KAGE: Kinetic Air-Water Gathering Envelope

Kinetic Air-water Gathering Envelope

Alta Scuola Politecnica - XV cycle

AKNOWLEDGEMENTS

We take this opportunity to express our profound sense of gratitude to everyone whose support and assistance led to completion of this project, as this work is an outcome of the combined efforts of many during the most uncertain times.

First and foremost, we thank Alta Scuola Politecnica, for providing a platform that made it possible to get to know and work with motivated and driven intellectuals; students, professionals as well as mentors and facilitating the research and development of the project. Also, the generous financial support is highly appreciated.

This work wouldn't have been possible without the guidance of our principal academic tutor, Prof. Stefano Mariani (Dept. of Civil and Environmental Engineering - Politecnico di Milano) who in spite of his very busy schedule and commitments, always made himself available to guide us throughout the project duration. His patience with us and belief in this project, that since the beginning turned out to be very unconventional and somehow incoherent to the proposed design brief, is praiseworthy. We feel indebted to him for encouraging us to go out of our comfort zones to explore opportunities that otherwise would have seemed impossible to pursue.

We also express our deepest gratitude to Prof. Stefano Invernizzi (Dept. of Structural, Geotechnical and Building Engineering - Politecnico di Torino) for being a kind mentor and a rational critic. His lucid feedbacks since the very conception phase have been fundamental for a mere idea to see the light of the day. His expectations and belief in us

and the project always kept us motivated and on our toes.

A personal vote of thanks from PoliTo students for being a reference point, a tireless motivator and for having believed in our potentialities more than we did.

A sincere appreciation to Prof. Francesco Braghin (Mechanical Engineering Dept. - Politecnico di Milano) and Prof.

Emiliano Descrovi (Dept. of Applied Science and Technology - Politecnico di Torino) whose technical expertise and assistance helped the project take its final shape.

A heartfelt acknowledgement to nonno Guido, who selflessly took this project to heart like it was his own and without who it would not have been possible to build a working prototype. Thank you for taking part in this important chapter of our lives and for enriching it with your experience and curiosity: I never stop learning from you.

A nonno Guido, che ha preso a cuore questo progetto come fosse suo e senza il quale non sarebbe stato possibile costruire un prototipo funzionante. Grazie per aver preso parte a questo importante capitolo della nostra vita e per averlo arricchito con la tua esperienza e curiositĂ : non si smette mai di imparare da te.

This project has been an unexpected journey, with the pandemic limiting the conventional ways of group work, yet a highly enriching experience for us all where we explored novel means to work as a team across continents, getting the best out of each other. We duly acknowledge the help and guidance, direct or indirect, of everyone, that led to the completion of our project during thesetesting and unpredictable times.

Mechanical Engineering

BABAK MOHAMMADI Sustainable Architecture and Landscape Design Architecture, Construction City

ERICK KATSUMI SETOGUCHI

ALI REZA HAKIM

Space Engineering

Architecture, Built Environment, Interiors

ANDREA ANDORNO

STEFANO DE SANTI

CHIARA TASSINARI

TUTORS

Interior and Spatial Design

Architecture, Built Environment, Interiors

TEAM

MATTEO ORNATO

STEFANO MARIANI

Department of Civil and Environmental Engineering Politecnico di Milano

STEFANO INVERNIZZI Structural, Geotechnical & Building Engineering Politecnico di Torino

FRANCESCO BRAGHIN Mechanical Engineering Politecnico di Milano

EMILIANO DESCROVI

Department of Applied Science and Technology Politecnico di Torino

CONTENTS

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02 OUR MISSION

2.1 Demographic Growth 2.2 Slums Growth 2.3 Informal Comunities 2.3.1 Makoko the Floating Slum 2.3.2 Karachi Community 2.3.3 TORRE DAVID, the emblematic case study

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03 REQUIREMENTS

3.1 Stakeholders Analysis 3.2 Power-Level of Interest Matrix 3.3 User Requirements 3.4 Design Requirements

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CONCEPT FUNDAMENTALS 5.1 Overview 5.1.1 Torre David

5.2 KAGE Kinetic Air-water Gathering Envelope

STATE OF THE ART

5.2.1 Module Overview 5.2.2 Kinetic building envelope

1.1 Necessity of Sustainable Building Envelopes

4.1 Kinetic Facades

5.3 Mechanism and technical aspects

1.2 Characteristics of Efficient Building Envelopes

4.2.1 Sliding and rotation 4.2.2 Sliding and retracting 4.2.3 Contracting and expanding 4.2.4 Snapping

INTRODUCTION

1.2.1 Sustainability 1.2.2 Energy Efficiency 1.2.3 Material Efficiency 1.2.4 Process Efficiency

1.3 Project Description 1.4 Project Objectives 1.5 Expected Result 1.6 Conception and Planning

4.2 Mechanisms

4.3 Fog Harvesting 4.3.1 Warka Water 4.3.1 Dropnet

CONCEPT DEVELOPMENT

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CONCLUSION AND FUTURE DEVELOPMENTS

5.3.1 Snapping tape 5.3.2 Actuation mechanism 5.3.2 Pype system

5.4 Net analysis

5.4.1 Water collection performance 5.4.2 Folding path

5.5 Comparative analysis 5.5.1 Moving rod material 5.5.2 Pipe material 5.5.3 Net mesh

ANNEX construction manual

EXECUTIVE SUMMARY MoBE Climate change and environmental protection are the most significant challenges of our time. Due to the increasing energy consumption of a steadily growing world population, CO2 emissions and therefore greenhouse effect are continuously increasing. Forecasts predict an increase in energy consumption by a factor of 140 in the next 100 years; raw materials as sources of energy will inevitably become scarce. To curb global warming to a maximum of 2°C, CO2 emissions worldwide must be dramatically reduced, resources must be managed in the best possible way and new renewable energy sources must be developed. The building sector provides great potential to reduce CO2 emissions, since more than 30% of the total energy consumption is to maintain thermal comfort in buildings.

The lack of water is another major concern that has become part of the reality in different regions of the world, amplified by social inequality and the lack of sustainable management and use of natural resources. These issues and similar ones are not limited only to rural areas, as even the current urban settings do not sometimes provide an adequate standard of living to their citizens. The lack of housing within cities has stimulated the growth of slums with limited or no access to basic commodities like potable

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water, electricity etc. Over the years, the phenomenon of appropriation has gradually extended from the concept of land to abandoned buildings, which still lack satisfactory thermal comfort conditions.

The current trend of urbanization and demographic growth will further trigger a series of issues and contradictions on a global scale, especially between the built environment in need for expansion and the natural resources. The Department of Economic and Social Affairs of the United Nations predicted a 2 billion increase in the global population by 2050. Also Ricky Burdett and Dejan Sudjic reported that urban areas will accommodate 75% of the world population by the same time. The UN-Habitat on the other hand, in the document named "the challenge of the slums" [8] identified the growth of slums as a planetary phenomenon, predicting that by 2040, 2 billion inhabitants will live in slums.

There is thus an urgent need to recognize the complexity of this reality which is compounding with time and respond to these scenarios with research, innovative technology, and efficient systems in the form of carefully designed building envelopes owing to their potential to improve the energy balance of the building. Although the cost of building envelopes normally comprises a small fraction of the total construction (approximately 20%), their impact is multifaceted. Therefore, the creative development and systematic application of new strategies, products, methods, technologies and tools is imperative. Conventionally, building faรงades have been conceived with invariant geometry and mechanical properties to withstand the environmental excitations. However, the current or projected resource crisis and the smart city context demand the ability to adapt and morph them under a continuously changing external environment, combining this with multi-functionality ensuring not only the energy efficiency of buildings but also a potential to generate energy, collect water and assure streamlined planning, construction and operating processes. The present work thus aims to design an adaptable, modular and multi-functional faรงade system to retrofit building faรงades in diverse geographical, physical and social contexts.

The analysis of the state of the art concerning sustainable solutions, manifested through a variety of kinetic or smart faรงades, brings to light their inclination towards sophisticated functional mechanisms and materiality. This comes

at an economic expense that limits the usage to a privileged class and leaves a major social segment behind. This is synonymous to the limited environmental or social impact of such design solutions, since the existing informal building stock inhabited by the economically weaker sections of the society cannot afford this luxury.

Building further on this awareness, the goal of this project has been maximizing the affordability of the technology through informed design choices along with minimizing the energy required for achieving thermal comfort conditions. The design solution exploits the potential of dynamic building envelopes, tailoring them to cater to the energy and resource needs of existing informal building stock, thus promising a greater positive environmental and social impact. In addition to the reduction of energy demand by exploiting a variable shading mechanism, the design provides an advanced water harvesting system based on fog collection, which would further improve the standard of living of the users.

In the conception phase several interdisciplinary approaches to the solution were set, with which the project-specific parameters and requirements defined in the objectives could be achieved. First the societal needs and the potential of energy saving pursued by the proposed retrofitting methodology were revised. Next the energy demands of informal communities living in spaces which are often re-appropriated were accessed, since the required thermal comfort conditions are usually not achieved. This was followed by reviewing the state-of-the-art in the field of morphing, kinetic building envelopes, highlighting the strengths and weaknesses of each approach and the attainable results. Building further on this research a novel approach to efficiently actuate and induce the morphing of the envelopes was proposed for an adaptable, user friendly and modular kinetic faรงade system with a special focus on the issue of social discrimination instilled by un-affordability, providing a particularly low-cost design solution applicable across diverse contexts. Multi-functionality was imparted to the shading device by embedding water harvesting systems, with minimal additional costs implications. Different materials for the design of the module components were considered and compared in terms of cost, efficiency and resilience. A trade-off among these criteria led to selecting the materials that are easily available, standardised and durable in harsh environments. The fun-

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ctioning and energy efficiency of the proposed solution has been accessed through prototyping as well as through digital models. Finally personalization through variation in aesthetics and performance efficiency has been allowed by varying the materials of the load-bearing frame and water collectors, retaining the functional mechanism.

The designed envelope is essentially an applicable skin composed of rhomboid-shaped modules, which can be opened on the transparent surfaces of the host building and are fixed on the remaining parts. The modules are characterized for most of their surface by a water collecting net, which at the same time provides shade to the internal spaces. In its lower part, the module is equipped with a semi-open PVC pipe for collecting the harvested water and storing the net when the module is closed. This element, besides functioning as the primary drainage of the system, represents the fixed part of the frame, with the net attached to it. In its upper part, the net is attached to two movable polycarbonate rods connected through a steel snapping tape. One of the rods is connected to a 15 cm long handle through an actuation mechanism for operating the module. Each module can be operated singularly, allowing a personalization of the interior shading based on the real-time necessities. A vertical thread is interwoven in the net, in order to ensure its correct folding path, avoiding the membrane to move out of the vertical plane of the module. Also, the constraint types attaching the net to the frame vary from fixed to sliding ones addressing the peculiar behaviour of the net that must be, in its central part, longer when the module is closed and shorter when it is tensed up.

The proposed facade system is characterized by scalability, low construction cost, easy assembly and the aesthetic value it would impart to the exterior appearance of the host building. The support structure consists of hollow steel tubes, 48 mm in diameter, with an inter-axle spacing of 0.95 meter, applicable to any type of existing faรงade and connected to the host building at each floor. The structure, besides its primary role to support the modules, also acts as a base for placement for all the accessories necessary for the operation of the skin. From the outside, the support structure is totally covered by the modules, while from the inside it coincides with the central part and the ends of the modules, creating a harmonic and aesthetically pleasing faรงade, characterized by soothing forms of geometrical

precision. The design of the system allows the operability of modules by a person of average height due to the placement of the handles between a height of 0.80 and 2 meters.

Also, the handles being placed on the support plates of the modules in small groups, allow the operation of 8 modules from the same position.

The dimensioning and the actuation corresponds to the definition of the bi-stable tape spring geometry. The behaviour of this element has been studied by adopting an analytical and semi-empirical model that has an accuracy higher that 90%. The geometry of the snapping tape has been optimized to minimize the actuation force resulting in a value equal to 20.61 N, which is roughly half of the 40 N upper limit considered. This allows the operation of the module also by children as well as other frail users.

To predict the rate of water collected by the net, an approach based on the combination of an impaction model and an aerodynamic model has been adopted. The parameters of the Raschel mesh, alongside with the fog droplet diameter, liquid water content of the fog and wind velocity have been used to determine the collection efficiency. An ad-hoc analysis has shown a capability of the fog collector to harvest water in the range of 100-500 ml/m2/hr, depending on the type of net and on the site-specific climate.

The novel bottom-up approach shifts away from the paradigm of dynamic skins, often seen as high-tech solutions for developed cities, to a socially engaging solution. Relying, as far as possible, on low-tech and energy efficient components, a hand-actuated and self-assembling faรงade has been conceived, following the criteria of modularity and affordability. This allows the design to be repeatable and scalable for the application to diverse built forms, owing to inherent heterogeneity of informal communities. Modularity also makes it flexible enough to be used for both new buildings as well as for retrofitting of old ones. The faรงade system providing interior thermal comfort conditions and potable water at affordable costs is designed to belong to and be operated by the end users themselves, which makes it a facilitator for the success of the project.

While shading is an inherent feature of all kinetic building skins, its combination with an atmospheric water harvesting system is a peculiar feature of KAGE (Kinetic Air-water Gathering Envelope). This additional feature has been incorporated for the obvious impact of access to water on the life quality of people that, along with electrical energy,

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is one of the very basic requirements to make an environment liveable. However, an envelope with energy harvesting capabilities would have required the implementation of solar cells, resulting in excessive costs which would not have been in coherence with the driving principle of affordability of the project. For the same reason, the implementation of electrical actuators and sensors has been discarded and the material palette has been chosen to be very standard and durable.

However, in the current context of globalization, the key to success is not in minimizing external variety of building facades through standardization, but rather in intelligent management of diversity to achieve greater consumer orientation. Thus, there is a huge scope for a shift from variant-oriented production to variant-oriented engineering. Further developments can aim to balance the required external diversity of variants (meeting customer wishes) while simultaneously maintaining the smallest possible internal variety of components and processes (reducing the costs of complexity). Exploring the use of context-specific local and recycled materials can further maximize the positive environmental, economic and social impact of KAGE, making it the key to a sustainable future.

01.

INTRODUCTION

1.1 Necessity of Sustainable Building Envelopes The design of the Building Envelope fulfils all the key functions to improve the energy balance of the building, combining these with architectural design. Climate change and environmental protection are the most significant challenges of our time. Due to increasing energy consumption of a steadily growing world population, CO2 emissions and therefore also greenhouse effect are increased. Forecasts predict an increase in energy consumption by a factor of 140 in the next 100 years [1]. Natural raw materials as sources of energy will inevitably become scarce. Another major development to note is the increase of the average global temperature. To curb the global warming to a maximum of 2o°C, CO2 emissions worldwide must be dramatically reduced, resources must be managed in the best possible way and new renewable energy sources must be developed.

The building sector provides great potential to reduce CO2 emissions since it has more than twice as much CO2 and energy saving potential as, for example the transport sector. More than 30% of total energy consumed is used to maintain thermal comfort in the buildings.

There is thus an urgency to respond to this need with research, innovative technology, and efficient systems in the form of architecturally sophisticated façade which not only enhance energy performance of buildings but also have a

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potential to generate energy, collect water etc. According to the estimates, around 80% of the energy consumed by buildings for heating, cooling and air conditioning can be saved when all the system components are combined [1].

With the morphable building envelope concept, optimizing and adapting the fenestrations according to individual preferences is possible. The modular construction makes it flexible enough to be used for both new buildings as well as for restoration and renovation of old ones.

1.2 Characteristics of Efficient Building Envelopes 20

Although the cost of the building envelope normally comprises a small fraction of the total construction (approximately 20%), its impact is multifaceted. The envelope has huge influence on a buildings' usefulness and longevity, helping to determine the level of interior comfort. Therefore, the creative development and systematic application of new strategies, products, methods, technologies and tools is imperative. Building envelopes today have to do more than enable optimum energy and material efficiency throughout the buildings lifecycle. They also have to assure streamlined planning, construction and operating processes.

1.2.1

Sustainability

Apart from taking ecology into account, a comprehensive approach needs to encompass economic and socio cultural factors. Ecologically viable results can be obtained only when easy to disassemble buildings are constructed using environmentally friendly fabrication and assembly techniques that conserve natural resources. Packaging must be kept to a minimum, and the same is true for transportation. While considering the economic aspects, apart from

planning, material, fabrication, assembly and commissioning costs, building utilization costs divided into operating and maintenance costs are also relevant. The socio-cultural aspects involve both the building's exterior and interior appearance.

1.2.2 Energy Efficiency Energy saving has been traditionally seen going hand in hand with inferior thermal comfort of living spaces.

However it is a fact that various degrees of comfort can be obtained with same energy consumption, depending on how the building is operated. The key is to decouple interior comfort from energy consumption. In a systematic extension of a simple principle expounded by Gertis and Hauser "First adapt the building to the climate, then adapt the air conditioning to the building", three consecutive steps present themselves. The best outcomes are achieved by combining all the three optimization steps.

In the first optimization step, suitable concepts and resulting components are used to enhance the comfort at the same time as reducing energy requirements. This is especially successful when the buildings interiors can be kept comfortable without the need of external sources of energy. This can be achieved through special building envelopes. On one hand they minimize impact of the outside climate on the interiors and on the other hand, limit extreme values by smoothing short-term oscillations in weather. A buildings efficiency can be increased still further if the envelope acts as a semi-permeable membrane. This not only reduces negative external influences, but also exploits positive external influences, taking advantage of natural heating, cooling, lighting and ventilation. The building envelope thus reacts dynamically to changing external and internal parameters, offering the right measure of permeability of sunlight and air at the right moment.

The second optimization step involves the dimensions of building's components and the way they work. The energy consumption of buildings could be substantially reduced if project specific requirements of interior comfort were applied rather than adhering to generally applicable standards. Ideally, relevant comfort limits should be individually defined for each building zone. The energy saving

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potential increases if lower standards for interior comfort are adopted when rooms are not actually in use. This is likely to succeed when buildings climate control, ventilation and lighting systems are demand controlled which can be done with the aid of sensors.

The third optimization step entails transforming the building envelope into an active solar power receiver area, thus reducing the building's consumption of primary energy without sacrificing comfort.

1.2.3 Material Efficiency

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Material-efficient building envelopes minimize the consumption of materials during the construction. Moreover, their components are optimized for maximum durability as well as enhanced recyclability. The overriding objective is to decouple the material consumption from the functional and the design quality of building envelope. The greatest lifecycle material savings are possible when the process of optimization starts during the planning phase. An additional increase in material efficiency can be achieved through production processes that reduce the volume of defective goods and reuse production waste. Warehousing, packaging and transport processes harbour further potential. An essential prerequisite is the recycling-conductive design of faรงade components. Designs that enable simple disassembly and problem-free separation of different materials are advantageous. The result is the faรงade that is optimized to minimize expenditure of materials as well as featuring enhanced durability and recycling potential.

1.2.4 Process Efficiency In current context of globalization, the key to success is not in minimizing external variety of building faรงades through standardization, but rather in intelligent management of diversity to achieve greater consumer orientation. This calls for a shift from variant oriented production to variant oriented engineering. The objective is to meet the required external diversity of variants (meeting customer wishes) while simultaneously maintaining the smallest possible internal variety of components and processes (reducing the

costs of complexity). This enhances profitability, quality and material efficiency as well as flexibility (construction sequence and dismantling), and reduces planning, processing and assembly times.

1.3 Project Description Conventionally, building faรงades have been typically conceived with invariant geometry and mechanical properties to withstand the environmental excitations. However, the current smart city context demands the ability to adapt and morph under a continuously changing external environment. Accordingly, the goals of making the structures adaptive under variable environmental conditions and of optimizing their behaviour are pursued by inducing changes in the geometry of their spatial configuration, as typical for the kinetic structures. To adapt the structure layout for actuating and fog water harvesting, functional materials and control strategies have to be suitably applied.

A specific focus is proposed on materials that allow a significant deformation which is used to change the system configuration to withstand the variable stimuli. Hence, very flexible spatial configurations can be investigated by focusing on lightweight structures, whose capability of adapting to changing environmental conditions is harnessed through interaction with humans, tailoring them to needs of the users. The technologic goal of this work is minimizing the energy required for achieving thermal comfort conditions and maximizing the affordability of the technology for a broader social impact through informed design choices and use of standard and durable material palette.

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1.4 Project Objectives

ghting the possibilities of its application in diverse geographical, physical and social contexts. Also the possibilities of personalization of the design according to user aspirations in terms of aesthetics and performance efficiency through variations in materiality will be underlined.

The present work aims to design an adaptable, modular and multi-functional kinetic faรงade system to retrofit building faรงades in diverse geographical, physical and social contexts. The main goal of this project is maximizing the affordability of the technology through informed design choices along with minimizing the energy required for achieving thermal comfort conditions.

Allowing for the aforementioned perspective on a timely topic within the current smart city age, the multidisciplinary project departs from the demand of even more energy efficient buildings to understanding how careful choice of materials and technologies can disruptively modify the conventional concept of adaptive faรงades to maximize the affordability for a greater social impact. The design solution exploits the potential of dynamic building envelopes, tailoring them to cater to the energy and resource needs of existing informal building stock, thus promising a greater positive environmental and social impact. In addition to the reduction of energy demand by exploiting a variable shading mechanism, the design provides an advanced water harvesting system based on fog collection, which would further improve the standard of living of the users.

1.6 Conception and Planning

1.5 Expected Outcome The expected result of the project is the design of a morphable faรงade system, able to interact with the users to mediate the external environment conditions. The investigation will be driven by resorting to digital modelling using appropriate softwares. The idea will be reinforced through a small scale prototype of the investigated geometries.

The application of the design on an emblematic case study will be elaborately demonstrated followed by the highli-

The project started by formulating the concrete definition of the project followed by conception and further planning and design of the building envelope. An affordable and adaptable system was thought of to amplify the positive impact that the design would have on existing environmental and social issues. The idea was reinforced by the limitations of the state of the art kinetic faรงades that have a restricted applicability as well as user segment.

In the conception phase an interdisciplinary team prepared several basic approaches to a solution, with which the project specific parameters and requirements defined in the project objectives could be achieved by exploiting the latest engineering and functional possibilities as well as taking design aspects into account. Diverse priorities dealing with economic, ecological and socio-cultural aspects were explored during this phase. Efforts were made for decoupling of functions and specialization of individual components for the benefit of not just planners and component suppliers, but also for later users.

Within the present multidisciplinary project, the work was chronologically organized as follows: 1. Identifying the societal needs and the potential of energy saving pursued by the retrofitting methodology.

2. Accessing the energy demands of informal communities living in spaces which are often re-appropriated and hence lacking required thermal comfort conditions.

3. Studying of the state-of-the-art in the field of adaptive structures and specifically of morphing, kinetic building envelopes, highlighting the strengths and weaknesses of each approach and the attainable results.

4. Proposing a novel approach to efficiently actuate and in-

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Problem

2019

Jun

Research phase

Concept formulation

Concept

Presentation /

Preliminary meeting

Jul

A.S.P. Summer School

Aug

A.S.P. First Project Report

Sep Oct Nov Dec

2020

Jan Feb

A.S.P. Second Project Report

Mar

A.S.P. Winter School / Mid Review

Apr May Jun Jul Aug Sep

A.S.P. Final Report Deadline 28/09

Oct

Conference Bern 26-27/10 Low Medium Core

Figure 1 GANT scheme

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duce the morphing of the envelopes.

5. Developing an adaptable, user friendly, modular kinetic faรงade system with special attention to the issue of social discrimination instilled by un-affordability, providing a particularly low cost design solution to retrofit existing building faรงades in diverse geographical, physical and social contexts.

6. Imparting multi-functionality by embedding variable shading and water harvesting systems, with a minimal additional cost.

7. Studying materials for the design of the module components and their comparison in terms of cost, efficiency and resilience. Obtaining a trade-off among these criteria by also selecting the materials that are easily available, standardised and durable in harsh environments.

8. Application of the retrofitting system to the emblematic case of Torre David in Caracas - Venezuela, considered as the world's tallest slum with very peculiar features.

9. Making provisions to allow personalization through design variations keeping the same structural system and functional mechanism 10. Quantitatively studying the energy efficiency of the proposed solution, through digital models 11. Building a small-scale prototype of the proposed solution, to also discuss relevant technological details.

OUR MISSION

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According to a forecast that the United Nations carried out in 2019 regarding the Population Dynamics [6], the global population will increase approximately 2 billions by 2050, almost reaching 10 billion inhabitants. This simple fact will trigger a series of contradictions and issues on a global scale that will involve the biosphere, the production of food, the soil consumption and the use of resources.

This data should be also considered in relation with the evolution of our cities in the net future: as reported in “Living in the Endless City� [7] in 2050 urban areas will accommodate 75% of the population. This is rather representative of the direction in which we are moving and, in conjunction with the previous evaluation of population growth, the situation raises a multitude of questions about

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Figure 2 World popolation growth

02.

2.1 Demographic Growth

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Figure 3 Urban and rural population Venezuela

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how this issue will be tackled.

Will the cities be ready to host so many people? Are the basic services going to be guaranteed? But, most of all, where will these people live?

The world’s population reaching 10 billions units will trigger massive clashes between the built environment, in need for expansion, and the natural resources.

Therefore, architecture shall play a primary role, considering that the first effect of such a human population growth will be the extension of cities and in general, the built environment.

Starting from this awareness, one of the objectives that the group set itself from the beginning as a mission was to develop a project that took this situation into account, which is not the problem of a single geographical area, but a global issue. The development of this project was therefore an opportunity to become more aware and try to find an answer for the future challenges that the society will have to face.

What has been analyzed about the state of the art that regards kinetic façades is that existing systems are mainly pursuing aesthetic purposes without exploiting their potential in other directions as well. So many of these examples are not really taking advantage of this potentiality to solve real issues.

Thus, being in an interdisciplinary team can allow us

2050: world’s population will reach almost 10 billions units.

to develop a more meaningful system, which takes into account and moves on several fronts, deepening the potential of a mechanism that allows Movable Building Envelope, exploiting the skills of our engineers, developing together with architects and designers a system that can have various areas of application starting from those who need it most urgently.

2.2 Slums Growth

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UN-Habitat has published a forecast that is a very important scientific document, named the challenge of the slums [8] where already in 2003 alarming data on the growth of slums as a planetary phenomenon were shown.

Prospects predict that in 2040 two billions inhabitants will live in slums. Although it is always necessary to reason about these numbers, what is quite certain is that they will certainly grow, as there are no alternatives or inversions of trend.

For a long time it was thought that slums were a residual manifestation, which was born in backward countries as a response to the inability of their governments to propose solutions or alternatives to this situation. This housing model was long looked upon as a symptom of backwardness and it was thought that it would disappear as these countries evolved. Already in the 1950s this concept was doubted because it cannot be guaranteed a coherency between a certain level of economic development and solutions adopted, since every country have different means and possibilities.

What we need to acquire is the awareness that this is a reality which is very difficult to manage, to govern, but which continues to grow and requires not to be ignored, but on the contrary to be thought and organized.

In this regard, there has been a series of important experiences of the last 50 years, both revolutionary and critical, based on a concept introduced by the Brazilian urban planner Ribero: The favela is the solution to the favela problem. This statement, which seems a tautology, means taking note of the fact that we are not able to solve the slum problem and that in the current context this type of living

is the appropriate solution to the problem of metropolitan growth.

This reflection is an extreme consciousness that is based on the awareness of the impossibility of eliminating the phenomenon, whose best intervention is therefore to accompany it, to improve it.

John Turner, an English anarchist architect, was equally convinced and an extreme supporter of this concept, to the point that he decided to spend decades of his life teaching self-construction and improving the living conditions of people in Bogota (where he lived for years with some students). This approach has been at the center of a big debate, but it certainly reveals that Turner was a courageous innovator, driven by a strong awareness: urban poverty is not solvable or arrestable. After this, and other experiences, which also included Caracas, he published a self-construction manual in which techniques for recovery and improvement of housing conditions were explained, recovering and including techniques learned in the field by the houses’ self-constructors.

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2.3 Informal Communities Slums are seen everywhere with a rather negative meaning, as places of intertwining poverty, crime and unhealthiness, which is why they are often defined with the triad of terms Dark, Danger, Dirty.

What often remains beneath the surface of a reality that frightens most people is the enormous potential and capacity that is hidden.

Area, an architecture magazine, dedicated the 128th publication to informal communities, bringing to light a very interesting aspect concerning the differences between formal (defined static) and informal (defined kinetic) cities.

What is fundamental in this context of a kinetic city is the centrality of collaboration between people, who even with very few resources become able to offer a huge innovative power, absorbing, recycling, providing services, building

Figure 5 Makoko was founded as a fishing village in the 19th century

Figure 4 Aeral view of the floating village in Makoko

networks that give access to new levels of solidity.

Aware of the potential that these communities have, it was decided to report case studies describing interventions by architects, who, following the experience of Ribero and Turner (previously described) have set themselves not as new planners, but as catalysts of the strong energy present in the inhabitants, not only guiding these communities, but accompanying them.

2.3.1 Makoko the Floating Slum Lagos is the fifth richest city in Africa, in the southwest of Nigeria. Despite this, true prosperity is concentrated in the hands of very few people and there is a large social disparity.

Makoko is a waterfront community on the Lagos lagoon, which started out as a fishing village about a hundred years ago and over time has become an extended floating slum, named the “Venice of Africa”.

It is not possible to know exactly how many people currently live in Lagos, according to United Nations and of the Lagos State government estimates, the numbers range between 14 and 20 millions, but it is not possible to know who is really right. What is known is that more than half of the inhabitants of Nigeria live in slum settlements.

The same uncertainty about the numbers also exists for the village of Makoko, where there are supposed to be about one million inhabitants, but without having any certainty, as no real census has ever been carried out.

The choice of this case study is due to the desire to highlight how even the most extreme conditions can discourage human beings from building a place they can call home.

And to do this, especially in these circumstances, there are many skills and knowledge put in action.

Two thirds of the village is built on water, only a third is attached to the land.

“The houses on water are built from hardwood, supported

by Wood stilts driver deep into the waterbed”. Tayo Aina, a Filmmaker living in Africa, defined Makoko as a “truly fascinating part of the world and despite the obious poverty and squalor of the place, it’s a testament to human ingenuity in the battle to survive and prosper.”

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2.3.2 Karachi Community Karachi is a port city and commercial centre and the largest city in Pakistan. It is considered to be the largest city in the world and 60% of its population of 15 million live in informal housing, known as Katchi Abadis.

Once these settlements expand and consolidate, there are several services that the community begins to need, and as the government hardly ever intervenes to help them, the inhabitants tend to find their own solutions and, to survive, they carry out small activities in their own homes.

Arif Hasan is an architect from Karachi, who started the Orangi Pilot Project (OPP) in 1980 in response to the needs of its inhabitants. The programme focused on 5 key issues to

Figure 7 Makoko Floating School, designed by architect Kunlé Adeyemi, groundfloor

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The structure has been made from recycled material or locally present. The platform, which is a floating prototype, is made out of plastic barrels, on which wooden planks are placed.

The school is composed of three floors: on the ground floor there is a common green space, while on the two upper floors there are the classrooms.

The project was an opportunity to merge a deep knowledge of the place, as the founder of the architectural firm is originally from Lagos, with a look at more advanced architectural systems, such as the Dutch ones, where one of the firm’s branches is located.

The result is interesting precisely because it strongly reflects the identity of the context in which it is located, as well as bringing innovations to the construction techniques of more traditional houses that are usually built on stilts. All this while remaining a replicable intervention that could give rise to future developments. For this reason it is an excellent example of how limited resources can still be a means of great improvement.

Figure 6 Makoko Floating School, designed by architect Kunlé Adeyemi

An interesting intervention that was carried out in this village with the help of the architectural studio NLÉ was the creation of a floating school.

It is a structure, which not only has a strong significance for its educational function, but is also an important example of collaboration with the community.

The effectiveness of this proposal can be recognised by the fact that the inhabitants have been able to manage, maintain and finance the activities and services that have been provided or implemented, such as sewerage, water supply, schools, clinics, solid waste disposal and security, to the point of obtaining recognition also from the government, which in response has provided additional facilities such as universities and hospitals.

As pointed out on the official OPP website “The component-sharing concept clearly shows that where government partners with the people, sustainable development can be managed through local resources.

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Another project started last year by Hansan, is in Punjab Colony, also near Karachi. This community is about ten years old and is starting to develop vertically, unlike the typical informal dwellings. Its goal here is to offer advice that will enable self-constructors to make their homes safer, earthquake-resistant and with improved lighting and ventilation.

“Apart from that, I think people should have complete freedom to do what they want,” said Hasan.

This process of collaboration is an excellent example of how support tools provide an opportunity to advance communities that already have important resources and capabilities within them and sometimes just need to be supported.

2.3.3 TORRE DAVID an emblematic case study Since the 50s, according to United Nations data, Venezuela has seen a significant population increase due in part to the economic boom of the country. With world’s largest oil reserves, the nation has become the richest country of South America.

During the 1980s an important drop in oil prices began to occur and this was the reason for the start of major problems within the country. The combination of the fall in oil prices and the failure of economic policies led to outof-control inflation.

An estimate by Euro News, predicted an increase in inflation of 10 million percent in 2019, with the irreparable consequence of a further spread of poverty, as many families are no longer even able to cover the feed expenses with their monthly salary.

Obviously the contingency of all these aggravating factors has had a very strong impact on the social issue of the country, leading millions of Venezuelans to live in poverty and increasing criminality, corruption and unemployment. Factors which cost Caracas the nickname of the most murderous city in the world in 2015.

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Another important aspect to consider is the issue of settlement. In Caracas, since the 1940s, there has been a strong wave of migration from the countryside to the city, for the Figure 8 A 5.3-pound chicken sits next to 14,600,000 bolivars, its price and the equivalent of $2.22 US

provide low cost sanitation, housing, health, education and credit for micro enterprise, in Orangi: an informal cluster of 1.5 million inhabitants in the suburbs of Karachi. This initiative was an opportunity to support the project that citizens themselves had started, providing social and technical guidance.

Figure 9 Development and customisation of Torre David facade after its occupation

amount of opportunities and services that only the city could guarantee. People from the countryside, however, did not have the economic possibility to reside in the center of the city and for this reason they started to settle illegally near the city, in spontaneous structures. Despite a failed attempt in the 1950s to eradicate these settlements, the population of the slums continued to grow at unimaginable levels, gradually becoming established settlements.

A truly significant data from the paper “The emergence of slums in Caracas: historical background, growth patterns, and countermeasures” by Carlos E. González R., underline that more than half of the population of Caracas lives in the slums (56% in 2015), with a population density 3 or 4 times higher than the formal city.

Over the years, the issue concerning abandoned buildings has become a political issue for social, economic and ecological factors.

Since the beginning of its mandate, the Chàvez’s government, in the name of the new constitution, began to support the appropriation of government land by the poors, accentuating the importance of “social property” over “private property”, progressively going to legalize, with a series of presidential decrees, the redistribution of public property among the underprivileged.

Over the years, the phenomenon of appropriation has gradually extended from the concept of land to abandoned buildings. Once again, the government began to organize itself to try to expropriate those buildings in order to give the possibility of housing to people who needed it.

The government in Caracas, failing in this pretentious intent, has gradually seen the number of illegally occupied buildings increase from 32 in 2006 to 155 in 2011. One of them was Tower David.

This building has a complicated history behind it, which led it to evolve from a project that identified it as a “beacon of luxury and prosperity” to the tallest squat in the world.

Briefly, the building, part of the commercial and office complex of the Centro Financiero Confinanzas, is a late 1980s project, the result of the significant financial growth that the country experienced following the oil revenues of the 1970s.

In 1990 the construction of this complex began, but four years after the beginning of the works, when the complex

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One of the fundamental characteristics of this place is the impulse that this community has had to improve itself, its possibilities and opportunities, which has resulted in constant development and growth.

Two years later the first sudden occupation, the residents founded a cooperative, structured in rules, procedures and bureaucracies. From an initial phase, in which the families lived inside tents, little by little the families cleaned up the entire tower of the rubble left over from the construction and abandonment of the building, to build real dwellings and spaces for each nucleus. In 2011 the building was the home of 750 families, for over 3000 people, spread over 28 floors of the tower.

There was a waiting list that neatly regulated the requests for transfer within the Tower.

This social experiment would never have been possible without the great organizational and cooperative skills of all its members.

From the very beginning, the occupants have been working to find a way to manage the waste system and above all to be able to have access to water and electricity. The entire electrical plan is the work of electricians living within the complex, as is the water distribution system. This is supplied from a city water main, and pumped up with two pumps to the main tank of the 16th floor, in the center of the tower. From here another pump distributes the water floor by floor, where every week the floor coordinator gave each family the opportunity to fill their 500 liters tanks. Water and electricity were paid by each family to the

Figure 11 Incomplete state of costruction and vertical connections in Torre David

In 2007, following a downfall that made hundreds of people vacant, a series of families moved from the barrios to the city in desperate need of shelter and found Torre David. What makes this case study extraordinary is the ability of its own citizens to evolve what could have been a simple invasion into an organization.

Figure 10 Interior of an apartment in Torre David, drying clothes

was 90% built, two situations irremediably changed the course of events: David Brillembourg, developer of the Tower died and the following year the Venezuelan financial sector collapsed, and funds for construction evaporated. The Tower became property of the government and remained one of the many abandoned buildings in the city of Caracas for 13 years.

local authorities. The residents of Tower David were not at all against the government, they progressively worked towards recognition and legalization.

The Tower itself, with its organizational, service and maintenance needs, became a job creator at the same time. The cooperative alone employed 33 people, including members of management and maintenance. There were security guards at the entrance, water and electricity crews, floor coordinators, people who offered a motor taxi service for the first 10 floors of the building using an adjacent building that was connected by a canopy (as there are no elevators in the tower).

The issue of complex accessibility led to the creation of additional services within the Tower itself to facilitate its use, and was an opportunity to combine the entrepreneurial capacities of the residents with creativity, necessity and

Figure 12 Development and customisation of Torre David facade after its occupation

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work. There were several grocery shops on different floors of the building, with a price regulation that provided the possibility of a supplement only for products that required a clear effort to be transported on the upper floors.

A hairdresser rented a closet, where to offer haircuts on set days at reduced prices.

There was a tailoring workshop in the living room of an apartment, a shop supplies in the family apartment of a student, a snack shop behind a barred window. Other activities were running: an auto workshop in the parking garage, to fix and repaint cars, a brick maker at the beginning of the occupation open a shop to supply families with the material needed to build the walls of their homes and to offer building constructors to the families that may need it.

In addition to the spaces for families, the founding part of the complex consisted, beside the spaces for the services described, also of spaces for common activities, such as sports, (including a gym and a basketball court) the administration spaces, where it was possible to meet for assemblies, a church.

Aware of all that has been previously described, calling Torre David a slum is rather improper. It’s way more than a squat.

In 2014 the building was completely evacuated and the families rehoused elsewhere as the building, despite the great efforts of its inhabitants to adapt it to worthy housing needs, was declared definitely incongruous to the function it was performing.

We have a great admiration for the experiment carried out, despite the evolution of events, so we decided to choose Torre David as an emblematic case study to apply our system.

The motivation is that we recognized this place and this type of community as an opportunity particularly congruous to our design objectives, in the desire to create an economically affordable, self-constructive device that can contribute to improve the current conditions of the building and especially the welfare of its inhabitants.

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03.

REQUIREMENTS

3.1 Stakeholders Analysis The project inserts itself in the field of smart development and aims to tackle the environmental control issue by an innovative design. The modular faรงade design is made flexible enough to be added to any existing building elevation considering the enormity of the existing built stock contributing majorly to the demand of thermal comfort in comparison to the new constructions. The expected changes are mainly technical, where a sustainable solution is also studied from an architectonic point of view. Another major consideration is affordability which in turn would lead to the use of the faรงade by the masses. This has been achieved by the careful selection of materials and design of components.

Informal settlements being the major area of application of the design, the main stakeholders are identified accordingly.

Being the end users and primary beneficiaries of the design, the major stake-interest is supposed to come from the space occupants. In case of the informal settlements, they are identified as the residents of the host structure. At a bureaucratic level, the municipality and the concerned governmental and non-governmental organizations play an important role.

Further to that, designers and researchers, building service specialists, component and material suppliers and assemblers involved in the project implementation, and investors can be also defined as additional stakeholders. Their scale of action and available resources can be summarised as follows:

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Space occupants (Residents of host structure)

Elected Community President

Municipality of area of application

Governmental Organizations

Stakeholder

Definition

Type

Scale of Action

Resource

Material Suppliers

Companies or Industries involved in the production and supply of various raw materials required for the manufacturing of the final modules

Special Interest

Local / Regional

Economic

Component Suppliers

Special Interest

Local / Regional

Economic

Political / Economic

Companies or Industries involved in the processing of raw materials into specific components required for the final modules

Assemblers

Special Interest

Local / Regional

Economic

Legal / Economic

Companies or Industries involved in the assembly of materials and components into final module

Researchers / Designers

Individuals or organizations involved in the design of the modules and research for improving the efficiency and affordability

Experts

Local / Regional / National / International

Cognitive / Economic

Building Service Specialists

Companies or organizations involved in installation and connection of the modules to existing building services like plumbing

Experts

Local / Regional

Cognitive / Economic

Definition

Type

Scale of Action

Resource

They are the primary users and beneficiaries of the designed system

Special Interest

Local

Cognitive

The main representative of all the residents elected through a highly organised voting system

The single urban administrative body having judicial powers granted by national and state laws to which it is subordinate

Special Interest

Political

Includes various associated departments Political / Burelike urban and regional aucratic planning, energy and water supply etc.

NGO’s

Includes various foundations and associations working for the welfare and upliftment of the less privileged

Private Investors

Individuals, organizations or companies investing as charity or under various Corporate Social Response schemes

Special Interest / Bureaucratic

Local

Local

Regional

Local / Regional / National / International

General Interest Local / Regional

Cognitive

Economic

Economic

Table 1 Stakeholders elicitation and analysis

Stakeholder

3.2 Power - Level of Interest matrix The importance of each of the identified stakeholders and the way the project affects them and vice versa can be projected through the Power and Level of Interest matrix.

It is evident that the key players are the ones having most important roles in the decision making, planning and designing process. The ones that have to be kept satisfied are the potential investors that would act under the Corporate Social Responsibility schemes. The Suppliers and specialists on the other hand don't have a major stake or power in any of the designing or decision making process. Finally The Primary beneficiaries and well wishers are the one who have to be kept informed due to a high level of interest but low power in any decision making.

Key players Keep satisfied

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Private investors

Elected Community President Municipality of area of application Governmental Organisations Researchers / Designers

POWER

Minimal effort Material Suppliers Component Suppliers Assemblers Building Service Specialists

Keep informed Residents of host structure NGO’s

LEVEL OF INTEREST

3.3 User Requirements Affordability The device to be composed of materials and components that are locally or easily available reducing the production

cost eventually leading to large scale use by people from all economic sectors Durability The device to be resilient to withstand the weathering processes from various natural forces like sun, wind, rain as well as vandalization User Friendly The device to be easy and simple to operate even without any prior knowledge of the functionality Personalized The device to be aesthetically adaptable in terms of colour or material according to user preferences

3.4 Design Requirements Modularity The device to be modular enabling installation on diverse surfaces as well as easy production, transportation and maintenance Flexibility The device to be adaptable enough to be used in diverse contexts with no changes in functioning mechanics and minimal changes in support structure Multi-functionality The device in addition to catering to the primary function of solar shading, to perform other functions like water harvesting through fog collection for added value Easy Replaceability The device to be easy to install, remove, repair or replace without any need of a specialist.

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04.

STATE OF THE ART

4.1 Kinetic Faรงades The Industrial Revolution was responsible for expanding the market limits of the construction industry, which started to mass-produce standardized materials to be applied in any climate context. New materials such as steel and the improvement in the manufacture of glass made possible the emergence of a new type of faรงade: curtain faรงade - faรงade as a constructive element independent of the structure of the building. Despite its wide acceptance, according to the research of the architect Thales Barnuevo about dynamic surfaces [2], the proliferation of the curtain wall as a typology of envelopes, the choice of standardized materials applied while ignoring the climatic context, and the mechanization of architecture with the total isolation of the internal environment, contributed to the increase in energy consumption and the worsening of the global climate system. For this reason, scientific and technological evolution combined with the ecological mentality of architecture has instigated the development of new alternative techniques to the faรงade with more dynamic and functional characteristics that can improve the internal conditions of the building and reduce the consumption of electrical energy of the building.

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Figure 13 American Pavilion for Expo ‘67 by Buckminster Fuller

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Two decades later, with the technological advances of the time, it was possible to implement a responsive façade system for the control of thermal and luminous radiation in the internal environment built in the Institut du Monde Arabe (IMA) project, according to Winstanley in article to Archdaily, designed by the architect French Jean Nouvel through collaboration with the countries of the Arab League and the French government. On the south façade of the building, Nouvel created a responsive surface incorporating geometric and operational characteristics similar to those presented by Buckminster Fuller at Expo ’67. The proposed system is formed by a façade plan of 24 m x 10 m, composed of 240 panels that form a reticulated mesh.

According to Barnuevo, each of the panels consists of a set of 108 kinetic components of photoelectric closure (movement similar to the diaphragm of a photographic camera) that controls a total of 25,920 cells, which are connected to photosensitive sensors that activate an actuator, transforming the component’s geometry in an oscillatory movement of contraction and expansion of the diaphragm, to control the level of luminous intensity inside the environment. Despite its popularity with tourists and the local population and its originality as a system of structure, protection, and connection with the environment, Nouvel

Figure 14 Hexagonal shaped responsive shading system

The façade responsive to climatic conditions had its first example proposed in the United States in the last century

by Buckminster Fuller, in his project for the American Pavilion for Expo ‘67, in which the architect tried to demonstrate the application of a kinetic system To control the internal space's environmental condition of its geodesic dome, which tried to regulate and control lighting, air, and humidity, as a physical divider between the interior and the exterior. In the study "Kinetic Facades: Towards for Environmental Design" [3], the architect Kamil Sharaidin, explains that the project was based on a responsive shading system in hexagonal shape, built-in plastic, and photochromatic glass, along with a metalized film that allowed the space to exchange air with the outside. The system was mechanically driven by 600 motors that were driven by sunlight at a predetermined angle. Unfortunately, the technology of the day was not prepared to meet Fuller’s idea, and his attempt to apply a responsive climate control system was unsuccessful.

Figure 16 The diaphragms of the reticular mesh

Figure 15 Facade of the Institut du Monde Arabe by Jean Nouvell

was criticized for the level of complexity of the mechanism he developed, due to constant “freezes” of the opening of the diaphragm of the system.

Sharaidin reaffirms that Nouvel’s adjustable kinetic system design should be used as a reminder to architects about care and risk in the application and choice of components for climate control on façades, since the high number of mechanisms and the complexity of activation can compromise the future performance and, therefore, the effectiveness of the system as an active device of a building. According to Barnuevo, the biggest challenge in the development of responsive components or materials is the ability to keep the system working within the pre-established operational configurations, which demands an extremely careful study that considers the wear and loss of performance, and consumption of energy over the life of the system.

With the spread of the idea of kinetic façades for climate control, techniques have been improved and this typology has been the object of increasing interest and application in buildings since the beginning of the 21st century. Following the proposal of Fuller and Nouvel for a responsive kinetic facade, but with optimized geometric and operational characteristics, in 2012 the building design known as Al Bahar Towers, by Aedas Architects, was inaugurated in Abu Dhabi. According to Franco, in Abu Dhabi extreme heat, sand winds, and 0% probability of rain, are strong limitations for the construction of tall buildings, since structural integrity can be compromised by sand and intense heat and light may preclude a comfortable indoor environment. Therefore, for the Al Bahar Towers project, a kinetic system with shading function was implemented.

The façade components were produced in PTFE (versatile and long-lived plastic) and follow a hexagonal geometry with references to the mashrabiya (traditional shading panel of Islamic culture). The kinetic system consists of 1049 components installed at 145 meters high on each façade two meters apart, east and west, which fold and unfold according to the orientation and trajectory of the sun throughout the year, regulating the solar incidence inside the building and increasing the comfort of indoor environments. According to Franco in his article to Archdaily, it is estimated that the screen reduces the sun’s rays by more than 50% and the need to use air conditioners. The kine-

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4.2 Mechanisms In dynamic surface designs, the geometric pattern of the faรงade is constantly changing and, therefore, it is necessary to understand the performance of the mechanical system, which arises from the union between the choice of material and the kinetic pattern. In this chapter, three kinetic patterns widely applied as solutions for dynamic faรงades will be addressed, in addition to the snapping mechanism which, despite being little explored by the civil construction industry, is extremely efficient and represents the most appropriate kinetic pattern for the development of this project.

Figure 18 Kinetic system operation

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The three mentioned buildings represent emblematic kinetic responsive systems in remarkable moments throughout 50 years of the scientific and technological improvement process dedicated to the design of manufacturing dynamic surfaces sensitive to external stimuli. The examples of Fuller, Nouvel, and Aedas, despite being executed at different times in history, demonstrate that kinetic faรงade are part of the architecture of a building, with authentic aesthetic and functional qualities. However, the cost, effectiveness, activation mode, and lifetime of each system must be taken into account, so that it can achieve maximum performance compared to what was planned in the test phase.

Figure 17 Night view of the faรงade composition of the Al Bahar Towers by Aedas Architects

tic components are part of sectors that can be individually controlled, operated by a solar tracking system that controls the activation sequence in three distinct phases: fully closed, half-open, and fully open. The negative aspect of the project is that the system has become extremely heavy, with each unit responsible for 1.5 tonnes, and so far there is no information on the effectiveness of the system for controlling and reducing thermal gain in the building after its occupation.

Figure 20 LIGO’s wavy dynamic surface activated by the wind

Figure 19 Nordic Embassies building’s facade by Berger + Parkkinen

4.2.1 Sliding and rotation Due to its aesthetic and functional simplicity, this type of mechanism is commonly applied to kinetic façades and, according to Sharaidin, it is usually triggered by employing a pulley system.

An example of the application of this type of system can be seen in the Nordic Embassies building in Berlin, in which horizontal panels can rotate 90 degrees to follow the path of the sun. The panels move slowly and gradually to avoid very sudden changes or unwanted noises for the offices’ users, and each panel is activated (opening and closing) individually according to a schedule based on a study of the angle of the sunbeam. However, due to the need for prior programming, the system is not responsive, which means that it does not respond in real-time to local external conditions.

The second example that incorporates the kinetic pattern for sliding and rotation is the Laser Interferometer Gravitational-Wave Observatory (LIGO, in California). LIGO’s surface can obtain wavy patterns on its façades thanks to rectangular aluminum bars suspended on low friction bearings at their center of gravity, coupled with electromagnetic devices at the ends of each bar, which respond to pendular movement triggered by passive energy - spontaneous action of the wind.

In both examples cited, there was no intention to incorporate direct and predictable responsive strategies. This operational choice aims to operate under low energy consumption and with the lowest possible mechanical friction to reduce the need for maintenance and maintain a greater lifespan for the entire system.

4.2.2 Sliding and retracting Among all kinetic patterns, this is the one with the greatest mechanical complexity and the one that requires the most maintenance. It is associated with articulating structures, among which the most common are: umbrella-like structure, as seen in the example Al Bahar Towers, and scissors. The latter, according to Sharaidin, was created by engineer Chuck Hoberman, for the Madrid City of Justice. Similar to this application, the kinetic component

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The contraction and expansion mechanism, according to Shairadin, requires less mechanical complexity and has less friction when compared to other patterns. However, this typology has limitations in the potential for kinetic transformation, which may compromise the user’s visual interactivity with the external environment.

To this mechanism, which explores the interaction with flexible structures, according to Sharaidin, the choice of material is essential for the proper functioning of the system, since materials with appropriate elasticity and flexibility characteristics are necessary, such as synthetic polymers and wood flexible. An example of the application of this mechanism in the installation called Interactive Wall at the Hannover Messe in 2009. This prototype transforms the wall from a static condition to a dynamic condition.

The installation, which expresses its state in terms of movement, light, and sound, was intended to explore different ways of using space and instilling new ways of living in people.

Another example of this application, according to Barnuevo, can be seen on the façade of the Media-TIC Building, designed by Cloud 9, in Barcelona. The building uses a structure composed of a malleable polymer that forms bubbles that inflate and deflate to filter the incoming light and shade the interior of the rooms. This system is known as a lenticular cloud, due to nitrogen injected between two layers of plastic, creating a “cloud” that makes it difficult for the rays of the sun to pass, and it is automatically activated according to the level of sunlight through sensors.

Figure 21 Madrid City of Justice’s kinetic ceiling designed by Chuck Hoberman

4.2.3 Contracting and expanding

Figure 22 Helio Trace component actuation

Helio Trace designed for the Center of Architecture in New York. This system is about overlapping-sliding panels that are retracted in response to lighting conditions. It is capable of producing dynamic and complex movements, creating varied geometric compositions on the façade, but its control is complex since it is composed of multiple subcomponents.

Figure 24 Media-TIC building’s facade components

Figure 23 Interactive Wall installation at Hannover Messe 2009

4.2.4 Snapping The innovative idea of the architect Jin Young Song emerged on the American scenario of 2018, in which, according to information collected on the official page of Song’s studio (Dioinno) 41% of all energy produced in the country was consumed by buildings, which were responsible for 38% CO2 emissions. The mechanism designed for dynamic buildings presents itself as an alternative to “traditional uninspiring shading controls”.

Unlike most of the mechanisms used in dynamic façades, which need extra energy to operate and require complex maintenance, Song’s proposal uses a snapping-induced motion to open and close to provide shade to the interior of the building and can be manually activated by the users themselves in an easy and fun way, saving the activation electricity. The entire system works through “weakening-induced bands tied within the elastic threshold which produces snap deformation with minimal stimulus”. The website of the Dioinno office says that although usually unstable movements are completely avoided in the construction of a building, the snapping mechanism tries to take advantage of the characteristics of the elastic instability by applying an opening and closing mechanism using the energy already embedded within the materials.

Figure 25 Snapping mechanism prototype designed by Jin Song

4.3 Fog Harvesting The lack of water has become part of the reality in different regions of the world, and this condition is worsened due to social inequality and the lack of sustainable management and use of natural resources. For this reason, in recent years water harvesting technologies have been widely explored and among them, fog harvesting is notorious for being an affordable, sustainable and low cost technology, and for representing a way of providing drinking water in rural and informal communities. This technique appeared in the period in ancient Greece, was replicated with little success in France around 1920, and currently represents a sustainable alternative to overcome the difficult access to treated water that some communities in the world face [4].

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4.3.1 Warka Water

Figure 27 Bespoke bamboo structure Figure 28 Warka tower on site

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For many communities around the world, especially in Africa, water gathering is not an easy task. On a visit to small villages on a high plateau in the northeast region of Ethiopia, Italian architect Arturo Vittori, faced the country’s dramatic reality of scarcity of water suitable for consumption. Water sources are rare and are often contaminated by human and animal waste. Faced with this situation, the architect developed Warka Water, a structure made of local bamboo designed to collect drinking water from the air, through a fine polyester mesh that captures and transports drops of water present in the air with a high level of humidity. According to Marchese, in article to Designboom, the first prototype of the project was installed in southern Ethiopia, Dorze, in May 2015, and continues to be monitored today.

The Warka Water project is a light tower with an independent structure, built simply and cheaply with local materials. Atmospheric water vapor from either rain, fog, or dew, condenses against the cold surface of the mesh, forming droplets of liquid water that trickle down into a reservoir found at the bottom of the structure, below the earth. A fabric canopy shades the lower sections of the tower to prevent the collected water from evaporating. performance is weather dependent, but each tower has the capability of providing a community with up to 100 liters of water per day.

In addition to being environmentally friendly, the project finds inspiration from nature, such as insects and plants that can collect and store water from the air and survive the harshest climatic conditions on the planet, in addition to taking into account local crafts and architecture techniques vernacular, which have been forgotten over the years.

Despite being designed by architects, the Warka tower was designed to belong to and be operated by the members of the villages themselves, which makes it a facilitator for the

Figure 26 og collector mesh

“An alternative water source for rural populations that face challenges in accessing drinkable water. Where infrastructure doesn’t exist and communities are isolated, a lightweight, easily constructed, and infrastructure independent system like Warka tower can be installed.” (Warka water)

success of the project. In addition to providing drinking water - a natural resource essential for survival - the initiative also promotes social interaction and fosters a sense of community.

The project intends to expand to other regions of the world such as Haiti, Madagascar, Brazil, Colombia, India, Sumba, and Cameroon, in addition to having plans to unfold in a series of additional projects, including temporary housing (Warka House) which seeks to solve the problem of water scarcity and adequate housing.

Figure 30 Tensioned structure designed by Imke Hoehler

Figure 29 Drinking water storage

4.3.2 Dropnet The project is an idea of the german industrial designer Imke Hoehler, who developed it as her bachelor degree thesis, after studying about drinking water shortages. According to Chin to Designboom, the fog collector created by Hoehler is capable of providing drinking water to isolated areas of the world that have a low infrastructure.

The structure of the new tool resembles the structure of a tensioned tent for easy assembly. The fabric that creates a 6 square meter surface is tensioned vertically and horizontally so that it can withstand strong winds. In fact, in an interview with Designboom, the German designer says that her project appears as a more resistant option to the traditional fog collectors that resemble volleyball nets and that have a very short useful life due to their little aerodynamic geometry.

Dropenet is not only a collection system but provides a system for storing water in external tanks connected to the collector through drains that transport the water after it has been filtered. The entire system was designed to be able to be installed on flat and sloping surfaces. Those on the hills are capable of providing a small village with drinking water if combined with other fog collectors (the Dropnet can collect 10 to 20 liters of water per m2 a day). An extremely positive point of the idea, according to Hoehler, is that “is also highly portable and can be rolled up, sleeping bag-like, into a plastic case for carriage from village to village�, which allows hard-to-reach and difficult places access, can take advantage of the technology, even if they do not have the same infrastructure as large urban centers.

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05.

CONCEPT FUNDAMENTALS

5.1 Overview As could be inferred from the considerations in Chapter 2, dynamic building envelopes are designed and intended for the implementation in highly developed geographical areas. The paradigm of kinetic skins is characterized, nowadays, by the application of high-tech devices and concepts in socially and economically developed cities. Thus, the presence of buildings implementing dynamic faรงades has become a sort of index of the wellness and development of the city.

Needless to say, the large use of highly technological hardwares and complex softwares results in a huge global cost of the installation. As a matter of fact, the concept of dynamicity of the faรงade is seldom confused with the ones of adaptability and responsivity. Kinetic envelopes are created not only as an elite product, but also as a sort of technological demonstrator; a display of the level of progress of the city.

Therefore, the cities that implement dynamic skins building usually do not really need them, but want them as an accessory feature to show. This results in an esthetic driven approach to the design of the envelope itself. The faรงade needs in first place to be pleasant and to generate ama-

71

‘comfort’ but ‘life quality’. As a matter of fact, the inhabitants of the target buildings of the project seldom lack the most basic services, such as water and electricity. Thus, before thinking to make their life comfortable, it is necessary to make it at least livable.

The problem that the team decided to address is the scarcity of water, that afflicts different areas all over the world, and is probably the most critical.

KAGE could be described as a socially engaged low-tech kinetic façade, designed with a data driven approach to improve the quality of life of the less advantaged communities.

The basis concept is that technology shall not be developed for technology’s sake, to demonstrate an alternative way of addressing an already solved problem. The final goal of technology is to make everyone’s life better, hence the application to environments that really need life improvements.

Figure 31 Module overview

72

ze and satisfaction at the eyes of the people who behold.

Then, the secondary feature is almost always limited to the shading of the interior spaces. Clearly, this feature is useful and has been demonstrated to result in a remarkable reduction in the building carbon footprint. The shade generated by the building envelope, that adapts in response to external stimuli or to the Sun motion, reduces the need of air conditioning saving energy and cutting down the production of air pollutants. Nonetheless, given the large use of cutting edge technologies and the huge budget to rely on, the application to only interior shading is restrictive. The potential of dynamic façades surely transcend their field of application, and their development margin is broad.

To shatter the paradigm of elite expensive products, designed leveraging high-tech components for developed environments; it is necessary to completely change the approach. KAGE has been developed with a bottom-up approach. The driving feature is no more aesthetic but consistent data, that highlights the needs of the environment of implementation. Hence the second difference: KAGE has been intended not for highly developed cities, but for under advantaged environments. Thus, the implementation of high-tech technologies is excluded. The whole project has been driven by the key features of modularity, self-assemblability and economicity. The underlying idea is the realization of an economic skin, based on low-tech devices, easy to operate and to repair. Hence the possibility for common people to assemble the modules themselves. The inhabitants themselves also become the actuators and the sensors. No sensors net is implemented to make the skin responsive or adaptive and no electricity powered actuator is used. The modules are designed to be hand actuated, so that any inhabitant can change the façade configuration according to its needs.

The inherent modularity shall broad the application of KAGE to different buildings, with different physical characteristics and different purpose.

But low-tech does not mean less useful. As a matter of fact, KAGE does not only address interior shading but tackles more challenging problems. When implemented in highly developed environments, kinetic façades become a means to provide internal comfort in an unconventional way, i.e. shading instead of using air conditioning. When dealing with disadvantaged environments the key word is not

As broadly stated in Chapter 2, the informal communities are experiencing a notable growth as abitative standard, and their number is increasing. Their heterogeneous nature forces the design of a dynamic skin installation to be as modular and versatile as possible. Hence the characteristics of KAGE that will be further explained and analyzed. Anyway, to give consistency to the whole project, the case study of Torre David has been addressed, being the most emblematic.

The first aspect to be analyzed is the weather in Caracas, where Torre David is located, as the climate conditions strongly affect the quality of living. In fact, factors such as temperature and humidity define both the problem to be tackled and the resources that can be exploited. Caracas is characterized by a mix of tropical savanna climate (due to its latitude) and subtropical highland one (due to its considerable altitude). This results in almost constant and high values of temperature and humidity along the year. The city experiences important precipitations during summer months (i.e. June-August) and abundant fog manifestations in the months of December and January.

The abundance of foggy days in such a period represents a favourable opportunity for the harvesting of atmospheric water. In fact, although the humidity is above 75 % during the whole year (thus meaning that the air is always rich in water), the collection of such humidity is possible only when it creates fog droplets, that can be easily collected into dew. As will be further explained, another factor important for air water harvesting is the presence of wind, that in Caracas touches its peak during the foggy months.

The interest in atmospheric water harvesting derives from the needs of informal communities, and in particular of Torre David. It is possible to appreciate that in such an informal community, the demands, per dwelling unit, for water, heating and electricity are way lower that the average in Venezuela. This does not mean that people in Torre David want to live such a different lifestyle, but that they are forced to, due to the lack of such resources. It is possible to see also that the peak in the demand is during the hours of lunch and diner, as forecastable.

Given the aforementioned favourable weather conditions and the impossibility to address the scarcity of energy with an economic and low-tech installation, the project has been focused on tackling the lack of water.

Moreover, given the high temperatures of the region, that coupled with a high degree of humidity concur to create a hardly livable environment, the need of internal shading is tacit.

4.8

170

5.5

130

4.0 2.5

2.0

1.8

43

Water Demand [m3/DU]

Heating Demand [MWh/DU]

DU = Dwellin Unit

0.8

Electricity Demand [MWh/DU]

Torre David

Venezuela

COâ‚‚ Emissions [ton/DU]

European Union

1 0.75 0.5 0.25 0 2

4

6

8

10

Electricity

12

14

Water

17

19

Energy Demand

21

23

Figure 32 Resources consumption comparison

Torre David

Figure 33 Resources consumption Torre David over the day

74

Figure 34 Sun radiation analysis on Torre David (December)

5.1.1

https://www.worldweatheronline.com

Caracas Average and Max Wind Speed and Gust (kmph)

Figure 35 Wind velocity in Caracas

+ 15 kmph

+ 10 kmph

+ 5 kmph

0 kmph

Jan ‘19

Mar ‘19

May ‘19

2010

Jul ‘19

Sep ‘19

Nov ‘19

2015

Max Wind (kmph))

Avg Gust (kmph)

2020

Avg Wind(kmph)

Max, Min, and Average Temperature (°C)

Figure 36 Temperatures in Caracas

+25°C

+20°C +17.5°C

+15°C +12.5°C

Mar ‘19

May ‘19

2010

Jul ‘19

Sep ‘19

Nov ‘19

2015

Max Temp (°C)

Min Temp (°C)

2020

Avg Temp (°C)

Caracas Average Cloud and Humidity (%)

Figure 37 Humidity in Caracas

+75%

+50%

+25%

0%

Jan ‘19

Mar ‘19

2010

May ‘19

Jul ‘19

Sep ‘19

2015

Humidity (%)

https://www.worldweatheronline.com

Kinetic Air-water Gathering Envelope KAGE is an acronym for Kinetic Air-water Gathering Envelope.

The design being essentially a shading device, metaphorically takes the name from the Japanese meaning of the word which is shadow.

5.2.1

Caracas

Jan ‘19

5.2 KAGE

Nov ‘19

2020

Module Overview

The project consists of a counter-façade equipped with rhomboid-shaped modules, which can be opened on the transparent surfaces of the host building and fixed on the remaining parts.

The modules are characterized for most of their surface by a water collecting net which at the same time provides shade to the internal spaces. In its lower part, the module is equipped with a semi-open tube with the function of collecting the harvested water and providing the storage of the net when it is closed. Such a pipe, beside functioning as the primary drainage of the system, represents the fixed part of the frame the net is attached to. In its upper part, the net is indeed attached to two movable rods that allow the operation of the module. One of the movable rods is connected to a handle through an actuation mechanism that guarantees the operability of the whole module.

As a matter of fact, the modules are hand actuated, eliminating the need for expensive electrical actuators and sensors. The opening and closing is carried out leveraging the potential of bistability. A bistable snapping tape is use as the conjunction element of the two rods and, given its inherent characteristics, helps the user bring the device in the desired configuration. Such configuration shall be either completely close or completely open, as the bistability of the tape does not allow any midway degree of opening. Each module can be operated singularly, allowing a personalization of the interior shading on the basis of the real-time necessities. Different devices are used as expedients to guarantee the correct folding of the net and the complete effectiveness of the device.

The description of the design and technical aspects of the KAGE module is carried out in the next section.

77

5.2.2 Kinetic building envelope

Figure 38 Closed frontal view of the module

B

42

B'

10

150

Front view

Side view

Section B-B'

Inside

10

Outside 163 cm

Top view

0

10

20

30

50 cm

Scale 1:10

REALIZZATO CON UN PRODOTTO AUTODESK VERSIONE PER STUDENTI

66

A'

150

10

Front view

Side view Inside

10

Outside 163

Top view

0

10

20

30

50 cm

REALIZZATO CON UN PRODOTTO AUTODESK VERSIONE PER STUDENTI

A

Section A-A'

Figure 39 Open frontal view of the module

Module open

REALIZZATO CON UN PRODOTTO AUTODESK VERSIONE PER STUDENTI

78

The proposed idea is based on the realization of a counterfaรงade characterized by scalability and low construction cost. At the same time, for the overall configuration of the envelope, an attempt was made to define a solution that could improve the exterior appearance of the building and not make it worse to the view from both the inside and the outside. The aim is to minimize the additions necessary for the optimal functioning of the modules. With these prerequisite KAGE has been developed.

The project is equipped with an upright structure in Innocenti tubes, of 48 mm in diameter, with an interaxle spacing of 1 meter, applicable on any type of existing faรงade and connected to the guest building at each floor. The positioning of the pillars, in synergy with the modules, marks the rhythm of the faรงade. In the analyzed case of Torre David they are connected directly to the outer side of the protruding insoles, for each slab.

The structure, besides its primary role of support for the modules, also acts as a base of placement for all the accessories necessary for the operation of the counter-faรงade, thus optimizing from a functional and aesthetic point of view the whole installation.

In particular, the structure is used as a base for the placement of the handles for opening and closing the modules, for the transparent surfaces of the guest building and as a guide for the drain pipes of the water collected from each module.

The first task of supporting the modules is accomplished by adding a metal plate directly connected to the small pillars. On this plate, the ends of the main water collection pipes, characteristic of the lower part of each module, are hooked by two brackets (typically used to support gutters).

Thanks to this connection it is possible to achieve a layout that maximizes the shady surfaces of the modules, near each other. From the outside, the structure (pillars and metal plates) is totally covered by the modules, while from the inside it remains visible. However, the structure itself coincides with the central part and the ends of the devices, keeping clear the rhythm of the modules and not disturbing the view. Such configuration, beside optimizing from a functional point of view the whole envelope, creates an harmonic and aesthetically pleasant facade, characterized

Module close

Figure 40 Madrid City of Justice’s kinetic ceiling designed by Chuck Hoberman Figure 41 Helio Trace component actuation

80

by soothing forms of geometrical precision.

In the example of Torre David, given the very high floors of 3.65 meters, the openable modules are placed at the bottom of each floor, so that they can be operated by a person of medium height. The highest handles are placed at 2 meters of height and the lowest at 80 cm. The handles to provide the opening of the modules are placed at the support plates of the modules in small groupings, thereby it was possible to reduce the movements of people by opening big portions of the envelope. This way, a person is able to operate 8 modules from the same position.

Moreover the handle, that is attached on the plate, is not visible from the outside giving a more compact look from the internal view.

The final purpose of the vertical pillars is to cover and support the water collection drain pipes coming from the various modules directly connected to it.

All the aspects introduced will be analysed in detail in the following paragraphs.

The developed façade implements modules with a relatively contained dimension. Such design choice fits the requirements of a hand actuation (which could not be possible with too big modules) but is driven by another criteria: the heterogeneity of informal communities. Given the dimension of the modules, their modular repetition is not the optimal pattern to entirely cover huge surfaces, as already existing kinetic façades do on the skyscrapers of the most advanced cities. Moreover, the operation of some modules may be difficult or even impossible due to their position.

Nonetheless, as already said, KAGE moves away from the paradigm of existing dynamic façades. Besides proposing different materials and means of actuations, it relies on a different utilization method.

KAGE has not been designed to be iterated as a pattern, but to be as customizable and economic as possible, thus addressing a completely different issue: the fact that each dwelling unit of informal communities may have different needs. Thus, each unit may implement a different number of modules, in different positions, according to their needs for shading and water.

Thus, the disposition of the modules is not unique and rigid, but reflects the multifaceted nature of informal communities, hence its peculiar and quivering aspect. As a matter of fact, the simplicity of assembly of the modules,

Figure 42 Faรงade from outside

allows the possibility to change their disposition when the needs of the dwelling unit change.

The faรงade shall change and grow with the community, resulting in a living entity, with a much more natural and spontaneous aspect, than a fixed and unyielding pattern of modules. The proposed installation shall not be seen as a cloak covering the faรงades, as most dynamic faรงades are conceived. KAGE free disposition is more similar to the blooming of flowers on a lawn: natural and apparently chaotic. However, as flowers do not bloom stochastically but where the best conditions occur, the modules of KAGE appear only in the positions and in the numbers that are needed.

Facade view - From outside

Facade view - From outside

5.3 Mechanism and technical aspects

Figure 43 Faรงade from inside

Facade view - From outside

5.3.1 Snapping tape

Facade view - From inside

The opening and the closing of the module is operated by hand, through an opening mechanism broadly described in Section 5.3.2. Nonetheless, the crucial element that drives the design and defines the needed actuation force is the snapping tape that connects the two moving rods.

In its general significance, the bistability of a dynamical system means the presence of two different states of stable equilibrium. From a mathematical point of view, this is due to the fact that the potential energy of the system itself presents two minima, which correspond to the stable equilibrium points. More practically, the system can rest indifferently in both the configurations, until an external stimulus rises. In spite of being broadly used in several fields, from electronics to mechanical systems, the implementation of bistable devices and shapes has been deliberately

Figure 44 Handle positioning scheme

Facade view - From inside

0,5

1

1,5

2,5 m

0,5

1

1,5

2,5 m

Facade view - From inside

0,5

1

1,5

2,5 m

83

Snapping tape Upright structure

Vertical thread

Handle Movable rods

Net

Figure 45 Module axonometry

Semi open PVC pipe

Water collection pipe Metal plate

0

10

20

30

50 cm

in architecture and structural design so far. As a matter of fact, the coexistence of two different, and usually diametrically opposite, configurations results in an inherent unpredictability of the system’s behaviour. This results in the lack of implementation of bistable shapes in architectural works, which rely on the stability and predictability of the structure behaviour under external loads and stimuli. Nonetheless, bistable shapes present peculiar characteristics which make them interesting for the implementation in dynamic devices, such as kinetic building envelopes. In particular, the transition from one stable configuration to the other can be obtained with relatively little external stimuli. This characteristic perfectly fits the application to a

hand actuated kinetic device. Once that the sufficient external energy is provided to the system, this will autonomously brings itself in the second stable state. Thus, it is sufficient to apply an action sufficient to provide the snap from one configuration to the other, and the inherent bistability of the system will automatically bring it in the desired state.

This said, in the developed module the bistable snapping tape helps the opening: once the tape snaps, it helps to bring the frame in the desired configuration. Given the inherent characteristics of bistability, the frame can be closed or open, with no halfway configurations between the two stable equilibrium points. This Chapter deals with the calculation of the actuation force necessary to operate the module, which is a crucial aspect of the performances of the device.

As a matter of fact, the study of the behaviour of the snapping tape is a complex issue as it involves: • Big Deformations • Big Displacements • Pre-stress The tape considered has its bistable behaviour due to its manufacturing process. The tape is not a simply forged metal tape: it is created deforming a flat strap of steel.

The analysis carried out is based on an analytical model describing the behaviour of tape springs. Such a model is extrapolated by FEM results (thus it is based on semi-empirical equations and coefficients derived from the results of the FEM analysis itself) and fully described at [9]. If particular hypotheses (that will be further described) are satisfied, the accuracy of the model is superior to 90%. Thus, the implementation of the chosen model allows a saving in time and resources (if compared to a complete FEM analysis) still providing accurate results.

First of all it is necessary to briefly define the phenomenology of a tape spring . It is common knowledge that, trying to bend a metal tape meter requires a different force depending on the direction of bending. Introducing the following nomenclature: • Equal sense bending

M-

85

α

M+

R

L

86

Figure 46 Relevant Moments

M max +

A

fold

M+

M *+ M *_ M max _

E DC

B

O

HG F fold _

max _

fold +

max +

The analytical expression of the moments described above is reported in [9] and is not here recalled for brevity. Being the behaviour derived from a FEM analysis, the expressions of such quantities are full of semi-empirical coefficients.

It is anyway important to highlight the fact that these values depend on the tape properties: • Material

The Young modulus and the Poisson ratio of the material of the tape are crucial for the definition of the moments.

In particular, a higher Young modulus means a stiffer tape, thus a greater snapping moment.

• Thickness A thicker tape requires a higher moment to snap.

• Geometry The geometry of the tape is defined by its curvature radius R and angle α. These entities are reported in Fig.47.

Again, it is important to remark that the theory adopted is retrieved through a fitting of FEM analysis results, thus it is not exact. Thus, the results have an accuracy greater than 90% only if the tape geometric characteristics fall in a certain region. In particular, these ranges are reported in Tab.2, and all the following analysis is carried out considering these limits. Given this, we are interested in a tape which is stiff enough to keep the module open, withstanding the weight of the net and of the moving frame, but not too stiff to require an actuation force higher than 40 N (which is the maximum force that can be generated by hands).

Dimension R α L t

Range 15 - 30 mm 90° - 180° 4 Rα - 8 Rα 0.1 - 0.3 mm

The influence of the wind does not affect the module equilibrium, since it is effect is considered as completely absorbed by the thread passing through the net, which is slightly visible in Fig. 45. This thread is used to guide the membrane’s folding, and is attached to two different fixed frames.

Thus, it does not apply any force on the moving rod. It is then crucial to understand which is the moment applied to the tape when the module is open. We can refer to one single bar of the moving frame, given the symmetry of the

87

Table 2 Admissible ranges for tape geometry

The moment required to provide the snap through of the tape in the opposite sense is higher than the one required to make it snap in the other way. Furthermore, once that the tape has snapped in one of the two directions, increasing the degree of folding requires a little moment if compared to the one necessary to provide the snap-through.

Given this, it is possible to introduce the following definitions, summarized in Fig.46: • M max + The moment connected to the snap through of the tape in the opposite direction.

• M max − The moment connected to the snap through of the tape in the equal direction.

• M* + The opposite moment that is necessary to increase the folding angle once that the snap has happened.

• M* − The equal moment that is necessary to increase the folding angle once that the snap has happened.

Figure 47 Tape geometry

t

• Opposite sense bending

θ = 22.5° l = 810 mm t = 4 mm R = 15 mm w = 2R

snapping tape L/2

l moving rod

Figure 48 Problem geometry

net

A-A

It is possible to express the forces applied to the moving rod, as in Fig.49. In particular: • Fnet Is the weight of the net. It is modeled as a concentrated load at 2/3 of the rod’s length, since in the reality it is a spread load with triangular distribution: Fnet = l2 sin(ϑ) cos(ϑ)δnetg

A-A

θ

t

to have a sufficiently stiff tape. It is the higher thickness for the tape that still lies in the admissible range in which the theory adopted is valuable. • R = 15 mm

• Frod Is the concentrated load representing the weight of the rod. The characteristics of the rod are recalled in Fig.48.

After a trade off study (reported in Section 5.5.1), Polycarbonate has been chosen as the material of the frame.

w

problem.

88

The geometry is described in Fig.48. The value of Ď‘ and the length of the rhombus side are imposed from the module’s geometry. It is important to underline that the length of the rod is not equal to the length of the rhombus side: as can be inferred looking at the geometry of the module, the length l of the side is made up of the rod’s length and half the length of the tape. Since the length of the tape is used as a variable of the study, the length of the rod is variable as well. The other variable of the problem is the angle Îą. As a matter of fact, the analysis carried out aims to find the optimal geometry of the tape, that is the one that minimizes the necessary actuation force but still manages to keep the module open. Thus, the analysis described in the following pages is carried out for any admissible tape configuration: varying both Îą and L. In the end, only the optimal result is displayed. The fixed characteristics of the tape are its material, its radius R and its thickness. In fact: • Steel: E = 10500 MPa đ?œˆ = 0.3 Steel has been adopted, since a less rigid material would not provide the necessary stiffness to the tape • Thickness equal to 0.3 mm Such a tickness has been considered for the same reason:

Frod = wt(l − L/2)δPCg where l is the length of the rhombus’s side, w and t are the width and the thickness of the rod transversal section and δPC and δnet are the densities of Polycarbonate and of the net. It is important to underline that the density of the net takes also into account the weight of the water droplets collected. In fact, the density of the net has been estimated empirically, measuring the weight of a wet sample of net.

The result is a surface density of: 0.085 kg/m2 . • Ftens Is the tension applied to the net in order to keep it tensed up enough to perform water collection. As a matter of fact, a little tension is sufficient since the net does not have to be stretched but only straight. Thus, a tension corresponding to a uniform distributed load over the rod of q = 0.4 N m is sufficient. This value is empirically derived studying the tension of a physical sample of the net implemented.

This yields, for the dimension of the module, to an equivalent force: Fnet = 0.387 N concentrated in the centre of the rod.

89

it is possible to calculate the moment necessary to open and close the module. The dimensioning actuation torque will be the one necessary to open the frame, as it has to win gravity. This actuation moment is:

Mst Mst

Mact = Mst + Mmax + Figure 49 Loads applied to the rod

Frod Fnet

Fnet

θ

A

a b

where the first term is necessary to win the gravity and the second to provide the snapping of the tape. Once that the snapping has occurred, the actuation force is no longer required, as the bistability of the systems allows the opening of the module. On the basis of what has been said, the optimal tape spring is the one that is connected to the minimum actuation moment Mact, but still satisfies the constraint defined by the inequality aforementioned.

In order to convert the torque in a force, it is necessary to define a handle length. With a 15 cm handle (which is 5 cm longer than the typical length of doors’ knobs), the minimum actuation force is: Fact = 20.61 N

With a rotation equilibrium around an axis perpendicular to the plane of the module and passing through point A, it is possible to derive the torque applied to the snapping tape: Mst. where:

Mst = aFrod + bFnet a = 1/2 (l − L/2) cos(ϑ) b = 2/3 (l − L/2) cos(ϑ)

From the preceding consideration, this moment has to be smaller than the one connected to the increase in the fold of an already snapped tape: M*+ or M*−. Since the moments in the opposite sense are higher than the ones in the equal direction, M*+ is considered. This means that the tape is mounted with its concave side upwards. If the following inequality is satisfied: Mst < M*+ the module remains open, because the torque applied to the tape is not sufficient to increase its folding angle. Thus,

this is related to the optimal geometry of the tape, described in Tab.3.

Dimension R α L t

Value 15 mm 102° 188.5 mm 0.3 mm

The actuation force is smaller than the human limit of 40 N, thus the module can be actuated by hands. The length of the handle has been designated in order to lower the actuation force without being too bulky: 15 cm has been considered as a good compromise. The resulting actuation force is almost half the maximum of the human limit.

It has been chosen to keep it way lower (implementing a slightly longer handle) in order to make actuation more comfortable and possible also for weaker people or children. Since the module might be operated several times a day, it is necessary for such action to be not only possible but also easy to do. It is possible to plot the behaviour of the actuation force with the variation of the geometry of

91 Table 3 Optimal tape geometry

90

1100

0.05

1.0

0.20

0.25

0.30

0.35

450.0

800 700 600 500 3.5 3

7

2.5

350.0

1.5

4

150.0 50.0 0.0 -50.0 -150.0 -250.0 0.0

8

0.10

0.20

0.30

0.40

0.30

0.40

0.30

0.40

Time (sec)

6

5

L/(Rα)

Angle (deg)

α rad

250.0

250 200

25.0 20.0 15.0 10.0 5.0 0.0 -5.0 -10.0 -15.0 -20.0 -25.0 0.0

1.0

0.20 Time (sec)

150 200.0

50

3 2.5 α rad

2

1 1.5

0

L/(Rα)

2

3

Angular Velocity (deg/sec)

100

100.0 0.0 -100.0 -200.0 -300.0 -400.0 -500.0 0.0

0.10

0.20 Time (sec)

Figure 53 Driven rod angle (with respect to the horizontal) and rotation velocity

2

0 3.5

0.15 Time (sec)

Angular Velocity (deg/sec)

Nmm

900

Fact N

Figure 51 Actuation force, as a function of the tape geometry

Figure 50 Moments graphical comparison

1000

92

25.0 20.0 15.0 10.0 5.0 0.0 -5.0 -10.0 -15.0 -20.0 -25.0 0.0

Figure 52 Actuated rod angle (with respect to the horizontal) and rotation velocity

dynamic model in MSC Adams has been built. Such a model is simplified, as it simulates the behaviour of the frame (without the net) under the actuation moment. The evolutions of the angle of inclination of the two rods with respect to the horizontal have been plotted, as well as the rotation velocity of the same elements.

The snapping of the module happens in less than a half of a second. While the rod connected to the handle is brought in the desired position with an almost linear evolution, the second rod shows a different behaviour. As predictable, the dynamic of such a rod is split in two moments. At first the second rod is dragged by the first one, then when the snap occurs is the tape that brings such element in its final position.

Angle (deg)

the tape. Looking at Fig.51 one can see that the longer the tape, and the smaller the curvature angle, the smaller is the actuation force. Nonetheless, it is not possible to consider as admissible the smaller forces, as they are connected to a tape which is not capable of keeping the module open.

In fact, looking at Fig.50, the conjunction line of the two surfaces (Mst and M*+) is the edge of the admissible geometries. For longer tapes, the structure can not stay open.

Also not admissible configurations have been plotted, to convey the concept that: the actuation moment is the one necessary to open the module, but the driving constraint is the capability of the tape of keeping the module open.

Both these two aspects have to be considered.

With moments defined by the aforementioned analysis, a

93

Figure 54 Isometric view of the actuation mechanism

Based on the previous explanations, the actuation of the system is based on manual operation and the feasibility of this type of actuation has been approved by the analytical calculations in the previous section. The detail of the actuation mechanism is explained in this part by describing all the consistent components.

The main idea for designing the actuation mechanism is to keep it as simple and cheap as possible to make it consistent with all the other parts of the system and also the main goal of the project which is the affordability and possibility of modification in the system by means of local inhabitants.

sm and it can be easily defined by considering the structure of the building.

More detailed drawings considering the dimension of the standard parts are illustrated in the following page.

Virtual prototyping of the actuation mechanism The 3d model of the mechanism is presented in Figure 54.

All the main components of the actuation mechanism can be seen in Figure 55. The exploded view shows all the main components which are used in this actuation mechanism.

94

The main components of this actuation system are: • Handle • Connecting shaft • Ball bearings • Rhombus rod fixture (Hinge) • Fixtures The length of the shaft in the Figure 56 is variable based on the limitations of the space. For this reason, the length of the shaft is not a design parameter in this project since the applied forces on the handle are not so much that can create structural damage for the mechanism from the buckling point of view.

As discussed in the previous section, the required actuation force is 20.61 N for a handle with 15 cm arm to satisfy the snapping mechanism which is smaller than the human limit of 40 N. The length of the handle is an important parameter to reduce the actuation force and for this reason, 15 cm has been considered as a good compromise between the shape of the handle from an ergonomic point of view and required force for the actuation.

It should be noted that in Figure 55, the details of fixture parts are not considered since it is not part of the mechani-

BALL BEARINGS

SHAFT

ROD FIXTURE (HINGE)

BOLT

HANDLE

Figure 55 Exploded diagram of the actuation mechanism

5.3.2 Actuation mechanism

5.3.3 m

0m

Ø2

Ø10 mm

R 12

.5 m

The water collected by the net flows down and is collected in the PVC principal pipe. Then it is necessary a system of secondary pipes to transfer the water and collect it into tanks. In order to minimize the pipe system, saving both materials and money, a connection between the various modules is provided. A solution implementing a pipe for each module, transferring water to the tanks, would have been too expensive and inefficient. In fact, the low amount of water collected by one single module would lead to not acceptable losses due to leakage. Moreover, if each module was provided with a pipe to drain its water, the global aspect of the façade would have been too bulky. The huge amount of pipes would strongly affect the façade looking, resulting in an unpleasant aspect and hindering the possibility of inhabitants to look outside.

Thus, another approach has been adopted to design the secondary pipes system.

Each module’s PVC pipe is connected to a vertical pipe that runs attached to an upright of the supporting structure.

Thus, the same secondary pipe collects all the water harvested by the modules which stand on its vertical. This connection runs from the module placed on the ceiling to the one on the floor.

12 mm

18 mm

12 mm

5m m

m

Pipe system

126 mm

20 mm 10 mm

R6

10 mm

R10

100 mm

R3.5

R10

Figure 56 Detailed engineering drawings of the actuation mechanism from different views

150 mm

10 mm

30 mm

10 m m

mm

10 m

5m

m

m

50

Given the inherent characteristics of Torre David, 5 modules exist vertically between the floor and the ceiling. Considering that Torre David has a distance between slabs greater than the average building, the following considerations are even more valid for other case studies. Considering the greatest possible amount of water that the nets can collect, it is possible to dimension the tubes that transfer water from one module to the other. In the most favourable conditions one module collects 8.3 litres of water per day (the details of the calculation are reported in section 5.4.1).

Thus, the lowest part of the vertical pipe may have to drain 41.5 litres in the most demanding conditions, receiving the water of 5 modules. Considering a uniform stream of water, this is equivalent to 0.028 litres per minute. Such an amount is roughly equivalent to half of a cup of coffee, meaning that little tubes are sufficient to provide the stream of water to be disposed of in the tanks. In particular, vinyl pipes with a diameter of ⅜ in are the optimal solution for

50

mm

m

0m

Ø2

Ø10 m

R 12

.5 m

97

the vertical tube that runs attached to the upright. To connect this pipe to the PVC tube of each module, small tubes (one for each module) with ¼ in diameter may be used.

The advantages of vinyl tubes are related to the fact that they are economic, flexible and transparent. Thus they are an elegant, minimal and non visually impacting solution.

These tubes are certified to operate correctly between -40° C and 70° C, thus in almost any environment. This property perfectly fits with the implementation of the tubes in the outside part of the façade. Moreover, being closed they do not have losses due to evaporation. The water is then collected into tanks and can be used by the inhabitants.

As far as informal communities are concerned, given the high level of independence of each abitative unity, the tank is private for each apartment. Thus, any family can decide how to manage the water collected by its façade modules.

Nonetheless, it is possible to broad the solution collecting the water in big tanks on each floor. Furthermore, given

Figure 57 Water path scheme

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the little stream of water that runs into the vinyl pipes, they allow the collection even every two floors. This means that, depending on the willingness of the inhabitants, it may be possible to collect water every two floor, leveraging the inherent autonomy of informal communities to share fairly the harvested humidity.

5.4 Net analysis 5.4.1 Water collection performance Fog collection is one of the most diffused means for atmospheric water harvesting. It is worldwide applied in regions with important fog phenomena, to supply the local population with fresh water. The advantages of fog collectors are their relative low cost and constructive simplicity.

They can be assembled by common people, cutting down costs, and making them a valuable solution for under advantaged communities. The operative principle, as well as the geometry of fog collectors, is relatively simple. Fog collectors implement a mesh netting, tensed up by a frame, and a pipe system for the drainage of the collected water.

The mesh netting is the critical element. It consists of thin threads knitted up to form a net, whose geometry can be almost arbitrary. Clearly, not all the meshes have the same efficiency: depending on the material, the geometry and the surface coatings, one net may be more effective than another. The fog droplets, brought by the wind, impact on the mesh and condense forming liquid water. To enhance the collection mechanism, the net has to be as perpendicular to the wind direction as possible, and its threads are very thin. The deposited droplets coalesce in bigger drops and, leveraging gravity, flow downstream to be collected by a pipe placed at the bottom of the net. Frames and pipes can be built exploiting local and recycled materials, resulting in relatively economical fog collectors. Clearly, besides the net’s characteristics, the implementation environment represents a crucial aspect for the efficiency of fog collectors.

To predict the rate of water collected by the net, a combined approach based on impaction (modelling the capture efficiency of fog water droplets due to the impingement

99

Figure 58 Raschel mesh geometry

on the net) and aerodynamic models (which considers the fraction of droplets that actually impinge on the net) has been adopted. Such a model allows to estimate the amount of water harvested on the basis of the mesh geometry and fog characteristics. Given the inherent parametric nature of the approach, it has been possible to model in a relatively simple way different types of net.

The model used to study the net water collection capability is the one reported in [10]. It is designed to forecast the collection performances of Raschel mesh, taking into account three different kinds of efficiencies derived by the geometry of the net itself and the characteristics of the fog.

The geometry of a Raschel mesh is represented in Fig 58.

In order to calculate the net efficiencies, the following parameters are computed: 100

SC =

X

Shading Factor

Then one can proceed calculating the efficiencies themselves, which model the interaction of the fog with the net and the dripping of the atmospheric water on the mesh: • Aerodynamic Efficiency This efficiency represents the fraction of water present in the fog that impacts on the net. In fact, only a part of the droplets impinges on the mesh: SC where: SC

Pressure loss coefficient

Drag coefficient

• Capture Efficiency Only a part of the the droplets that collide with the net is actually deposited on it and is captured:

where: St =

paDgV

Stoke’s number

ρa is the density of water, µg the dynamic viscosity of air, V the wind velocity and Dg the droplet diameter.

• Deposition Efficiency The deposition efficiency is the efficiency that takes into account both the deposition on the net and the drainage mechanisms that makes the collected droplets flow downward into the pipes: With this efficiency it is possible to estimate the drainage efficiency, which represents the fraction of fog that goes into the gutter after impinging the net (thus considering also the evaporation effect): With it, it is possible to calculate the amount of water collected per square meter: Q = LWC ηcollV where LWC is the liquid water content of air. This quantity is related to the fog droplets’ dimension, and depends on the thickness of the fog. Its dependence on the droplet’s diameter has been derived, with a polynomial interpolation, from the data in [11] and is represented in Fig.59.

The common Raschel nets available on the market all have the same R and S (both equal to 0.9 mm), and for that value the water collected has been calculated. Also FogHa-Tin, a particular net produced in Germany, has been considered as a possible solution for the module. The geometry of this net is inspired by spiders’ webs. For the collecting capability of FogHa-Tin, taking into account the considerations in [12], an increment of 25% in the water collection has been considered, if compared to a standard Raschel mesh.

An optimization of the Raschel net geometry has been carried

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out, modifying the values of R and S to maximize the water collected. The results of the variations in the geometry are reported in Fig.60. Thus, it is possible to define the water collected by an optimized mesh, which is characterized by S = 1.3 mm and R = 0.5 mm.

It is possible to appreciate that the optimized net is characterized by thinner threads, which facilitate the condensation of the fog droplet across the impact. Moreover, the threads are more vertical, thus improving the drainage efficiency, since the drop flow faster downwards, to be collected in the pipes with lower losses.

0.6 0.5 0.4 0.3 0.2 0.1 0 10

12

14

16

18

20

22

0.35

Standard Raschel Mesh

FogHa-Ti

Optimized Raschel Mesh

R (mm)

0.9

-

0.5

S (mm)

0.9

-

1.3

Qthin (l/daym2)

4.69

5.87

8.96

0.20

Qthick (l/daym )

17.83

22.29

30.44

Qthin (l/hm )

0.1956

0.2445

0.3734

0.15

Qthick (l/hm2)

0.7430

0.9288

1.2683

0.30

0.25

Q [Kg/hm²]

Figure 60 Water collected for different mesh geometries

Droplet Diameter µm

2

2

R = 0.5 mm R = 0.6 mm R = 0.7 mm R = 0.8 mm R = 0.9 mm R = 1 mm

0.10

0.05 0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

S [mm] 1.6 1.4

Water Collected Kg/hm²

Figure 61 Optimized and standard Raschel mesh performance

Threads even thinner would have resulted in higher collection capability, but their shading performance would have been insufficient. Thus, threads thinner than 1 mm have not been considered.

Standard Raschel Mesh Optmized Raschel Mesh

1.2 1.0 0.8 0.6 0.4 0.2 0 10

12

14

16

18

Droplet Diameter µm

20

22

The results, comparing the three different types of nets are reported in Tab.4. In particular, two different types of fog have been considered: • Thick Fog: D = 10 µm LWC = 0.25 g/m3 • Thin Fog: D = 20 µm LWC = 0.65 g/m3 The typical wind velocity of Caracas in the fog period as been used, that is to say: 9 km/h.

In Figure 61 is also a graphical comparison between the collecting performances of a standard and an optimized Raschel mesh, with different types of fog but with fixed wind velocity (9 km/h as mentioned before). It is possible to appreciate that the gap between the two nets’ performance increases for thicker types of fog. A graphic representing the water collected for various wind velocity and fixed fog thickness would have been qualitatively similar, with the optimized net’s advantage growing for faster wind.

Nonetheless, it is possible to trace the amount of water collected with both variable wind and fog thickness. This is reported in Fig.63, for a standard Raschel mesh geometry.

Table 4 Mesh performance intercomparison

0.7

Liquid Water Content g/m³

Figure 59 LWC dependence from droplet diameter

0.8

103

η

Figure 62 Standard Raschel mesh efficiency

0.1 0.05 0 20 15 10

1 0

3

2 Wind Speed m/s

Droplet Diameter µm

Water collected kg/h/m²

Figure 63 Standard Raschel mesh performance

104

0.15

1

0.5

0 20 15 10

2

1 0

3

Wind Speed m/s

Droplet Diameter µm

5.4.2

Folding path

Once the mechanical characteristics of the frame and the water collecting performances of the net are analysed, it is necessary to consider the connection between these two components. In particular, it is necessary to define the folding path of the net, that has to be tensed up when the module is open and shall be tucked into the pipe when closed. A problem, concerning the folding of the net, rises.

As a matter of fact, despite what could be inferred at first glance, if the net was simply attached to the frame it would need to be longer when the module is closed, and shorter when open. a

0.866a

Looking at the previous scheme, it is possible to understand the preceding statement. When the net is tensed up, the central horizontal strip of net is roughly 13% shorter than the part of the net attached to the frame. Thus, it would need to deform such a percentage to be folded at the close. The characteristics of the snapping tape and the limited elasticity of the Raschel mesh do not allow such deformation. Therefore, it is necessary to change approach and to have no fixed attachment of the net to the frame elements.

The solution adopted is the implementation of sliding constraints. To provide such kind of constraint at the interface with the moving rods, plastic ties (the same used to keep wires together) are used to attach the net to the frame. These could be tight, fixing the net, or loose, allowing the sliding.

On the lower part, hidden into the PVC pipe, the sliding is provided by elements that pass through both the net and the pipe. These rods are allocated inside two eyelets that work as railways on which the rods can slide, carrying the net with them.

Providing these two characteristics to the device, it is possible to fold the net properly. Indeed, the net does not have to stretch when the module is closed, since the sliding of its attachment points to the frame brings the net to the needed shorter length.

Nonetheless, this is not sufficient to guarantee an effective folding of the net. In fact, the inherent fast dynamic connected to the snapping mechanism creates another issue.

When closing, the velocity of the transition may cause the net to go out of the plane, instead of being stored into the pipe. This off-design behaviour, beside being unpredictable and not controllable, strongly affects the water collection capability of the module. When closing the module, the net might be still wet and the close into the pipe concurs in squeezing the mesh collecting all the possible water still present on it. Clearly, if the net goes out of the vertical plane the water still present on it is lost.

To prevent these problems, a thread interwoven into the net is implemented. Such a thread is attached at the bottom to the PVC pipe of the module it is implemented in and at the top to the pipe of the upper module. Thus, being attached to two fixed elements, the thread is firm. This element acts as a guide that forces the net to follow the same

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106

5.5 Comparative analysis In order to define the optimal materials for the various components of the module, it has been necessary to carry out a structured trade-off analysis. For any part of the device different materials, with strength and weakness points, have been considered. To find out the one that best suits the fundamental criteria and key values of the project, the following approach has been adopted.

The first step has been the definition of the criteria for the evaluation of the materialsâ&#x20AC;&#x2122; performances. Each material has been assigned a score on the criteria defined, representing its performance for that particular index . Then a particular weight has been associated with each criteria, on the basis of its importance and consistency with the values of the whole project. Finally, following some mathematical operations here not recalled for sake of conciseness, the weight and the score of each material on each criteria have been combined to derive a final score. The sum of all the materialsâ&#x20AC;&#x2122; final scores is equal to one, and the material with the highest index is the ona winning the trade-off. Clearly, since all the considered materials have some characteristics useful for the project, the superiority of the winning

material on the others is not broad, but usually limited.

Some materials have a better performance on certain criteria, and some criteria are more relevant than others. The goal of the trade-off analysis is to define the material that has the better global properties.

5.5.1

Moving rod material

As far as the material constituting the moving rods is concerned, it has to be economic, lightweight and resilient.

Indeed, economicity is one of the driving features of the whole project, since it has been intended for the implementation in disadvantaged environments. On the other hand, the weight of the rods is a crucial factor. On the basis of what has been said in Section 5.3.1, if the rods are too heavy, the tape can not manage to keep the module open.

Last but not least, the resilience (the resistance to shocks) of the material is essential. In fact, the snap through connected to the actuation results in frequent shocks on the rods. If the material constituting them is not resilient, the rods may be shattered after a few actuations due to the shock impact.

On the basis of these considerations, the attention is focused on polymeric materials. The ones that best suit the described criteria are: polycarbonate, polyvinyl chloride (PVC) and Poly(methyl methacrylate) (i.e., PMMA, usually referred to as Plexiglas). The characteristics of these polymers are summarized in table 5.

Cost $/m Charpy test kJ/m2 Density kg/m3 2

PCV <16 3 1360

PMMA 82 <20 1200

PC 100 25 1200

PVC is the most economical material, but on the other hand it is the heavier and the less resilient, thus it has the lowest final score. On the other hand, PMMA and PC are pretty similar: they have the same density, but have opposite performances on cost and resilience. Their final score is really close.

The winning material is polycarbonate, that, in spite of being the more expensive, is the more resilient. Looking at Fig.64 it is possible to see that the gap between PC and

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Table 5 Materials characteristics

folding path of a folding fan.

To implement this thread, it is necessary to create a hole in the moving rod to make it pass through it, and then through the net. Such holes need to be made in a buttonhole shape, and not a circular one. In fact, when closing the moving rod follows a circular trajectory, while the thread as said stays still. Therefore, during the close it passes in different positions through the moving rod: the hole must allow this operation.

The implementation of the thread comes with a double win. Indeed, it is useful also when the module is open, helping to maintain the net straight and withstanding the wind force that is perpendicular to the module. Thus, it allows the net to work in its optimal conditions, resulting in a better efficiency of the water collection.

0.7

Cost

0.6

PVC

Figure 64 Rods material trade-off

0.5 0.4

PMMA

0.3

PC

PMMA in resilience is wider than the one in terms of cost.

Since cost and resilience have almost the same weight â&#x20AC;&#x201D; meaning that these two performances are equally importantâ&#x20AC;&#x201D;, PC wins the trade-off.

0.2

5.5.2

0.1 0.0

Weight

Resilience

Cost

0.9 0.8 0.7 0.6 0.5

Rigidity

Weight

Pipe material

For the constituting material of the big collection pipe placed under the net, the analysis has been more complex. Four different materials (aluminium, PVC, steel and polyethylene) and six criteria (cost, weight, thermal deformation, long term behaviour, water resistance and rigidity) have been considered. In the end, the winning material is PVC, thanks to its good performance on the three most important criteria: water resistance, cost and long term behaviour. As a matter of fact, PVC is worldwide used for gutters, thus its superiority does not surprise.

0.4 0.3

Figure 65 Pipe material trade-off

0.2

5.5.3

0.1 0.0

Water Resistance

Termic Deformation

Aluminium

Long Term Behavior

PVC Steel PE

0.7

Cost

0.6 0.5 0.4

Figure 66 Net trade-off

0.3

Standard Raschel Mesh FogHa-TiN Optimized Raschel Mesh

0.2 0.1 0.0

Availability

Water Collected

Net mesh

The water collection performances of the three considered net has been broadly described in section 5.4.1. Nonetheless, other important criteria have to be taken into account.

As always, economicity drives the design along with, in this case, availability on the market. FogHa-TiN has a cost which is 15 times higher (2 $ instead of 0.05/0.2 $ per square meter) than a standard Raschel mesh. In fact, this particular net is produced only by a german manufacturer, a fact that strongly hinders the availability on the market. The same considerations are even more true if the optimized Raschel mesh is concerned. In order to implement such a net, it would be necessary to have it custom made by a net manufacturing factory. This, for sure, would result in high costs. Furthermore, not all the net manufacturers provide custom made meshes.

Thus, the standard Raschel mesh wins the trade-off. In fact, as can be inferred by Tab.4, although it is the last in terms of efficiency it is the cheapest and the easiest one to find on the market. Since economicity is one of the driving criteria of the whole project, the standard Raschel mesh is the best option.

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06.

CONCEPT DEVELOPMENT

The proposed kinetic faรงade has been developed to tackle the problems introduced in Chapter 2, and a bottom-up approach has been adopted. Being affordability and modularity the driving criteria of the design, the faรงade envelope has been conceived as a mosaic of identical modules. This allows the installation to be repeatable and scalable for the application to different buildings, being heterogeneity an inherent feature of informal communities. The implementation of electrical actuators and sensors has been discarded for sake of affordability, focusing on the development of a hand actuated module. Different physical phenomena have been explored and, in the end, bistability has been chosen. Once the actuation principle (i.e. snapping) has been chosen, the shape and the orientation of the module have been defined accordingly, resulting in a rhomboidal shape of the element itself. Materials and manufacturing techniques have been chosen on the basis of the actuation principle as well, and according to the driving criteria.

Hereby the implementation of lightweight and common materials for the module composition. The module itself has been conceived in order to allow a relatively simple assembly and maintenance, even by people with little or no

111

Figure 67 Closed KAGE seen from the interior spaces Figure 68 Open KAGE seen from the interior spaces

112

preparation in structure assembly. The module was conceived with two inherent capabilities: shading and water collection. While shading is the common feature of almost any kinetic building skin, atmospheric water harvesting is a pretty unique and peculiar trait of the proposed envelope. This feature has been developed for the obvious impact of water availability on the life quality of people, that along with electrical energy is one of the essential requirements to make an environment liveable. However, an envelope with energy harvesting capabilities would have required the implementation of solar cells, resulting in excessive costs, not coherent with the principles of the project.

Thus, the module has been tailored on the needs of informal communities, to improve the quality of life quality of inhabitants.

The functioning of the module, the dimensioning of its components and its water collection performance have been analyzed and defined relying on mathematical models. However, the complexity of bistable shapes and their inherent peculiar behaviour result in the need for a physical test of their dynamics. Virtual and theoretic models are not sufficient to demonstrate the effectiveness of the module operativity. Hence, the need for a prototype that could erase all doubts on the real functioning of the module, by proving its effectiveness. Thus, the prototype is not realized for its own sake or to simply have a physical model to display, it is an integrated part of the design process. A 1:2 scale prototype has been developed to prove the consistency of the theoretic analysis.

Since the crucial aspect to be demonstrated is the capability of the snapping tape to provide the opening and closing of the module, the prototype has been developed focusing attention on this issue. Since the behaviour of the actuation mechanism is predictable and free of uncertainties, it has not been replied equal to the original. A different version, whose constructive process better suits the requirements of prototyping (instead of a serial production), has been implemented to guarantee the motion of one of the rods.

The prototype has been developed following three main steps corresponding to three different versions: each of them assesses a particular functional aspect of the design.

Figure 69 Open frame Figure 70 Closed frame

Mockup 1: Snapping Frame The first prototype has been built with the purpose of demonstrating the functionality of the snapping frame.

Thus, it is made up of the two rods connected by the snapping tape and of the hinges that allow their rotation. The rods of the prototype are in PMMA. Since the prototype is not designed to work for a high number of cycles, PMMA has been chosen over PC for its lower cost. The two materials have the same density, so they have the same influence on the actuation. The snapping tape is simply a piece of metal flexometer, and is riveted to the rods. Rivets are used also to connect the rods to the hinges. As mentioned before, the actuation mechanism is simplified compared to the one developed for the final module.

The hinge is formed by two plates between which the rod can be inserted and then riveted. The two parallel plates are connected through a cylindric guide in their shorter side. Such a guide coincides with the axis of rotation of the rod itself. The rotation is possible thanks to a nail (100 mm long with a 5 mm diameter) that passes through the hinge and is then fixed with bolts to a wooden frame. Half of the nail is smooth (the one that is connected to the hinge) to avoid wear, while the other half is filetted (the one that fixes the module to the wooden frame). A metal washer is inserted around the nail between the hinge and the wooden frame, to reduce the friction during the actuation. The scaled mockup is operated by moving directly one of the rods, thus no handle has been implemented.

The prototype shows the capability of the tape to keep the frame open and to provide its opening and closing.

The realization of this model highlighted two aspects of the behaviour of the module that emerged thanks to the empirical observation of its functioning: The tape does not always bend symmetrically. As predictable from the theoretical analysis, the folding of the tape is concentrated in a small region. Unfortunately, the folding region does not always form in the center of the length of the tape. Due to the dynamics of the actuation, the folding sometimes occurs at the attachment of the tape to the rods, resulting in a not symmetrical opening of the module. Given the limited dimension of the tape with respect to the whole frame, such asymmetricity can be accepted as it does not modify the shading (and water collecting) surface, but only affects the aesthetic of the module.

It is preferable, from the point of view of the actuation ef-

115

Figure 72 Closed net

116

Mockup 2: Snapping Frame & Sliding Net The second mockup aims to demonstrate the effectiveness of the net folding path. Thus, the sliding and fixed constraints are created using loose and tight fixed cable ties to connect the net to the frame. It is worth highlighting that the ties do not apply their action directly on the net since they would tear it apart. As a matter of fact, they are attached to a nylon wire that passes throughout the perimeter of the net, thus absorbing the force applied by the ties at the moment of the opening.

It is possible to appreciate the effectiveness of the folding expedients implemented. The sliding constraints allow the net to be folded, without the need for stretching, when the frame is closed. On the other hand, when the prototype is open the net is tensed enough to provide water collection effectively.

The implemented snapping tapeâ&#x20AC;&#x2122;s geometry is not tailored for the purpose it is used for, thus it is a bit overdimensioned. This means that it shows an overwhelming stiffness that arises during the operations: not only is the tape capable of opening and keeping open the module withstanding the weight of the net, but it would be capable of doing so also if the net was heavier. This demonstrates the capability of the chosen physical principle (i.e. snapping) to guarantee the functioning of the developed module.

Clearly a more stiff tape is connected to a required actuation force higher than the optimal one. Anyway, in the case of the prototype this is not a problem, since it is a 1:2 mockup (thus requiring a lower actuation force)

Figure 71 Open net

fort, to open the module with a quick twitch applying from the beginning the maximum force; instead of applying an increasing force. Following this second strategy, the low force applied is wasted in the bending of the rods and in the deformation, without snapping, of the tape. As stated in the previous Chapter, a force smaller than the one necessary to provide the snapping of the tape does not result in the opening of the frame, thus it is simply a waste of time and energy. Moreover, a sudden actuation increases the probability of a symmetrical opening of the module, mitigating the problem introduced in the previous point.

Figure 73 Open module Figure 74 Closed module

Mockup 3: The Module The third and final prototype, is the 1:2 version of the whole module with all its components. Thus, the prototype is provided with the PVC tube for the collection of the harvested water in its lower part. The purpose of the prototype is to show the effective coupling of the snapping frame with the open PVC tube, demonstrating the capability of the first to pass through the split in the pipe and storing the net effectively.

For this last mockup a slightly more complex hinge system has been implemented, to provide a suitable coupling of the mechanism with the tube. To avoid the sliding of the hinge along the nail (inside the tube) two bushings (one on each side of the hinge) have been inserted on the nail. The function of these two elements is to keep the hinge centered while also keeping open the PVC tube, hindering a problem that will be further discussed. This way the rod is guaranteed to pass smoothly through the split in the tube, without hurting it.

Two bolts are then used, one on each side of the wood frame, to fasten the mockup to the support itself.

The module is opened pulling a cable tie, left appositely longer in order to emerge from the tube when the module is closed.

The prototype exhibits complete functionality, proving not only the accuracy of the theoretic calculations but the effectiveness of the whole design project and the operability of the system.

Nonetheless, during this last prototyping phase, the tube displayed an unforecasted behaviour during the cutting process. In particular, it has been noted that after being cut throughout its length, the tube shrinked due to its circular section. Thus, the deformation of the tube reduces by 3-8 mm the width of the split created during the cut. The existence of such a behaviour results in the need for some manufacturing expedients to avoid its insurgence: â&#x20AC;˘ The width of the practiced split shall be broader than its desired final dimension, so that such a safety margin hinders the previously described effect. â&#x20AC;˘ Two bolts shall be added on the threaded shaft that supports the PVC tube. Thus, the shaft is used not only as a support but also as a dilator of the tube itself. Putting a bolt both on the interior and on the exterior side of the tube it is possible to keep it open.

The two proposed solutions do not affect the global design and need, for their implementation, only few additional components, i.e two nuts, whose cost is clearly negligible.

119

Figure 75 KAGE retrofitting Torre David

07.

CONCLUSION AND FUTURE DEVELOPMENTS

Although the cost of the building envelope normally comprises a small fraction of the total construction (approximately 20%), its impact is multifaceted. The envelope has huge influence on a building usefulness and longevity, helping to determine the level of interior comfort. Therefore, the creative development and systematic application of new strategies, products, methods, technologies and tools is imperative. Conventionally, building faรงades have been conceived with invariant geometry and mechanical properties to withstand the environmental excitations. However, the current or future resource crisis and the smart city context demand the ability to adapt and morph them under a continuously changing external environment, combining this with multi-functionality.

The analysis of the state of the art concerning sustainable solutions, manifested through a variety of kinetic or smart faรงades, brings to light their inclination towards sophisticated functional mechanisms and materiality. This comes at an economic expense that limits the usage to a privileged class and leaves a major social segment behind. This is synonymous to limited environmental or social impact of such design solutions, since the existing informal building

123

124

stock inhabited by the economically weaker sections of the society cannot afford this luxury.

Building further on this awareness, the goal of this research has been minimizing the energy required for achieving thermal comfort conditions, and maximizing the affordability of the technology for a broader social impact through informed design choices within an interdisciplinary approach. Apart from taking ecology into account, the comprehensive sustainable approach adopted encompasses economic and socio-cultural factors. The design solution exploits the potential of movable building envelopes, tailoring them to cater to the energy and resource needs of existing building stock of informal communities across diverse geographical contexts, thus promising a greater positive environmental and social impact.

The novel bottom-up approach shifts away from the paradigm of dynamic skins, often seen as high-tech solutions for developed cities, to a socially engaging solution.

Relying, as far as possible, on low-tech and energy efficient components, a hand-actuated and self-assembling faรงade has been conceived, following the criteria of modularity and affordability. This has allowed the design to be repeatable and scalable for the application to diverse built forms, owing to inherent heterogeneity of informal communities. Modularity also makes it flexible enough to be used for both new buildings as well as for retrofitting of old ones. Exploring various physical phenomena, bi-stability has been chosen as the most suitable actuation principle: a snap-through mechanism, connected to the switching between the two stable equilibrium configurations of a bi-stable shape, provides the opening and closing of a module. The shape and the orientation of the module has been defined accordingly as a rhomboid, with the support system offering least visual obstructions. The use of lightweight, affordable, standardized and easily available materials like PVC pipes and Raschel mesh has been dictated by the actuation principle as well as the design criteria.

The module itself has been conceived with the two major capabilities of shading and water collection, through a design that allows simple assembly and maintenance, even by end users without any prior experience and knowledge.

Merging the physical phenomena of snapping, bi-stability and air water harvesting, the proposed concept offers potential for improving the quality of life of its users.

The faรงade system is designed to belong to and be operated

by the end users themselves, which makes it a facilitator for the success of the project. In addition to provide the interior thermal comfort conditions and potable water at affordable costs, the system could promote social interaction and foster a sense of community.

While shading is an inherent feature of all kinetic building skins, its combination with atmospheric water harvesting system is a peculiar trait of the proposed design. This additional feature has been incorporated in the module for the obvious impact of access to water on the life quality of people that, along with electrical energy, is one of the very basic requirements to make an environment liveable.

However, an envelope with energy harvesting capabilities would have required the implementation of solar cells, resulting in excessive costs which would not have been in coherence with the principle of affordability of the project.

Since the research identifies affordability as a driving design criterion, the implementation of electrical actuators and sensors has been discarded, focusing on the development of a hand actuated module. Similarly, the material palette has been chosen to be very standard and durable. However, in current context of globalization, the key to success is not in minimizing external variety of building faรงades through standardization, but rather in intelligent management of diversity to achieve greater consumer orientation.

Thus, there is a huge scope for a shift from variant-oriented production to variant-oriented engineering. Further developments can aim to balance the required external diversity of variants (meeting customer wishes) while simultaneously maintaining the smallest possible internal variety of components and processes (reducing the costs of complexity). Exploring the use of context-specific local and recycled materials can further maximize the positive environmental, economic and social impact of the kinetic faรงade system, making them the key to a sustainable future.

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BIBLIOGRAPHY [1] D. U.Hindrichs, H. Winfried, "Façades:Building Envelopes for the 21st Century", Birkhäuser, 2010 [2] T. Barnuevo, "Superfícies Dinâmicas Funcionais: O potencial de tecnologias responsavas para a construção de fachadas.", Universidade de Brasília, 2017, pp. 49-57 [3] K. Sharaidin, "Kinectic Facades: Towards design for Environmental Performance", Spatial Information Architecture Laboratory, School of Architecture and Design, RMIT University, PhD Thesis, 2014, pp. 41-52 [4] L. Caldas, A. Andaloro, G. Calafiore, K. Munechika, B. Taube, M. Oliveira and S. Cabrini, "Water Harvesting from Fog Using Building Envelopes – part II", Water and Environment Journal, April 2018, p.02 [5] A. Brillembourg, H. Klumpner, "Torre David : Informal Vertical Communities ", Lars Muller Publishers, November 25, 2012 [6] United Nations: Department of Economic and Social Affairs - Population Dynamics, "World Population Prospects 2019", [Online] , Available at :https://population. un.org/wpp/Graphs/Probabilistic/POP/TOT/900 [Accessed 15 July 2020] [7] D. Sudjic, R. Burdett, " Living in the Endless City : The Urban Age Project by the London School of Economics and Deutsche Bank's Alfred Herrhausen Society", Phaidon Press, 2011

[8] United Nations Human Settlements Programme, " The challenge of slums : Global report on human settlements 2003", Earthscan Publications Ltd, London and Sterling, VA, 2003 [9] K. A. Seffen, S. Pellegrino, G. T. Parks, “Deployment of a Panel by Tape-Spring Hinges”, IUTAM-IASS Symposium on Deployable Structures: Theory and Applications, 2000.

[10] P. Gandhidasan, H. I. Abulhamayel, F. Patel, “Simplified Modeling and Analysis of the Fog Water Harvesting System in the Asir Region of the Kingdom of Saudi Arabia”, Aerosol and Air Quality Research, Vol. 18, 2018, pp. 200213.

[11] A. Ritter, C. M. Regaldo, G. Aschan, “Fog Water Collection in a Subtropical Elfin Laurel Forest of the Garajonay National Park (Canary Islands): A Combined Approach Using Artificial Fog Catcher and a Physically Based Impaction Model”, Journal of Hydrometeorology, Vol. 9, 2008,pp. 920-935.

[12] Fernandez, Daniel M., Justin Kleingartner, Andrew Oliphant, Matthew Bowman, Alicia Torregrosa, Peter S. Weiss-Penzias, Bong June Zhang, Deckard Sorensen, Robert E. Cohen, and Gareth H. McKinley. “Fog Water Collection Effectiveness: Mesh Intercomparisons.” Aerosol and Air Quality Research 18, no. 1 (2018): 270–283.

ANNEX construction manual 2A

2A 2A

4A 3A

4F

4E

3B 3D 5D 4D

4G 5A

5C

3C 4B

4C

1B

1A

1C

2B 5B

IDENTIFICATION CODE

CATEGORY

COMPONENT

NUMBER/ MODULE

DIMENSION

1A

PVC tube

Main PVC tube

2

Ø: 10 cm L: 77 cm

1B

45°bend

1

Ø: 10 cm

1C

Pipe closing cap

2

Ø: 10 cm

Vertical tube

-

Ø: 1/4"

Connection pipe

1

Ø: 3/8" L: 10 cm

Steel tube

-

Ø: 48mm

3B

Metal plate

4/ 2 modules

L: 50 x 4,8 cm

3C

Brackets of gutters support

2

Ø: 11 cm

3D

Screws

4 / 2 modules

-

Handle

1

-

4B

Shaft

2

L: 17 and 11 cm

4C

Rod fixture

2

-

4D

Movable rod

2

L: 72x3 cm

4E

Snapping tape

1

L: 25x3 cm

4F

Ball bearings

4

-

4G

Bolt

2

-

Net

1

Diagonals: 150 / 60 cm

5B

Metal clamps

10

-

5C

Iron wire

10

-

5D

Vertical wire

1

L: 50 cm

2A

Vinyl tubes

2B 3A

4A

5A

Support structure

Actuation mechanism

Net

Step 0 – Cut the PVC tubes and the connection, throughout their length in their upper part, with a 5 cm wide split to allow the opening and closing of the net. The components are provided with holes to accommodate the metal wire used for the connection of the net. The tubes have two further holes for the insertion of the shaft of the actuation mechanism, while the connection is provided with a hole in its lower part for the drainage of the collected water into the vinyl pipe.

Step 1 – Wedge the two principal tubes in the central curved connection.

Step 2 – Connect the 2 rods to the relative hinges through the application of two rivets on their central vertical axis, using the apposite holes.

Step 3 – Gradually insert the shaft in the designated holes practiced in the PVC tubes. The shaft is inserted from the side oriented to the interiors. Once the shaft has been inserted through this first hole, the hinge-rod assembly is bolted to the shaft itself. Finally, the shaft is pushed through the second hole and the fastening ball-bearings are applied. The same procedure is carried out for the opposite side of the module, implementing the shorter shaft and two fastening ball-bearings.

Step 4 –Keeping the rods open connect them with the snapping tape through the application of two rivets on the longitudinal axis of each rod.

Step 5 – Cut a portion of the Raschel net in a rhomboidal shape directly from the supplied roll, ensuring to have the longer diagonal of the rhombus parallel to the straight threads of the mesh. Stretch the net from one extreme to the other and connect it to the PVC tube thanks to the passage, inside the specific holes, of the metal wire. Carry this step starting from the extremes towards the center.

Stretch the net upwards and insert the cable ties from the centre outwards to connect the mesh to the rods. Finally, the vertical wire can be interwoven in the net to keep it vertical during the operation of the module.

133

step1 Slot PVC tubes in the connection

Step 6 – Insert the corks in the PVC tubes leveraging the lateral split to couple them with the shafts.

Step 7 – Implementat the two support clamps on the extremities of the module which are subsequently screwed to the PVC pipe.

Step 8 – Insert the first segment of the 1/4 in vinyl pipe in the central hole located in the lower part of the PVC connection.

134

Step 9 – Anchor the steel tubes vertically to each slab of the building, with a 0.95 m interaxle. Attach the metal plates on the steel tubes structure. Attach the water drainage system, made up of 3/8 in vinyl tubes, to the steel tubes which connect the modules to the tanks.

Step 10 – Connect the module, by means of the two clamps, to the metal plates of the structure previously applied on the façade. Then, each module’s 1/4 in vinyl connection (previously inserted in the PVC pipe) is inserted in the principal drainage system of vinyl pipes.

Step 11 – Slot the handle into the shaft of the actuation mechanism.

step2

step3

Rivet rods to hinges

Bolt shaft to hinge-rod assembly

2 6-9 2

7

8

1

3

2

10

10 1

2 1-4

1

2

3 5 1

step4

step5

Rivet snapping tape to rods

Attach net to frame (with cable tie, metal wire) and interweave with vertical thread

2

2

2

2

3

1 2

1 1

1

2 1

step6

step7

Insert PVC cork

Join frame to support clamps

2 1 1 2 2 1 3

1 3

3

step8

step9

Insert vynil tube connection

Prepare support structure

2 1 1

3

2 1

1 3

3

step10

step11

Assemble with the structure

Insert handle

2

1

2

1

Alta Scuola Politecnica XV cycle October 2020