Building exteriors: more than a facade

Impressive architecture and clever use of building materials can transform a medium height, medium-sized building into something that commands respect and admiration without consulting the Guinness Book of Records. The way that an architect uses cladding and glass plays a crucial role in how a building will look, and ultimately be perceived.

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By  Colin Foreman Published  April 25, 2004

Building exteriors: more than a facade|~|Glass Cladding2body.jpg|~|Modern buildings are a far cry from the masonary dominated facades of the past. But masonary did have one advantage: the buildings did not kill birds in the numbers that today’s glass clads do.|~|Superlatives are the order of the day when it comes to building projects in Dubai. Biggest, longest, and largest are just three of the words we have all become accustomed to. With so many projects making such grand claims many of these tags no longer seem to impress like they should. It would also appear that some have forgotten that records do not need to be broken for a building to be impressive. It is fairly easy to guess the age of a building from its appearance. For the older cities in Europe this is not surprising as the age difference between the old and the new may be hundreds of years. However, it is also possible in newer cities where architectural styles move quickly with large numbers of new buildings being built. The skyline of cities like Hong Kong and Singapore clearly show how architecture in cities has moved with the decades. It is now roughly ten years since Dubai began to go down the high-rise route and trends are beginning to show as architects attempt to create a facade that will make a building stand out from the rest. The popularity of materials can be for a number of reasons. A material may become popular simply for its appearance, but it is more likely that its popularity is driven by a combination of factors including appearance, price, performance and technological advances. Regular readers of Construction Week will be all too aware that steel prices are currently going crazy, largely on the back of massive demand from China. Prices are at all time highs, orders cannot be fulfilled, and uncertainty is undermining the market as many fear that the bubble will one day burst. Although Dubai’s highly corrosive atmosphere meant that steel was often shunned as a cladding material, the current market crisis has forced anyone wishing to design a steel building to look for alternatives. Aluminium One such alternative is aluminium. Although aluminium, like all metals is itself experiencing some market difficulties, the situation is not as dire steel’s predicament as it is not as widely used. One project in the region where aluminium is currently being used is the Khalifa Stadium in Qatar and is one of the biggest of the facilities under construction for the Asian Games 2006. The stadium roof will be constructed with an aluminium roof and will be painted with a bright blue finish. “The stadium will have flat panels of aluminium fixed to a Kalzip standard seam roof to ensure water tightness. The shape is tapered with special sheets so that it can be fixed without screws. When finished it will be the biggest indoor stadium in the world,” says Azad Nouri, general manager, Kalzip Systems Middle East. “The benefits of using aluminium are numerous. There is no corrosion, its lightweight, and it can be used to create modern futuristic shapes, we are definitely moving towards more sophisticated roofs with more complicated shapes requiring better cladding solutions,” he adds. However, back in Dubai, several projects are also utilising aluminium for cladding. Projects include the Snow Centre, Dubai’s first indoor ski slope with “real” snow, and the Garden Shopping Centre on Sheikh Zayed Road. prestige According to Nouri the market for cladding is currently enjoying a boom period. “There are a number of prestigious projects on the horizon, such as the new concourse building at Dubai Airport,” he says. High-rise buildings have developed considerably since they we first pioneered in the USA. The early skyscrapers such as the Empire State Building have predominantly stone facades perforated with windows. As tall buildings developed, so did their facades, and by the 1980s large monolithic glass elevations became the order of the day. This trend has continued, and today the majority of high rises feature a curtain wall that is predominantly made of glass. This has been rationalised to some extent as solid cladding is now often used for the façade to conceal services and the building’s structural frame so that the glazing appears uniform. Buildings such as Emirate’s Towers have a mixed façade. Modern glazing technology allows architects to design buildings with vast expanses of glass without losing building performance. Products such as low emissivity and reflective glazing have now been developed to give a building the desired performance. As any car driver will testify, glazing performance in the UAE is all about blocking out the fierce sunlight. By shielding the building interior from the sun a comfortable environment can be created. This is of obvious benefit to the occupants, and at the same time of benefit to the environment as the level of artificial temperature controls such as air conditioning declines, reducing power consumption. With a rapidly expanding population, controlling power consumption is high on the agenda for the city of Dubai. One way that this dilemma is being tackled is through legislation stipulating that glazing must meet certain performance criteria. In essence, glazing must cut out the sunlight to lighten the load placed on air conditioning and electricity consumption. The legislation, which came into effect one year ago, states that if the vision area (glazed area) of a building is 10-40% then the U-value of the glass should be a maximum of 3.27, and the shading coefficient should be no less than 0.4. If over 40% of the façade is glass then the U value should be a maximum of 2.1 with a shading coefficient of 0.35. In case of showrooms the U value should be 2.5 and the shading coefficient should be 0.76. Ground floor areas are excluded from these calculations. This legislation reflects the fact that glass is the weakest link in a building façade as it allows light through and so heat. “By promoting these green building principals Dubai Municipality has told architects to that they must consider this issue, because there are now a set of minimum target levels that they have to meet. Architects can now specify low performance glass that lets in lots of daylight and does nothing to save energy,” says Arthur Millwood, technical and marketing manager, Emirates Glass. The legislation represents a big step forward, as no other state in the Middle East has adopted such a policy for energy control. The policy is also enforced, as a building permit will not be granted unless it is demonstrated that the installed glass meets the requirements. “This is the way it should be, rather than having some legislation that everyone just pays lip service to,” says Millwood. The legislation has also forced the glazing market to become more sophisticated. “Before people could get away with just using clear glass. Now they have to look for a glass with performance,” says Pradeep K. Sharma, general manager, Al Abbar Architectural Glass. constraints Although constraints have now been placed on the use of glass the options available to architects are quite considerable. Modern technology now allows for high performance glass to be completely transparent. “This is proving to be a popular concept as designs try to create buildings that you can see through and do not shut out the external environment. People want to enjoy the outdoors with the comfort of the indoors,” Sharma says. These are mainly multifunctional low ‘e’ glass types that have good light transmission and a low internal reflection. “It is a fairly recent development, but there does appear to be some concern from occupants who want to have a night view that is as clear as possible. They want to look out at night without looking into a mirror,” says Millwood. ||**||

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