A hybrid primary structure is nominated of reinforced concrete columns and core and dry fire proofed steel beams with mechanical joints that can be readily disassembled. Bill Lawson of the University of New South Wales has been involved as an embodied energy adviser and an embodied energy analysis concludes that the building has a very high embodied energy at 14.2 GJ /SQM compared to a quoted norm in the range 6-8 GJ/SQM for a similar conventional structure.

The high figure is attributed to the high embodied energy content in photovoltaic solar panels and other energy saving devices. It is claimed, be repaid in utilisation energy savings over the life cycle of the building. The scheme includes a proposal to replace concrete floor slabs with timber floor cassettes that reduce the embodied energy figure by 1.6 GJ/SQM but the solution to fire separation issues has not been defined at the present stage. An ingenious solid waste recycling system is also describes the segregates paper, plastic, Aluminium, glass and garbage using a waste disposal chute dropping the full height of the building into rotating basement hoppers where the waste is compacted and removed from site.

Mixed Mode

It is understood that in-used energy in buildings are far overshadows, the embodied energy and it is correct to set out in a life cycle analysis to ensure the energy demands are minimised and that methods of meeting these demands are 'greened'. The passive design strategies of the proposed building, with sun shading and access to natural vegetation should moderate the energy load required to deliver environmental comfort.

It is not possible to achieve an acceptable working environment in Singapore without air conditioning and the proposal suggests a 'mixed mode' or, as it has become commonly known a 'Hyvent' system where natural ventilation is used to the maximum and supplemented where necessary by mechanical air-conditioning. An integrated arrangement for sun shades to window glazing, light shelves, rainwater catchment scallops and the location of the proposed photovoltaic panels exemplifies the necessary total systems approach and combines to reduce solar load on the windows, collect water and bounce light onto the ceilings and back into the building, thus reducing energy demand and cooling load.

The proposal does not document any thermal modelling or relate to utilisation energy demand. It was suggested that the building could be 40% energy self-sufficient through energy sourced from solar photovoltaic panels, but it has been revised downwards to 20.4% based on photovoltaics yielding a perhaps over optimistic 1.05 kWh/SQM/day (0.75 kWh/SQM/day would be more realistic).

Regain of Water collection

A fascinating system of water collection and reticulation is describes involving a sculptural rain scoop on the roof and a system of water collection scallops down the facade combined with a proposal to recycle grey water through soil bed filters in the vertical landscaping. It was suggested that the building could be 55 percent self-sufficient in terms of water supply but this has been revised downwards to 31% based on a Singapore rainfall of 2344mm per annum and a collection area of 518 SQM yielding 3300 litres per day average.

At the initial calculation of the volume of sewage sludge to be collected and recycled appeared to be excessive at 15,190 CUM per year but was revised down to 8,850 CUM. It still seems high and it is not explained how this could be recycled on site. The water demand appears to be overstated and the need for an elaborate filtration system for rainwater is unclear. A more conservative water demand could be used as the basis of calculation and segregation of the black and grey water and the use of recycled grey water should reduce the overall water consumption.

Summary

The main tenet of 'green' architecture is that it must deliver energy and resource efficiency and environmental comfort: it is not a style. The EDITT Tower is a concept project that will fall under 'bioclimatic' big building design. The formal and stylistic qualities of the design are seductive, but the technical detail appears to need more careful consideration and refinement. The building has a very high embodied energy (and is probably very expensive) but it does not yet appear to demonstrate commensurate utilisation energy savings and associated thermal comfort.

EDITT HIGHLIGHTS

Natural Ventilation+ Mixed-Mode Service

Mixed-mode servicing is Yeang's strategy of reducing mechanical air conditioning and other active systems by optimizing passive systems, such as cooling from the site. Wind is used to create internal comfort conditions by means of introducing natural ventilation and 'wing-walls' placed parallel to prevailing wind in order to direct airflow to internal spaces and skycourts to assist with breeze cooling.

Solar Energy Use

Heavy solar-shielding along the east facade reduces solar heat gain. This is primarily accomplished through the inclusion of an opaque unified 'wall' of stair towers, lifts and restroom accommodation. Extensive use of photovoltaic panels as a major formation on the east facade assists with the energy demands of the building. In addition, passive lighting systems such as light-shelves are employed to reduce dependency upon artificial lighting systems.

Solid Waste Recycling

Solid waste recycling is handled through a vertical chute accessible from all floors which delivers materials directly to a mechanical waste separator at the basement levels of the building which sorts materials and prepares for efficient waste collection for recycling.

Water Recycling/Purification

The building serves as a rainwater collection device primarily through the curvilinear rooftop collector and a system of scallop-shaped facade collectors. Once collected the water is subjected to a largely passive gravity filtration system.

Building Material Reuse

Compatible with Yeang's theory of 'loose-fitting' (see strategy to right) programmatic divisions within the eco-skyscraper, the vast majority of 'temporary' building materials are designed and installed in such a way as to facilitate ease of dismantling and reuse. This is largely executed through well planned mechanical jointing of sheet materials and connections and removable partions and floors.

Loose-Fit

Yeang's 'loose-fit' design strategy is a way of considering the likelihood of a building's programmatic evolution from the outset of the design process. Each eco-skyscraper is designed to absorb change and refitting over a life-span of 100-150 years with a high level of floor occupancy efficiency. This involves removable partions and floors, reuse of skycourts, mechanical jointing to enable future recovery of materials - all with a matrix based on flexibility as a paramount condition. In the case of the EDITT tower, Yeang allows the building to evolve to an office or residential program long after the original exposition tower program has been retired.

Vertical Landscaping

Yeang's projects advocate for internal integration of biomass into a building's inorganic mass by means of internal landscaping, and internal air quality considerations. This further assists with creating ambient cooling, easing the demands on active mechanical systems. Yeang advocates for an exhaustive analysis of the native ecosystem hierarchy at the outset of the design process. The design approach focused on the restoration of organic mass to enable ecological succession to replace the inorganic nature of the site in its current state of devastation. Species were selected through the conduction of a survey of indigenous planting within a one mile radius of the site so as to select species that would not compete with those already present.

Place-Making

The term 'place-making' represents yeang's solution for solving the failures of the modern skyscraper. The major problem he identifies in the contemporary high-rise is one of poor spatial continuity between street-level activities and those on the upper floors of the tower, which is conventionally based on repetitious, physical compartmentalisation of floors within an inherently sealed envelope.

Instead, yeang argues for a civilized vertical urbanism - a continuous extension of street life into the elevated levels of the skyscraper including skycourts, atrial spaces and plazas as one would find in a horizontal city.

Features Of EDITT

Areas of vegetation rise in a continuous linked, landscaped spiral from the ground floor to the top floor, enabling a more diverse and more stable ecosystem.

The vegetation is intended to protect against the sun's rays, facilitating ambient cooling of the building's facades.

A third of the tower is planted with vegetation.

The flexible design means that the building initially conceived as a multi-use exhibition building, could be used in future as offices or residential apartments.

Photovoltaics are used to collect solar energy, thus further improving the building's self-sufficiency.

By positioning "wind walls" parallel to the prevailing winds, wind can be directed to internal spaces for cooling purposes.

The design won 2nd prize in the 1998 Urban Redevelopment Authority (URA) EDITT (Ecological Design In The Tropics) competition.

The building's design aims to reduce the use of mechanical air-conditioning systems and artificial lighting.

55.1% water self-sufficiency is achieved through the re-use of collected rainwater and grey water; mains water is only used for potable purposes.

The building employs what the architect terms "loose-fit" design, featuring removable partitions and floors and mechanical jointing of materials as opposed to the use of chemical bonding; this will aid future re-use of the building and recycling of materials.