The Pennsylvania State University
The Graduate School
RESPONSIVE SKIN: DESIGNING AN ADAPTIVE BUILDING ENVELOPE FOR WARM-HUMID CLIMATE USING BAMBOO VENEER AS A HYGROSCOPICALLY ACTIVE MATERIAL
A Thesis in
Architecture
by
Manal Anis
2019 Manal Anis
Submitted in Partial Fulfillment of the Requirements for the Degree of
Master of Science
May 2019
ii The thesis of Manal Anis was reviewed and approved* by the following:
Marcus Shaffer Associate Professor of Architecture Thesis Advisor
Ute Poerschke Professor of Architecture Interim Head of the Department of Architecture
Benay Gursoy Toykoc Assistant Professor of Architecture
Rebecca Henn Associate Professor of Architecture Director of Graduate Studies of the Department of Architecture
*Signatures are on file in the Graduate School
iii abstract
Architectural facades that are able to adapt themselves in response to changing climatic conditions have typically been identified with having high-tech complex automated mechanisms, using electronic sensors and actuators. The low-tech and no- tech passive strategies of adaptive façade design based on material responsiveness are still in their infancy. Passive strategies minimize energy and material use while maintaining occupant comfort. This is precisely why such methods require a greater emphasis today as we investigate deeper into the realms of Responsive Architecture.
Materials such as bamboo and wood undergo a natural, biological reaction to environmental changes, and, therefore, offer an opportunity for non-mechanical adaption. Bamboo, due to its hygroscopic nature, undergoes constant expansion and contraction with changing levels of atmospheric humidity. From a crafting and constructing perspective, this spontaneous dimensional change – material instability - was seen as an inherent drawback of working with bamboo, with attempts being made to control, mitigate, or counteract the change. But in order to develop an energy-efficient and technologically- independent passive system of responsive architecture, it is time we start looking at the hygroscopic movement intrinsic to bamboo as an opportunity, rather than a challenge, and try and integrate it within the material performance of architecture itself.
This research presents an exploration into bamboo veneer as an adaptive material to help rethink building facades as organic, breathable skins rather than a mechanized barrier between humans and nature. The methodology incorporates an investigation into the different kinds of adaptive envelopes being researched using wood, after which a series of physical experiments were conducted to study the deformation of iv a bilayer bamboo composite consisting of a bamboo veneer bonded with a clear cellulose film. The film, being non-reactive to climate, amplifies the curving motion of bamboo, along with its return to the initial position. The resulting module was then used to explore different façade patterns to study the opening and closing mechanism that could potentially generate ideal conditions of ventilation. The outcome of the research consists of a working, demonstrable prototype for a no-tech adaptive façade pattern that, while undergoing a bio-mechanical response, performs particular functions including shading and/or ventilation, leading to a truly material-integrated architecture. v table of contents list of figures ...... viii acknowledgements ...... xii chapter 1 ...... 1 introduction...... 1
problem statement ...... 3 gaps in knowledge ...... 4 research aims ...... 5 methodology ...... 5 thesis structure...... 7 chapter 2 ...... 10 the case for bamboo ...... 10
the plant ...... 11 understanding hygroexpansion in bamboo ...... 15
chapter 3 ...... 19 natural ventilation for passive cooling ...... 19
ventilation and thermal comfort ...... 20 ventilation and the built form ...... 21 chapter 4 ...... 29 literature review ...... 29
adaptive façade - definitions ...... 30 adaptive façade through the ages ...... 31 adaptive façade – a new direction ...... 34 active materials – a brief overview ...... 36 chapter 5 ...... 41 case study ...... 41
architectural building skin, institute for computational design (icd) ...... 42 material selection ...... 43 experimentation ...... 44 limitations and conclusion ...... 46 vi chapter 6 ...... 48 exploring bamboo responsiveness ...... 48
workflow ...... 49 a climate-controlled environment ...... 51 veneer behavior study ...... 52 active layer ...... 52 passive layer ...... 54 binder layer ...... 57 generating modular patterns ...... 57 experiment 1(a) ...... 58 experiment 1(b) ...... 60 experiment 2 ...... 61 experiment 3 ...... 62 incorporating façade with climate ...... 64 experiment 4 ...... 65 experiment 5 ...... 68 full-scale prototyping ...... 71 chapter 7 ...... 74 computer analysis ...... 74
parametric modeling...... 75 generating design alternatives for a responsive system...... 76 wind simulation ...... 78 shadow analysis ...... 81 scale of application ...... 83 chapter 8 ...... 85 background ...... 85
architecture and climate ...... 86 understanding warm-humid climate ...... 88 façades in warm-humid climate ...... 89 chapter 9 ...... 92 geo-climatic context ...... 92
vietnam ...... 94 topography ...... 94 climate ...... 95 bamboo availability ...... 96 bamboo architecture in vietnam ...... 98 vii
bangladesh ...... 100 topography ...... 100 climate ...... 101 bamboo availability ...... 102 bamboo architecture in bangladesh ...... 103 florida, usa ...... 106 topography ...... 106 climate ...... 107 bamboo availability ...... 109 bamboo architecture in florida ...... 109 comparative analysis ...... 110 chapter 10 ...... 113 future research and conclusion ...... 113 appendix ...... 116
generating grasshopper modules ...... 116 creating triangular flaps ...... 118 glossary ...... 120 bibliography ...... 122 viii list of figures
Figure 1-1: Bedouin tents. Source: (Shutterstock) ...... 2
Figure 2-1: Global bamboo habitat. Source: (National Geographic, 1980) ...... 11
Figure 2-2: Comparison between Moso bamboo culm and southern pine. Source: (Rui Liu, 2015) ...... 13
Figure 2-3: Microscopic feature of Moso bamboo. Source: (Vos, 2010) ...... 16
Figure 2-4: Moso bamboo specimen along radial-tangential and radial- longitudinal direction. Source: (Huang et al. 2016) ...... 17
Figure 2-5: Hygroexpansion in bamboo along radial, longitudinal and tangential directions. Source: (Huang et al. 2018)...... 18
Figure 3-1: Forces affecting natural ventilation. Source: (Sharag-Eldin, 1998) ...... 22
Figure 3-2: Effects of position of openings in cross ventilation. Source: ( Koenigsberger, 1973) ...... 23
Figure 3-3: Effects of pressure build-up at inlet. Source: ( Koenigsberger, 1973) ...... 24
Figure 3-4: Traditional ventilator used in warm-humid climate. Source: ( Shutterstock) ...... 24
Figure 3-5: Inlet treatment for pressure build-up. Source: (Bainbridge and Haggard, 2011) ...... 25
Figure 3-6: Outlet treatment for increased wind speed. Source: (Bainbridge and Haggard, 2011) ...... 26
Figure 3-7: Effects of inlet- outlet size and position on wind pressure and wind velocity. Source: (Author, 2019) ...... 27
Figure 4-1: Construction of the US Pavilion, showing the installation of the acrylic panels. Source: (Buckminster Fuller Institute)...... 32
Figure 4-2: Institut du Monde Arabe, Jean Nouvel. Source: (Tim Winstanley, 2011) ...... 33
Figure 4-3: (Left): Bloom. Source: (Alison Furuto, 2012), (Right): HygroSkin Pavilion. Source: (ICD University of Stuttgart) ...... 35
Figure 4-4: (Top left): Thermobimetal. Source: (Doris Sung, 2012), (Top right): Shape memory alloy. Source: (Creative commons), (Bottom left): Shape ix memory polymer. Source: ( Università degli studi di Pavia), (Bottom right): Thermochrmoic paint. Source: (Berzina, 2008) ...... 37
Figure 4-5: Photochromic glass. Source: (Gear, 2018) ...... 39
Figure 5-1: By controlling fabrication parameters the specimen is made to react within a certain humidity range, with specimen 1 closing at high humidity and specimen 2 opening. Source: (Reichart et al. 2015) ...... 44
Figure 5-2: Localized response in wood due to local changes in humidity. Source: (Reichart et al. 2015) ...... 46
Figure 6-1: Illustration of the workflow ...... 50
Figure 6-2: Humidity chamber setup. Source: (Author 2018) ...... 51
Figure 6-3: Parameters for hygroscopic explorations of bamboo veneer. Source: (Author 2018) ...... 52
Figure 6-4: Rectangular bamboo veneers reacting to increasing humidity level. Source: (Author 2018) ...... 53
Figure 6-5: Bilayer bamboo composite. Source: (Author 2018) ...... 55
Figure 6-6: Bilayer bamboo composite testing with cellulose and polycarbonate film. Source: (Author 2018) ...... 56
Figure 6-7: Generating modular patterns. Source: (Author 2018) ...... 58
Figure 6-8: Bilayer bamboo composite testing. Source: (Author 2018) ...... 59
Figure 6-9: Bilayer bamboo composite bending in high humidity. Source: (Author 2018) ...... 59
Figure 6-10: Perforated bilayer bamboo composite testing. Source: (Author 2018) .. 60
Figure 6-11: Perforated tetrahedron module testing. Source: (Author 2018) ...... 62
Figure 6-12: Experiments with 3D modular patterns to generate maximum opening. Source: (Author 2018) ...... 63
Figure 6-13: Wind rose diagrams for Vietnam, Bangladesh and Florida, USA. Source: (Climate Consultant 2018) ...... 64
Figure 6-14: Façade pattern addressing wind direction. Source: (Climate Consultant 2018) ...... 66
Figure 6-15: Reactivity of composites with varying densities of perforation. Source: (Author 2018) ...... 67 x Figure 6-16: Relationship between deformation axis and base of the units. Source: (Author 2018) ...... 68
Figure 6-17: Bamboo veneers opening along up to an angle of 40 degrees. Source: (Author 2018) ...... 69
Figure 6-18: Stages of responsiveness. Source: (Author 2018) ...... 69
Figure 6-19: Veneer behavior at a micro scale. Source: (Author 2018) ...... 70
Figure 6-20: Fabricating an angled surface on the façade frame. Source: (Grasshopper Butterfly 2018) ...... 71
Figure 6-21: Angled surfaces on either side of the façade frame. Source: (Grasshopper Butterfly 2018) ...... 72
Figure 6-22: Full-scale prototype. Source: (Grasshopper Butterfly 2018) ...... 73
Figure 7-1: Control parameters for digital modeling. Source: (Author 2018) ...... 77
Figure 7-2: Inlet-outlet size affecting wind simulation studies. Source: (Author 2018) ...... 79
Figure 7-3: Wind simulation studies. Source: (Author 2018) ...... 80
Figure 7-4: Shadow analyses. Source: (Author 2018) ...... 82
Figure 7-5: Different scales of application. Source: ( Author 2018) ...... 84
Figure 8-1: Open façade system for warm-humid climate. Source: (Koenigsberger, 1973) ...... 90
Figure 9-1: Types of woody bamboo distribution, with their subfamilies, according to region. Source: (http://www.eeob.iastate.edu/bamboo/ maps.html) ...... 94
Figure 9-2: Bamboo forest areas in Vietnam for 2001. Source: (Vu and Le, 2005). .. 97
Figure 9-3: Bamboo architecture in Vietnam. Source: (ArchDaily, 2013)...... 99
Figure 9-4: Bamboo architecture in Bangladesh. Source: (ArchDaily, 2010)...... 105
Figure 9-5: Comparative analysis of climatic features. Source: (Climate consultant, 2019)...... 111
Figure A-1: Generating hexagonal parameters. Source: ( Grasshopper 2018) ...... 116
Figure A-2: Creating hexagonal modules. Source: ( Grasshopper 2018) ...... 117
Figure A-3: Scaling hexagonal modules. Source: ( Grasshopper 2018) ...... 117 xi Figure A-4: Creating triangles and NURBS curve. Source: ( Grasshopper 2018) ...... 118
Figure A-5: Creating triangular surfaces. Source: ( Grasshopper 2018) ...... 118 xii acknowledgements
I would like to thank my thesis adviser Marcus Shaffer for his continuous guidance and words of encouragement throughout the development of this research. It would not have been possible for me to produce this work without his support. I would also like to express my sincere gratitude to Benay Gursoy for her support and patience, and for making herself available whenever I needed any help. I would like to thank Ute
Poerschke for her valuable critiques, and for always encouraging me to take my research further through university scholarships and research exhibitions.
I am deeply indebted to the Department of Architecture and to Mehrdad Hadighi for helping me support my graduate education.
I would like to thank my colleagues and friends in the Stuckeman School for their love and support. Finally, thanks to my family for their constant encouragement without which I would not be where I am today.
ii
chapter 1
introduction
2 One of the earliest forms of adaptive envelopes that made use of embedded material properties to create a responsive architecture was the black Bedouin tent
(Figure 1-1). By employing passive strategies, the fabric of the tent absorbed moisture and ensured a continuous airflow, thereby reducing air temperature through evaporative cooling. Thermal comfort was achieved throughout the interior space while ensuring little to no energy waste.
Figure 1-1: Bedouin tents. Source: (Shutterstock)
When this concept of climatic adaption was taken on in the 1960‟s to create iconic architecture, such as the United States Pavilion in the Montreal Expo, it marked the beginning of a design strategy that allowed building systems to respond to the external environment with the help of a technologically-imposed “intelligence”. However, as much as these contemporary high-performance buildings offer improved internal comfort, this design approach often gets overshadowed by the associated dependency on external energy, higher cost, and complex construction and maintenance issues. In order for people to reduce the depletion of the planet‟s resources, it is time building systems are rethought for a more sustainable solution. Buildings are already consuming more than
40% of all energy that humans produce; if building materials could be made to passively 3 adapt themselves to the climate, there is a chance that our reliance on active, mechanized systems leading to energy waste could be reduced.
problem statement
In addressing climate responsiveness, many of the building envelope strategies currently being developed by architects incorporate automated high-tech systems with higher rates of energy-consumption; design solutions that target fast-growing urban centers.
Low-tech passive systems – with the potential to deliver more performance for less energy– are restricted to rural areas, primarily because of the lack of experienced technical know-how in these regions. As our reliance on non-renewable energy sources continues to rise, low-tech passive systems employed in envelope design require a more thorough investigation to adapt them for large-scale application in urban centers. This includes an in-depth focus on sustainable building materials that have the potential to generate a technologically independent, carbon-negative building façade. Extensive research has already begun exploring passive envelope systems using timber, even though bamboo, being a rapidly renewable, carbon sequestering plant, is the greenest material on the market. Furthermore, similarities in the material-embedded properties of timber and bamboo; particularly with respect to their hygroscopic (absorption and release of moisture) nature, create a potential for bamboo to be used to develop a more efficient building envelope system. In response to these issues, my research inquires how the hygroscopic property of bamboo can be utilized to design a low-tech adaptive building envelope for warm-humid regions. 4
gaps in knowledge
Even with all the carbon-negative features of bamboo, its application continues to be overshadowed by timber in mainstream construction. Lack of recognized sustainability standards and certifications, such as Forest Stewardship Council (FSC) certification, is preventing bamboo from competing in the global market (Buckingham,
2015). Even though Rainforest Alliance is pursuing the Alternative Natural Fibers
Standard for natural fibers, there is a long way to go before it can become a certification scheme, and even then there is no guarantee bamboo will enjoy worldwide recognition of its potentials (Buckingham, 2015). Absence of a comprehensive knowledge and experience of bamboo construction is preventing western researchers from exploring the potentials of bamboo as an active material for adaptive façades (Buckingham, 2015).
Besides, bamboo has always been left out while outlining official climate change frameworks, including the Marrakech Accords (MA), Clean Development Mechanism
(CDM), IPCC Assessment Reports etc. Being a grass and not a tree, while also being labeled as „poor man‟s timber‟ has played an important role in bamboo being overlooked within the climate change narrative (Lobokov et al., 2009). On the other hand, the designers and craftsmen who are in fact skilled in bamboo construction, being mostly native to Asia and South America, often do not have the resources necessary to pursue experiments on adaptive façade systems (Buckingham, 2015). Therefore, it is my belief that instead of looking at the hygroscopicity of bamboo as an inherent drawback and attempting to control or mitigate it, we can take this specific quality as a unique strength and devise new ways to integrate it within architecture itself. Although some experimental works on bamboo are being done in Scandinavian countries, particularly in 5 the Netherlands1, it is still practically an uncharted territory. As such, bamboo offers a greater scope of creating newer, experimental façade systems, with bamboo finally at the helm of things.
research aims
Through my research I aim to investigate the property of responsiveness embedded in bamboo. Using bamboo veneer as an atmospherically active material, the research focuses on developing a low-tech façade system that is able to adapt to varying levels of atmospheric humidity levels as a bio-mechanical response. In doing so,
I hope to utilize the dimensional changes in the material, and a systemic array of dynamic parts, to perform particular functions including ventilation and/or shading, leading to a truly material-integrated architecture.
methodology
The research consists of a three-phase process, including: a case study research with an exploratory purpose; formal analyses of bamboo‟s material properties; a computational model and a full-scale façade prototype for field-test.
Phase 1: The case study research looks into the architectural building skin developed by Architects Achim Menges, Steffen Reichart and David Correa in Germany; research that served as a basis for the “HygroSkin Pavilion”, a temporary building
1 Initiatives of BAMBÚ SOCIAL, a Netherlands-based non-profit organization, include sharing knowledge and expertise of bamboo construction through workshops and building projects (http://www.bambusocial.com). Additionally, TUDelft is actively engaged in exploring future possibilities of adaptive facades through research and experimentations under its Façade Research Group, presented through the Journal of Façade Design and Engineering (JFDE) (https://www.tudelft.nl). 6 system that utilizes the hygroscopic property of wood veneer to design an adaptive building façade. The strategies undertaken by the team is analyzed in terms of the nature of wood samples tested, the kind of non-hygroscopic passive layer selected for the project, and the resultant reactive properties exhibited by the wood composite.
Considering certain similarities and dissimilarities between the micro-structure of wood and bamboo, as mentioned above, the case study analysis informs my research decisions regarding the hygroscopic changes that can typically be expected when a fibrous veneer is laminated with a synthetic or a natural polymer.
Phase 2: The formal analyses consists of an in-depth material study of bamboo through constructing a controlled humid environment where bamboo veneer samples of different shapes, sizes and grain directions are studied with respect to their “action”, i.e. the degree of deformation, the time taken to deform, and the time taken for them return to their initial position. Differences in hygroscopic reactions are also analyzed through comparisons between the effects of the natural and synthetic polymer backing material as the non-reactive passive layer. Several modular configurations are analyzed with a goal to create a composite sample that is most reactive as humidity levels are increased and decreased, in order for it to act as ventilation and shading device. The façade is also assessed in terms of its aesthetic quality, since different biomechanical deformation patterns can give rise to different visual aesthetics over time.
Phase 3: The final phase consists of a computational analysis that is used to obtain performance data of the facade through wind simulation and shadow analysis in the Rhino Grasshopper software. This is demonstrated through a computational model of the facade, where entrance and exit paths of airflow are determined in order to estimate how much the façade pattern is enhancing or negating airflow through a space.
This simulation has the potential to predict the performance of the façade structure in 7 relation to the long-term annual hygroscopic performance of bamboo composites. This performance analysis would not be possible through a physical experiment at this point in my research.
thesis structure
The following paragraphs briefly explain the overall structure of the thesis.
The second chapter makes the case for bamboo as an active material whose hygroscopic responsiveness can be utilized to carry the domain of adaptive envelopes forward. The chapter delineates the geographical distribution of bamboo and presents a summary of its morphological features. It expounds on the nature of hygroexpansion as perceived in bamboo by looking into its chemical composition and anatomical makeup.
The chapter concludes by presenting the results of an experimental research that investigates the hygroscopic performance in bamboo along radial, longitudinal and tangential grain directions, as moisture in the air gradually is increased.
The third chapter discusses the significance of ventilation in thermal cooling of human bodies and built forms. Through passive cooling literatures and computer simulations performed by the author, this chapter touches upon the different ways ventilation in buildings can be manipulated to intensify indoor airflow and increase comfort.
The fourth chapter describes adaptive façade technologies that have slowly gained momentum since 1987. The chapter begins by outlining different ways in which researchers and architects have attempted to define adaptive envelopes and goes on to offer a historical summery of technologically intensive adaptive facades with associated limitations. This is followed by a discussion on how the domain of adaptive façade 8 design has had a paradigm shift in the wake multiple technical malfunctions, soaring costs, and intense maintenance - as researchers began to look for passive ways to approach climate adaption in architecture. The chapter then presents contemporary explorations in the field of passive adaptive systems, including manipulating material embedded responsiveness. This leads to a characterization and discussion of different types of natural and synthetic materials that are able to actively adapt to different changes in the environment including, temperature, light and humidity.
The fifth chapter explores the material experiments with wood veneer undertaken by Reichart, Menges and Correa; work that conceptualized their prototype HygroSkin
Pavilion as a case study and investigates the methodology adopted, the materials used, the testing parameters, and limitations encountered in the process. Because of similarities between wood and bamboo many of the results achieved in the fabrication of the HygroSkin Pavilion could be utilized to predict the performance behavior of bamboo in this thesis. Consequently the case study helped inform the research by providing the thesis with valuable insight into the nature of natural cellulose materials and the influence of humidity on them.
The sixth chapter presents a detailed description of the experiments that were performed. The chapter begins with illustrating the general workflow adopted for this stage beginning with the process of building a climate controlled chamber within which humidity testing could be carried out. It goes on to detail the different hygroscopic experiments performed on bamboo veneer samples, which led to veneer composites, and ultimately to modular patterns using the composites that could potentially act as responsive façade panels. The chapter ends by explaining how local wind parameters for three warm-humid regions were incorporated into the responsive mechanisms of the 9 modules so that they could potentially function effectively in all the three locations being studied; Vietnam, Bangladesh and Florida.
The seventh chapter describes the computational analyses that were conducted to analyze the ventilation performance of the facade. It explains the Rhino Grasshopper components that were used to generate the digital model, in addition to the Butterfly plugin for wind simulation. The digital model is then used to observe indoor airflow through the façade. Additionally, a basic shadow analysis is done using the digital model to understand changes in shadow pattern provided by the façade system throughout the day.
The eighth chapter presents a review of five climatic regions based on Koppen classification, and how human settlements have adopted to them over the years.
Following this, an overview of the nature of warm-humid climatic regions is presented, along with architectural strategies of building façades that have been developed and applied over the years to create comfortable living condition.
The ninth chapter offers a contextual analysis of the three geographic locations selected for this thesis work, including: Vietnam, Bangladesh and Florida, USA. The analysis consists of the climatic, social and economic backgrounds of the three regions while trying to articulate the various strengths and limitations with regards to bamboo architecture. The chapter concludes by presenting a comparative analysis among the three locations with regards to their climatic features, and technological and material resource availability.
10
chapter 2
the case for bamboo 11
the plant
A rapidly renewable plant, bamboo is a more sustainable alternative to wood.
With some species shooting up to approximately 0.6 m (2 feet) per day, it is the fastest growing plant found in nature. A member of the grass family Poaceae, and subfamily
Bambusoideae, bamboo can survive extreme temperature of -20°C (-4°F) and intense precipitation from 812 to 1270 mm (32 to 50 inches) (Goyal, 2012). Within 2-4 months bamboo can reach approximately 15 m (50 feet) height. The stem is hollow, except at nodes, and can range in heights from 100 – 150 mm (4-6 inches) to about 40 m (130 feet). Most bamboo species become mature within 2 to 3 years.
Figure 2-1: Global bamboo habitat. Source: (National Geographic, 1980)
The Forest Stewardship Council (FSC) certifies bamboo as NTFP (Non-timber forest product), while Clean Development Mechanism (CDM) considers bamboo as a tree (Buckingham, 2009). The International Network for Bamboo and Rattan (INBAR) recognizes bamboo as NTFP and believes it is of utmost importance in our fight against climate change (Nedkarni and Kuehl, 2013). Bamboo is native to Asia, Latin America and parts of Africa (Figure 2-1). According to a study titled “Global Forest Resources 12 Assessment 2005”, undertaken by FAO and INBAR, global bamboo resources were found to constitute over 36 million hectares, of which Asia was found to maintain 24 million hectares, Latin America had 10 million hectares and Africa had 2.7 million hectares of bamboo resources (Lobovikov et al., 2007). India and China are the Asian countries with the richest resources of bamboo, followed by Indonesia and Laos. Brazil and Chile have the highest amount of bamboo resources in Latin America. African countries of Nigeria and Ethiopia have abundant bamboo resources as well (Lobovikov et al., 2007).
Colombian architect and bamboo enthusiast Simon Velez explains, “When we cut a bamboo, we are cutting a blade of grass that grows very fast. When we cut a tree you have to wait many years until the new tree is able to be harvested.” He goes on to say, “The relationship [of bamboo] to weight and resistance is the best in the world.
Anything built with steel I can do in bamboo faster and just as cheaply” (Velez, 2014).
Termed as “vegetable steel” bamboo is lighter than steel and five times stronger than concrete. The hollow cylindrical part of bamboo is called culm, which is divided into nodes and internodes. The direction along the vertical height of the culm is the longitudinal direction; the one that follows from the center of the cylindrical stem to the outer surface is the radial direction, and that along the perimeter of the stem is tangential.
Bamboos can be categorized into monopodial or single-stemmed erect, as seen in Melocanna and Phyllostachys, sympodial, as seen in Dendrocalamus, Bambusa etc., and climbing, as seen in Dinochloa (Lessard, G. and Chouinard, A, 1980). Monopodials are common to sub-tropical and temperate regions while sympodials grow in tropical regions (Lessard and Chouinard, 1980). Monopodials are termed as runners, since they spread aggressively through a network of long underground rhizomes that send up 13 shoots several feet away from the parent bamboo and are difficult to contain, while sympodials grow in a compact clump with short rhizomes that produce closely-spaced shoots and spread only a few inches wide each year. Runners are, therefore, perceived to have a bad reputation for their invasiveness.
The two most common species of bamboo used for structural purposes in the west are Chinese Moso bamboo and South American Guadua bamboo (Liu, 2015).
However, in the US and European countries application of bamboo has mostly been restricted to a superficial ornamental level with flooring and furniture, even though the rapid reproductive capacity of bamboo makes it the most suitable for sustainable building construction. In fact, while most wood forests take 20 to 50 years to be harvested, bamboo forests take a mere 4 to 5 years (Lobovikov, 2003). Comparing tension, compression, bending and shear tolerated by a Moso bamboo culm to that of a southern pine dimension lumber common to US it is seen that bamboo possesses strength several times that of wood and is far more elastic (Liu, 2015) (Figure 2-2).
Figure 2-2: Comparison between Moso bamboo culm and southern pine. Source: (Rui Liu, 2015)
The hollow tubular structure of bamboo that has naturally evolved over centuries to resist wind loads contributes to such enhanced tensile strength, which is why bamboo is now being researched and developed as reinforcement in place of steel (Walker, 14 2014). However, with an increase of moisture content the strength and elasticity of bamboo decreases (Liu, 2015).
Owing to its proliferation through a network of underground rhizomes, bamboo helps in reducing soil erosion. Its never-ending sustainable qualities include carbon-di- oxide sequestering, reducing atmospheric temperature, low embodied energy, low use of nutrients, resistance to earthquake, extremely high tensile strength, light-weight construction and low-cost (Vos, 2010). In fact being a rapidly growing plant it absorbs large quantities of CO2, meaning bamboo cultivation has the potential to reduce the rate of climate change (Walker, 2014).
The major drawbacks of using bamboo are perceived to be its high cellular starch content, leading to fungal attacks, and vulnerability to moisture, leading to dimensional changes. Starch content in bamboo is mostly found in parenchyma cells, and can vary in amount depending upon the season, the culm‟s age and location on the culm wall (Vos,
2010). A study by Sulthoni (1987) on starch content in bamboo species of Java revealed an increase of starch in Bambusa vulgaris from 0.24% in the rainy season of January to
7.97% in the dry season of November. Starch content was also found to increase as bamboo matures. Additionally, the bottom part of bamboo culm was observed to have the least amount of starch compared to the middle and top parts, while the outer part of the culm wall has less starch than the inner part. Traditionally, newly harvested bamboo is soaked in running water to dissolve the starch. Boiling the bamboo is another effective method to reduce starch content. On the other hand, moisture content in bamboo is calculated to be the weight of its water content in relation to its weight in dry state, expressed as a percentage (Gernot, 2016). Immature bamboo can have moisture content as high as 70%, which decreases to roughly 20% in its mature stage, contracting and hardening the bamboo (Gernot, 2016). Humidity issues with structural bamboo are 15 easily avoided now-a-days by using laminated bamboo lumber or ply-bamboo. Through lamination bamboo plywood becomes hydrophobic and dimensionally stable (Vos,
2010).
understanding hygroexpansion in bamboo
It is said that one of the most significant differences between synthetic fiber and natural fiber is their reaction to humidity. While the former is typically hydrophobic, the latter shows a distinct hydrophilic behavior (Célino et al., 2013). To utilize the moisture reactivity inherent in bamboo in architecture it is essential to understand its hygroscopic nature.
R. B. Hoadly (2000) defines hygroscopicity as the ability, usually found in porous materials, to exchange humidity with the surrounding environment through absorption and desorption. The term is explained further by Dinwoodie (2000) as the ability of a material that allows it to maintain a condition of relative equilibrium with its environment by constantly absorbing and releasing moisture from the atmosphere. This kind of moisture reactivity is seen in trumpet gentian flowers, a nocturnal variety, which open and close through differences in turgor pressure (Doorn, Meeteren, 2003). Being a metabolic process, it requires chemical energy to be transformed into mechanical energy within living cells of the flower for such nocturnal opening to occur. However, hygroexpansion in bamboo is an embedded quality of the material, independent from its biological systems. And therefore, it eliminates the need for any additional energy or actuation processes to bring about dimensional changes in bamboo.
The structural nature of bamboo, with its remarkable tensile strength, reveals that the strength and stiffness that it tends to achieve along its grain following the longitudinal 16 direction is far greater than that in the transverse direction. Similar to wood, the major chemical constituents of bamboo are cellulose, hemicellulose and lignin. The cellulose micro-fibrils are present in an amorphous matrix of lignin and hemicellulose (Tomalang et al. 1980). Any such fibrous material absorbs moisture in two forms: bound water and free water. The absorption or release of free water, occurring inside cell cavities, has negligible impact on bamboo, however significant swelling and shrinkage occurs with changes in bound water content, occurring inside cell walls. As bound water is absorbed the cellulose micro-fibrils expands transversely along with the lignin matrix, leading to swelling of bamboo. Conversely, as bound water is removed, shrinkage of bamboo is observed. (Dinwoodie, 2000)
The microscopic features of Chinese Moso bamboo reveal a finer grain due to smaller vascular bundles, majority of which is concentrated toward the outer edge of the culm. This results in the outer surface being more striped than the inner one. (Vos, 2010)
(Figure 2-3)
Figure 2-3: Microscopic feature of Moso bamboo. Source: (Vos, 2010) 17
Anatomically, a transverse section of bamboo is seen to be made up of vascular bundle tissue surrounded by lignified parenchyma tissue. Two large vessels in each of the vascular bundles, moving vertically along the longitudinal direction, are responsible for water movement within bamboo. At the nodes, however, the vascular bundles are seen to bend toward the tangential direction. Toward the outer surface of the bamboo culm the vascular bundles, acting as continuous vertical cavities, gradually increases while the amount of parenchyma ground tissue decreases (Grosser and Liese, 1971).
Hence, density of bamboo is typically higher toward the outer surface than the inner surface, and so it is more difficult for water vapor to diffuse through the external surface than the internal surface. (Huang et al., 2017)
Figure 2-4: Moso bamboo specimen along radial-tangential and radial-longitudinal direction. Source: (Huang et al. 2016)
Huang et al (2016) analyzed the hygroexpansion in Moso bamboo along longitudinal, radial and tangential directions by taking specimens from the external, middle and internal surface of the culm (Figure 2-4). He concluded that along the radial direction the fluctuation of hygroexpansion was the maximum, with the external surface having the highest value of expansion and the internal surface having the lowest (Figure 18 2-5). According to Tu and Xu (2008), the high hygroexpansion in the external surface can be credited to the increased presence of vascular bundle tissue and vessels.
Figure 2-5: Hygroexpansion in bamboo along radial, longitudinal and tangential directions. Source: (Huang et al. 2018).
Additionally, comparing the data obtained from analyzing thermal expansion under temperature variations with hygroexpansion under moisture variations Huang et al. (2016) concluded that Moso bamboo shows a much higher swelling and shrinkage when exposed to humidity variations than to temperature variations. ii
chapter 3
natural ventilation for passive cooling bamboo house, kengo kuma 20
Straaten (1967) identifies two fundamental requirements of natural ventilation, thermal comfort and health. Thermal comfort pertains to both the effect of air movement in creating a comfort condition for the human body where it is cooled down by releasing heat and moisture to the environment, and in the release of heat by the building through structural cooling.
ventilation and thermal comfort
Heat exchange between a human body and its surroundings takes place through metabolism (M), convection (C), radiation (R) and evaporation (E). Thermal balance in a human body is maintained if:
M – E ± C ± R = 0
To ensure a thermal equilibrium exists between a human body and the environment, all of the four climatic factors - including air temperature, humidity, radiation and air movement - must be considered simultaneously, because each of these effects the heat exchange processes in one way or another. In fact, heat loss through convection and evaporation is fundamentally influenced by ventilation.
Straaten (1967) claims that in a temperate climate when the indoor air temperature is 18°C (64°F) with an air velocity of 0.25 m/s and humidity between 40-
60% human bodies can very easily dissipate excess heat through convection, radiation and evaporation. As the air temperature increases and reaches the skin temperature of
31-34°C (87-93°F), convective and radiation heat loss will decrease. After one point only evaporative heat loss will continue to provide thermal balance to some extent. As sweat from the body evaporates it releases the latent heat of evaporation from the skin, 21 thereby cooling down the body. According to Givoni (1976), evaporation of one gram of water is accompanied by nearly 0.58 Kcal of heat loss. But in order for that to happen, air needs to be adequately dry to allow a continuous evaporation rate. When the air becomes humid evaporative cooling can still be maintained if a constant air movement is allowed to take place. The humid air will absorb some moisture from the skin and be replaced with new air, thereby continuing the evaporation process (Koenigsberger,
1973).
ventilation and the built form
The heat exchange processes in buildings include conduction (Qc) through walls, solar heat gain (Qs) through windows, ventilation (Qv), internal heat gain (Qi) through human bodies and domestic appliances, mechanical controls (Qm) through external energy sources, and evaporation (Qe) through a water source, if present (Koenigsberger,
1973). Building thermal balance will be maintained if:
±Qc + Qs ± Qv + Qi ± Qm - Qe = 0
Natural ventilation within a building can be either thermally induced or wind induced (Figure 3-1). Thermally induced ventilation requires inlet and outlet openings to be located at different heights which, coupled with a difference in temperature, creates a pressure gradient that pulls in outside air through the lower inlets and forces used air to exit through the higher outlets. However, this kind of ventilation creates very little air speeds. Wind-induced airflow, on the other hand, is a function of the wind pressure difference between the fenestration surfaces of a building. The pressure gradient in this case is influenced by the prevailing wind flow (Givoni, 1976). This kind of ventilation creates the most cooling effect in warm-humid climates. 22
Figure 3-1: Forces affecting natural ventilation. Source: (Sharag-Eldin, 1998)
The wind pressure created is proportional to the velocity of air, and can be expressed as:
P = ½ ρ v2
Where, P = air pressure (N/m2)
ρ = density of air (kg/m3) = 1.2 kg/m3
v = wind velocity (m/s)
For pressure difference created by wind forces, typically the size, position and orientation of air inlets and outlets play important roles in generating air flow though the building. Koenigsberger (1973) identifies the following six factors effecting indoor airflow,
1. Orientation
2. External features
3. Cross-ventilation
4. Position of openings
5. Size of openings
6. Control of openings
An inlet surface that is oriented perpendicular to the prevailing wind direction creates the maximum pressure on the windward side of a building, thereby generating the maximum wind velocity. If, however, wind direction is at a certain angle to the 23 building elevation, providing a wing-wall facing the prevailing wind can help increase the positive pressure by creating a funneling effect. As mentioned earlier, cross ventilation is created when there is a pressure difference between inlet and outlet surface. For effective cross-ventilation the depth of the room cannot be more than five times its height. Additionally the position and height of openings also create a pressure difference which in turn governs the direction of the incoming air flow (Figure 3-2). Fenestrations having a small inlet and a larger outlet opening help generate a higher wind velocity.
Koenigsberger (1973) accredits this phenomenon to two conditions. One is the increased force acting on a much smaller inlet surface pushing air through at a high pressure, and the other is due to the „venturi effect‟ where the sideways expansion of air entering through a small opening and its subsequent funneling through to the larger outlet increases its acceleration.
Figure 3-2: Effects of position of openings in cross ventilation. Source: ( Koenigsberger, 1973)
Additionally, inlet openings should be positioned in a way that it directs airflow through the „living zone‟. Inlets located at a higher elevation have a larger solid surface on the windward side which creates a pressure build-up below the opening, forcing air upward toward the ceiling and away from the living zone (Figure 3-3). This can be 24 avoided in section by introducing a parapet wall. In plan, a similar treatment with open casement window or wing walls can produce similar results.
Figure 3-3: Effects of pressure build-up at inlet. Source: ( Koenigsberger, 1973)
For passive cooling through natural ventilation in warm-humid climate
Koenigsberger (1973) proposes the use of „permanent ventilators‟ in the form of grilles of
„air bricks‟ incorporated within the façade surface (Figure 3-4).
Figure 3-4: Traditional ventilator used in warm-humid climate. Source: ( Shutterstock) 25
Bainbridge and Haggard (2011) illustrate several conditions of opening size and position of inlet and outlet influencing interior and exterior air speed that echo
Koenigsberger (1973) (Figure 3-5). They also propose the use of a wing wall as a barrier to channel air into a desirable location in the interior. Having a gap between the same barrier and the wall surface will, however, lessen its effectiveness.
Figure 3-5: Inlet treatment for pressure build-up. Source: (Bainbridge and Haggard, 2011)
Wind speed is largely dependent on outlet size in relation to inlet size. By showing interior air speed as a percentage of exterior air speed Bainbridge and Haggard
(2011) demonstrated that as the outlet size is doubled indoor air velocity becomes twice as high (Figure 3-6) as it enters a space. Additionally, positioning outlet at a higher level decreases the speed of air flow from 86% to 74% as it changes its direction of flow to spread over a wider area within the interior.
26
Figure 3-6: Outlet treatment for increased wind speed. Source: (Bainbridge and Haggard, 2011)
Similar airflow studies were conducted in Rhinoceros with the Grasshopper plugin to understand changes in the interior wind pressure and wind velocity (Figure 3-
7). Row (a) in the following image shows a room with a single inlet and outlet of the same size and height. Color of the arrows represent wind velocity with red being the maximum and blue being the minimum. Similarly, wind pressure in the room is represented by horizontal and vertical planar surfaces with changing color from red to blue indicating regions of high pressure and low pressure respectively. When inlet size is decreased, as shown in row (b), air velocity increases as expressed by red arrows, and low pressure zone is created on either side of the airflow.
27
Figure 3-7: Effects of inlet- outlet size and position on wind pressure and wind velocity. Source: (Author, 2019) 28 In row (c) inlet size is decreased and placed at a lower height than the outlet, creating a Venturi effect where air is being „funneled‟ through the small opening onto a bigger area which increases its velocity. The following row shows the opposite situation with a bigger inlet and a smaller outlet. An extremely high pressure zone is created with very little wind velocity. The following two rows illustrate multiple inlet and outlet openings, with the first row having inlets equal in size to outlets and the second having inlets smaller than outlets. The second one generates a higher wind velocity with similar wind pressure zone.
chapter 4
literature review http://expo67.ncf.ca/expo_67_usa_great_nightview.html
30
adaptive façade - definitions
Loonen et al. define climate-adaptive buildings as being characterized by their ability to repeatedly and reversibly change their features and configurations with changing climatic parameters, with a view to achieving an improved building performance (Loonen, 2013).
According to Kirkegaard, adaptive buildings can “adapt their performance, in real time, to environmental changes and use less energy, offer more occupant comfort, and feature better overall space efficiency than static buildings do” (Kirkegaard, 2011)
Knaack uses the term „adaptive‟ and „intelligent‟ interchangeably and maintains,
“Buildings able to adapt to changing climatic conditions are called intelligent buildings.
Since the term intelligent can be misleading when used in the context of buildings or façades, we will use the term adaptive façade instead. Adaptation generally means that buildings and façades adapt to current weather conditions.‟ (Knaack et al., 2007)
Hasselaar, however, differentiates between the two terms by stating, “Adaptive means the ability to adjust and adapt to changing circumstances by itself” while intelligent means “the ability to vary its state or action in response to varying situations and past experience. This implies the presence of a computer or a central control center, since past experiences are used to determine the action to be undertaken next.”
(Hasselaar, 2006)
“Responsive” is another term frequently used in relation to adaptability. It refers to a reactive system that establishes an interaction between the building, the inhabitants and the environment to generate adaptability. Nicholas Negroponte defines responsive
31 system as one where the environment takes an active role and, through computation, initiates physical changes in the architecture (Negroponte, 1975).
However, responsive architecture need not incorporate computation in order to generate its response. Extensive researche is being done to implement and manipulate biological systems found in nature as a way to replace technology involved in computation. Biomimetic designs tend to mimic “the functional basis of biological forms, processes and systems to produce sustainable solutions” (Pawlyn, 2011). Therefore, adaptive façade strategies can, typically, be seen to follow two approaches. One, where the entire system of climatic response is mechanized with automated devices and a host of complex electronic sensors and motors, and the other, where façade responsiveness relies upon material behavior and properties with varying climatic conditions of temperature, humidity, light, radiation etc., without the need for any intricate mechanical system. The former is identified as being an active system with extrinsic control while the latter is a passive system having intrinsic control (Loonen, 2013).
adaptive façade through the ages
The discourse on active adaptive façade goes back in architecture history when, in 1967, Buckminster Fuller built the stunning geodesic dome for the United States
Pavilion in the Montreal Expo (Stanton, 1997). The original façade for the dome consisted of transparent acrylic sheets (Figure 4-1) that, through integrated computer- controlled shading system, were able to retract themselves with changing levels of solar radiation (Stanton, 1997).
32
Figure 4-1: Construction of the US Pavilion, showing the installation of the acrylic panels. Source: (Buckminster Fuller Institute).
Although the façade was never reinstalled after the dome burned down in 1976, the concept of climate-adaptive building envelope continued to gather momentum, especially with Jean Nouvel‟s 1980‟s creation, Institut du Monde Arabe in France (Figure
4-2). The building that was intended to serve as a testament to the growing relationship between the Arab culture and France ended up being one the most innovative technological marvels of its time. Taking the traditional Arabic mashrabiya2 as an inspiration for the façade pattern, the institute incorporates hundreds of light sensitive apertures which open and close with changing sunlight levels in the environment and corresponding user needs (Millard, 2015). Even though the system stopped working
2 John Feeney in his article The Magic of Mashrabiyas describes mashrabiya as a wooden open latticed balcony that provides a constant current of air and served, at one and the same time, as window, curtain, air conditioner and refrigerator (Feeney, 1974).
33 after a few years, as the Institut struggled to provide the maintenance required for the apertures to function, the design continues to be visually striking and widely popular
(Millard, 2015).
Figure 4-2: Institut du Monde Arabe, Jean Nouvel. Source: (Tim Winstanley, 2011)
Other examples of active adaptive facade system include Medina Umbrellas by
Bodo Rasch in Medina that deploys itself to shade the public during morning prayers, Al-
Bahr Tower in Abu Dhabi that reacts to increase in sunlight and unfolds itself to shade the tower, Yeosu Expo 2012 in Korea etc. The challenges that typically plague such active facades are mechanical failures coupled with excessive cost of construction. Even before it was engulfed by fire, Buckminster Fuller‟s dome suffered its fair share of technical difficulties. Speaking about its failures, Brand (1995) bluntly revealed, “Domes leaked, always.” Fuller, on the contrary, defended the excess maintenance required in his design by likening it to modernism‟s controversial legacy of „machines for living in‟: “If you build it like a machine, you must maintain it like a machine, not like a building.''
(Baldwin, 1997)
34
adaptive façade – a new direction
Holstov, Farmer and Bridgens (2017) argue in favor of combining the benefits of high-tech intelligent building systems with low-tech passive systems to develop an adaptive system that responds to changing climatic stimuli through smart materials with embedded responsiveness. They suggest an investigation into biological systems with embedded response mechanism found in nature as a basis for such hybrid design systems.
While arguing for a low-tech, passive system of adaptive façade Menges and
Reichart suggests that materials with an innate responsiveness can be exploited to investigate „passive‟ responsive architecture (Menges, Reichart, 2012), shifting the focus away from tech-heavy building systems. They explain that adaptive bioclimatic architecture can find inspiration in natural organisms that, through inherent material properties, are able to create a passive dynamic response. The authors echo Holstov,
Farmer and Bridgens, in arguing against technologically-intensive architectures as they rarely go beyond landmark buildings due to associated cost and complexities involved.
According to Berge, after studying residents of low-energy homes equipped with automatic temperature controls in Sweden there was found to be an overwhelming positive response from the people. However, after a thorough investigation it was seen by Berge that almost none of them knew how to operate it nor had used it. This shows a remarkable lack of interest in learning technological systems by the common users which Berge views as “techno-stress” and insists that such “Smart Homes” turn architecture into incubators instead of forms of self-expression (Berge, 2011). On a similar vein, Richard Neutra advocates for architecture to create a range of sensory challenges that, he believes, is necessary to experience architecture.
35 The passive system, as Loonen defines it, of adaptive architecture has two acclaimed pilot projects so far: Doris Sung‟s research pavilion in Los Angeles called
Bloom and Achim Menges‟s HygroSkin Pavilion in Germany (Figure 4-3). Bloom and
Hygroskin are both passive systems because they take advantage of a material‟s inherent climate reactive properties, such as temperature reactive thermo-bimetal (Sung,
2010) and humidity reactive wood respectively (Reichert, Menges, Correa, 2015).
Figure 4-3: (Left): Bloom. Source: (Alison Furuto, 2012), (Right): HygroSkin Pavilion. Source: (ICD University of Stuttgart)
Calling the building envelope a third “skin”, Sung believes that this kind of passive responsive architecture has the potential to bring human closer to nature by incorporating an elevated sensitivity in its surface. Reichart, Menges and Correa (2014) agree with this idea of “material as a machine” and explain that material embedded actuation can eliminate any instance of technical malfunction by incorporating the atmosphere for control and actuation. While advocating for an increased interaction with environmental dynamics, they suggest materials be physically programmed rather than be superimposed with technical devices. This, as they believe, will “enable a shift from a mechanical towards a biological paradigm of climate-responsiveness in architecture”.
(Reichart, Menges, 2012)
36 In fact, there are a number of smart materials that display either property changing character or energy exchanging character (Addington and Schodek, 2004).
Property changing materials include different kinds of chromics or color-changing and dimension-changing smart materials under different climatic conditions, while energy- exchanging smart materials include piezoelectric materials, photovoltaics, fluorescent and phosphorescent materials and so on (Addington and Schodek, 2004).
active materials – a brief overview
In high-tech mechanical adaptive systems sensors and actuators perform their own set of functions; the sensor detects and analyzes the changes in an external stimulus while the actuator, getting the information from the sensor, acts out the response through the structure (Fiorito et al, 2016). However, there are certain materials that combine the performance of sensors and actuators while responding to external stimuli when they undergo changes in one of their properties. These are called smart materials or active materials.
Lopez et al., in their research on active materials, outlined three distinct climatic factors that trigger a range of property changes within different reactive materials, namely temperature, light and humidity (Lopez et al., 2015).
Temperature:
Thermo-Bimetals are temperature reactive sheet metals that consist of two metals of different thermal expansion coefficients bonded together. At higher temperature the metals expand at different rates causing the surface to deform, creating a dynamic façade (Sung, 2011) (Figure 4-4, Top left). The curvature of deformation, being directly proportional to temperature change, is predictable and repeatable (Sung,
37 2011). This is the principle adapted by Doris Sung in the design of her pavilion “Bloom”.
By curving upward the bimetallic strips allow ventilation inside the pavilion when outside temperature is high and returns to its initial position as temperature cools down. These materials have long been used in household thermostats, clocks and thermometers but their recent adoption in architecture is creating exciting possibilities for breathable facades.
Figure 4-4: (Top left): Thermobimetal. Source: (Doris Sung, 2012), (Top right): Shape memory alloy. Source: (Creative commons), (Bottom left): Shape memory polymer. Source: ( Università degli studi di Pavia), (Bottom right): Thermochrmoic paint. Source: (Berzina, 2008)
Shape-memory alloys (SMA) are temperature reactive metals that, when heated, are able to „remember‟, and go back to, their original shape after being deformed
(Peters, 2011) (Figure 4-4, Top right). Nickel-titanium alloys are most commonly used as
SMA but there are several other materials as well, including copper-zinc-aluminum,
38 copper-aluminum-nickel, gold-cadmium etc. SMAs are classified into two categories based on the number of shapes they can „remember‟: one-way memory and two-way memory. Alloys which, when forced to deform, can go back to their original shape when heated and remain like that when cooled are said to have one-way memory, whereas those that „remember‟ two shapes, one when heated and another when cooled, are said to have two-way memory. These are already being used in space engineering, biomedical industries and load-bearing architecture (Peters, 2011).
Shape-memory polymers (SMP) are polymers with similar properties as SMA, where they can return to their initial permanent shape from a temporary deformed one under higher temperature (Addington and Schodek, 2004) (Figure 4-4, Bottom left). One of the applications of shape memory polymeric strands is in surgical operations to tie blood vessels, where the strands with a specific shape are looped around a blood vessel and as the body heat triggers it to revert back to its original shape it ties itself into a knot
(Addington and Schodek, 2004). SMPs can also be stimulated by electric or magnetic field to „remember‟ their initial shape.
Thermochromic materials are widely used smart material that change color when exposed to changes in temperature. At higher temperature these materials absorb heat and induce a chemical reaction resulting in a visible change of color (Figure 4-4, Bottom right). Widely used as „band thermometer‟, thermochromic materials are able to detect as small a temperature change as 17°C (0.2° F) (Addington and Schodek, 2004).
Light:
Photochromic materials are light sensitive materials that undergo reversible changes in color under varying intensity levels of light. In an un-activated state photochromic molecules are colorless. When exposed to ultraviolet light the molecules get excited and begin to reflect photons at certain wavelengths. In the absence of light
39 the material goes back to its initial colorless state (Addington and Schodek, 2004).
Photochromic materials are used in sunglasses as well as in various window and façade treatments (Figure 4-5).
Figure 4-5: Photochromic glass. Source: (Gear, 2018)
Similarly, photopolymers are polymers that can sense a change in the surrounding lighting condition and undergo a shape change as a response (Lopez et al, 2015).
Humidity:
Implication of moisture-reactivity in nature is observed in the cracking of dried mud, swelling and shrinkage of wood, wrinkling of wet paper and wet skin, curling of dry leaves and so on (Reyssat, Mahadevan, 2009).
One of the humidity-reactive smart materials is Hydrogel. It is a polymer that is capable of storing water several times its own weight. As it does so, the acid in the polymer ionize, creative negative charges which repel each other, forcing the material to swell up and undergo a dimensional change (Lopez et al., 2015).
Wood is another humidity-reactive material that displays constantly fluctuating moisture content (MC) levels by adjusting its bound water content in order to respond to changes in relative humidity of the surrounding air. The fiber saturation point (FSP) of
40 wood is at around 27-30% which means that at this point wood has absorbed its maximum capacity of bound water (Simpson, TenWolde, 1999). As the MC in its cell walls decreases below FSP, wood starts to dry out and undergo shrinkage, whereas it swells up as MC rises toward FSP. Beyond FSP any additional water is retained as free- water that has little to no influence on wood‟s dimensional changes (Simpson,
TenWolde, 1999).
Bamboo, like any other natural fibrous material, also has hygroscopic properties and constantly tries to achieve an equilibrium moisture content level (Jiang et al., 2012).
While bamboo and wood have nearly similar reactions regarding their mechanical properties under varying moisture content levels differences in their chemical compositions lead to different specific relationships. The FSP of a young Moso bamboo is at around 28% while that of a mature one is at 23% (Jiang et al., 2012). However, bamboo becomes more sensitive to mold and fungal attack with increasing hygrothermal environment (Huang et al., 2017).
chapter 5
case study achimmenges.net
42
Wood, being a biological tissue, exhibits a much more dynamic character, on a physiological level, than the typical static structural materials used in building construction. According to Dinwoodie (2000) this has been made possible because of the evolution that it has gone through in being able to provide structural support and storage requirement to trees, eventually emerging as a “highly efficient biological system”. Apart from its structural benefits, when Holstov (2017) began to chart the chronology of research and exploration into hygroscopic composites beginning with studies in 1997 of the opening mechanism observed in pine cones to the earlier attempts at developing a moisture-responsive composite in 2009 followed by the current increasing research into synthetic hygroscopes it was found that nearly all of the natural hygroscopic researches incorporate wood as the primary moisture-responsive material.
Holstov (2017) points out the fact that wood, having been naturally provided with a dense network of vessels for water absorption and transport, exhibits a higher magnitude and speed of hygroscopic motion than other synthetic polymers. Timber construction, therefore, can be informed by new insight into material performance to develop novel approaches to modular light-weight responsive wood structure. Following is a description of such an exploration into the movement of wood in order to enable it to perform a building function.
architectural building skin, institute for computational design (icd)
The “Hygroscope” installation and the “HygroSkin- Meterorosensitive Pavilion”, designed and installed by Reichart, Menges and Correa in 2012 and in 2013 respectively, are architectural prototypes that demonstrate material integrated
43 responsiveness within a functional adaptive façade system, utilizing wood composites.
After studying the opening and closing mechanism of seed-bearing conifer cones in response to moisture, Reichart, Menges and Correa adapted the system in the development of a hygroscopic composite for the prototypes consisting of an active wood layer and a synthetic or natural passive layer. The initial research, funded by the Institute for Computational Design (ICD) in Germany, that included an exploration into the hygroscopic behavior of wood, development of a bilayer composite and real-time simulation of the bending action served as a case study for the thesis. Following is a description of the research methodologies adapted by Menges and his team in developing a unique architectural building skin that would later inspire the HygroScope installation in Centre Pompidou, Paris and the HygroSkin Pavilion at Stuttgart, Germany.
material selection
In order to find the most suitable wood type for the research, Reichart and his team looked into several parameters of wood including durability, fungus resistance, homogeneity of grain, density, brittleness and commercial availability. Eventually maple veneer was selected as the active layer. Since hygroscopic behavior in wood is a function of its cellular structure, grain directionality has a significant role to play in the bending motion of wood. The hygroscopic deformation is seen to occur perpendicular to the grain direction, which can be used to predict the bending motion in wood. For the passive layer glass fiber was used with epoxy bonding, leading to a semi-synthetic composite. The presence of the passive layer restricts planar hygroexpansion in wood, leading to bending or twisting. Reichart et al. (2015) suggests that the passive layer of the composite could be made to face outward to protect wood veneer from long-term
44 exposure to UV radiation and direct contact with precipitation. They further propose future investigation into natural fiber reinforced polymers, including hemp, jute flex etc., for biodegradability and low embodied energy. The resultant size, thickness and grain directionality of the composite were taken into account for controlling the bending action.
Since the geometric configuration of the façade pattern plays a significant role in the degree of openness, consistency of performance and directionality, several configurations were studied with different orientations, including linear and polygonal, thereby creating different opening patterns, such as centered, alternate, adjacent openings and so on.
experimentation
Figure 5-1: By controlling fabrication parameters the specimen is made to react within a certain humidity range, with specimen 1 closing at high humidity and specimen 2 opening. Source: (Reichart et al. 2015)
To create a climate controlled environment, a steam-producing humidifier and a dehumidifier was used, while temperature control was established through the use of a thermal radiation source. Menges shows that by carefully controlling climatic conditions it is possible to link a certain climatic state to a particular deformed condition in wood,
45 thereby allowing the opening and closing mechanism to be reversed, when necessary
(Figure 5-1).
A 5X5 array of the reactive components was tested under two different kinds of climate conditions, one where a homogenous humidity condition was set up across the climate chamber with a relative humidity range of 80 ± 5%, and another where humidity within the chamber was localized using a localized emitter to generate and observe a gradient of decentralized responsiveness across the specimen (Figure 5-2). The composite was observed to undergo continuous hygroscopic cycles in trying to achieve an equilibrium moisture content level, the shortest opening and closing time being 4 minutes and 17 minutes respectively.
The array was tested outside the controlled environment over a two-year period to monitor the long-term diurnal and seasonal performance of the material. The results for the outdoor test showed incredibly consistent responsiveness in the material through a number of daily hygroscopic cycles.
46
Figure 5-2: Localized response in wood due to local changes in humidity. Source: (Reichart et al. 2015)
limitations and conclusion
In discussing the limitations of the study, the researchers agreed that a lack of homogeneity between grain curvatures of wood samples of the same species can limit the scope of investigation into this field. Besides, continuous exposure to changing levels of humidity can, over time, weaken the material and make it prone to fungal attack. Decaying may also take place because of long-term exposure to UV radiation
47 and weathering agents, which could be somewhat reduced by sheltering it from the direct contact of rainfall and radiation. The researchers conclude by suggesting the use of synthetic multilayer composites with moisture-reactive hydrogels to overcome the limitations of wood and to have the ability to manipulate fiber direction according to requirement, potentially creating a more complex system.
The above research is thought to have created a paradigm shift in design by actuating hygroscopic wood composites and incorporating the actuation into design functions. Additionally, using digital design tools to enhance the dynamic design space the research was able to create higher complexities with increased efficiency and less chance of malfunctions.
chapter 6
exploring bamboo
responsiveness
49
In order to investigate the responsiveness embedded in bamboo, a number of bamboo species is explored that are native to the regions being studied and, at the same time, are also easily available in the region where the research was being conducted. Finally, the species Phyllostachys edulis or Phyllostachys pubescens (Moso) was selected for the study as it is a north-temperate bamboo species and commonly grows in the regions being studied. It is a monopodial bamboo with running rhizome and erect, rounded stems. It is suitable for USDA hardiness zone of 7 and up which, in turn, corresponds to all three regions being considered. Moreover, being the most widely available bamboo species in the US, the ease of availability was also a major determining factor in selecting this particular type. The veneer was 0.5mm (0.02 inches) in thickness and was kiln dried by the supplier to 6-9% of its moisture content.
workflow
The physical experimentation phase started with building a humid chamber, and acquiring the particular bamboo species along with two different kinds of passive layers, a clear cellulose film and a polycarbonate film (Figure 6-1).
The first stage consisted of veneer sample studies, where bamboo veneers of different shapes, sizes and grain directions were tested under changing humidity levels, and the findings were recorded through photographs taken at regular intervals. The goal was to understand the nature and extent of bamboo responsiveness. Some of the tests were significant enough to inform subsequent experiments and helped guide the research forward. The expected outcome of this stage was to come up with a sample specimen that would exhibit the most responsiveness under increasing humidity levels.
50
Figure 6-1: Illustration of the workflow
The second stage involved using the sample specimen obtained from the previous stage to design modular façade patterns and create openings that would be significant enough to generate airflow through them. This stage involved numerous sketches and drawings to guide the physical modeling of the patterns.
After a considerable number of modules were produced and their performance tested it was time to incorporate the different wind parameters of the three selected geographic locations into the module construction in the third stage. This stage involved looking into the prevailing wind angles of the locations and designing a module pattern that would work best with that. The intended outcome of this stage was to design a module that is easy to construct using the simplest tools, takes into account specific wind angles during its hygroscopic action, and is flexible enough to be placed inward or outward an exterior wall according to incoming or outgoing air.
The final stage consisted of building a façade prototype using the module obtained from the third stage, while being mindful of the façade frame and the
51 mechanical fixing to be used. Simultaneously a digital model of the façade was generated through Rhino Grasshopper in order to conduct a digital wind simulation. The computer model acted as a tool to understand and predict the hygroscopic behavior of the façade under wind conditions, something that would not have been possible in real- life within the short period of time available.
a climate-controlled environment
In order to create a controlled environment for conducting humidity experiments, a 0.9m X 0.45m X 0.45m (3‟ X 1.5‟ X 1.5‟) rectangular wood-framed volume was made, covered with plastic sheeting. One end of the chamber was connected to a stem- producing humidifier through a duct, while the opposite end was connected to a dehumidifier.
Figure 6-2: Humidity chamber setup. Source: (Author 2018)
52 The edges of the volume were duct taped to seal the container and a hygrometer was put inside (Figure 6-2). The back of the chamber had a grid of 25mm (1 inch) to determine dimensional changes in the material.
veneer behavior study
active layer
Figure 6-3: Parameters for hygroscopic explorations of bamboo veneer. Source: (Author
53 2018)
A series of physical experiments were conducted to understand the hygroscopicity of bamboo veneer. These experiments looked into different shapes, sizes and grain directions of the active veneer (Figure 6-3).
The explorations began with an experiment consisting of two sets of three rectangular pieces, each of which had veneers 7”, 6”, 5” in length and 2” in width. Three of these had grains perpendicular to the longer dimension and three had grains at an angle of 15 degrees. After the humidity was raised from 51% to 93% it was observed that the higher the width-to-height ratio of a veneer the greater was the deformation. The deformation was also higher in pieces that were perpendicular to the grain direction. So the 7” long piece with grains perpendicular to the longer side showed the maximum deformation. (Figure 6-4)
Figure 6-4: Rectangular bamboo veneers reacting to increasing humidity level. Source: (Author 2018)
A similar experiment was conducted with triangular pieces and was observed to have a greater deformation than rectangles. The reason is that in a triangular piece as the veneer extends forward from the base toward the vertex it has increasingly less material and hence less resistance to bending motion. However, when the humidity was
54 decreased it was found that the veneer, on its own, was unable to return to its initial state, and it nearly took a period of 24 hours before it came back to its original state.
Thickness of the composite was also an influencing factor in the curving motion.
Thicker veneers were observed to have more inherent stability and were able to resist the bending motion while thinner veneers were more reactive. Seeing a similar result in wood composites Holstov suggests using thicker active layers to express long-term monthly or seasonal humidity variations and using thinner active layers to express hourly changes quite rapidly. (Holstov, 2015)
passive layer
In order to enhance the hygroexpansion in bamboo and also allow the veneer to return to its initial position within a relatively short time a bi-layer composite unit was made with a non-reactive layer bonded to the veneer. This passive layer also created homogeneity in the responsive performance of the otherwise heterogeneous fibrous bamboo veneer. Moreover, as Holstov has observed in his own research, having a passive layer creates a constraint on the planar hygroexpansion of an active material, forcing it to bend (Holstov, 2015) (Figure 6-5).
55
Figure 6-5: Bilayer bamboo composite. Source: (Author 2018)
Two different materials, a cellulose film and a polycarbonate film, both 0.005 inches thick, were tested as the passive layer to see the nature of the responsiveness generated by each of them. At high humidity the composite with the cellulose layer exhibited curving motion toward the inner surface of the veneer layer, while the polycarbonate layer showed curving motion toward the outer surface of the veneer layer
(Figure 6-6). For the purposes of the research and the intended outcome the non- reactive layer was chosen to be the clear cellulose film, 0.127 mm (0.005 inches) thick.
The bi-layer unit with the cellulose film attached to the veneer allowed the composite to come back to its initial state much faster. As humidity was raised from a room humidity level of 65% to 95%, the recorded time for curving motion was 10 minutes, and for returning back to the original state was 5 minutes.
56
Figure 6-6: Bilayer bamboo composite testing with cellulose and polycarbonate film. Source: (Author 2018)
Because of the similarity in the responsive nature between hygroscopic bilayers and thermo-bimetals, Timoshenko‟s theory of bimetallic thermostat can be applied, using hygroexpansion coefficient (α) in place of thermal expansion coefficient and change in relative humidity (Δφ) in place of temperature, to understand the hygroscopic mechanism of the bamboo composite. (Holstov, 2015; Reyssat, Mahadevan, 2009)
The equation is as follows:
K = = +
where,
f (m, n) = ; Δα = αa – αp ; m = ; n =
Here, K = change in curvature, t = thickness of a layer, E = Young‟s modulus
(stiffness) and R = radius of curvature.
57 binder layer
From the case study research epoxy resin was selected to be the bonding layer.
After applying a thin coat of epoxy in between the two layers, the composite was vacuum-pressed for 2 hours to ensure complete bonding.
generating modular patterns
Following the veneer study, the research continued with constructing various patterns of modular façade and observing the degree of opening a particular façade would generate (Figure 6-7). The intention was to arrive at a certain geometry that would produce maximum opening to allow for maximum ventilation.
58
Figure 6-7: Generating modular patterns. Source: (Author 2018)
experiment 1(a)
The testing started with two-dimensional façade systems, with a simple configuration of diamond shaped composite units. The particular shape, being wider in the middle and narrower toward the two ends, forced the composite to curve faster at its ends. Humidity was first raised from 50% to 92% and then lowered to 56%. As previously observed with this type of bamboo cellulose composite, it took 10 minutes for it to curve in increasing humidity and 4 minutes to return to the initial stage in decreasing
59 humidity (Figure 6-8). During this time the units curved a total of 9° creating an opening of 3 inches in length (Figure 6-9).
Figure 6-8: Bilayer bamboo composite testing. Source: (Author 2018)
Figure 6-9: Bilayer bamboo composite bending in high humidity. Source: (Author 2018)
60 experiment 1(b)
The same configuration of composites was adopted for a second experiment, but during this stage small perforations were made throughout the body of the veneers through laser cutting to study the behavior of perforated bamboo veneers and compare it with that of previously tested non-perforated bamboo veneers (Figure 6-10). The intention was to observe whether getting rid of excess material aid in the deformation process by making the veneers more reactive.
Figure 6-10: Perforated bilayer bamboo composite testing. Source: (Author 2018)
The performance period was observed to be similar to non-perforated units.
Moreover, from initial observations it appeared to generate increased bending in
61 composites, resulting in a longer opening dimension compared to the previous experiment.
experiment 2
The analysis later moved on to three-dimensional module studies to give the veneers an elevation to begin with. The triangles were configured into simple tetrahedrons. As humidity was increased from 53% to 80%, the modules took 10 minutes to fully deform. However the modules were observed to have created a much bigger opening while deforming the same amount as seen in the previous experiment
(Figure 6-11). The resultant opening was 4.5 inches in length.
62
Figure 6-11: Perforated tetrahedron module testing. Source: (Author 2018)
experiment 3
The following experiment consisted of using the tetrahedrons to create two façade patterns, one where the triangular pieces were of the dimension 4”X6”, similar to
Experiment 2, and another where they were 5”X6” (Figure 6-12). The intention was to find a pattern that would not only generate a considerable amount of opening but also have a pleasing aesthetic effect. The former having longer and narrower triangular pieces created openings that were nearly 8”X8” while the latter having shorter triangles
63 created openings 3”X3” in dimension. An interesting thing to note was the modules in the former pattern, while exhibiting synchronized opening and closing during Experiment 2, were seen to be behaving inconsistently when arranged in a larger pattern formation, creating a lot more visual noise than the latter where the triangles were nearly equilateral. Even at a lower humidity the modules having larger tetrahedrons would not entirely close, unlike the smaller tetrahedrons. One could assume gravity having a much bigger effect on veneers of larger dimension, preventing them to curve up and close the opening.
The following experiments looked into manipulating the pattern configuration in order to address the issue of inconsistent closing of openings while addressing the different climatic parameters of the selected geographic context for the study.
Figure 6-12: Experiments with 3D modular patterns to generate maximum opening. Source: (Author 2018)
64
incorporating façade with climate
Once a suitable modular pattern with a certain shape and size was selected through a number of experiments with tetrahedrons, the wind directions of the three selected warm-humid regions, Vietnam, Bangladesh and Florida, USA, were studied to integrate them with the modules. With the help of Climate Consultant software wind rose data for all three of them were analyzed, with respect to wind direction, wind speed and atmospheric humidity. The following figure shows the wind rose diagram for all three regions for the summer months, i.e. May-July (Figure 6-13).
Figure 6-13: Wind rose diagrams for Vietnam, Bangladesh and Florida, USA. Source: (Climate Consultant 2018)
According to the diagram, summer wind in Vietnam is dominated by the south- east wind, which also corresponds to an increased humidity. Wind speed is fairly high for this south-east wind, as indicated by the comparatively longer orange colored triangles, although the maximum wind speed is seen in the north-east wind. Bangladesh experiences summer winds predominantly from the southern direction, while summer wind with the maximum velocity comes from south-east. Both the winds correspond to high humidity levels. Florida experiences summer winds from nearly all four cardinal directions, with east/south-east receiving the highest wind in terms of hours per day, as
65 indicated by the length of the brown colored rectangles in the diagram. In terms of humidity, southern wind in Florida is seen to be more humid than eastern wind, as shown by the dark green segments. The wind speed of this south-east wind is also relatively high, as indicated by the longer orange colored triangles.
Therefore, it can be concluded from the wind rose data that all three regions have summer winds coming in from roughly south/south-east direction, which was utilized to further modify the façade modules in the following experiments.
experiment 4
To allow the south-east wind inside, a range of angles between 40-50° from the horizontal line was determined to be incorporated into the façade structure. In order to do that, the façade was constructed in a way that the veneers would be attached to the frames at an angle of approximately 22-25° (Figure 6-14). The regular tetrahedrons became distorted toward one side having two regular triangles with a base x height dimension of 4”X6” and 4”X2.5”, and two obtuse angled triangles of 4”X 2.5”. For ease of ventilation, the surface of the façade with the modules pointing outward would be oriented toward outgoing air, while the surface with modules pointed inward will face incoming air. However, when humidity was raised from room humidity level of 20% to
80% only the 4”X6” triangular units were was seen to curve out, while the obtuse angled triangular units showed minimal reactivity. The obtuse angled triangles were then studied separately to understand which factors were inhibiting their performance.
66
Figure 6-14: Façade pattern addressing wind direction. Source: (Climate Consultant 2018)
Several obtuse angled triangles were placed, each with different density of perforations, in the humid chamber and their performance was observed in increasing humidity levels. During this stage densely perforated veneers were seen to deform less than others, since the grain of the bamboo ended up being divided at closely spaced intervals due to the perforations. To further confirm the results another experiment was setup with two sets of veneer composites arranged horizontally and vertically, with each composite having different densities of perforation. As a result, it was concluded that
67 perforations on the composite were restricting their reactivity, instead of enhancing them as previously assumed (Figure 6-15). Hence, the research went back to using non- perforated veneers in a three dimensional modular pattern.
Figure 6-15: Reactivity of composites with varying densities of perforation. Source: (Author 2018)
Moreover, from Experiment 4 it was observed that to have a responsive bending motion the deformation axis of the composite needs to be not only perpendicular to the grain, as previously observed, but also to the base of the triangle. Naturally, in the obtuse angled triangles, the deformation axis was making an angle greater than 90° with its base (Figure 6-16).
68
Figure 6-16: Relationship between deformation axis and base of the units. Source: (Author 2018)
experiment 5
Taking into consideration the observations of the earlier experiments, the module configuration was modified for a final time. The four triangular composites arranged on a square base to form tetrahedrons were converted into three triangular units arranged on one half of a hexagon base. The resultant configuration making up a module ended up having the deformation axis in each of the unit perpendicular to their base to generate maximum deflection. As humidity is increased the veneers, attached to the frame at an angle of nearly 25°, began to absorb the humidity and opened up to an angle within the range of 40-50° at roughly 93% relative humidity level. As such, the cool south-east wind would be allowed inside the space (Figure 6-17).
69
Figure 6-17: Bamboo veneers opening along up to an angle of 40 degrees. Source: (Author 2018)
Figure 6-18: Stages of responsiveness. Source: (Author 2018)
70 What is interesting to note is the behavior of the triangular veneers at a micro scale. At high humidity, when the veneers reached their most „open‟ state the maximum angular difference was observed to occur in the middle of the triangles. The veneer would begin to increase its deformation angle from the base of the triangle and arrive at a maximum difference in the middle, after which it goes up and down in its angular differences as it moves toward its apex. The observation, although unpredictable, was confirmed after doing multiple experiments with different veneer units from the same pattern. (Figure 6-19)
Figure 6-19: Veneer behavior at a micro scale. Source: (Author 2018)
The resultant façade design would have the veneers facing inwards toward the interior space when constructed on facade that faces incoming fresh air, and outwards on facades facing outgoing, “used” air. Since the three regions have incoming air from south-east, the southern façade will have veneers angled toward the inner space, whereas the northern and western façade, mostly utilized to expel air, will have veneers angled toward outside. On a micro scale, the latter creates a shaded surface on the façade keeping it cool throughout the day, which is essential for west facing facades in warm-humid regions. On the other hand, the former case where the veneers would face inward on the southern façade will create a Venturi effect, where the outside fresh wind coming in will be forced to pass through smaller inlets throughout the façade into a much
71 bigger interior space, thereby increasing wind speed leading to a cooler and more comfortable interior. Being angled toward the inside will also help protect the veneers from the onslaught of strong southern winds, a common occurrence in warm-humid regions.
full-scale prototyping
The full-scale physical prototyping stage began by constructing the façade frame using CNC machine. The dimension of the frame is 1.8 m x 0.9 m (6‟ x 3‟), and is made out of 38 mm (1.5 inches) thick plywood (Figure 6-20). While the frame is not expected to take any structural load, it still needs to be stiff enough. The width of the frame on both sides is made angled not only to have a surface to attach the veneer units but also to give them an angular surface to enhance airflow along that direction (Figure 6-21).
Figure 6-20: Fabricating an angled surface on the façade frame. Source: (Grasshopper Butterfly 2018)
72
Figure 6-21: Angled surfaces on either side of the façade frame. Source: (Grasshopper Butterfly 2018)
Even though the facade consists of the same hexagonal modules repeated all over the surface it incorporates different degrees of transparency, with some modules left open, some with louvers, and some with the active veneers. The idea was to utilize the surfaces that do not have the veneers, so that they too can contribute in ventilation.
Therefore, instead of being solid surfaces all of the modules were incorporated into the design, with the upper part of the façade having more open modules and the lower part
73 having more solid modules, since used air, being warmer and lighter, rises up and tends to exit along the top of a window surface (Figure 6-22).
Figure 6-22: Full-scale prototype. Source: (Grasshopper Butterfly 2018)
chapter 7
computer analysis
75
parametric modeling
As mentioned before, the primary aim of the design was to create an adaptive kinetic pattern that, while being governed by atmospheric humidity changes, would generate different open and close conditions, allowing varying degrees of cross- ventilation. Fabricating a full-scale façade that exhibits a hygroscopic action, and assessing its cross-ventilation performance in real-time is a difficult process through physical modeling. A digital model that can be made to mimic the hygroscopic action through performance simulation makes it easy to explore the wind performance for a full scale façade system. Additionally, digital modeling helps in effectively exploring multiple design alternatives within a short period of time that would not have been feasible with physical modeling. In contrast to the earlier stage, which adopted a bottom-up approach of exploring material properties, leading to a suitable façade pattern configuration, the computer analysis described in this chapter demonstrates a top-down approach of embedding material properties, that were explored in the previous stage, into a computer model. These properties are used to define the threshold of material performance in the digital model. Besides, once the performance has been simulated in real-time, the digital analyses help in guiding further design alternative studies. In this way the physical and the digital modeling informed each other throughout the course of the research.
The computer application called Rhinoceros, and its visual programming language and environment plugin called Grasshopper, is used to model the parametric design, while the Butterfly plugin is used to observe the performance of the façade in terms of cross-ventilation. What follows is a discussion about the strategies that were adopted to make the digital model for the parametric design and, subsequently, to
76 conduct a basic analysis of its performance through wind simulation and simple shading analyses (see Appendix for a description of the digital modeling steps).
generating design alternatives for a responsive system
Several control parameters were set in order to fabricate the digital model. These are: size of the enclosure, number of modular openings, shape and size of the openings, and angle of openings (Figure 7-1). Each of these parameters directly influences indoor airflow. Consequently, by controlling these parameters a façade system can be made to generate a number of alternate solutions, based on the velocity of indoor airflow.
Figure 7-1 (a) illustrates the parameter concerning the size of the enclosure.
Different sizes of enclosure generate different wind movements within it, thereby effecting indoor airflow. Number of openings, as shown in Figure 7-1 (b), can be incorporated independently for inlets and outlets. The hexagonal shape of the modules was determined from the previous material exploration but different shapes for inlets and outlets, as shown in Figure 7-1 (c), will not only lead to different velocities of airflow but also change the nature of material deformation, and will necessitate further explorations.
As discussed in chapter 3, size of inlet and outlet openings directly influences indoor wind velocity. When inlets are smaller than outlets it results in a tunneling effect, forcing wind to enter at a much higher velocity. Finally, the angle of openings (Figure 7-1 (e)) can also lead to differences in indoor wind velocity by either allowing or restricting outside air to enter inside the enclosed space. The angles explored in this chapter for wind simulation tests came from previous material study experiments that represent the threshold of the opening and closing of the veneers. To control the different angles of openings an attractor point was defined, that represented a humid source. Therefore,
77 instead of using actual atmospheric humidity values, the software uses angles, based on the distance between the attractor point and the façade, to represent responsiveness in the material.
Figure 7-1: Control parameters for digital modeling. Source: (Author 2018)
78 Apart from the above mentioned parameters the hygroscopic action of the material can vary depending upon various other external conditions, such as location of any adjacent structure casting shadows, presence of external shading devices on the façade surface etc. These factors can lead to variations in localized humidity levels, and hence differences in material behavior.
wind simulation
To simulate indoor wind-driven airflow, once the digital model was set up, and to observe the behavior of the façade in terms of its ventilation effectiveness Butterfly, a
Grasshopper plugin, is used. Butterfly creates and runs advanced computational fluid dynamics (CFD) simulations using OpenFOAM, an open-source CFD engine.
A number of pattern configurations were tested to see their performance under wind conditions similar to those of the three geographic contexts being considered.
Relationship between inlet- outlet size and position regarding increased or decreased indoor airflow was determined from previous literature reviews, which informed the wind simulation tests of this phase. The test results indicate similar observations as previous studies cited in the literature review. Figure 7-2 demonstrates a simple case where a rectangular enclosed space has hexagonal modular openings as inlets and outlets. The first row indicates a situation where the inlets and outlets are equal in size, while the second row has outlets 1.5 times bigger than inlets. The simulation results express the two conditions in terms of indoor wind pressure and wind velocity, with colors ranging from red to blue. For wind pressure diagrams, red signifies areas of high pressure while blue signifies areas of low pressure. Similarly, for wind velocity diagrams red arrows indicate higher velocity while blue indicates lower velocity. After running the simulation it
79 was seen that the second condition generated a higher wind velocity than the first one, with denser red arrows. The result corresponds to the ones discussed in chapter 3, regarding the influence of inlet-outlet sizes in inducing a higher wind velocity. As a result, this particular ratio of inlet-outlet size was taken on to produce further tests with veneer openings.
Figure 7-2: Inlet-outlet size affecting wind simulation studies. Source: (Author 2018)
Figure 7-3 shows three different cases of indoor airflow, generated due to different opening angles of the veneers. All of these cases have outlets that are 1.5 times bigger than inlets, since it produces better result than when the inlets and outlets are equal in size.
80
Figure 7-3: Wind simulation studies. Source: (Author 2018)
Similar to Figure 7-2, each of the three conditions illustrated in Figure 7-3 is expressed in terms of indoor wind pressure and wind velocity. The façade for the first case under (a) consists of modular openings with veneer surfaces that are positioned at an angle of 490-500 i.e. at their maximum open condition. When air enters from an angle of 450 the velocity of indoor airflow generated is quite high. This situation corresponds to the evening time when relative humidity is high, causing the veneers to open fully and bring in outside cool air. In case (b) the veneer surfaces are kept open at an angle of
450-460, resulting in a decreased airflow than case (a). This case corresponds to early afternoon and late afternoon when humidity is sufficiently low, and the veneers are partially open, limiting entry of outside heat. Case (c) is where the veneers are at an angle of 420-430, and are not letting in any outside air. Consequently there is very little air circulation occurring inside. This occurs in the middle of the day when temperature is
81 high enough to create a low relative humidity, so that the veneers remain closed, blocking out any solar heat gain during the day.
Therefore, it becomes evident that as the veneer surfaces open up they allow a cross-ventilation to happen by letting outdoor cool air pass against them, and out through to the other end.
shadow analysis
The digital model is also observed under different light conditions at different times of the day. Based on the relationship between temperature and relative humidity the shading provided by the façade system, with varying humidity levels, demonstrates its adaptability to both of these climatic parameters. Figure 7-4 illustrates a square enclosed space, with a corner section through the south and west wall. As illustrated by the figure, the shading created by the hygroscopic units on the southern and western façade changes with the changing position of the sun, and hence changing temperature and relative humidity levels. When the temperature is high during the middle of a hot summer day i.e. from 1-2 pm, as shown in Figure 7-4 (a), the sun is at a higher elevation in the sky, and the corresponding relative humidity is low. The veneer units at such a stage will remain closed. This stage corresponds to the wind simulation study shown previously in Figure 7-3 (c), where the veneers were curved at an angle of 420-430. As the day progresses, the temperature decreases, and at around 4-5 pm, as shown in
Figure 7-4 (b), the sun is at a comparatively lower elevation with an increasing relative humidity. The veneers start absorbing moisture and begin opening up letting cool air in.
This stage corresponds to Figure 7-3 (b) which shows the veneers to be curved at an angle of 450-460. Finally, around 6-7 pm, when the temperature has sufficiently cooled
82 down, and the relative humidity has increased, the veneers are at their maximum „open‟ state, as shown in Figure 7-4 (c). The cool evening breeze is allowed in without any excess heat. The indoor airflow occurring at this stage corresponds to the one shown in
Figure 7-3 (a), where the veneers were open at an angle of 490-500.
Figure 7-4: Shadow analyses. Source: (Author 2018)
83 As mentioned before, using a horizontal shading device over the façade can help create a bigger shadow, while also protecting the veneer material from outside weathering agents such as rain, UV radiation, dust etc. However, this will depend on the width and the height of the particular shading device used.
When the same modular system is placed over the west façade, the veneers are oriented outward (Figure 7-4). As a result, the veneers projected outwards help keep the west wall in a cool shade, thereby cutting off solar heat coming from the west.
scale of application
Holstov, Farmer and Bridgens (2017) outlined four possible types of application for hygroscopically actuated passive technologies, (a) as functional devices integrated with other building systems, (b) as performance-oriented systems that focus on occupant comfort, (c) as an aesthetic device and (d) as a contextual indicator, representing local environment and climate.
In terms of the first typology of application, concerning the functionality of the façade system, there can be varying scales of application. While the composites are expected to act as individual units that make up the adaptive façade, the façade itself can incorporate the pieces in different scales (Figure 7-5).
84
Figure 7-5: Different scales of application. Source: ( Author 2018)
When the location and the context permit, the façade can act as an adaptive one entirely and create a stunning visual effect throughout the day, for example in the case of a museum lobby or an exhibition space where the architecture itself becomes a thing to „see‟. However, whenever the functional aspects of the façade is expected to dominate, the modules can act together as a component of certain size and shape instead of discrete units and be „plugged-in‟ as a component itself. This will eliminate the need to construct the entire façade as an adaptive one if it gets in the way of furniture placement in the interior, and instead the particular component can be fitted in places where the wind direction is most favorable and it allows a cross ventilation to take place.
85
chapter 8
background blooming bamboo house, h&p architects
86
architecture and climate
The noted 20-century professor of Geography, Dr. Ellsworth Huntington, popular for his studies on the effect of climate on human progress, concluded in his book
„Civilization and Climate‟ (1915) that climate is one of the three great factors having a profound impact on the conditions of civilization; racial inheritance and cultural development being the other two. For human progress to prevail, Dr. Huntington put forward an optimum climatic condition with average temperature between 4°C (40°F) and 21°C (70°F), occasional storms and winds to generate rain and maintain a balanced relative humidity level, and moderate and frequent changes in temperature to stimulate human physical and mental development.
Virgil stated “Five zones possess the sky, of which one is ever/ Red from blazing sun and ever burnt by fire” (Lonsdale, 1883). He believed that the central zone between the tropics is uninhabitable because of the excess heat from the sun, as are the zones in the poles because of excess cold, as the sun is far removed from them. He concluded that only the temperate regions were ideal for human habitation. Consequently, regional adaptation to climate has been an essential aspect in architecture since civilized habitation.
Vitruvius wrote, “For the style of building ought manifestly to be different in Egypt and Spain, in Pontus and Rome….For in one part the earth is oppressed by the sun in its course; in another part the earth is far removed from it; in another it is affected by it at a moderate distance” (Vitruvius). On a similar vein, American physiologist Dr. Walter
Cannon maintained that climatic and environmental condition is one the most significant
87 factors in architecture construction when he asserted, “The development of a nearly thermo-stable state in our buildings should be regarded as one of the most valuable advances in the evolution of buildings” (Olgyay, 1963). This becomes evident when we consider the myriad of housing forms developed throughout the world by people when encountering different climatic regions.
Due to the harsh winters and lack of fuel, habitation in the Arctic regions has typically made use of compact shelter design with hemispherical domes set low in the ground in order to have minimum surface exposed to the inclement weather, and to conserve heat (Olgyay, 1963). Snow is utilized for its insulating value, limiting air seepage, which results in an interior temperature of around 15°C (60°F), even when outside temperature -45°C (-50°F) (Olgyay, 1963).
The temperate region, being more forgiving to dwellers, generates shelters that are more freely organized and flexible to migration. It encouraged architectural freedom and experimentation.
The hot-arid zones, characterized by excess heat and glare, demand compact living with inward-looking buildings to reduce solar radiation, dusty winds and create shading. Thick walls and roofs, most often made of adobe, brick or stone, with small windows typically provide protection from intense solar radiation in such regions. An awareness of building orientation becomes essential in such conditions to get the lowest heat loads on the larger dimensions, thereby keeping interior spaces cool.
Lastly, the warm-humid regions require a reduction of solar radiation in buildings along with evaporation of moisture through wind movement. Dwellings typically tend to have a rooms arranged linearly with large openings oriented to catch the prevailing wind and allow cross ventilation. Large overhanging pitched roofs are designed to keep out rain, and floors are elevated to allow ventilation underneath.
88 It is evident from these age-old building practices that people have been adapting dwellings to particular climatic challenges long before Adaptive Architecture was conceptualized in theory. Over the course of many years, our fundamental needs of survival and comfort have helped us to develop remarkable traditions of craftsmanship that integrate an acute awareness of climate. So much so that in his book „Design with
Climate‟, Olgyay exclaims how fascinating it is to observe how tribes in different parts of the world facing similar climatic challenges all seem to have independently come up with similar building solutions to combat them. This just goes to show the unique relationship between architecture and climate that people have an innate understanding of; a relationship that can be exploited to create better living conditions.
understanding warm-humid climate
One of the five major climatic regions of the Köppen classification, warm-humid climate, is typically distinguished by high air temperatures all throughout day and night, between 21°C-35°C (70°F- 95°F), with equally high humidity, ranging from 77-88% daily.
Although solar radiation gets diffused by frequent and heavy cloud cover, it is still quite high throughout the day. Because of constant cloud cover, the heat absorbed during the day is not readily re-radiated at night, contributing to further heat gain. Precipitation in the warm-humid climate is plentiful, well over 2500 mm (100 inches) annually, and occurs in the form of torrential rains. Wind speed is generally low, with one or two dominant wind directions.
Vegetation in the warm-humid climate grows in abundance due to heavy rainfall and adequate heat: which in turn boosts animal and insect growth and proliferation.
Plant life grows in two layers, the top layer or canopy, which often reaches a staggering
89 height typical in dense rainforests, and the lower layer consisting of orchids, bushes, ferns etc., which requires low light to survive. Studies show that more than half of the world‟s plant and animal species are found in this zone. At the same time, high humidity also leads to a rapid growth of mold and algae, along with rust and decay of building materials.
Warm-humid regions occupy areas near the equator, between Tropic of Cancer and Tropic of Capricorn, extending from 15° N to 15° S.
Köppen classification identifies two processes that can generate this type of climate. The largest expanse of this climate occurs in southern and southeastern Asia where monsoon circulation brings in humid maritime wind to converge toward the low- pressure zone of the Himalayan range during the summer, resulting in orographic precipitation. In winter, on the contrary, cool dry air from the north diverges toward the land bringing in a relatively short spell of cold and dry conditions. The warm-humid regions of the Americas and Africa experience a similar orographic monsoon during the summer, due to humid trade winds passing over toward the mountain ranges. Dry periods occur briefly during the winter months due to changes in the intensity of trade winds.
façades in warm-humid climate
Warm-humid countries have long been characterized by a very narrow difference between outdoor air temperature and bodily skin temperature, which inhibits the body‟s effective heat dissipation to the environment. As the skin is continually surrounded by a near-saturated air envelop, the rate of its moisture evaporation is reduced a
90 considerable amount. In such a state, only by replacing this saturated air can the body experience physical comfort. Thus, cross ventilation comes into play.
Buildings in humid climates are typically designed to be as open as possible, allowing outdoor breezes in. This notion of open plans with wide verandas and of large openings with shading devices for the tropics was formalized when German architect
Otto Koenigsberger travelled to India in 1940, working as a Chief Architect for nine years, and ultimately writing his Manual of Tropical Housing and Building, a book still taught in undergraduate architecture classes in the tropics (Baweja, 2014). What
Koenigsberger wrote in his book placed a greater emphasis on ventilation and shading
(Figure 8-1), with a warning that a lack of both risk creating interior spaces that are considerably warmer than exterior spaces which are subjected to frequent air movement
(Koenigsberger, 1973).
Figure 8-1: Open façade system for warm-humid climate. Source: (Koenigsberger, 1973)
Since there is no appreciable reduction of temperature at night in the warm- humid climate, surface temperatures of walls and roofs tend to come to a balance with the outside. This balancing out is further created by an exchange of wind between the exterior and interior.
91 Traditionally the strategy adapted by humid countries to deal with excess humidity has always been to opt for locally available natural materials including rammed earth, timber, bamboo, thatch, palm leaves and so on (Koenigsberger, 1973). While earth-walled houses, being naturally insulated, tend to keep the interior cool in summer there is a possibility of creating a damp indoor condition if not ventilated properly.
Consequently, in place of mud, building facades constructed of layers of thatch, frames of timber or bamboo with open-weave matting as infill, often placed on stilts, offer a greater opportunity for a lighter, well-ventilated structure (Koenigsberger, 1973, pp. 220).
However, with time, as buildings started getting taller a greater need for advanced materials and technology able to withstand different loading conditions took center stage, and climatic determinants were pushed aside (Sung, 2016). The situation worsened with the advent of glass and concrete architectures in the humid tropics.
Buildings with hermetically sealed windows and increasingly inward looking facades achieved occupant comfort through mechanized ventilation and air-conditioning, instead of taking advantage of outside air dynamics. It is unfortunate to note that, as people became increasingly dependent on energy-consuming mechanical systems, building facades began to turn their back on the outside environment altogether (Sung, 2016).
92
chapter 9
geo-climatic context nesdis.noaa.gov
There are nearly 1500 species of bamboo distributed worldwide extending from
51°N latitude to 47°S latitude, with the highest species diversity being in Asia, followed by South America. On the other hand, Europe and the Poles are the only continents where bamboo does not grow (Gernot, 2016). Bamboo grows in plains that are just above the sea level up to an altitude of 4,000m (Behari, 2006), with diverse ecology ranging from extremely humid forests of Colombia to semi-arid regions of India (Gernot,
2016). The subfamily Bambusoideae consists of two kinds of bamboo, herbaceous and woody. The woody variety is typically categorized into three kinds, paleotropical woody, neotropical woody and north-temperate woody (Das et al, 2008). The woody bamboos are found to be more widely distributed, in terms of altitude and geographic location, than herbaceous bamboos. The tropical and subtropical regions of Africa, Madagascar,
South and South-East Asia, Southern China, Southern Japan and Oceania are the locations where paleotropical woody bamboos naturally grow. Neotropical bamboos are found in Southern Mexico, Argentina, Chile and West Indies. The north temperate woody bamboos are distributed in north temperate zones, as well as in higher elevations of
Africa, Madagascar, Southern India, Sri Lanka and South-east Asia (Figure 9-1)
(http://www.eeob.iastate.edu/bamboo/ maps.html).
Though the research was aimed toward a warm-humid climate, and not any particular geographic location, three locations were selected to be representatives of the climatic region namely, Vietnam, Bangladesh and Florida. Each of these regions has their own share of strengths and challenges concerning bamboo availability and constructions. While architecture constructions in Bangladesh and Vietnam have incorporated bamboo in a myriad of ways for a long time, in Florida, however, despite the easy availability and suitable climate bamboo still has not became the material of choice for many. What follows is an overview of the geographic and climatic features of
94 these three regions, in order to assess their strengths and limitations as locations where an experimental approach to adaptive façade can be attempted using bamboo veneer.
Figure 9-1: Types of woody bamboo distribution, with their subfamilies, according to region. Source: (http://www.eeob.iastate.edu/bamboo/ maps.html)
vietnam
topography
Vietnam is a land of distinctive landscape features with tropical lowlands, hills and highlands, the latter two consisting of almost 80% of the total area (Cima, 1989).
Stretching from north to south, the topography is particularly distinct between the northern highlands and the Red River Delta, and the southern coastal lowlands, plateaus and the Mekong River Delta (MCIA, 2005). The two delta regions are the most
95 populated, with Ho Chi Minh city and Hanoi as the largest urban centers located north and south respectively (MCIA, 2005). The Red River Delta is situated at an elevation of only 3m above sea-level, resulting in frequent flooding and flood-control being an economic priority (Cima, 1989). The Mekong Delta, also vulnerable to constant flooding, is home to dense forests and mangrove swamps. It is also one of the leading rice producing regions in the world (Cima, 1989). Spanning across a range of latitudes and having a diverse topography has resulted in Vietnam enjoying a rich bio-diversity consisting of evergreen and deciduous forests. Nearly 1500 species of woody plants ranging from hardwoods to palms, bamboos etc. grow abundantly in Vietnam. Oaks and
Pines are common in mountainous regions, while bamboos and tall grasses grow in areas around human settlements. Forestry is one the important economic sectors of the country, regarding the domestic market. Lumber, plywood, bamboo and rattan products contribute significantly to the economy. However, as the domestic demand for such products continues to increase it leads to deforestation and soil degradation.
climate
Vietnam has two climatic zones- tropical and temperate. The north has hot and humid summers and cold winters, while the south has less pronounced seasonal changes. Average summer temperature in the north is around 22°- 27°C, while winter temperatures range from 15°- 20°C. In the south, however, temperatures remain within
26°-29°C annually (USAID, 2017). According to MCIA (2005), for every 100m increase in elevation the average annual temperature is observed to decrease half a degree.
Consequently, the regions that are at a 500m elevation from sea-level experience a subtropical climate while those at 2000m elevation enjoy a more temperate climate
96 Average annual relative humidity is 85%, which increases to 87% in mountainous regions toward the north with high precipitation and decreases to 78% toward the coast in the south (MONRE, 2008). Relative humidity in the north remains quite low in winter, only increasing during winter monsoon, and high in summer. In the south, relative humidity is typically low in winter and high in summer (MONRE, 2008).
The climate is predominantly influenced by summer monsoon, coming from south-west during a five-month period from May to October, and winter monsoon, which follows north-easterly direction from November to April (Cima, 1989). During summer months, the hot air over Gobi desert, north of Vietnam, rises causing humid air to rush toward the land from the sea in the south-west. Vietnam experiences torrential rainfall during the summer, with annual precipitation being as high as 1200mm to 3000mm
(Cima, 1989). On the other hand, the winter monsoon brings cold air from the Chinese coast toward north-east and picks up moisture as it moves over the Gulf of Tonkin, bringing rainfall during winter months. Generally, precipitation is higher in the northern regions than in the southern regions (MONRE, 2008).
In the southern part of Vietnam, summer winds are predominantly south- westerly, whereas in the northern part summer winds are south-easterly (MONRE,
2008). Average annual wind velocity in the coast is 4 m/s. Because of its location on the tropical typhoon belt, Vietnam regularly witnesses extreme weather events such as tropical storms and typhoons (USAID, 2017).
bamboo availability
According to the statistics of the Department of Forest Protection (2008), total forest area in Vietnam occupies roughly 13,118,773 ha of land, of which pure bamboo
97 forests account for almost 17% or 767,122 ha (Figure 9-2). Apart from pure bamboo forests, bamboo is also found to grow in woody-bamboo mixed forests. Bamboo grows extensively all over Vietnam, from lowlands to mountainous regions, except the Red
River and the Mekong River deltas.
Figure 9-2: Bamboo forest areas in Vietnam for 2001. Source: (Vu and Le, 2005).
A number of studies were conducted to classify the different kinds of bamboo found in Vietnam. Camus (1993) classified bamboos in Vietnam into 12 genera with a total of 57 species. Pham (1999) estimates that there are 123 species of 20 genera, while Vu and Le (2004) claims that Vietnam has almost 200 bamboo species. Recently
Nguyen (2004) classified Vietnamese bamboo into about 216 species in 24 genera.
Vietnam uses its wide variety of native bamboo species in paper and pulp industries, construction materials, domestic items and crafts, and bamboo shoots as food items. In fact Vietnam uses nearly 150,000-180,000 tons of bamboo each year for their paper and pulp industries, while producing wood-based panels with bamboo generates 15,000-
98 130,000 tons of products per year (Vu and Le, 2005). Bamboo and rattan handicraft products is another booming business in Vietnam giving rise to 1400 handicraft villages, producing export quality bamboo products (Phan, 2004).
bamboo architecture in vietnam
Bamboo is a traditional housing material in Vietnam. Bamboo used for housing construction accounts for nearly 50% of the total harvested bamboo in the country (Do,
2006). In recent times Vietnam-based VTN architects and H & P Architects are coming up with innovative ways to approach this age-old material in architecture design.
wind and water bar, vtn architects
Constructed in 2008 by Vo Trong Nghia (VTN) Architects, the Wind and Water bar is a thatched bamboo dome siting in the middle of an artificial lake. Using 48 prefabricated units made of several bamboo culms bound together a structural arch system was made, covered with thatch on the exterior. The structure rose to a height of
10m with a diameter of 15m. Cool air from the lake was made to enter inside and help in natural ventilation. In order to exhaust indoor hot air a skylight of 1.5m diameter was made on top of the roof (Figure 9-3). Except the foundation the design does not incorporate steel anywhere in the structure. The project has won several prestigious awards including ARCASIA Gold Medal Awards in 2011, FuturArc Green Leadership
Award, in 2011, Green Good Design Award in 2010 and International Architecture
Awards in 2009 (Vo Trong Nghia Architects).
99
Figure 9-3: Bamboo architecture in Vietnam. Source: (ArchDaily, 2013).
blooming bamboo house, h & p architects
Completed in 2013 by H&P Architects, the Blooming Bamboo House in Hanoi was designed to withstand major natural disasters common to Vietnam such as tropical storms and floods. The design makes use of 3.3m and 6.6m long bamboo culms with
10cm and 8cm diameter for the structure. The interior was designed to be flexible enough to function as a residential, educational, medical or community center, with the potential to be expanded, if needed. The façade surfaces incorporate bamboo slats that create openings throughout the entire surface, resulting in a continuous cross-ventilation
100 (Figure 9-3). The house can be built within 25 days, costing as low as $2,500, proving bamboos unique quality of easy constructability and affordability (www.hpa.vn).
The project was awarded the Red Dot Award in 2018, American Architecture
Prize of 2017, German design award special 2017; R+D Awards 2016, Architizer A+
Award 2016 (Special Mention), Green Good Design Award 2015, WAN Small Spaces
2014 Award, IAA Award 2014, and many others (www.hpa.vn).
bangladesh
topography
Bangladesh, a deltaic plain situated at the confluence of the Ganges and
Brahmaputra, is located in south-east Asia bordered by India on the north, east and west, and opens on to the Bay of Bengal toward the south. The topography of the country primarily consists of deltaic lowlands, a mountainous region on the south-east, and highlands on the north-east and north-west. The lowland plains are at an elevation of only 2-13m above sea level, which is why according to UNDP statistics (2004)
Bangladesh ranks sixth as the most flood-prone country in the world.
The lowlands further decrease gradually toward the south where it merges with the Bay of Bengal. This low-lying floodplain consists of rich, alluvial soil making up nearly 32% of the total land area of the country. On the other hand, the hill tracts of south-east, located in Chittagong district, rise up to a height of 600-900m above sea level (Rashid, 1991).
Consisting of steep, longitudinally oriented mountainous ridges and valleys, springs, lakes and dense forests, this region is part of a much larger mountain chain extending from the west of Myanmar to the eastern Himalayas in China. Sandstone and shale are
101 the primary constituents of the mountains (Hutchinson, 1909), which remain covered by virgin evergreen and deciduous forests. The numerous rivers crisscrossing through the region were once the only mode of transportation through the inaccessible mountain ranges. The Chittagong Hill Tracts, predominantly inhabited by a growing indigenous population, consist of three hill districts of Khagrachari in the north, Rangamati in the middle and Bandarban in the south. The highlands of north-west, called the Barind Tract, are one of the oldest terrains of the country. These are characterized by reddish-brown clay soil, lack of vegetation and high elevation (Rashid, 1991). The north-eastern highlands, located in Sylhet district, are at an elevation of nearly 100m above sea level, and covered with dense rubber plants, tea-gardens, bamboo forests and cane bushes.
Bangladesh has four distinct kinds of vegetation: in the hill tracts of the north-east and south-east regions bamboo and rattan are abundant, the central zone is mostly flat with swampy vegetation, the north-west and south-west regions grow cultivated plants and orchards, and the southern region along the Bay of Bengal is home to the vast mangrove forests of the Sundarbans.
climate
Bangladesh is characterized by heavy monsoon climate with high temperature and humidity during summer months and mild winters. Average summer temperature from March to May is typically around 30°C. Summer heat waves are common during this time, when a low pressure zone is created over West Bengal in India and the surrounding north-western part of Bangladesh due to intense localized surface heating.
This low pressure zone induces strong warm and moist wind from Bay of Bengal to rush inland and mix with the northern cool winds, causing frequent convective thunderstorms
102 called Nor‟wester (Tyagi, 2012). During this time wind speeds can rise to nearly 40 miles
(60km) per hour. With average rainfall varying between 250-750mm, Nor‟westers contribute to nearly 15% of the total annual rainfall (Ahmed and Karmakar, 1993).
The monsoon season in Bangladesh typically continues from June to October, bringing strong southern and south-western trade winds, high humidity and continuous rainfall (Ahmed and Karmakar, 1993). Average precipitation during monsoon ranges from 1200mm toward the west and around 3000mm toward the eastern regions. This is followed by a slight drop in temperature during the day due to incessant rainfall. Average temperature during this time is typically 28° -29°C, but can rise to around 36°C on a clear day (Ahmed, Alam and Rahman, 2016). Due to heavy rainfall landslides are often known to occur in the south-eastern hilly regions of the country. Besides, monsoon floods are common occurrences during this time, causing great damage to crops, livestock and properties.
As the monsoon leaves around mid-October, north and north-eastern cool wind brings in winter, beginning from November to February. Winter is characterized by mild temperature, usually around 20°C, low humidity and light northern winds (Khatun,
Rashid, Hygen, 2016). Mean temperature gradient for winter is oriented south to north, with south being 5°C warmer than the north (Shahid, 2010). Sometimes when the westerly low mixes with the easterly trough it creates a brief spell of winter monsoon
(Khatun, Rashid, Hygen, 2016).
bamboo availability
According to Global Forest Resource Assessment 2005, natural bamboo forest in
Bangladesh covers an area of 211,373 ha, mostly in the south-eastern hilly region of
103 Chittagong, while bamboo plantation around the hilly tea estates of Sylhet in the north- eastern region of the country and the villages covers an area of 10,118 ha and 270,000 ha respectively (FAO, 2005). However, bamboo is found to grow more or less everywhere in Bangladesh except the mangrove forest of the Sundarbans. Melocanna baccifera is the species of bamboo predominantly found in Bangladesh. With an area of
90,000 ha this species covers nearly 70-90% of the total bamboo forest of the country
(Banik, 1994). More than 33 species of bamboo grow in Bangladesh, out of which 7 occur naturally in forests and 26 are found in plantation areas in villages (Banik, 2000).
Bamboo is used in Bangladesh as edible young shoots in villages, an ingredient in medicine, a raw material in construction, scaffolding, handicrafts and furniture-making, utensils, pulp and paper industries, production of rayon etc. (Banik, 2000). People in the northern districts of the country extensively use branches, leaves and rhizomes of bamboo as fuel wood (FAO, 2005). However, nearly 90% of the total annual bamboo harvest of the country is used in housing construction (Boa, E.R. and Rahman, M.A.,
1987).
bamboo architecture in bangladesh
Bamboo houses in rural areas of Bangladesh typically incorporate woven bamboo mats as walls, structural bamboo posts, and bamboo paneling for walls or partitions. With simple chemical preservatives these walls are made to last for 15-20 years (ADPC, 2005).
104 meti handmade school, anna heringer
Completed in 2005 for the NGO, Dipshikha Society for Village Development,
METI School in Rudrapur, Bangladesh adopts bamboo as both a structural element and a façade treatment to create a durable and comfortable learning space. The ground floor incorporates mud-wall construction with strategically placed windows and doors to allow light and airflow. The ground floor with its the thick earth walls, opening toward the back into a system of „caves‟, is designed for exploration and concentration. In contrast, the light and airy first floor uses bamboo posts as structural frames, with beams made of four layers of bamboo joined together, tied with a vertical and a diagonal bamboo post toward the edges and anchored to the mud wall. Bamboo was used because of its high tensile strength to withstand strong winds and earthquake. The façade articulation juxtaposes these vertical bamboo frames with horizontal slatted bamboos to create a stimulating experience. The horizontally slatted windows of the first floor are camouflaged neatly with the surface treatment of the wall. The bamboo slats throughout the surface allow light to filter in and generate a continuous cross-ventilation (Figure 9-
4). The ceiling, the roof and the façade of the structure utilizes 2,300 bamboo poles and the façade further utilizes 2,500 bamboo slats. The total construction cost was $22.835
(Lim, 2007). The building received the prestigious Aga Khan Award for Architecture in
2007 and the Curry Stone Design Prize in 2009.
105
Figure 9-4: Bamboo architecture in Bangladesh. Source: (ArchDaily, 2010).
desi center, anna heringer
Based on the idea that the concept of a design and its technical installation should be easy to comprehend and apply, DESI (Dipshikha Electrical Skill Improvement)
Center, a vocational institute for electrical training was designed using earth and bamboo. The strategy was to fuse locally available resources and skill with modern knowledge through community participation to create a design that would have a positive environmental impact and restore the cultural identity. The first floor incorporates a lattice-work of bamboo slats allowing light and air to filter in. This technique of wickerwork is used extensively in Bangladesh in making furniture, baskets and other household items. The façade of the classrooms in the first floor is made up of closely
106 spaced bamboo slats to create a constant airflow (Figure 9-4). The design uses small solar panels to power the building, which was adequate enough owing to the building‟s passive heating and cooling techniques along with its reliance on natural light and ventilation.
florida, usa
topography
At a maximum of 105m (345 feet) elevation above sea level, the state of Florida is one of the most biologically diverse places in the US. The peninsula is mostly consisted of sandy or loamy soil on top of a deep limestone foundation. This limestone base has given rise to several unique geological features including underground rivers, vast springs and aquifers. Orlando has the largest concentration of lakes in the state, the largest being Lake Okeechobee. Of the many rivers, most are short and partly subterranean. However, over the years the state‟s agricultural and extraction industries have contributed to large scale changes in its natural landscape and resources. Tung oil, citrus and sugarcane were some of the top agriculture crops being produced in the
1900s, along with tomatoes and strawberries. Land clearing for farm fields, introduction of invasive species, altered drainage patterns due to drying of wetlands are some of the destructive outcomes of intensive agriculture (Stone and Legg, 1992). On the other hand, mining industries have resulted in erosion of natural land cover and soil composition. Large scale deforestation of Florida‟s old growth trees, particularly cypress and pine forests, has resulted from its lumber industries (Florida National Areas
Inventory, 2015). In fact by 1930 many of the forests were left entirely depleted due to
107 the lumber industries abandoning them without replanting (Florida Forestry Association,
2016).
climate
Most of Florida falls under humid subtropical zone with extremely warm-humid summers and mild winters. The southern part is mostly tropical savannah with high precipitation during the summer months. Average annual maximum temperature in
Florida is 28°C during warmest months of July or August, and average minimum is 18°C during the coldest month of January. Because of its proximity to the Atlantic Ocean and the Gulf of Mexico, along with large lakes, the seasonal temperatures in the state remain fairly moderate, particularly in the winter months. In fact the Atlantic coast typically experiences a higher winter temperature than the Gulf coast since wind coming from the
Atlantic over to the Gulf remains relatively warmer, whereas the prevailing winter wind coming from land in the west is cooler (The National Climatic Data Center). Summer winds come from south, south-east and south-west bringing humid air inside homes.
During fall and early spring prevailing wind directions are east, south-east and north-east
(Black, 1993). Average wind speed is 7.6 mph and average relative humidity is 73%.
During the middle of the day relative humidity ranges from 50-60%, while the cooler times of the day experiences an increased relative humidity range of 70-80%. This means that the warmer periods of the day has far more moisture in air than the cooler periods, leading to uncomfortable daytime hours. Consequently, homes in Florida tend to consume high amount of energy, in the form of air-conditioning which accounts for nearly 36% of the total energy used in the state (Black, 1993). The extended period of
108 sunshine that Florida enjoys, typically from April to November, tends to extend air- condition use in homes well beyond summer months (Black, 1993).
Florida is the second wettest state in USA, behind Louisiana. Average annual precipitation ranges from 1870mm to 760mm. The wettest parts of the state are The
Panhandle and southeast Florida, while the driest are Florida Keys and Cape Canaveral
(The National Climatic Data Center). Due to frequent thunderstorms precipitation in
Florida is often variable, meaning adjacent areas may receive vastly different amounts of rainfall at any given time (McCollum et al, 2002). Precipitation is highest, and typically comes with thunderstorms, during summer months, beginning from May to November, and lowest in spring.
Florida is extremely vulnerable to frequent tropical storms and hurricanes.
Hurricane season spans from mid-August to late October and is found to be dependent upon two critical phenomena called El Nino and La Nina. According to Bove and Elsner
(1998) El Nino is “an anomalous warming of the eastern tropical Pacific Ocean.” Every four to seven years the equatorial region of the Pacific Ocean will experience sudden warming of as high as 9°C above average temperature, disrupting climate patterns and often bringing hurricanes. This is called El Nino. La Nina is the opposite event where the same area of the Pacific Ocean experiences an abnormal cooling. El Nino contributes to heavy rainfall in spring and is typically followed by tornados and hurricanes. NOAA‟s storm data reveals that in central and south Florida from 1950 to 2009 nearly 15 tornados occurred per year because of El Nino (www.weather.gov).
109 bamboo availability
Bamboo was first introduced into the continental United States from China in
1882 through Alabama, from where it spread to the entire southeastern Coastal Plain. It is said that soon after its introduction Thomas Edison started experimenting with light- bulbs using bamboo filaments (Farrelly, 1984). Chicago Daily Tribune (1957) reported that filament of Florida bamboo was a common element in all electric lamps for a long time. As of yet, USA still does not have any large-scale bamboo plantation. Within small- scale plantations, there are 21 genera of temperate or running bamboo currently being cultivated in the US, of which the three main genera that are oriental in origin but have been naturalized to the West are Phyllostachys, Arundinaria and Sasa (Young, 1961).
Avery Island in Louisiana has a considerably large Moso bamboo plantation (Gernot,
2016). There are 11 genera of tropical or clump-type bamboo being cultivated in USA of which Bambusa and Dendrocalamus are predominant and grows well in southern
Florida (Young, 1961). In fact, Florida is a region where both temperate and tropical variety of bamboo is found to grow well.
Despite suitable climate and topography for bamboo growth uses of bamboo in
Florida, as well as all over USA in general, have been limited to ornamental purposes, furniture-making, visual screening for privacy and sound barriers.
bamboo architecture in florida
Examples of well-designed bamboo architecture in Florida are extremely rare.
Except some beach-side structures along the coasts of Florida, bamboo is hardly utilized in construction. However, over the last few years bamboo as a flooring material has
110 gained popularity in the domestic market due to various bonding and laminating methods. Bamboo lumber has recently been recognized as a structural component in
USA by ASTM D5456: Standard specification for evaluation of structural composite lumber products (ASTM, 2013). Most of the bamboo being used in America comes from
Colombia or China. While it might seem to lead to a high energy consumption with a higher cost to export bamboo from other countries, the low energy used in the harvesting and processing of bamboo more than make up for the ecological footprint (Gernot,
2016).
comparative analysis
Comparing the climatic and technological data it is evident that while the three regions are quite similar with regards to their climatic features, such as daily summer temperature, rainfall, relative humidity and wind flow, they have varied traditions of bamboo architecture and availability of technological and material resources to construct an adaptive façade system. Climatically all three places experience summer highs of around 300 C (860 F) and average rainfall of more than 280 mm (11 inches) during summer (Figure 9-5). While rainfall is seen to occur more or less all around the year in
Vietnam and Florida, it is more concentrated during the summer months in Bangladesh, which is when heavy thunderstorms called Nor‟westers occur. In terms of humidity, only
Florida experiences a noticeable fluctuation between daytime and nighttime relative humidity. However, for all three of them, as the daytime temperature gradually increases the corresponding relative humidity decreases, since hot air has a greater capacity to hold moisture. Conversely, as the temperature begins to decrease during the evening
111 the corresponding relative humidity gradually increases. As explained earlier in the chapter, the dominant wind direction for all three of them is south-east.
Figure 9-5: Comparative analysis of climatic features. Source: (Climate consultant, 2019).
112 As explained previously in chapter 6, the wind rose diagrams indicate that all three locations have summer winds coming from the south-east direction, which often corresponds with a higher velocity.
Regarding bamboo architecture, Vietnam has seen a lot of innovative designs over the years that utilize the true potential of bamboo as a construction material in terms of its tensile strength, aesthetic quality and so on. In Bangladesh, the tradition of bamboo architecture is still restricted to vernacular houses in rural villages. Urban centers of the country hardly get to experience well-designed bamboo architecture anywhere. In Florida, the situation, as indicated before, bamboo is mostly used for flooring and ornamental purposes. However, due to that reason bamboo veneer is widely available all over USA, while in the other two countries the veneer itself is not a common material of use, and would have to be made commercially or imported.
113
chapter 10
future research and
conclusion
114 The unique quality of responsiveness inherent in bamboo, coupled with its easy constructability, makes it a favorable material to investigate deeper into adaptive envelopes. In order to gain increased control over the nature of responsiveness, bamboo can potentially be bred to be more reactive and, at the same time, possess greater material durability under different weathering conditions of sunlight, radiation, rainfall etc.
Additionally, a deeper understanding of plant biology will certainly help guide the research toward achieving a more controlled performance regarding material behavior.
Understanding the different potentials of the particular research it can be carried forward focusing on manipulating the orientation of bamboo grains on a more micro level to further control the curvature of the bilayer composite. Similarly, instead of a homogenous cellulose film, passive layers with different grain directions can be selected to observe how the composite reacts as the grain directions in both the active and passive layers influence each other, possibly resulting in interesting and unpredictable results. One of the limitations to working with bamboo being its vulnerability to fungal attack, exploring adhesives that can double as preservatives against fungal and insect attacks will contribute to increasing the durability of the composite. Due to limitations of time the exploration of façade pattern configurations needed to be finished at a certain point in order to move ahead with the later phases of the research, but there is no denying that there is potential to generate more optimal configurations with better performance, particularly in response to inclement weather including heavy rain, storm, hurricane and so on. Moreover, using a monitoring and tracking system to monitor the deflection in the composites more accurate results could be achieved. Apart from veneer deflection, material degradation, fading of color and strength of the bonded composite could also be monitored over a one-year period to assess their long-term performance. The motion sensing method to track the hygroscopic response in wood samples in real-time by
115 Abdelmohsen et al. (2018) can be adopted to express the physical material on a computational interface to get accurate measurements.
Up until very recently, facades in architecture that are able to adapt themselves in response to changing climatic conditions relied on technically imposed solutions associated with complex automated mechanisms. The low-tech and no-tech passive strategies of adaptive façade design based on material responsiveness were still in their infancy. It goes without saying that passive strategies minimize energy and material use while maintaining occupant comfort. This is precisely why such passive methods require a greater emphasis today as we investigate deeper into the realms of Responsive
Architecture. This can potentially lead to an architecture that is forever in harmony with fluctuating internal and external environments, enhancing our physical and psychological comfort and stimulating our visual experience by providing us with a visual reference to the dynamic environmental conditions that surround us. The thesis certainly adds to our understanding of the performance of climate responsive materials as façade control elements.
appendix
generating grasshopper modules
1. Creating hexagonal modules with user defined vertical and horizontal radii,
number of columns and rows, and the spacing between the modules using
Number Sliders.
2. Determining horizontal and vertical offsets between adjacent, where the
vertical offset corresponds to the vertical radius of the hexagons, and the
horizontal offset is the horizontal radius times the cosine value of 45° (Figure
A-1).
Figure A-1: Generating hexagonal parameters. Source: ( Grasshopper 2018)
117 3. Setting up a YZ-grid with a series of points in the Y and Z coordinates that act
as the center points of the hexagons, with the help of a Series component.
4. Shifting every alternate column up by adding the spacing factor so that the
modules, instead of lying side-by-side, are positioned into the corners of the
one above and below it (Figure A-2).
Figure A-2: Creating hexagonal modules. Source: ( Grasshopper 2018)
5. Scaling the hexagons to the desired proportion (Figure A-3).
Figure A-3: Scaling hexagonal modules. Source: ( Grasshopper 2018)
118
creating triangular flaps
1. Creating triangles using the vertices of the hexagons and a Nurbs curve
drawn along the curved path of the veneers (Figure A-4).
Figure A-4: Creating triangles and NURBS curve. Source: ( Grasshopper 2018)
2. Creating a surface from the Nurbs curve by sweeping it along a rail with the
Sweep component.
3. Projecting the triangle created in the previous step onto the newly-created
surface.
4. Splitting the surface using the projected triangle into three distinct parts
Figure A-5: Creating triangular surfaces. Source: ( Grasshopper 2018)
119 5. Using an attractor point in front of the modules, whose distance to the
modules determines the open condition of the surfaces (Figure A-6).
Figure A-6: Opening the triangular surfaces with the help of an attractor point. Source: ( Grasshopper 2018)
120 glossary
Active façade system: A façade system that undergoes a dynamic behavior with the help of external stimuli and controls
Adaptive envelope: Building envelope that has the potential to, repeatedly and reversibly, change itself with changing environmental parameters
Automated: Operated by an automatic system
Biomimetic architecture: A contemporary philosophy of architecture that seeks solutions for sustainability in nature by taking inspiration from biological systems and understanding the rules governing them
Cross ventilation: A natural method of cooling that relies on wind force entering through an inlet on a wall surface and exiting out through an outlet on the opposite wall or roof
Grain: The longitudinal arrangement of fibers in wood, paper, bamboo etc.
High-tech: Involving complex, advanced, and often cutting-edge, technology
Hygroscopy: The property of certain materials to absorb moisture from air and undergo a physical deformation
Low-tech: Involving simple, often traditional, technology
Morphological features: The specific features of the form and structure of biological organisms
Non-reactive: Lacking reaction or a response to an external stimulus
Orographic monsoon: A monsoon period when rainfall is caused by a change in elevation, primarily due to mountains
Passive façade system: A façade system that undergoes a dynamic behavior without the help of any external energy
121 Responsive Architecture: Architecture than can physically transform itself as a response to any particular environmental change
Smart materials: Designed materials that have properties that can be significantly changed in a controlled fashion by external stimuli
Synthetic polymer: Man-made polymers
Venturi effect: The phenomenon that occurs when a fluid that is flowing through a pipe is forced through a narrow section, resulting in a pressure decrease and a velocity increase
122
bibliography
Addington, D. M., & Schodek, D. L. (2005). Smart Materials and New Technologies: For the Architecture and Design Professions. Burlington, MA: Architectural Press. Ahmed, R. and Karmakar, S. (1993). Arrival and Withdrawal Dates of the Summer Monsoon in Bangladesh. International Journal of Climatology, vol. 13, 727-740. Ahmed, R., Alam, M.S., Rahman, M. (2016). Long-Term Trend of the All-Bangladesh Summer Monsoon Rainfall, and its Association with the ENSO Index. Journal of Environment and Earth Science, vol. 6, No.4. ADPC. (2005). Hand Book on "Design and Construction of Housing on Flood Prone Rural Area of Bangladesh". Bainbridge, D. and Haggard, K. (2011). Passive solar architecture: heating, cooling, ventilation, daylighting and more using natural flows. Chelsea Green Publishing, Baldwin, J. (1997). Buckyworks: Buckminster Fuller‟s Ideas for Today. John Wiley & Sons. Banik, R.L. (1994). Distribution and ecological status of bamboo forests of Bangladesh. Bangladesh Journal of Forest Science 23(2): 12-19. Banik, R.L (2000). Silviculture and Field-Guide to Priority Bamboos of Bangladesh and South Asia. Publication of Bangladesh Forest Research Institute, Chittagong. ISBN984-753-033-3. Baweja, V. (2014). Otto Koenigsberger and the Development of Tropical Architecture in India 1939-1951. ARRIS: The Journal of the Southeast Chapter of the Society of Architectural Historians, 25. 2-17. Behari B. (2006) Status of Bamboo in India. Compilation of papers for preparation of national status report on forests and forestry in India. Survey and Utilization Division, Ministry of Environment and Forest, 109–120 Beaman, Michael, and Bader, Stefan. (2010). Responsive Shading | Intelligent Façade Systems. In Proceedings of the 30th annual conference of the Association of Computer Aided Design in Architecture (ACADIA), New York, 263-269 Black, R.J. (1993). Florida climate data. University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS.
123
Boa, E.R.and Rahman, M.A. (1987). Bamboo blight and the bamboos of Bangladesh. Bulletin 1, Forest Pathology series. Chittagong: BFRI. Bove, M.C. et al. (1998). Effect of El Niño on U.S. Landfalling Hurricanes, Revisited. Published in the Bulletin of the American Meteorological Society, 79, 2477-2482. Brand, S. (1995). How Buildings Learn: What Happens After They‟re Built. Penguin (Non-Classics), 10. Buckingham, Kathleen. (2009). Deep roots in culture, shallow roots in nature: identifying sustainable bamboo management challenges for China and the implications for multidisciplinary research. In International Association of Agricultural Economists Conference, pp. 16-22. Buckingham, Kathleen. (2015). The Legitimacy of Bamboo Certification: Unpacking the Controversy and the Implications for a “Treelike” Grass. Society and Natural Resources, 28(6), 575-592. Célino, A. et al. (2014). The hygroscopic behavior of plant fibers: a review. Frontiers in chemistry, 1, 43. Cima, R. J., Library Of Congress. (1989). Federal Research Division. Vietnam: A Country Study. Washington, D.C.: Federal Research Division, Library of Congress Das, M. et al. (2008). Bamboo taxonomy and diversity in the Era of molecular markers. Advances in Botanical Research. 47:225–268 Dinwoodie, J.M. (2000). Timber, Its Nature and Behavior. London: Taylor & Francis. "Edison Lured to Florida by Tall Bamboo." (1957). Chicago Daily Tribune (1923-1963), Jan 27, 1-d10. http://ezaccess.libraries.psu.edu/login?url=https://search- proquest-com.ezaccess.libraries.psu.edu/docview/180042246?accountid=13158. Elghawaby, Mahmoud. (2012). Breathing Façades: A New Concept to Create Dynamic Thermal Ambiances in Buildings Located in Hot Climates. In Ambiances in action/Ambiances en acte (s)-International Congress on Ambiances, Montreal 2012, 215-220. FAO (2005). Country Report on Bamboo Resources Bangladesh. Global Forest Resources Assessment 2005, Working Paper 112. Rome 2006. Farrelly, D. (1984). The Book of Bamboo. San Francisco, CA: Sierra Club Books.
124
Frey, Pierre. (2011). Construire en bamboo, Simon Vélez. In L'Architecture d'Aujourd'hui, 387, 78-85. Gernot, M., et al. (2016). Building with Bamboo: Design and Technology of a Sustainable Architecture. Basel, Switzerland: Birkhäuser. Givoni, B. (1976). Man, Climate, and Architecture. New York: Van Nostrand Reinhold. Goyal, AK et al. (2012). Inventorying bamboo biodiversity of North Bengal: a case study. Journal of Fundamental and Applied Science 1:5–8 HanKun, Wang et al. (2010). Measurement of Saturation Point of Bamboo Fiber from Different Age. Journal of Nanjing Forestry University (Natural Sciences Edition), 34(6), 91–94. Hasselaar, B. L. H. (2006). Climate Adaptive Skins: Towards the new energy-efficient façade. In Management of Natural Resources, Sustainable Development and Ecological Hazards, 99. WIT press. Holstov, Artem, Graham, Farmer, and Bridgens, Ben. (2015). Hygromorphic Materials for Sustainable Responsive Architecture. Construction and Building Materials, 98, 570-582. Holstov, Artem, Graham, Farmer, and Bridgens, Ben. (2017). Sustainable Materialisation of Responsive Architecture. Sustainability 9 (3), 435-455. Huang et al. (2016). Thermal and hygroscopic expansion characteristics of bamboo. Proceedings of the Institution of Civil Engineers, Structures and Buildings. Bath: University of Bath. Pure [Online] Huang, Zujian, Yimin Sun, and Florian Musso. (2017). Experimental Study on Bamboo Hygrothermal Properties and the Impact of Bamboo-Based Panel Process. Construction and Building Materials 155 (November), 1112–25. Huang P, Chang W, Ansell MP et al. (2018) Thermal and hygroscopic expansion characteristics of bamboo Proceedings of the Institution of Civil Engineers – Structures and Buildings 171(6): 463–471 Huntington, Ellsworth. (1922). Civilization and climate. Yale University Press. Hutchinson, R. H. S. (1909). Chittagong Hill Tracts: District Gazetteer. Allahabad, India: Pioneer Press.
125
Jiang, Zehui et al. (2012). Sensitivity of Several Selected Mechanical Properties of Moso Bamboo to Moisture Content Change under Fiber Saturation Point. BioResources, 7(4), 5048-5058 Khatun,A., Rashid, B., Hygen, H. O. (2016). Climate of Bangladesh. MET report. Bangladesh Meteorological Department. No. 08 Lessard, G., and Chouinard, A. (1980). Bamboo research in Asia: proceedings of a workshop held in Singapore, 28-30 May 1980. IDRC, Ottawa, ON, CA. Lim, J. (2007). Hand-Made School, Rudrapur, Bangladesh. 2007 On Site Review Report. 2007 Award Cycle for Aga Khan Awards. Limon, Jafor Ahmed, and Shabbir Ahmed Osmani. (2017). An Analytical View on Variation of Humidity, Temperature and Rainfall in Bangladesh. Journal of Geotechnical Studies 2 (1), 1-7. Liu, Rui, & Li, Yushun. (2015). Bamboo-steel composite structures. In Proceedings of the ARCC 2015 Conference Architectural Research Centers Consortium Future of Architectural Research, Chicago, 37-44. Lonsdale, James, Lee, Samuel. (1883). The Works of Virgil. London: Macmillan and Co. Loonen, Roel et al. (2013). Climate Adaptive Building Shells: State-of-the-art and Future Challenges. Renewable and Sustainable Energy Reviews, 25, 483–493 López, Marlén, Ramón Rubio, Santiago Martín, Ben Croxford, and Richard Jackson. (2015). Active Materials for Adaptive Architectural Envelopes Based on Plant Adaptation Principles. Journal of Facade Design and Engineering 3 (1), 27–38. McCollum, J.R. et al. (2002). Evaluation of biases of satellite rainfall estimation algorithms over the continental United States. Journal of Applied Meteorology. 41: 1065-1080. Menges, A., Reichert, S. (2012). Material capacity: embedded responsiveness. Architectural Design. 82 (2), 52-59 Ministry of Natural Resources and Environment (MONRE). 2008. Viet Nam Assessment Report on Climate Change (VARCC). Institute of Strategy and Policy on Natural Resources and Environment. Murali, Sindhu. (2013). Design of a Climate Adaptive Façade System Using Bamboo for Urban India. Master‟s Thesis, Delft University of Technology.
126
Nadkarni, M. & Kuehl, Y. (2013) Forests beyond trees: NTFPs as tools for climate change mitigation and adaptation. INBAR Working Paper No. 74. International Network for Bamboo and Rattan (INBAR), Beijing China. Negroponte, N. (1975). Soft Architecture Machines. In Intentionalities. Cambridge: MIT Press. Nguyen Thi Bich Ngoc. (2004). Bamboo Preservation: Some Simple Methods Used in onstruction. Le Thanh Chien, Guido Broekhoven, Nguyen Thi Bich Hue, Vu Van Dung: NTFP Newsletter. Pp. 8. Olgyay, V. (1963). Design with climate: Bioclimatic approach to architectural regionalism. Princeton: Princeton University Press Park, Kyung-Soon, Sang-Woo Kim, and Seong-Hwan Yoon. (2016). Application of Breathing Architectural Members to the Natural Ventilation of a Passive Solar House. Energies 9 (3), 214. Pawlyn, M. (2011). Biomimicry in Architecture. London, United Kingdom: RIBA Publishing. Phan, S. (2004). Export of Vietnam Bamboo and Rattan Handicrafts. Le Thanh Chien, Guido Broekhoven, Nguyen Thi Bich Hue, Vu Van Dung: NTFP Newsletter. 2: 4- 5 Rashid, H. (1991). Geography of Bangladesh . 2nd edition. Dhaka: The University Press. Reichert, Steffen, Menges, Achim and Correa, David. (2015). Meteorosensitive Architecture: Biomimetic Building Skins Based on Materially Embedded and Hygroscopically Enabled Responsiveness. Computer-Aided Design, Material Ecology, 60 (March), 50–69. Reyssat, E., Mahadevan, L. (2009), Hygromorphs: From Pine Cones to Biomimetic Bilayers, J. R. Soc. Interface, 6 (39), 951–957. Shahid, S. (2010). Recent trends in the climate of Bangladesh. Climate Research. 42(3): 185-193. Shim, Brigitte. (2010). Green School, Bali, Indonesia. On-Site Review Report. Aga Khan Award for Architecture. Simpson, William and TenWolde, Anton. (1999). Physical Properties and Moisture Relations of Wood. Chapter 3. Wood handbook—wood as an engineering
127
material. Madison, WI. US Department of Agriculture Forest Service, Forest Products Laboratory, Report FPL–GTR-113, 463. Straaten, J. F. (1967). Thermal Performance of Buildings. Amsterdam: Elsevier Publishing Company. pp 228-283. Sung, Doris. (2010). Skin Deep: Making Building Skins Breathe with Smart Thermo bimetals, Where Do You Stand. In Proceedings of the 2011 ACSA National Conference, Washington, DC: ACSA Press.145-152. Sung, Doris. (2016). A New Look at Building Facades as Infrastructure. Engineering 2 (1), 63–68. Tomalang, F.N. et al. (1980). Properties and utilization of Philippine erect bamboo. In International Seminar on Bamboo Research in Asia. Singapore, May 28-30. Singapore: International Development Research Center and the International Union of Forestry Research Organization. pp. 266-275. Tyagi, Ajit, D. R. Sikka, Suman Goyal, and Mansi Bhowmick. (2012). A satellite based study of pre-monsoon thunderstorms (Nor‟westers) over eastern India and their organization into mesoscale convective complexes. Mausam 63, no. 1: 29-54. USAID. (2017). Climate Change Risk Profile Vietnam. Climate Change Adaptation, Thought Leadership and Assessments (ATLAS) Task Order No. AID-OAA-I-14- 00013. Vitruvius. (1931). On Architecture [De Architectura]. Cambridge, MA: Harvard University Press. Vo, V. (2010). Bamboo for Exterior Joinery. A research in material properties and market perspectives. Thesis report of Larenstein University. BSc „International Timbertrade‟. Vu Van Dung, Le Viet Lam. (2004) Re-identify and Update Scientific Names of some Bamboo Species in Vietnam. Le Thanh Chien, Guido Broekhoven, Nguyen Thi Bich Hue, Vu Van Dung: NTFP Newsletter. 2: 9-10. Vu Van Dung, Le Viet Lam. (2005). Research results of bamboo resources of Vietnam. Forestry Science and Technology. Hanoi. Thang 4. Young, R. A., Haun, J. R. and Floyd, M.A. (1961). Bamboo in the United States: Description, Culture, and Utilization. No. 193. US Department of Agriculture, Crops Research Division, Agricultural Research Service.
128
websites
Bamboo. n.d. Accessed February 16, 2018. https://www.britannica.com/plant/bamboo. Groundfloor - Where the Building Meets the Town. n.d. Accessed January 21, 2018. http://www.iaacblog.com/programs/groundfloor-where-the-building-meets- the-town/. HygroScope: Meteorosensitive Morphology | Achimmenges.Net. n.d. Accessed January 21, 2018. http://www.achimmenges.net/?p=5083. HygroSkin: Meteorosensitive Pavilion | Institute for Computational Design and Construction. n.d. Accessed January 21, 2018. http://icd.uni- stuttgart.de/?p=9869. Feeney, John. (1974). The Magic of Mashrabiyas. Accessed March 24, 2018. http://archive.aramcoworld.com/issue/197404/the.magic.of.the.mashrabiyas.htm Frearson, Amy. (2012). Wind and Water Bar by Vo Trong Nghia. Accessed January 21, 2018. https://www.dezeen.com/2012/09/03/wind-and-water-bar-by-vo-trong- nghia James, Caroline. (2010). The Green School. Accessed February 15, 2018. https://www.domusweb.it/en/architecture/2010/12/12/the-green-school.html Millard, Bill. (2015). The Poetry, Pitfalls and Potential of Kinetic Façades. Accessed March 25, 2018. http://www.enclos.com/site-info/news/the-poetry-pitfalls-and- potential-of-kinetic-facades-part-two Naidoo, Ridhika. (2010). Karawitz Architecture: Passive House, Bessancourt. Accessed January 21, 2018. https://www.designboom.com/architecture/karawitz- architecture-passive-house-bessancourt. Raad, Hazem. (n.d.). T4 Madrid Barajas Airport | Richard Rogers Partnership + Estudio Lamela. Accessed March 24, 2018. https://www.arch2o.com/t4-madrid-barajas- airport-rshp. Rogers Stirk Harbour + Partners. (2017). Selected Projects 2017. Accessed March 24, 2018. https://www.rsh-p.com/publications. Stanton, Jeffrey. (1997). EXPO 67 – Architecture. Accessed March 24, 2018. http://www.westland.net/expo67/map-docs/architecture.htm.
129
United State Green Building Council. (2012). The 2012 Greenest School on Earth: Green School Bali. Accessed January 21, 2018. https://www.usgbc.org/articles/2012-greenest-school-earth-green-school-bali. Walker, C. (2014). Bamboo: A Viable Alternative to Steel Reinforcement?. ArchDaily. Accessed 22 October 2018. https://www.archdaily.com/513736/bamboo-a-viable- alternative-to-steel-reinforcement/ Velez, Simon. (2014). Personal interview with Marcus Faires. Accessed January 19, 2018. https://www.dezeen.com/2014/07/21/simon-velez-giant-bamboo- architecture-domaine-de-boisbuchet-interview/