Innovative materials and global initiatives are transforming the skyline in Dubai.
Architects the world over agree that façade materials must be carefully chosen for their aesthetic appeal, durability, cultural suitability, environmental sustainability and low embodied energy. While these are the practical considerations that clients, developers and architects generally negotiate throughout the masterplanning process, there is a highly subjective, yet equally important, consideration influencing their decisions: style. Especially in Dubai-the world's fastest developing city; one of the world's richest cities; the commercial icon of the Middle East-what is perceived as cutting-edge or avant-garde is generally preferred over that which may be more practical, and often, over that which may be environmentally beneficial. This is not to say that eco-friendly façade materials have been cast aside in favour of glitz and glamour, but in a city where every new building aspires to outdo the last one and everyone wants to see and be seen, that which is shiny and new draws attention, and glass is often the preferred medium.
"Choosing the right façade for a structure is vital...the façade is the [building's] face and therefore it's important for it to reflect what the rest of the building is like...here in the Middle East, traditionally, a façade has been very much just a skin to be clad onto a structure-a mask, so to speak-which does not express what is on the inside," says Janus Rostock, senior design architect for Atkins Middle East. As Rostock points out, Dubai's economic and creative potential is attracting ‘signature' architects everyday and neither they, nor their financially flamboyant clients, will be satisfied with a façade that does anything short of dance, sing and sparkle in the desert sunlight. For this reason, says Rostock, transparent façades are popular because they allow the people inside the building, and the myriad functions they perform, to contribute to the diversity and individuality of the façade by providing an ever-changing image.
There is however, another school of thought that is weighing heavily in the debate over transparency versus reflectivity. "Architects want transparency. It's fashionable right now. They want to see the people, the furniture and everything that's happening in the building," says Arthur Millwood, technical manager of Emirates Glass. "But, with the amount of sunlight in the UAE, with transparent glass, there will always be a problem with too much light. More transparency means higher heat gain, higher heat gain means less energy efficiency."
Millwood offers the Burj Dubai as an example of a building whose architects used reflective glass intelligently to keep its inhabitants cool and the sun out. Whereas BurJuman, on the other hand, "uses a type of glass that has 50% light transmission so its inhabitants need to keep their blinds shut most of the time." According to Millwood, because Burj Dubai has achieved such worldwide recognition, it has the potential to single-handedly quell the use of transparent glass and actually point the industry back in the direction of highly reflective glass façades.
Is glass the way forward?
It's true that glass can provide a building with a rainbow of external options in terms of colour, design and scope, but there is more to the argument than just aesthetics. A major reason for choosing a glass façade is the technical advantage of keeping heat out and daylight in. Unglazed, transparent glass, by nature, allows direct sunlight in, which increases the amount of energy needed to keep a building cool and thereby, decreases its energy efficiency. This process is known as ‘thermal bridging' or ‘solar gain', and because of a relatively inhospitable environment and poorly insulated materials, thermal bridging in the Middle East can significantly increase operational costs.
"With the regional ambient temperatures and extremes in humidity levels there is a necessity for the system designers to be aware of the physics of a building façade," says Nael Afieh, director of Schüco International KG. "Façade physics in the Middle East...are opposite to those applied in more temperate climates...it is important to ensure that humidity never passes the water vapour line of the façade." The rationale being, that if the water vapour line is exceeded, condensation occurs on the inside of the façade and small particles of heat are passed through the water into the room.
Given the climate in Dubai, the state of the building industry here and the myriad innovations in glazing and insulation technology, glass remains the favourite and, potentially, best material for a building's façade. Nevertheless, sceptics cite heightening levels of solar gain and increasing temperatures as reason to move away from glass façades in this region. Nick Lander, regional head of sustainability for Atkins Middle East, ranks non-insulated materials-including glass-among the worst possible façade choices for this region. In fact, Lander looks to traditional building customs to help prove his point.
"Glass is not great [as a façade material], and if you look at traditional architecture in this region, you won't see a lot of windows." And, while Lander condones using well-insulated glass with high shading coefficients, his point about unfired earthen materials and their inherent energy efficiency is valid, and often overlooked. In fact, rammed earth, as a building material, has an excellent thermal mass, which means it absorbs heat and moisture slowly during the day and releases it during the evening. But, while rammed earth materials can reduce the need for air-conditioning, they are not good insulators, and thus, inefficient.
Concrete is an easily attainable façade material but it tends to carry with it a heavier, more earthy feel and creates buildings that mimic this feeling. One would be hard-pressed to find a building clad in steel in the Middle East because of the region's high humidity and steel's corrosive nature. Aluminium, on the other hand, won't rust, it's cost-efficient, local and lightweight, but its embodied energy-the energy that goes into processing and manufacturing it-is quite high. Carbon-fibred reinforced plastic (CFRP) is a material that is beginning to see more and more use in the Middle East as it's durable, lightweight, cost-effective and has a low embodied energy, but it's only slowly gaining a following here. Rapidly renewable materials like bamboo or timber from sustainably managed forests can be useful in the region but, again, have a higher embodied energy and don't always correspond with the client's preferred look.
"There are many factors to consider when choosing the right façade including aesthetics, cost, technical feasibility, life expectancy of the building, maintenance and, of course, getting planning permission," says Matthew Fan, senior architect with Kerr Blyth Associates. "When we choose the best material for a façade, we consider multiple aspects...we look at a range of factors and try to strike a balance between them," adds Lander.
Passive energy efficiency
Façade materials, whether glass, steel, aluminium, bamboo or adobe, are not the only way to achieve sustainability and improve energy efficiency. For decades, architects have employed passive methods of increasing shading and diverting sunlight away from high-traffic areas. "In this part of the world, high performance glass façades can be used to keep rooms cooler, but it's more about the surrounding architecture...a balcony is very useful. Not to lounge on, but to act as a shading device" says William Yuen, co-director of the Dubai branch of P&T Engineers and Architects.
Another method, which incorporates knowledge of the physics of rammed earth or adobe, is the use of a trombe wall (non-insulated earthen wall) to absorb direct sunlight. Earthen walls, because of their density and thickness, lend themselves to extremely slow temperature penetration and thermal conductivity. While trombe walls are usually used in front of a curtain wall, large window, patio or car park, they can be included within an interior to absorb heat from lights and office equipment, which can then be released at night. In fact, if properly built and cured, trombe walls can be constructed so efficiently that it can take 12 hours for warmth or cold to penetrate a 14-inch thick wall.
Passive energy efficiency is a method indigenous to this region, and the durability, suitability and low embodied energy of the products make them an attractive option in the UAE. Certainly, passive solar architecture is being utilised at the moment, but too often it's relegated to a secondary consideration.
The future of glass faCades
"Glass is an amazing material, when used in the right configuration and with the right systems, it can perform very well in terms of strength and durability and has the added benefit of controlling heat and it's visibly pleasing," says Tony Campbell, managing director of Creative Glass. Undoubtedly, glazing and insulation has greatly improved in the last decade, and-with the myriad advances in products available in the UAE-will continue to answer aesthetic and environmental challenges in the future.
As an example, Schüco's ‘TipTronic' is "the first mechatronic range of fittings to combine energy management, security and design into the façade," says Afieh. While its ‘Advantec' concealed fittings, "provide clean, uninterrupted lines to the elevational appearance and increase security levels." In fact, one of Schüco's core competencies involves providing a variety of intelligent façade materials that can be simply integrated into existing buildings and keep occupants safe.
Emirates Glass, on the other hand, is expecting to launch its line of ‘post-temperable sputter-coated' glass in July 2008, which, for the first time, will allow consumers to temper and cut stock pieces of sputter-coated reflective glass to their specifications. A development that has been anticipated since sputter-coating was developed, this will make the industry's most eco-efficient glass available in any shape, for almost any space.
UK-based Creative Glass is looking to break into the glass industry in the Middle East and has recently been touting ‘photo laminate glass', which uses double-glazed walls of glass to convey a specific image or company logo, while also acting as another form of reflectivity both inside and outside a building. Photo laminate glass is also taking the place of more traditional block, brick or sheetrock partitions inside a building, and can be used to divide office blocks into boardrooms, meeting rooms, offices and reception areas.
The future of façades in the UAE is not only limited to products. At the moment, Bahrain is the Middle East leader in legislation that curbs the use of transparent glass in building projects. In Bahrain, the reflectivity levels and shading coefficients that can be used on glass are strictly enforced to keep down cooling costs in buildings and some, including Millwood of Emirates Glass, agree that the UAE is moving in that direction. "The Emirates Green Building Council has drawn up a Dubai standard [for using glass with low reflectivity], which could become the federal standard in the UAE," he says. "Bahrain is much stricter, but Dubai will move toward Bahrain...even architects in Abu Dhabi are building structures that adhere to the Dubai code because they see its coming."
It would seem that if, indeed, glass is the future of façades in the UAE, it will serve architects, clients and developers very well to carefully consider the type of glass they use. For if the Dubai code becomes the UAE's nationwide standard, or if the idea of Green Buildings gains momentum and becomes an industry standard, a bit of foresight will prove prophetic when compared to the millions of dirhams it will take to replace eco-unfriendly glass in the future.