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CTBUH Technical Paper http://technicalpapers.ctbuh.org Subject: Sustainability/Green/Energy Paper Title: Environmental Performance of the TTDI Author(s): Suraksha Bhatla Joana Gonçalves 1 Affiliation(s): 1 Publication Date: 2012 Original Publication: CTBUH Journal 2012 Issue II Paper Type: 1. Book chapter/Part chapter 2. Journal paper 3. Conference proceeding 4. Unpublished conference paper 5. Magazine article 6. Unpublished Universidade de São Paulo © Council on Tall Buildings and Urban Habitat/Author(s) CTBUH Journal International Journal on Tall Buildings and Urban Habitat Tall buildings: design, construction and operation | 2012 Issue II Capital Gate, Abu Dhabi Securing Iconic Structures Environmental Performance of the TTDI Developing Rotterdam’s Skyline Talking Tall: The Skyscraper Index Debating Tall: Is UNESCO Going Too Far? Tall Buildings in Numbers: Occupiable Telecommunication & Observation Towers Inside News and Events 02 This Issue Steve Watts, CTBUH Trustee 04 CTBUH Latest Antony Wood, CTBUH Executive Director 05 Debating Tall: Is UNESCO Going Too Far? 06 Global News Highlights from the CTBUH global news archive Case Study CTBUH 12 Case Study: Capital Gate, Abu Dhabi 46 Helsinki: Developing a Finnish Vernacular for the High-rise? Antony Wood Jeff Schofield Author Jeff Schofield, Associate RMJM Floor 27, Monarch Office Tower PO Box 6126 Dubai UAE t: +971 4 702 7626 f: +971 4 329 6444 e: [email protected] www.rmjm.com Jeff Schofield Since moving to RMJM Dubai in 2005, Jeff Schofield has lent his design expertise to a variety of large scale building developments, including mixed use, hospitality and high-rise projects. 48 CTBUH Young Professionals Committee Launches Ambitious Agenda Kevin Brass 49 CTBUH Research Development Initiative: An Update Payam Bahrami 51 CTBUH on the Road CTBUH events around the world. As an Associate at RMJM, Jeff leads the effort in providing sustainable solutions to all design projects in the office. He has developed a holistic approach to design that integrates sustainability, structure and architectural expression with the built form, in order to provide meaningful solutions for high-quality building designs. Jeff seeks to design in a contemporary yet contextual manner, to create modern sustainable buildings using the latest technology. g his Jeff currentlyy lives and works in Dubai. He began career in New York City and pursued his professional practice for more than 15 years in Paris, France. Jeff has projec pro jectt mana m anagem gement ent an and d desi d esign gn exp experi erienc ence e on on a project management design experience range of high profile projects. Jeff has specific exp erienc i e in i sustainable sustain i abl ble design design i and d project proje j ctt experience manage man agemen mentt of of llarg arge-s e scal cale ep publ ublic ic pro projec jects ts thr throug oughou houtt management large-scale public projects throughout Europe, U.S.A and the Middle East. 18 24 32 Securing Iconic Structures Sean Ahrens & Stephen Yas The Environmental Performance of the TTDI Suraksha Bhatla & Joanna Gonçalves 18 Developing Rotterdam’s Skyline Frank van der Hoeven & Steffen Nijhuis Sean Ahrens Stephen Yas Aon Fire Protection Engineering Security Division 1000 Milwaukee Avenue, 5th floor Glenview, IL 60025 United States 51 Diary Upcoming tall building events t: +1 847 461 9359 f: +1 847 953 7793 [email protected] www.aonsecurity.com Stephen Yas, Design Principal MulvannyG2 (Shanghai) Architecture Ciro’s Plaza Suite 1905 388 Nanjing Xi Road Shanghai 200003 China Features 38 Tall Buildings in Numbers A Look at Occupiable Telecommunication & Observation Towers 40 Design Research University of Nottingham 42 Talking Tall: The Skyscraper Index Andrew Lawrence 52 Reviews Review of new books in the CTBUH Library Sean A. Ahrens Sean leads the security consulting practice at Aon FPE with over 19 years of experience, a majority of which has been in a security consulting function. He has been responsible for providing security threat and risk analysis, contingency planning, loss prevention, and force protection design and planning. Sean has provided design and construction administration for government, public, and private entities that encompass telecommunications, security, surveillance, and access control systems. He is well versed in the various trade and local authority issues impacting projects, and has specialized professional competence in security, access control systems, and force protection systems. Stephen Yas Stephen has over 35 years experience working internationally. He specializes in architecture, urban design and interior design for large mixed-use projects. As design principal in the Shanghai office of MulvannyG2 Architecture, he is the design leader in china for the firm. Prior to MulvannyG2, Stephen leads his own firm in Chicago for 22 years. Prior to that he was a senior designer at SOM Chicago and Lohan Associates, as well as working in England and the Middle East. 52 CTBUH in the Media Selection of media coverage 53 What’s on the CTBUH Web? Featuring new content now available on the website The Concept In 2005, the Abu Dhabi National Exhibitions Company (ADNEC) was created to drive forward the development of Abu Dhabi’s events sector. Plans were created with RMJM to build a state-of-the-art exhibition centre which would be the largest in the Gulf region and provide world class facilities for live events to flourish in Abu Dhabi. It was strongly felt that the entire development required a signature tower, a cutting-edge structure with a futuristic design, • The vertical and horizontal cross-sections of the tower are all unique First of its Kind There are several innovations within the project’s design, including the dramatic 18-degree westward lean, which has earned it the title of “world’s furthest leaning manmade tower” from the Guinness book of world records (see Figure 1). It is also the first building in the world to use a pre-cambered core with a built-in lean of 350 millimeters that has been engineered to straighten with the addition of the upper floors. And it is the first building in the world to use vertical post-tensioning of the core to counter movement and support stresses created by the building’s overhang. aesthetic splendor and technical excellence to celebrate human achievement and reflect the dynamism of Abu Dhabi. Capital Gate is the result. The tower’s curvaceous shape draws strongly on the sea and desert – two elements that have great resonance in Abu Dhabi. The building’s form is meant to represent a swirling spiral of sand, while the curved canopy, known as the “splash,” which runs over the adjoining grandstand and rises on one side of the building, creates a wave-like effect, CTBUH C CTB CT TBU TB UH H Jo JJou Journal ou ourna rn rn naal | 2011 20 011 11 1 1 Issue Isssue Is Iss su ue IIII ue “In sophisticated urban planned environments, security should be subtle, but allow for the potential for heightened threats. The key is to find a suitable balance between security and preserving the designer’s vision. A security program for any structure should employ a variety of controls to deter, delay, detect, deny and respond to threats, as well as mischievous or potential accidental acts.” This paper emphasizes the importance of integrating security programming into building design, allowing for different uses and threat levels for the life of the building. Security strategies will be evaluated that can be applied to any building, as well as review procedures to address concerns early in the design process, especially in politically and economically charged international environments. General concepts and approaches to building security will be examined, demonstrating the benefit of collaboration between architects and security professionals at an early stage to meet the project’s goals without detracting from the planner’s vision for the project. The “Fortress” To the untrained eye, this graphic (see Figure 1) may appear “fortress” like. However, in its most basic format, the diagram describes the security program for building at any security level. Early dialogue between security professionals and the designer can limit the fortress or bunker aesthetic by careful placement of technical security, including cameras, setbacks, gates, fencing and spatial provisions for security staffing. In many cases, consideration is not given to the potential for a future modification to the building, such as the addition of a casino, parking garage, skate park or theater, which may increase the potential for malevolent acts. The addition of new tenants, such as a dignitary or VIP, may require a change in the security status not considered in the original design process. The modification of the physical and architectural security component is the most important, most expensive and, therefore, most difficult to modify post-design. Done early in the design process there is significant indirect and direct return on investment that can be achieved by preplanning. When planning a facility, design professionals need to think outside-the-box. Although fear of terrorism typically drives the mindset for iconic building security, there are other more likely threats, including workplace violence, domestic spill over issues, intellectual theft, property theft and other malicious acts against persons or property that can affect the building and its occupants. Unforeseen dangers can create significant security challenges for building owners post-design and may detract from the marketing, image and status of the project. Planning for a single threat may not be effective and may miss potential threats in the future. The best approach is to create generalized controls designed to address a broad range of threats. Unlike other building elements, there are no standards for the provision of security based on building occupancy. As a result, the evaluation and development of security controls is purely based on a quantitative risk and consequence analysis which evaluates all aspects of the proposed building, not simply such critical assets as electrical and telecommunications systems. Conducting a risk and consequence analysis will assist the 18 | Securing Iconic Structures 32 • Four hundred and ninety foundation piles were driven 20 to 30 meters underground to support the structure and counter stresses. The piles, which were initially in compression during construction to support the lower floors of the building, are now in tension as the stresses caused by the overhang have been applied. The construction also adopted a variety of leading-edge approaches to create the desired result, including: • Asymmetric shape – no two rooms are the same (see Figure 2); every single pane of the 12,500 panes of glass on the façade is a different size although each pane is triangular • Floor plates change shape and orientation to create the distinctive “overhang” moving from “curved triangular” to “curved rectangular,” while increasing in overall size and migrating from east to west as they progress up the tower • Capital Gate is one of few buildings in the world that use a diagrid structure; it also features two diagrid systems, an external diagrid defining the tower’s shape and an internal diagrid linked to the central core by eight unique pin jointed structural members. • All 8,250 steel diagrid members are different thicknesses, length and orientation Figure 2. Typical hotel floor plan © ADNEC CTBUH Journal | 2011 Issue II Capital Gate, Abu Dhabi | 13 Securing Iconic Structures Sean A. Ahrens, Practice Leader/Manager 53 Comment Feedback on the past journal issue By integrating with the National Day Grandstand – one of Abu Dhabi’s most historic structures – Capital Gate underscores the bond between the traditional and modern that is characteristic of Abu Dhabi’s developmental approach. Figure 1. Typical section © ADNEC t + 86 21 6032 0100 f + 86 21 6217 8525 e: [email protected] www.mulvannyg2.com Research reflecting the building’s proximity to the water and the city’s sea-faring heritage. Throughout history, a strong link has existed between iconic architecture and exhibitions. One of the best known examples is Paris’ Eiffel Tower, which was built as a visual symbol of the Exposition Universelle, World’s Fair of 1889. More recently cities like Seville have used powerful and innovative architecture as a way to highlight the cultural significance of their exhibitions. 12 2 | Cap Capital pit ittaal ita al G Gate, aatte ate te, A te, Abu bu Dha bu Dh Dhabi haab h habi bii Authors 12 Capital Gate, Abu Dhabi Jeff Schofield “From the beginning of concept design, the architects and engineers integrated many passive and active sustainable systems into Capital Gate, its most visible sustainable feature is the “splash,” which twists around the building towards the south to shield itself as much as possible from direct sunlight.” CTBUH Journal | 2011 Issue II designer with understanding the exposure to threats. For example, a building near a proposed or existing mall will make criminal incidents more likely. In similar fashion, integrating a train or metro into a large high-rise project could increase exposure to chemical or explosive attacks, while the creation of a building near a government facility or embassy may escalate the tertiary terrorism risk. The type of building and its tenants may also affect risk rating, which can change over time. Understanding the risks early in the process will assist organizations in making decisions. The planner should ensure that the security analysis provides specific guidance and recommendations on vehicular access, security placement of cameras, access control and the overall security compartmentalization program. From a security perspective, designers need to think about the “what-ifs.” They need to have a vision. That does not necessarily mean implementing controls from day one, but designing provisions into the architecture so security controls can be easily and quickly adopted in the future if higher threat scenarios arise. The downside of shortsighted preplanning is evident in the airports built 20 years ago. The functions and usage of airports have changed dramatically. The free flowing public environment of yesterday is now a series of mazes and security compartmentalization which could have been avoided, if only designers had taken a more open-minded approach during the design process. Preparing for the Future To prepare for tomorrow’s uncertainties, today’s international planners should start by evaluating the site and potential setbacks and standoff distances from the façade of the building. Even with constricted site layouts, there are opportunities that can be explored. Setback can be achieved through a number of programming elements. To increase the affect of clear space, the perception of setback can be somewhat masked through architectural programming, such as the creation of multi-tiered planting areas, water features, structures and natural boulders. The proposed US Embassy in London employs an enveloped glass façade and a water feature to support security. The water feature provides a visual element to the project, but it also creates a defined perimeter and clear zone. When developing building placement, roadways should be carefully evaluated. Centralized or limited roadway access is preferred, while incorporating standards and requirements for emergency access. In some cases, emergency access roadways will need to be secured and may create a conflict with first responders. Proper signage and clear access routes can limit frustration by people who are not familiar with the site, which could be a key to minimizing negative interactions with security. Site confusion can lead to anger. Roadways are integral to the project, but simple and cost effective techniques, such as using a serpentine access road, can create elegant and effective solutions to reduce the potential for a vehicle to approach a building at high speed. Counter terrorism and counter surveillance techniques are extremely beneficial to identifying an aggressor. For this reason, building layout, whenever applicable, should afford natural sight lines to allow the detection of an intruder. As a result, landscaping is extremely important. Trees and other foliage that can obscure sight lines should be discouraged. Lighting, the number one deterrent to crime, may become obscured by growing tree canopies. As a result, lighting plans and photometric should take into account tree growth over the life of the tree and the effect on the light distribution. By doing this more effective light placement can be identified. Hotels will often employ a porte cochere, which can expand setback from the primary structure while providing continuity in architecture and limit the perception of distance from the entry to the building. Setback is more than maintaining vehicle proximity, setback increases natural lines of sight as well as the area that must be traversed prior to accessing a facility, while supporting the potential for early detection of an aggressor. Designs should limit components that may be used by aggressors for criminal acts. Loose rocks of substantial size could be used to break windows to gain entry to a building or be picked up as a makeshift weapon in an ambush scenario. If rocks are integral to design, they should be kept small or be large enough that they can’t be easily picked up. The Worst Case Scenario When designing setback and site placement, consideration should be equally afforded to the planning for emergency vehicles and muster points for evacuating tenants. Muster points need to account for the expected mass of people and should be as far away from Figure 1. The “fortress” © Aon CTBUH Journal | 2011 Issue II Securing Iconic Structures | 19 Developing Rotterdam’s Skyline Frank van der Hoeven Steffen Nijhuis Authors Frank van der Hoeven, Associate Professor Steffen Nijhuis, Assistant Professor Delft University of Technology Faculty of Architecture Julianalaan 134 2628 BL Delft The Netherlands t: +31 15 278 9805 e: [email protected] e: [email protected] www.graduateschool.abe.tudelft.nl Frank van der Hoeven Prof. van der Hoeven is an associate professor of urban design at the Faculty of Architecture at the Delft University of Technology, the Netherlands. He conducted his PhD research in the field of underground space technology and multifunctional and intensive land-use. The core of his work deals with urban design issues related to mixed-use development: transit-oriented development, urban greenhouse horticulture, the use of underground space, high-rise urban areas and climate change. Currently he combines his associate professorship in urban design with the position of Director of Research of the Faculty of Architecture. 54 Meet the CTBUH Kevin Brass Steffen Nijhuis Prof. Nijhuis is an assistant professor of landscape architecture at Delft University of Technology (the Netherlands). His PhD research, entitled “Landscape Architecture and GIS,” focuses on the application of geographic information science in landscape architectonic research and design. The core of his work deals with theories, methods and techniques in the field of landscape architecture and urban design, visual landscape assessment and visual knowledge representation. He is leader of the architecture and landscape research program, series editor of RiUS and advisor to governmental and regional authorities in the Netherlands. 55 CTBUH Organizational Structure & Member Listings “The framework as presented carries the potential to underpin a city’s guidance on tall building development. This framework presents the context of a tall building design, providing a more balanced evaluation of a design proposal compared to studies that focus solely on individual tall buildings.” The planning and construction of tall buildings is often controversial, polarizing the public debate on architecture and urban life. In many cases the emotional discourse focuses on aesthetics and view corridors, more than city planning or economics. This paper introduces a framework that analyzes the visual impact a developing skyline has on a city and its surrounding region, using Rotterdam as a case study. By studying the height and completion year, identifying the tall building cluster as it is perceived visually and conducting a GIScbased visibility analysis, the framework provides context to tall building designs. The results make the assessment of individual projects more scientific and balanced, removing many of the emotional elements that often enter into the discussions. Introduction Research on the visual impact of tall buildings has the potential to make or break a tall building proposal. In the UK, debates over the appropriateness of projects in London and Liverpool are focused on view corridors, with UNESCO threatening to remove world heritage designations from historic complexes if the new developments damage their aesthetic impact (see “Debating Tall”). Concerns about the appropriateness of tall buildings in the urban environment, the quality of the architecture and the impact on local real estate markets is increasingly reflected in municipal and metropolitan policymaking. Prominent cities with a longstanding tradition of urban management, building regulations and zoning plans often feel the need for additional instruments to control the development of what is described by McNeill as “an extremely complex spatial phenomenon” (McNeill, 2005). Scientific literature, however, often neglects the substantial impact skyscrapers and their visual footprint can have on urban life. “The significance of these buildings – in terms of height, levels of human occupancy, aesthetic impact and popular representation and use – is in need of careful geographical interpretation.” (McNeill 2005) In 2007 the Netherlands Institute for Spatial Research (Lörzing et al. 2007) published an investigation on the visibility of the proposed Belle van Zuylen tower. At 262 meters the Belle van Zuylen tower would become Holland’s tallest residential building and the centerpiece of Leidsche Rijn, the new city district, west of Utrecht. But the Netherlands Institute for Spatial Research analysis showed that the Belle van Zuylen could be seen from most of the “Green Heart,” the semi-rural region enclosed by the cities of Rotterdam, Amsterdam, The Hague and Utrecht. The report was the last blow for the proposed development – construction was cancelled soon after the release of the report (Lörzing 2011). The Belle van Zuylen case is a fine example of using research for tactical purposes through the selective presentation of findings. The study did not present the Belle van Zuylen in its true context. The joint visual impact of all the tall buildings in the region on the Green Heart was not considered, nor how much that impact would change as a result of the construction of the Belle van Zuylen. If the study had included these elements, it may not have caused such stir. In fact, a nearby television tower, the 367-meter Gerbrandytoren tower, built 42 years earlier, dominates the visual impact of the area. A framework that helps to picture the context of a proposed tall building can potentially neutralize public and political debates that so often lead to polarization. This framework is based on three key elements: Rotterdam’s tall building development Rotterdam is one of the prominent European tall building cities with a mature tall building policy in place (see Figure 1). Several databases, including the CTBUH’s The Skyscraper Center, make it clear that only four Figure 1. Rotterdam as a prominent west European tall building city © authors 30 | Developing Rotterdam’s Skyline CTBUH Journal | 2011 Issue II CTBUH Journal | 2011 Issue II western European cities possess this type of mature skyline: London, Paris, Frankfurt, and Rotterdam. The leading position of Rotterdam is furthermore underscored by DEGW’s report on London’s Skyline, Views, and High Buildings commissioned by the Greater London Authority (GLA). The London policy document uses the same four European cities to compare established European practices of tall buildings policymaking: London, Paris, Frankfurt, and Rotterdam. The tall building policy document that emerged in the Netherlands is called hoogbouwbeleid or hoogbouwvisie. The Dutch policies resemble a number of policy documents recently produced in the United Kingdom and Germany. Height regulation is a key component of all these tall building policies. Height also translates into visibility. A modern history Over the years, the city of Rotterdam has carefully cultivated an image as a “city of architecture.” But “historic” architecture is not Rotterdam’s strong point. Few buildings were left standing after the bombing and fire of May 1940. The few buildings that survived were relatively modern buildings from the 1920s and 1930s. The city had to rebuild its center from scratch. Planners seized this opportunity to experiment with architecture and urbanism, which is why the Rotterdam city center now contains numerous monuments and icons from the modern and modernist period, sometimes referred to as “reconstruction architecture.” Discussions about the appropriateness of tall buildings surfaced from time to time, but never reached the emotional levels experienced in cities with a historic center. Tall buildings are now generally accepted and most are concentrated in the city center. While Rotterdam as a whole uses modern and modernist architecture to promote itself, tall buildings are an essential ingredient in the profile of the city: the skyline, including the famous Erasmus Bridge, has become the city’s iconic image (Ulzen 2007). Rotterdam’s semi-official tall building history portrays a 100-year prelude from the late 19th century, with the completion of the 42-meter Witte Huis, built in 1898, to the so-called “first wave” of high buildings in the mid-1980s. Prominent city planners suggest that the city at the turn of the century was on the verge of a “second wave” of tall buildings, which would feature supertall buildings (Maandag 2001). However, this tale cannot be underpinned with facts. Neither the height nor the location of the high buildings dating from this early period relate to the municipal policy on high-rises. It was only in the 1970s that the current tall building area in the middle of the city center began to emerge. Essential data on tall buildings can be easily presented by means of a scatter plot. In the case of Rotterdam, the building height and the year of completion were plotted, including the primary use of such buildings. The beauty of Rotterdam’s scatter plot lies in the clear patterns that emerge. In her book Form Follows Finance, Carol Willis explains that the end of a tall building wave is typically marked by the construction of the “tallest building so far.” If we would consider these “tallest buildings so far” as anomalies and disregard them, the development of the Rotterdam tall building cluster is characterized by a remarkable continuity. However, if Carol Willis’ insights are applicable to Rotterdam, then the year in which the tallest building so far was completed could be used as the breaking points between tall building waves. Three such buildings stand out in Rotterdam: the Faculty of Medicine of the Erasmus University, also known as Hoboken (1969, 112 meters), the Delftse Poort (1991, 93 and 151 meters) and the Maastoren (2009, 165 meters). If the tall building history of Rotterdam is indeed characterized by waves, then these buildings are indicative of three such waves, as represented in the scatter plot (see Figure 2). The end of the wave is determined by the latest and tallest building in a development cycle. A first wave of tall building construction began in Rotterdam in the early 1970s and a second wave followed in the late 1980s and early 1990s. This second wave is not only defined by architectural height. The Developing Rotterdam’s Skyline | 31 “Although commonly classified as a typology of high-energy demand, tall buildings can be beneficial in hot, humid climates. Considering both urban and building scales, the typology enhances the exposure of the built form to wind flow, generates more wind at the ground level and provides desirable shadows upon the immediate surroundings. ” Suraksha Bhatla & Joanna Gonçalves, page 24 CTBUH Journal | 2012 Issue II Inside | 3 The Environmental Performance of the TTDI Suraksha Bhatla Joana Gonçalves Authors Suraksha Bhatla t: +91 98400 94314 e: [email protected] Joana Gonçalves Laboratório de Conforto Ambiental e Eficiência Energética, Universidade de São Paulo Rua do Lago 876, Cidade Universitária São Paulo-SP, CEP 05508-080 Brazil t: +55 11 30914538 f: +55 11 30914539 e: [email protected] Suraksha Bhatla Suraksha graduated with honors from the School of Architecture and Planning, Anna University, Chennai in 2007 and went on to practice at T.R Hamzah and Yeang Sdn, Bhd in Kuala Lumpur. She was closely involved with the design phase of several large scale mixed-use, residential and commercial tower projects in Asia that were driven by sustainable concerns, including the Fusionopolis Office Tower, Singapore and PutraJaya Commercial Development, Kuala Lumpur, Malaysia. In 2009 she chose to return to academica and pursued her Masters in Sustainable Environmental Design at the Architectural Association, London. Her research at the AA, “Tall Communities: Passive Urban Housing for the Tropics” focused on the analytic exploration of basic bioclimatic strategies for hot humid climates and its consequent social impacts through passive design, with an emphasis on residential towers in keeping with the Asian mass housing market. Joana Gonçalves Joanna is an architect and urbanist from the faculty of Architecture and Urbanism of the Federal University of Rio de Janeiro, where she graduated in 1993. She practiced as an architect in Ana Maria Niemeyer SA, in Rio de Janeiro between 1992 and 1995. In 1996 she moved to London to study environmental design in the Architectural Association Graduate School, obtaining a MA degree from the Environment and Energy Studies Program in 1997. In the same year she moved to Sao Paulo to engage in teaching and research in the Faculty of Architecture and Urbanism at the University of Sao Paulo, where she received a PhD in 2003 with the thesis entitled, “The Sustainability of the Tall Building.” Since 1998 she has been involved in teaching, research and consulting related to environmental design, collaborating with institutions in Brazil and in the U.K. Since 2009 she has been part of the teaching staff of the Masters Programme in Sustainable Environmental Design of the Architectural Association, London. In 2011 she was a visiting lecturer in the Harvard Graduate School of Design. Main research projects include the recent publication of the book The Environmental Performance of Tall Buildings. 24 | The Environmental Performance of the TTDI “Through detailed analysis of occupant behavior, the predicted energy consumption patterns shown in modeling and performance assessment techniques can be further improved, challenging the preconceived theoretical notion of comfort and behavioral patterns.” Tropical Asia is accelerating towards vertical densification of its urban communities. With this movement comes an increase in the cooling demand in the building sector. Currently, it is estimated that 60% of the world’s electricity consumption, usually affiliated with high CO2 emissions, is attributable to residential and commercial buildings, creating the need to look at ways of reducing energy consumption in these buildings (Laustsen 2008). Although commonly classified as a typology of high-energy demand, tall buildings can be beneficial in hot, humid climates. Considering both urban and building scales, the typology enhances the exposure of the built form to wind flow, generates more wind at the ground level and provides desirable shadows upon the immediate surroundings. Introduction Across southeast Asia several proclaimed “bioclimatic towers” stand as examples of the contemporary environmental approach to tall buildings in the tropics, including the two residential towers of the Taman Tun Dr. Ismail (TTDI) condominiums in Kuala Lumpur (see Figure 1). Completed in 2006, the 21- and 28-story towers were designed by T.R Hamzah & Yeang, who is widely known for advocating his ideas on ecological architecture for the tropics. Ken Yeang’s buildings are designed to encourage the inhabitants to connect with the natural environment through semi-outdoor transitional spaces and other elements which help reduce energy use. His design approach incorporates shading elements such as balconies, sky lobbies and brise-soleil, with shafts and structural cores often strategically positioned to buffer the interior spaces from solar exposure. Wind catchers are also commonly used to enhance natural ventilation and vertical landscaping is claimed to act as a means of facilitating micro climatic mediation (Yeang 1996). To evaluate the effectiveness of these different strategies, including shading devices and wing walls, a review of the environmental performance of the TTDI tower was based on the outcomes of a post-occupancy evaluation (POE). This included real time data measure- ments of internal environmental conditions, namely temperature and humidity, interviews with the occupants and the assessment of energy bills. While the field work brings insight into the reality behind the various energy and thermal comfort demands of residents, it also sheds light on their adaptive behavioral response to environmental conditions and architectural features offered by principles of Figure 1. Taman Tun Dr. Ismail (TTDI) condominiums, Kuala Lumpur © T.R Hamzah and Yeang CTBUH Journal | 2012 Issue II Base Case - Thermal Analysis Simulation (TAS) inputs Floor Area 100 m² (10 x 10 m) Floor Height 3 m W/F Ratio 25% Internal Gains 5562 kwh year Thermostat Upper Limit 30 C Lower Limit 18 C U-value 0.3 / 0.8 / 3.0 W/m²K Aperture Type Natural Ventilation Infiltration 0.5 ach Ventilation Rate 0 ach partially open - 20C fully open - 28 C Table 1. Inputs for Base Case TAS model bioclimatic design. Findings from the study, as well as a technical review, revealed the method and extent by which the annual cooling demand in residential tall buildings located in the tropical region can be curtailed. Figures as low as 5–7 kWh/m² per year in the best case scenario were found, mainly due to the occupants’ behavior, which had a fundamental role to play in achieving strong environmental performance. The Study The POE was carried out in two phases: the first phase included a general survey in a Figure 2. Relationship of annual cooling load and horizontal shading depth in different orientations, based on thermal dynamic simulations using EDSL, 2010 (TAS v 9.1) group of flats, which in turn, informed a more detailed study of three residential units in the second phase of the evaluation. Prior to the case study, basic practices of environmental design for the tropics were tested in a series of analytical studies with the support of advanced simulation tools. The studies were carried out for the climatic context of Kuala Lumpur and supported the subsequent technical critical assessment of the TTDI residential complex. The main aim when dealing with warm humid climates is to keep the building envelope protected from the typically high solar radiation, both direct and diffused, while ensuring effective heat dissipation by means of controllable ventilation. The tropical city of Kuala Lumpur (3.1˚N, 101.5˚E), has a warm, humid climate throughout the year with average hourly temperatures remaining at 27˚C for 76% of the year and humidity levels ranging between 60 to 80%. During the hottest period of the year, between February and April, external temperatures exceed 30˚C. In this context, the diurnal temperature differences range between 8 and 12 K, indicating the potential of night time cooling by means of natural ventilation (ASHRAE 2009a). Due to the proximity to the equator, Kuala Lumpur receives high levels of solar radiation (170–200 W/m² per day on the horizontal plane), highlighting the importance of shading. Apart from the direct component, the diffuse radiation is also high (>100 W/m²), as a consequence of high cloud cover that occurs for 80% of the year. Given the average monthly temperatures, based on Auliciems adaptive model (1981), a theoretical comfort zone was established as 22.9 –29.9˚C 1. It is important to note that the prevailing winds in Kuala Lumpur blow mainly from west and southwest for most of the year, with an average speed below 2 m/s for 70% of the time. Bioclimatic Strategies In order to demonstrate the energy saving potential of passive strategies for tall buildings in the tropical context, the efficiency of shading was tested through computer simulation techniques using thermal analysis software 2. Parametric studies were carried out using a base-case of a 10 x 10 meter residential unit positioned in an intermediate floor of a hypothetical tall building in Kuala Lumpur. Considering the limit of 29.9˚C established by the theoretical comfort zone, the annual cooling loads for the base case was simulated with the thermostat set point at 30˚C for a continuous occupation period of 24 hours (see Table 1). This set point was also determined based on research precedents 3 and findings from the fieldwork survey of TTDI residents, which identified the threshold temperature varying between 29˚C and 30˚C. The performance of varying shading depths was analyzed for a 25% window to floor ratio4, using north-south and east-west orientations. Looking at orientation only, 15% reduction of annual cooling loads was found when comparing the east-west to the north-south orientations. With the introduction of a one-meter horizontal shading device, the loads reduced further by nearly 28% (see Figure 2). With three-meter deep shading, the cooling loads reduce further to become similar for windows facing either north-south or east-west, making orientation a nondifferentiating parameter for the environmental performance of the residential unit. In addition, simulations verified that there is no negative impact 5 on the internal daylight distribution for the given base case, even with a three-meter deep shading device (see Figure 3 and Table 2). Insulation produced a perhaps surprising initial reduction of 42% in annual cooling loads by improving the U-value of the external walls from 3.0 W/m²K, which is Auliciems, A.(1981). The comfort equation (Tn = 17.6 + 0.31To ± 2.5°C) was used as the neutral temperature found, was closest to the values accepted by tropical subjects in fieldwork survey. Environmental Design Solutions Limited 2010, (TAS v 9.1) Dynamic thermal simulation TAS model uses hourly values of incident solar radiation and outdoor temperature, to simulate internal temperatures and cooling energy requirements based on a given set of specific internal environmental, constructional and occupancy conditions for the entire year. 3 BUSCH (1992) Bangkok, Thailand (1100 surveys) 28.5 ET (NV) 24.5 ET (A/C). DeDear (1991) Singapore (583 NV/ 235 A/C surveys) 28.5 ET (NV) 24.2 ET (A/C). Indraganti, M. (2010) Hyderabad, India (100 surveys) 29.23 (NV). 4 The 25% window to floor ratio (WFR) was chosen for the parametric studies, as simulation test results of different WFR and the consequent cooling load demand revealed that at this point the ventilation is effective, thereby causing a slight reduction in the cooling loads. Also mass housing schemes in the tropics usually use large glazing areas with WFR between 20–35%. 5 Even with a 2.5-meter shading depth for 10x10 meter unit, double side lit, with a 25% window to floor ratio, it was found that the average daylight factors of 5% can be achieved above the recommended 1–1.5% for living spaces as per CIBSE 1999 (see Table 2). 1 2 CTBUH Journal | 2012 Issue II The Environmental Performance of the TTDI | 25 Figure 3. Performance of daylight distribution along the ten-meter-room depth of the base case, using Radiance (v3.5) and Ecotect 2010, (v 4) Figure 4. Annual loads of concrete building structure with different U-values in W/m²K oriented north south, based on thermal dynamic simulations using EDSL, 2010 (TAS v 9.1) conventional construction practice in concrete without insulation, to 0.8 W/m²K, when 400 millimeters of mineral wool insulation is applied to external walls (see Figure 4). Moreover, the cumulative positive impact of shading and insulation resulted in more than 50% reduction in annual cooling loads in comparison to the base case (no shading and no insulation), effectively decreasing from 100.3 kWh/m² to 49.4 kWh/ m² per year. At this stage, the potential of cooling through natural ventilation had not yet been considered. must be said that the reduction was marginal, approximately 4 to 8%, in comparison to the optimum combination. The findings from the first steps of the analytical work are summarized in Table 3, showing the reductions in cooling loads of different combinations, with various degrees of shading depths and U-values. The most cost-effective and optimum combination proved to be the one-meter overhang with the U-value of 0.8 W/m²K 6. The further reductions in cooling loads were possible with increased shading depth from 1 to 3 meters and increased insulation. However, it Once the envelope was made robust with shading and insulation, the analytic work focused on the study of different ventilation scenarios and its consequent effect on the reduction of annual cooling loads. At this point, size, form and layout of the theoretical base case were modified to represent a typical layout within the residential unit, commonly observed within the typology. This was done to explore if the differences in the performance was similar for the different ventilation conditions, and heights, owing to the various degrees of exposure to the outside (namely one, two, and three façades) (see Table 4 and Figure 5). Expectedly, the overall performance is similar in different exposures and orientations, due to the solar protection optimization tactics. Results show some slight variations between the different ventilation strategies, as indicated in the cooling loads. The most problematic case was identified in the west-facing orientation, with single-sided ventilation. For this specific case, the analytical work showed that by providing opportunities for cross ventilation, including vertical floor voids (as seen in the TTDI project) and better aperture distribution, the thermal performance of the west-oriented and single exposed unit could be improved significantly. Annual cooling consumption dropped by 25% at typical intermediate floor levels (30 meters above ground) and by only 19% at top floor level (60 meters above ground). This difference in reduction is due to the impact of high horizontal solar radiation, despite the higher wind velocities at the top. With the addition of a double roof 7 painted white, the top floor units’ performance could be further improved to 30% to emulate the typical units. Case Study: The TTDI Tower, Kuala Lumpur The TTDI residential complex consists of two towers, one oriented north-south and the other east-west. Due to the impact of solar radiation, in principle, the north-south oriented tower is likely to have a better environmental performance, which is why it was chosen for this study. The 21-story north facing tower includes 120 apartments, which house middle and upper middle class families with two- to four-people per household. Some of the signature bioclimatic features incorporated in this project are the continuous 1.2-meter deep shading device; white concrete façades to reflect solar radiation (see Figure 6); 0.6-meter-wide wing Window to floor ratio/shading depth 15% 20% 25% Insulation (U-Value, W/m2K) 30% Shading (m) 3.0 1.0 -41.5% 2.0 -49.0% 3.0 -52.4% 83.6 -16.6% 76.3 -23.9% 73.1 -27.1% 1m 5.05 6.65 7.69 8.33 1.5 m 4.45 5.79 6.68 7.19 2m 4.11 5.27 5.91 6.41 2.5 m 3.84 4.9 5.53 5.91 Table 2. Showing above 5% average daylight Factor for different Window to Floor Ratios and shading depths, based on simulations for Kuala Lumpur using Radiance (v3.5) and Ecotect 2010, (v 4) -22.6% 40.0% 0.8 49.4 -50.8% 41.7 -58.4% 38.3 -61.8% -57.0% 8.0% 0.3 -63.3% 43.2 -57.0% 35.3 -64.8% 31.9 -68.2% Table 3. Findings from the analytical work showing the combined contribution in reduction of cooling loads, with respect to degrees of shading and insulation. The percentage below is the amount of reduction The U-value of 0.8 W/m2K can be achieved with 400 mm mineral wool added to the external concrete walls or simply with lightweight concrete blocks (hollow blocks) commonly found in the local construction sector, to which high-reflectance colors can be easily applied. 7 A double roof is a non-structural exterior slab placed over the structural roof of a building, common in tropical buildings, it protects the top floor against horizontal solar radiation. The analytic work prescribes a Super insulated Inner roof slab of 0.3 W/m2K, shaded by outer roof both with a surface reflectance of 0.6 and U-value of 0.8 W/m2K 6 26 | The Environmental Performance of the TTDI CTBUH Journal | 2012 Issue II Figure 5. Modified base case for the TAS model EDSL 2010, (TAS v 9.1) walls located on the east-west faces to capture wind and enhance air flow across the center of the building; and, finally, a double roof covering the top floor flats. The typical layout of the floor plate is divided by a six-meter wide corridor flanked by four flats on either side, Figure 6. TTDI tower, north-south orientation, white façades and shading devices to reflect incident solar radiation © T.R Hamzah and Yeang each 10 meters deep. The floors are connected vertically by two-meter wide voids, which allow light and airflow, designed to serve the communal circulation areas of the flats (see Figure 7). The fieldwork took place during the summer period, from June 30 to July 7, 2010. Of the 120 flats, 42 households responded to the general survey on their lifestyle and occupational pattern, as well as their thermal comfort expectations. This data revealed that the air-conditioning thermostat settings during summer varied from 22 to 26˚C for middle-aged people (<50 years) and 26 to 28˚C for elder residents (>50 years). Interestingly, 90% of inhabitants who were interviewed expressed their preference for natural ventilation to mechanical and declared that they exercised window control as their first response to dealing with higher indoor temperatures. However, the survey also showed that occupants’ satisfaction levels varied based on occupant perception, floor height and window adaptability. In this respect, residents in the west-facing corner flats, with three external façades in the plan Flats A and E, considered the bedrooms “hot” in the afternoons, while occupants of those facing east, in the plan Flats D and H, found bedrooms and kitchens “warm” in Optimized Base Case with Internal Layout TAS inputs Mean height of surroundings - 40 m 100 (10 x 10 m) Floor Area Living Room 50 m2 Bedrooms 25 m2 Floor Height 3 m W/F Ratio 25% Internal Gains 5562 kwh year Thermostat U-value Aperture Type Upper Limit 30 C Lower Limit 18 C External Walls 0.8 W/m²K Glazing 5.6 W/m²K Natural Ventilation Infiltration 0.5 ach Ventilation Rate 0 ach partially open: 20C fully open: 28 C Table 4. Inputs for TAS model of the Modified Base case EDSL 2010, (TAS v 9.1) CTBUH Journal | 2012 Issue II Figure 7. Typical floor plate with the naturally ventilated corridor and vertical floor voids to bring in daylight access and enhance air movement across the inner parts of the building (Source –T.R Hamzah and Yeang). © T.R Hamzah and Yeang The Environmental Performance of the TTDI | 27 Figure 8. Shallow depth of floor voids Figure 9. Detailed post occupancy evaluation of flats located at different heights facing north late mornings. Such responses imply that the impact of solar radiation was experienced by occupants in those critical times as a consequence of the disproportionate shading depth, in relation to the considerably large window areas, with 30–35% of the windowto-floor-ratio, on the east and west façades. The rooms adjacent to the vertical floor voids, which should be the ones that benefit the most from the internal cross ventilation through the stack effect, also had an issue, but this time related to the restricted access to ventilation. The occupants kept the windows closed for privacy reasons, due to the perceived narrow depth of floor void of just under two meters (see Figure 8). On the other hand, the design of the open perforated wide corridors at all levels, allowed ample cross air movement that ameliorated the heat dissipation from the flats, when windows and/ or doors were partially opened. Energy Clothing Occupant Cases Consumption Insulation Profile year (Clo) Flat A Flat B Flat C 15 (kWh/m2 per year) 40 (kWh/m2 per year) 25 (kWh/m2 per year) Room Occupancy Getting Closer Following the more generic survey, a more detailed post occupancy evaluation took place in three residential units located on three different floors, including Flat A located at the 13th floor, Flat B on the 7th and Flat C on the 18th floor, all facing north (see Figure 9). In this case, all three flats had two occupants of Indian origin over the age of 53. The differences in floor heights were crucial to demonstrate the impact of height on the effectiveness of ventilation and solar protection strategies, and ultimately, the resulting energy performance of the flats. Table 5 shows the occupancy pattern of the three flats, including time schedule, thermal comfort conditions, window operability and overall energy consumption. The energy bills for the year of 2010 showed significant variations among the three flats with a range of 25 to 45%. Considering air-conditioning systems and fans account for 30 to 45% of the total consumption (CETDEM 2005) of the average electricity consumption breakdown by the end user of residential flats in Kuala Lumpur, it could be assumed that out of the 15 Kwh/m² per year consumed in Flat A, the energy for space cooling can be as low as 5 to 7 Kwh/m² per year based on varying occupancy patterns. This figure indicates that Flat A is not only the least dependent on air conditioning, but also probably the only one among the three which is naturally ventilated for most of the year. Given the similarities in the occupancy pattern, differences between flats can be narrowed down to two factors: the differences in comfort standards, and the degree of climatic adaptation. For instance, it was identified that during the summer nights, the residents of Flat A prefer the use of fans rather than air-conditioning, unlike the occupants in Flats B and C. Pattern of Occupation (hours) 0:00–7:00 8:00–12:00 13:00–15:00 16:00–20:00 21:00–24:00 Metabolic Window/Door Operation Schedule Rate (Met) Morning Noon Evening Night Mother (age 74) 0.54–0.84 Son (age 46) 0.29–0.36 Bedroom Wife (age 57) 0.54–0.84 Living Husband (age 60) Kitchen 2 0.29–0.36 Mother (age 76) Son (age 53) Living 1–1.7 open close open close Kitchen 2 open open open close 0.8 close close close close 1–1.7 open close open close open close open close Bedroom 0.8 close close close close 0.54–0.84 Living 1–1.7 close close close close Kitchen 2 open open open close 0.29–0.36 Bedroom 0.8 close close close close Table 5. Comparative data from the POE of the three flats (A, B & C) in the TTDI north-south residential tower 28 | The Environmental Performance of the TTDI CTBUH Journal | 2012 Issue II 100 % RH 35 C Air-conditioning in use 90 % RH Solar gains from east 30 C 80 % RH 25 C 70 % RH Alucieums comfort zone 23-29°C 60 % RH 20 C 50 % RH 15 C 40 % RH 0C 0 % RH 7/7/2010 WEDNESDAY 7/8/2010 THURSDAY 0 +1 +2 7/10/2010 SATURDAY Datalogger Occupant thermal perception Slightly warm -3 -2 -1 ASHRAE scale 7/9/2010 FRIDAY +3 Internal temperature External temperature Internal humidity External humidityy Occupied Figure 10: Flat B, air temperature and humidity measured in the master bedroom between 7th July and 10th July 2010, compared to the external climatic conditions. Figure 10. Flat B, air temperature and humidity measured in the master bedroom between July 7 and July 10, 2010, compared to the external climatic conditions 100 % RH 35 C Insufficient shading for give glazing area – Gains from West Windows closed when occupied 30 C 90 % RH 80 % RH 25 C 70 % RH Alucieums comfort zone 23-29°C 60 % RH 20 C 50 % RH 15 C 40 % RH 0C 0 % RH 7/1/2010 THURSDAY 7/2/2010 FRIDAY Occupant thermal perception Neutral -3 -2 -1 ASHRAE scale 0 +1 +2 +3 Internal temperature External temperature Internal humidity External humidityy Occupied 7/3/2010 SATURDAY 7/4/2010 SUNDAY Datalogger Figure 11.A,Flat A, air temperature and humidity measured in the1stmaster between June, 30 and Julyconditions. 7, 2010, Figure 11: Flat air temperature and humidity measured in the master bedroom between July and bedroom 4th of July 2010, compared to the external climatic compared to the external climatic conditions CTBUH Journal | 2012 Issue II In addition, in some particular rooms in Flats B and C, where natural ventilation was preferred, ergonomic issues such as improper room dimensions for furniture layout and privacy requirements inhibited more flexible use of windows, which was seen previously in the wider survey. As a result this caused poor ventilation, closure of the internal blinds and the inevitable increased dependency on artificial cooling, mechanical ventilation and artificial lighting (see Figure 10). In terms of solar exposure, Flat B on the 18th floor receives considerably more solar gains than the other two flats due to its position at a higher floor, despite the double roof. In addition, the architectural layout of the building floor plate, allowed direct solar radiation from the internal open corridor and adjacent voids in the central part of the building heating the service and secondary bedrooms of the flat. Furthermore, the kitchen was found to be “hot” in Flat B due to the closed plan layout. In comparison to Flat B, Flat A has an advantageous position in the TTDI Tower. With the main orientation towards north and west, the exposure of three façades coupled with the proximity to the wing wall creates the appropriate conditions for good airflow within all rooms. The open-plan conversion created by the resident enhanced cross ventilation in the kitchen area where the most internal gains are concentrated. It also improved the daylight penetration from both sides, namely west and north, reducing the demand for artificial lighting. The west facing service areas were shaded in the direction of the prevailing winds and flanked with wing walls, enhancing the cross airflow. Data loggers measuring temperature and humidity were placed for four days in the living room, master and secondary bedrooms in Flat A. In all cases the air temperatures remained relatively stable and below 30˚C, except in the west facing master bedroom due to overheating. Based on the findings from the simplified analytical studies, the overheating effect was presumably a consequence of the impinging afternoon sun on an uninsulated wall (see Figure 11). In this case, the surface temperatures recorded on the west facing walls were 2˚C higher than external temperature at 7 p.m., after sunset. The Environmental Performance of the TTDI | 29 Nevertheless, the overall thermal conditions of the rooms in Flat A indicated good thermal and energy performance. Apart from the capacity of the architectural design to modulate the variable and sometimes undesirable indoor and outdoor conditions, the good environmental performance of Flat A is inextricably linked to the willingness of its residents to exercise adaptive behavior. These included opening and closing windows, controlling the internal blinds and curtains, as well as sleeping close to the ground or under the ceiling fans. Considerations and Key Findings The initial analytic work showed that shading of windows and walls is the most effective passive approach for the tropics. The base-case considered a window-to-floor ratio of 25%, which proved to have a good impact on daylight and ventilation, yet was still large enough for generous views of the scenery outside. For windows of such proportion, a shading solution between one to two meters deep, in principle, can be efficient. However precise shading devices need to be determined based on glazing area and orientation. Moreover, contrary to common belief, insulation has a huge potential to reduce the overall cooling load demand in ...Pritzker “ The fact that an architect from China has been selected by the jury represents a significant step in acknowledging the role that China will play in the development of architectural ideals. ” Thomas J. Pritzker, explaining the selection of Chinese architect Wang Shu for the 2012 Pritzker Prize. From “Chinese ‘Amateur’ Wins Prestigious Architecture Prize,” CNN, February 28, 2012. 30 | The Environmental Performance of the TTDI warm-humid climates like Kuala Lumpur, while contributing to more stable internal temperatures throughout the day. The study recommends insulating concrete walls with U-values of 0.8 W/m²K (400 millimeters mineral wool) to be beneficial when applied externally. Environmentally, shading and insulation improves energy performance by 50%, making the unit robust to climatic variations and, therefore, passively conditioned for longer periods. Apart from providing a comparative benchmark of 15 kWh/m² per year for electricity consumption for future residential units in tall buildings in the tropics, the fieldwork also provided some useful insights into the validity of previous analytical research simulations with regards to shading and natural ventilation. In fact, residents from the middle and upper middle class groups, where the use of air conditioning is a cultural trend, have actually proven to prefer to naturally ventilate their apartments, despite the warm humid climatic conditions of Kuala Lumpur. Constant air movement has proved to enhance the residents’ perception of comfort, which is achieved by exercising adaptive mechanisms such as opening windows, doors and/or using low-powered ceiling fans. As a consequence, ambient air temperature around 30˚C was found acceptable. On a more critical observation, the fieldwork also showed the importance of the relationship between the internal furniture layout, position and size of windows. Equally important is the issue of privacy that must be addressed, especially when facing common corridors. By designing buildings with a range of adaptable options– primarily through smaller windows and blinds to address privacy, gusty winds and security– designers can influence occupants to utilize them and tolerate climatic variability in naturally ventilated apartments. It is crucial to understand the way occupants of existing buildings contribute to overall energy performance, which provides a fundamental measure for the achievement of true environmentally responsive design. Through detailed analysis of occupant behavior, the predicted energy consumption patterns shown in modeling and performance assessment techniques can be further improved, challenging the preconceived theoretical notion of comfort and behavioral patterns. The findings from the post-occupancy evaluation of the TTDI tower offers insight on the real potential of climate responsive design and the impact of the occupants’ behavior and their thermal expectations from the building. A set of effective design guidelines for the tropics can be formulated for future projects by studying the real environmental performance of more existing tall buildings in a wider fieldwork study. With the help of more comprehensive measured data and detailed analytical investigations, specific design solutions can be found. References ASHRAE. 2009a. “Climate Design Information.” ASHRAE Handbook – Fundamentals, Atlanta: ASHRAE. ASHRAE. 2009b. ASHRAE Handbook – Fundamentals. Atlanta: ASHRAE. AULICIEMS, A.1981. “Towards a Psycho-physiological Model of Thermal Perception.” International Journal of Biometeorology Vol. 25, No 2:109–122. BHATLA. S. 2011. “Tall Communities: Passive Urban Housing for the Tropics.” MArch in Sustainable Environmental Design diss., Architectural Association London, 2011. BUSCH, J. 1992. “A Tale of Two Populations: Thermal Comfort in Air-conditioned and Naturally-ventilated Offices in Thailand.” Energy and Buildings 18: 253–243 CENTRE FOR ENVIRONMENT, TECHNOLOGY & DEVELOPMENT, MALAYSIA (CETDEM). 2005.Malaysian Urban Household Energy Consumption Patterns, Results of a CETDEM Study 2005. Kuala Lumpur: CETDEM. CIBSE. 1999. Daylighting and Window Design. London: CIBSE. DE DEAR, R., K. LEOW, and S. FOO. 1991. “Thermal Comfort in the Humid Tropics: Field Experiment in Air-conditioned and Naturally-ventilated Buildings in Singapore.” International Journal of Biometeorology 34, No. 4: 259–265 INDRAGANTI, M. 2010. “Thermal Comfort in Naturallyventilated Apartments in Summer. Findings from a Field Study in Hyderabad, India.” Applied Energy 87: 866–883. LAUSTSEN, J. (ed.) 2008. Energy Efficiency Requirements in Building Codes, Energy Efficiency Policies for New Buildings. http://www.iea.org/g8/2008/Building_Codes.pdf. SZOKOLAY, S. 2008. Introduction to Architectural Science: The Basis of Sustainable Design. Second Edition. London: British Library Publications. WONG, N., H. FERIADI, P. LIM, K. THAM, C. SEKHAR, and K. CHEONG. 2002. “Thermal Comfort Evaluation of Naturally-ventilated Public Housing in Singapore.” Building and Environment 37, Issue 12 (December): 1267-1277. YEANG, K. 1996. The Skyscraper Bioclimatically Considered: A Design Primer. London: Wiley-Academy. POWELL, R. 1999. Rethinking the Skyscraper: The Complete Architecture of Ken Yeang. New York: Whitney Library of Design. CTBUH Journal | 2012 Issue II