Chenyang Li
9.20.2013
Illumin Article
WRIT 340
Prof Elisa Warford
Modernizing the Mashrabiya: Smart-skinned Al Bahar Towers
Nature and culture are the most powerful sources of inspiration for high-rise architecture. The Al Bahar Towers studied on both of these and developed a smart-skinned system which integrated the building with its cultural background and responded directly to the climatic requirements of the region. The “mashrabiya” form of the shading system anchors the buildings in the Islamic tradition, meanwhile the dynamic movement of each of the individual panels respond to the native environment.
Introduction
Since sustainability became a popular social issue, it is now covering all fields are related to our daily lives. Architecture, as a significant part of our society, is putting a great deal of effort into sustainability nowadays. In the general context, sustainable architecture pursues to lessen the negative environmental impact of buildings by raising efficiency and innovating the use of materials. Modern architects are striving their designs and decisions today which do not restrain the development for future [1].
A recently completed project in Abu Dhabi, named Al Bahar Towers (see Fig 1), expresses the idea of sustainability, and brings it to another level both architectonically and technologically.
Aedas, the architecture firm who designed the buildings, creates a more comfortable interior space by having the dynamic facade opens and closes in response to the movement of the sun which will reduce solar gain by more than 50 percent [2].
Figure 1: Al Bahar Towers
Physical Condition of the Site
The weather condition for Abu Dhabi where the Al Bahar Towers is located is extreme. The city has intensive sunshine all year long. In summer, the average temperature is steadily above 100 degrees Fahrenheit with low chances of rain [3]. In such extreme weather conditions, architects from Aedas listed the environmental design as their first priority on the design agenda. After a long-term research on both the local culture and possible technology, architects decided to build a responsive facade which takes cultural cues from the “mashrabiya”(see Fig 2), a traditional Islamic lattice shading device for the Al Bahar Towers [4].
Figure 2: Mashrabiya
Mashrabiya
Mashrabiya is the Arabic term given to a type of window enclosed with carved wood latticework. It is an important element in Arabic architecture since the middle ages [5]. The wooden screen with operable windows has two significant environmental functions. It gives shade and protection from the hot summer sun. Meanwhile the openings on mashrabiya allow the cool air from the street to flow through. Especially, the smaller openings are in the bottom part and larger openings are in the higher parts (see Figure 3). This allows air moving in the room[6].
Figure 3: Mashrabiya
Design Procedure
The Masharabiya-style shading system is one of the main concepts led the design firm Aedas. During the competition stage, the design team developed a self-customized program. And powered by the computational program, the architects and engineers were able to find a parametric shape for the movable panels on the facade and simulate the motions in response to sun exposure during different days of the year [4] (see Fig 4).
Figure 4: Comparisons of Shading Units fully Opened and Closed
The design for the project began with two simple cylinders, because the circular plan giving the most efficient floor area usage while also creating the greatest volume with the least surface area which will highly reduce the sun exposure surface area (see Figure 5).
Figure 5: Cylinder Volume
An integrated building model (see Figure 6) consisting both the geometry of the buildings and the mashrabiya shading devices was created, providing a fully general view of the project.
Figure 6: Integrated model
The shading system operates as a curtain wall, located two meters outside the building’s exterior on an independent frame. Each unit responds to the movement of the sun. However, in the evening, all the screens will open.
“At night they will all fold, so they will all open, so you’ll see more of the facade (see Figure 7). As the sun rises in the morning in the east, the mashrabiya along the east of the building will all begin to close and as the sun moves round the building, then that whole vertical strip of mashrabiya will move with the sun.” said Peter Oborn, the deputy chairman of Aedas.
Material
The major material of the shading panels (see Figure 8) is PTFE. PTFE is synthetic of fluoropolymer. It’s now becoming a popular material in architecture field because it’s heat-resistant, corrosion-resisting and has great tensile strength [7]. All the panels are driven by a linear actuator. The building also combines the use of solar thermal panels for water heating and it will be one of the first buildings in the Arabs to receive a LEED (Leadership in Energy & Environmental Design) Silver rating Prize. [4]
Figure 7: Al Bahar Towers at night
Figure 8: Panel Units under Construction
Performance
The effects of this system are tremendous: improving the penetration of daylight, reduce glare and less artificial lighting. By running the self-customized program, the Aedas team did a comprehensive solar analysis (see Figure 9). The result shows that over 50% solar gain has been reduced, which results in a reduction of CO2 emissions of 1,750 tons per year [4]. In addition, the shading ability to filter light has allowed architects to be more alternative in the choice of glass. "This allows us to use more naturally tinted glass, which allows more light inside and less need for artificial light. It is an ancient technique used in a modern way, which also responds to the aspiration of the emirate to take a leadership role in the field of sustainability. "says Peter Oborn of Aedas [4].
Figure 9: Solar Analysis
Future Importance
The design of Al Bahar Towers may also be seen as a response to the future development of the Emirate. Since the publication of the Abu Dhabi 2030 Plan, the city planners have schematized a comprehensive development framework based upon the principles of cultural and environmental responsibility[4].
Conclusion
The Al Bahar Tower’s facade system challenges the typical high-rise building typology. By having a more responsive and dynamic techniques to climactic conditions and a culture-based architecture concept, Al Bahar Towers provides us a combination which meets both the standards of efficiency and aesthetics.
The Al Bahar Towers won the 2012 Tall Building Innovation Award. Such an award acknowledges the great innovation, and the sustainable way that the facade treats the building as a responsive interaction to the environment rather than normal fixed sustainable strategy will be a trend in the future.
References
[1] Doerr Architecture, Definition of Sustainability and the Impacts of Buildings[online]. Available: http://www.doerr.org/services/sustainability.html
[2] CTBUH, 2012 Tall Building Innovation Award handout[online].
Available:http://www.ctbuh.org/Awards/AllPastWinners/12_AlBahar/tabid/3362/language/en-US/Default.aspx
[3] Abu Dhabi City Municipality, Abu Dhabi City Facts[online].
Available: http://www.adm.gov.ae/en/Menu
[4] Cilento, Karen, "Al Bahar Towers Responsive Facade / Aedas" 05 Sep 2012. ArchDaily. Accessed 20 Sep 2013
[5] John Feeney, "The magic of the mashrabiyas", 1974, Saudi Aramco World
[online]. Available:http://www.saudiaramcoworld.com/issue/197404/the.magic.of.the.mashrabiyas.htm
[6] Ching, Francis D. K. “A Visual Dictionary of Architecture Van Nostrand Reinhold”, New York, 1995
[7] J. Blumm, A. Lindemann, M. Meyer, C. Strasser. "Characterization of PTFE Using Advanced Thermal Analysis Technique". International Journal of Thermophysics 40 (3–4), 2011