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Sat 12 Jul 2008 04:00 AM

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Looks do matter!

The outside of a building is as important as the inside, and the demand for cladding is rising.

The outside of a building is as important as the inside - the demand for cladding is rising with the pace of construction in the UAE and worldwide picking up speed, reports Shikha Mishra.

I'll just come out and say it - we live in a superficial world and physical appearance is important.

And the same holds true for buildings too. Its exterior ultimately decides the speed at which it will be snapped up by buyers and the number of tourists that will pose in front of it taking countless photos.

Fire retardant cladding is becoming popular in the UAE and is superior to regular cladding. Fire retardant cladding panel consists of mineral fibre along with the polyethylene which delays the structure from catching fire for two to three hours.

Cladding has been likened to the skin of a building and is the protective, insulated or the aesthetic fixed layer that is added to the exterior of a building in the final stages of construction.

And with the construction sector sky-rocketing in the region, the cladding business as an associated industry is reaping the benefits too.

According to a study commissioned by the Freedonia Group, an independent US-based industry research group, world demand for cladding is forecast to climb 3.8% annually to reach 5.1 billion m2 in 2010 and is valued at US $69 billion.

Market advances will be stimulated by a pick up in non-residential building construction activity as global economic growth accelerates and industrialisation efforts continue in less developed parts of the world.

Single-layer construction methods will continue to be used in many countries, but rising standards of living will help make finished cladding more affordable, resulting in increased product use. China will record the largest gains of any national market.

Annual product demand in the nation will expand by 400m2 from 2005 to 2010, and China will surpass the US to become the world's largest cladding market. Sales growth is also expected to be strong in India, as well as in lower-volume markets such as Saudi Arabia, the Ukraine, Turkey, Indonesia, Poland and Iran.

Demand for cladding used in non-residential applications will expand at a faster pace, stimulated by a step-up in associated construction expenditures in Western Europe, Latin America and the Africa-Middle East region, and supported by renewed strength in the US and Japanese markets following a period of extreme sluggishness.

The global growth of cladding is also reflected in the segment's growth in the UAE, with the success of events such as the Front, Roof and Cladding exhibition held in March this year at the Sharjah Expo Centre and the Building Futures Gulf by Batimat in Abu Dhabi in April.Feroz Ahmad, assistant project manager of Expo Centre Sharjah, says that the "cladding market in the UAE is growing very quickly; the demand is so high that the manufacturers are not able to meet the requirements.

"This has led to more advanced cladding technology in building designs and service capability range extensions, meaning big demand in cladding products and business for companies. There are hundreds of skyscrapers coming up, which means its cladding systems must meet special requirements regarding wind pressure."

The importance of studying the impact of wind pressure and heat to the façade of tall buildings is being scrutinised to a greater extent than before.

World demand for exterior cladding is forecast to climb 3.8% annually to reach 5.1 billion m2 in 2010, and is valued at $69 billion.

"The use of double-skin facades, for example, is one way to achieve an effective thermal barrier without compromising the transparent look of a building," says Tony Rofail, director of Windtech Consultants.

"Another way of achieving a thermal barrier is to apply a highly reflective film on the glazing to reflect the heat. The problem with the latter approach is that this can result in unacceptable and even dangerous levels of glare from the facade onto drivers. For super-tall buildings, the use of highly reflective facades can even pose a danger for aircraft due to the impact on visibility of pilots," says Rofail.

Windtech Consultants carried out a solar glare impact study for the Burj Dubai Tower. In cities such as Dubai, a report on the glare impact of a development is only raised when it is perceived by the authorities or planners to be a potential issue.

Sometimes when the double-skin facade system is not straight forward - as when the system is partially naturally ventilated - a wind tunnel testing needs to be carried out at two different scales.

A smaller scale, typically in the range of 1:300 to 1:500, is used to determine the pressures acting on the outer skin and vents with the effect of the surrounding buildings and landform included.

A second, larger-scale model is then made of a typical section of the facade, including the vents and the cavities in the ventilated double skin to accurately determine the relationship between the pressures at the vents and the exterior and the net pressures on both the eternal and inner layer of the double skin facade.

One such example is Windtech Consultants' study for the 200m tall office tower development at 1 Richard Johnson Square, Sydney.

Natural ventilation is also achieved by allowing operable windows and doors on the building façade.This situation results in additional wind loads on the facade due to the wind pressure.

"Natural ventilation can also be achieved by allowing operable windows and doors on the building façade. This situation results in additional wind loads in the facade as wind can pressure the inside of a building if the window or door are left open. This higher internal pressure when combined with the external pressure can result in an increase in the design pressure by as much as 30% to 50% over an effectively-sealed building," says Rofail.

In climates such as that in the Middle East region, extreme winds can occur at short notice and therefore there is a need to look at the possibility of a critical door or window being left open.

Windtech Consultants have applied this approach in the analysis of the wind pressures on the facades of buildings with operable windows and doors to numerous projects in the Gulf region.

Xavier Richard, sales manager of TBC, says that the future of cladding lies in unusual colours, finishes and appearances.

"Cladding panels can now be bent or curved to give it a different shape that can mould the curves of a building. Companies such as Swiss-based Alucobond, Belgium-based Eternit, Etex and Trespa produce cladding in 5mm to 7mm. The properties of these panels are very good, and have proven resistant to wind pressure and expansion under high temperatures."

Apart from just its aesthetic appeal, cladding can also effectively cover a building's defects.

Biju Purushothaman, assistant cladding manager of Arabian Aluminium says, "cladding is essential as most buildings use concrete, block work and plaster which is extremely susceptible to the sun's heat and makes the interior of the building unbearably hot. Cladding acts like an insulator and can save the building's energy bills as the need to continuously run a building's air-conditioning system gets eliminated. Usually in most buildings in the region, aluminium composite cladding is used as it is inexpensive. Solid aluminium cladding panels, such as the ones used on the façade of the Emirates Towers on Sheikh Zayed Road are extremely expensive," says Purushothaman.

Arabian Aluminium is currently working on projects such as the Reef Tower in Lake View and the Metropolis and Al Manara, both in Business Bay.

Current research and development being conducted on cladding materials will enable reduced costs and increased safety standards.

"I always advise my customers to avoid cheaper materials. Fire retardant cladding is becoming popular in the UAE and is superior to regular cladding. Regular cladding made out of polyethylene compound tends to catch fire immediately but the fire retardant cladding panel consists of mineral fibre along with the polyethylene, which delays the structure from catching fire for two to three hours - enough time for help to arrive," says Purushothaman.

Although it works out costlier than regular cladding (normal cladding costs $21.80 per m2 and a fire retardant cladding can tack up an additional cost of $2.70 to $3.70 per m2), fire retardant cladding is being commonly used in the UAE as safety is seen as a priority.

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A Jones 11 years ago

This article purports to be a study of the 'cladding' industry, yet it seems the writer has only focused on the aluminium composite panel (ACP) market, which whilst large is not the be-all and end-all of the industries products. Architectural cladding materials can also be in the form of foam insulated panels (with skins of various metal options; steel, stainless steel, aluminium, zinc faced steel,etc) which can be sculpted like ACP's but have the benefits of quicker and easier installation and being factory manufactured have better engineered joints and therefore superior function than many ACP installations in terms of thermal and moisture protection for the building. Metal cladding systems also include plate and honeycomb cored panels, many of which are probably too sophistcated and with user benefits not apparent to most designers and contractors in the GCC market. The majority of cladding in the GCC is ACP with simple wet sealed joints that seal in any vapour in the wall cavity which can lead to long term problems for the building and its occupants. However as most buildings here are still relatively new the problems with this technique of cladding which were seen in the US and Europe many years ago, have not surfaced here yet. More sophisticated cladding techniques are often talked about by architects and suppliers in the GCC yet the reality is that most of these advances are simply in the sculpting of ACP panels and not in the way they are attached to the structure, the way they are jointed and/or sealed and not in the insulation and vapour control system behind them. We are lucky we don't have more weather and precipitation in this region as the typical cladding used here would be shown to be lacking in many important areas were that the case.