Designs on the Desert

Airport designers and planners have had their work cut out. Developing state-of-the-art facilities in what can be characterised as an extreme environment requires a unique understanding of the local environment.

The main challenge is the desert climatic conditions. Depending on the location, the hot and high climate can result in temperatures that peak above 40 degrees for more than half of the year. The scarcity of water resources and the pollution associated with sand and dust are also cited as problems.

Foster + Partners is behind the design of the on-going Queen Alia International airport 20 miles south of Amman. The company was challenged in its quest to design an energy-efficient terminal building that would provide a comfortable environment for passengers and the operations of the airport.

“We apply a combination of passive and active strategies,” said Mouzhan Majidi, chief executive at Foster + Partners. “This can mean making the most of filtered daylight, encouraging natural ventilation or, in some cases, integrating photovoltaic installations that take advantage of the abundant sunlight to generate power.”

Majidi quickly points to the problem of dust and sand: “This can make maintenance a challenge. There is need to choose robust and durable materials for the building’s facade.”

The issue also comes up when talking to Claire Mazelet – building, engineering and environment director at global architectural and engineering firm ADPI. She warns that proper filtering devices are required for ventilation systems in order to preserve indoor air quality.

ADPI is a specialist in the design and construction of airport passenger terminals of all sizes and in the renovation of terminals in operation . It is project manager for Muscat International airport as well as Salalah airport in Oman.

The firm has been involved with several other MENA airport projects, including sites in Libya, Egypt and the Dubai International terminal three. In Saudi Arabia, ADPI has been involved in the design concept for King Abdulaziz International airport, for the construction of a state-of-the art terminal that will handle up to 30 million annual passengers once complete.

“Precautions should always be taken to prevent sand and dust accumulating at specific locations such as air intakes or rain collection downpipes to avoid deterioration of filters, or clogging of the network,” said Mazelet.

“When external temperatures are in the range of thermal comfort during a limited period of the year, natural ventilation should be envisaged. When outside temperatures are fluctuating throughout the day, a large thermal mass within the insulated portion will contribute to the building’s overall performance.”

Mazelet explained that the dense materials used gradually heat up when exposed to daytime solar energy. “These materials then gradually cool down during the night, thus radiating heat during the cool evenings and coldness during the hours of daylight.”

The on-going construction at Queen Alia is scheduled for completion in 2012. The new facility is designed to allow the airport to grow by six % per annum for the next 25 years, increasing annual capacity from three million passengers to 12 million by 2033. The plan is to equip the airport with the capacity to become a hub for the Levant region.

“An airport is the first thing you see when you arrive in a country and your first experience of its culture, so the design of a terminal must be of its place,” points out Majidi. “Our work is equally driven by an understanding of and respect for local traditions – hospitality, for example, is an important part of Jordanian culture, so our design for Queen Alia airport is conceived as a welcoming gateway.”

According to Foster + Partners inspiration for the Queen Alia terminal building is drawn from traditional architecture of the region. The design incorporates a variety of outdoor spaces and open-air gardens. In the courtyards, water pools reflect daylight into the building and form a natural focus that directs passenger movement. A broad canopy, its dark external surface evocative of Bedouin tents, shelters the large external public area and evokes the excitement of a Middle Eastern bazaar.

A closer look at the design of the underside of the roof unveils a geometric pattern inspired by traditional Islamic forms. “We worked with a local artist to develop the pattern for the carpet in the piers,” added Majidi. The design also responds to social customs: the forecourt has been enlarged to create a landscaped piazza where relatives can gather to welcome or bid farewell to passengers.

Successful construction of airports in such regions has increasingly taken into account the issue of sustainability, in addition to the usual on-time and budgetary target demands.

However, this arid environment can provide rare opportunities to utilise and benefit from the use of natural energies. Intense and regular sun exposure is excellent for renewable energy – thermal or photovoltaic – said Mazelet, but she also pointed out that it does not always represent a realistic solution. “This is in a context where there is no benefit from any subsidies and relies on very low energy costs that would result in very low profitability. Night ventilation concepts work in buildings where maximum occupancy is not at night – which did not apply to Muscat Airport – and where significant differences of temperature occur between day and night.”

At Queen Alia, Majidi indicates that the terminal has taken a highly efficient form and Fosters + Partners designed a number of features that will reduce energy demand, before looking at active measures to generate power.

“Firstly, the roof has a deep overhang and a sequence of horizontal louvres that shelter the facades from direct sunlight. Again, maintenance can consume a great deal of energy in a desert, so the louvres are perforated to avoid a build up of sand and dust,” he said.

The roof also has an innovative double skin. A metal canopy sits above the concrete and shields the structure from direct sunlight. Majidi said that a cavity between the metal and concrete allows hot air to be released. “There are also environmental benefits in building a concrete structure. It acts as a thermal store for the heating and cooling of the terminal, plus it means we can incorporate local gravel as a material, which harmonises with the natural shades of local sand.”

Majidi points out that one of the key challenges in a hot dry climate, where the sun is so intense, is to illuminate the interior with indirect sunlight so that the passenger areas are comfortable and easy to navigate without generating excessive heat.

“We have filtered daylight into the terminal through split beams at the junctions between the concrete domes – the effect is a little like a desert palm whose leaves extend and widen from very slender branches close to the trunk,” he said.

The airport’s open-air courtyards also contribute to the environmental strategy. They feature modest linear pools, which are lined with dark tiles so that they are highly reflective – they ‘bounce’ indirect daylight back into the baggage reclaim areas.

It seldom rains in desert regions such as Oman but when it does these rains can turn into heavy downpours. One of the biggest challenges is to provide adequate drainage of the construction area.

At Muscat Airport one of the areas where rainwater collects on its way into the sea is a flat, low-lying section where the new runway is being built. The ground was raised by three metres to prevent the new runway and roads from ending up underwater. This was achieved by driving almost 12 million cubic meters of desert sand and crushed rock to the site.

Protecting the rest of the airport involved the installation of three giant outlets to the Bay of Oman with a combined capacity of 500m² of water a second.

“For Muscat Airport, an extensive drainage system of open concrete channels and culverts was constructed as part of the preliminary works and before building construction started,” said Mazelet.

“The overall drainage design is based on a modelling simulation that considered the worst scenarios to make sure critical operational areas of the airport would not be affected in case of heavy rain falls.”  Following cyclone Gonu in 2007, modifications were made to the design, whenever it was possible.

Mazelet said the design should incorporate maintenance aspects to guarantee the full capacity of the drainage system at any time. “Oil interceptors are implemented for the drainage areas of runway and taxiway systems, aprons and roads to avoid pollution of ground and surface water,” she said.

“Water conservation and re-use measures should be especially encouraged to reduce potable water demands,” she added.

At Dubai International’s terminal three the s tatistics from the Dubai Airports Company are eye-watering. The mega-project required the excavation of more than 10 million cubic metres of earth, enough to fill 4,000 Olympic-size swimming pools, and some 2.4 million cubic metres of concrete, enough to fill 950 Olympic-size swimming pools, was used in the construction of the project. As much as 450,000 tonnes of steel was used for reinforcement and another 33,000 tonnes of steel was required for the structure; that’s approximately the weight of 850 A380s.