Living Facades by Roel Rutgers

living faรงades

A study on the sustainable features of vegetated faรงade cladding

By Roel Rutgers Faculty of Architecture Delft University of Technology

Mentors: S. Broersma A.C. van der Linden F.R. Schnater

living faรงades A study on the sustainable features of vegetated faรงade cladding

By Roel Rutgers Faculty of Architecture Delft University of Technology

Mentors: S. Broersma A.C. van der Linden F.R. Schnater 1

summary

This research focuses on the answer to the question: “What is the absolute contribution of façade planting around the glass of a glass façade compared to a regular glass façade?” From a preceding study on plants, possible sub-questions on the sustainable aspects are formulated. The vegetated cladding will be called a living façade in this report. The report answers this question by giving requirements to a preceding design project that makes use of a living façade system. The practical and quantitative data that are useful for this design will be collected. The project is placed in Manhattan, which has about the same climate as The Netherlands, just somewhat more extreme. There are about 350.000 different species of plants. Plants have an influence on the air composition, human sight, water, sound, soil composition, warmth, food production and biodiversity. All will be discussed in this report. Five different systems to make living façades can be distinguished. The first is the modular green façade, which is a container filled with soil in which the plants grow. The second is the industrial felts system that makes use of an artificial growing medium. Other media than felts can also be used, such as coconut fiber mats. In this system, the plants are constantly irrigated with water and nutrients to prevent the roots from dehydrating. The next system is the façade greening system, which makes the plants grow over the façade instead of on the façade. The system consists of growing containers placed on the ground or hung on the façade and a trellis system that helps the climber plants grow over the façade. The vegetative tiles or stony surfaces are the last system. Most systems in this category are overgrown with mosses. These systems are quite delicate and need a lot of moisture and not too much sunshine. Of all these systems, the façade greening system offers most advantages, because it is light, easy to make and does not need a lot of water. It is pretty artificial though, and does not provide room for other plants than climber plants on the building. The industrial felts or the modular green system would be a better choice if the building should really offer place for nature and more plants should get the possibility of growing on the building. The aspect ‘food’ is the first of sustainable aspect to be discussed in the report. The urge for alternative ways of food processing exists, because of large population growth. However, living façades are too inefficient and delicate to form the answer to this problem. Urban Farming towers had better be used instead. One of the biggest impacts of plants on the environment is bio-filtration, which in a broader sense is called phytoremediation. In this process, the microorganisms living between the roots of the plant eat or break down contaminants, which become food for the plant. Plants can also absorb or capture toxic substances and in this way remove them from the environment. Plants can be used for grey water treatment. The design would need 6.000m2 to treat all grey water of its users.

Leaves of plants have their effects on the surrounding air. They capture all kinds of pollutants that come from cars and industry. These pollutants are absorbed on the leafs or washed away and treated in the bio filtration process of the roots of the plants. Through their photosynthesis process, plants are able to make oxygen and capture CO2. An average-sized tree releases enough oxygen throughout one day to keep a family of four breathing, in terms of oxygen generation. To compensate for CO2 pollution each citizen needs 122 trees or 550.000 m2 of moss. Plants are able to reduce noise. The reduction is small however; only 5dB and mainly in the higher frequencies. Living façade systems of the modular green system category act best as sound insulators. The presence of plants on the façade means the biodiversity increases, which can be seen as a good thing. These plants can also sustain other forms of wild life by providing food sources and shelter. They also have an impact on humans. People surrounded by plants show fewer symptoms of discomfort and stress, have a lower blood pressure and heal faster. This can partially be explained by the sensitivity of the human eye to the colour green, at 555nm. Plants are an important factor for the conservation of water cycles. This is important, because water cycles regulate the climate on earth. Plants contribute by their evaporation process, which makes them function as valves in the cycle. Thus the plants form an important solution to the Urban Heat Island Effect. Plants can also contribute to this effect, because they do not absorb solar heat and therefore living façades help provide a cooler city. Plants also have thermal influence on the building by their evaporation processes. Further, they contribute because the air in-between the leaves insulate, wind is blocked, wind speed around the building lowers and leaves provide shades. The air near a living façade is up to 3°C colder in summer, which influences convection streams. A plant lets through a factor of 0.55^LAI of solar energy, in which the LAI is the leaf area index, the amount of leaves that is projected on the planted surface. In order to prevent overheating of the building, 40% of the façades that face the sun should be closed. Only 5% of the glass in the façade can be exposed to direct solar radiation in summer and does not have to be shaded. In winter this can be 40%. A horizontal volume should even have a 50% closed façade according to the same calculation. The modular green container system and the industrial felts system are more sustainable. Principle details for implementation of these systems are given in Appendix E. The modular containers can be applied best on straight surfaces and is suboptimal on curved surfaces or planes with multiple angles. The felts system is easier to use on complex shapes but is less sustainable. The choice for either one can be made on the basis of the shape of the building.

The sustainable aspects that can be influenced most with the façade are heat, bio filtration, the Urban Heat Island Effect, air quality and the water cycle. Air quality can only be influenced by the amount of plants. The others can be influenced by the details of the façade. Appendix E gives optional details to improve these aspects.

preface

This report is written as a technical addition to my SADD master graduation project on the UN Environmental Council at the faculty of architecture of the Delft University of Technology. In this project, I tried to learn as much as possible about designing a sustainable building. The aim of this research described in this report was to learn the sustainable benefits of plants and to discover design criteria that can influence my design for a living façade. Apart from the ‘green’ looks of plants I was not fully aware of the quantitative sustainable benefits that the plants could bring before writing this report. The report is meant to be a guideline for the façade design in the process of my architectural design. The knowledge of implementing the data from this report is reviewed in the last chapter of this report. In the making of this report, I was helped by a critical review from my mentors who lead the way to a more complete contemplation on this topic. I would therefore like to thank Siebe Broersma, Kees van der Linden and Frank Schnater for their help, time and guidance with this project. Roel Rutgers Master graduation student Architecture & Building Technology SADD studio, Delft University of Technology Februari 2012

Contents 1. Introduction

11 11 11 11 11 12 12 13

2. Architectural concept

16 16 17 18 20

3. Precedents

21 21 23 24 25 26 27 28 29 32 33

4. Sustainable aspects

35 35 36 37 38 39 39 39 41 41 41 42 42 43 45 46 47 48 49

1.1. 1.2. 1.3. 1.4. 1.5. 1.6. 1.7.

2.1. 2.2. 2.3. 2.4.

3.1. 3.1.1. 3.2. 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.3.

4.1. 4.1.1 4.2. 4.2.1 4.3. 4.3.1 4.3.2 4.3.2 4.3.3 4.3.4 4.4. 4.4.1 4.4.2 4.4.3 4.4.4 4.4.5 4.5. 4.5.1

Background Problem Research question Goals Sub-questions Method Structure

Political goals Architectural appearance Sustainability and the green city Faรงade

Plants Sustainable aspects of plants Vertical Greening Systems Modular green container Industrial Felts Faรงade Greening Vegetative tiles or stony surfaces Comparison of the systems Conclusion on vertical greening systems Climate New York

Urban agriculture Conclusion Bio-filtration Conclusion Air quality Urban air pollutants Air filtration by plants Oxygen production CO2 reduction Conclusions Noise reduction Indoor plants Living walls Singapore Living walls Delft Comparison Conclusions Biodiversity Conclusion

4.6. 4.6.1 4.7. 4.7.1 4.7.2 4.7.3 4.7.4 4.8. 4.8.1 4.8.3

Social and psychological improvements Conclusion Water The water cycle Importance of the water cycle Rainwater Conclusions Heat island effect Absorption of heat Conclusion

5. Heat

5.1. Thermal influence 5.2. Calculations on thermal behaviour 5.2.1 Model 5.2.2 Leaf coefficients 5.2.3 Ambient temperature of the leaves 5.2.4 Winter situation 5.3. Interior climate 5.3.1 Comfort temperature 5.3.2 Heat transfer through the faรงade 5.3.3 Solar radiation 5.3.4 Internal loads 5.3.5 Influence of building mass 5.3.6 Ventilation 5.3.7 Influence of greenery 5.4. Calculations on climate 5.4.1 Setup of the model 5.4.2 Outcome of the model 5.4.3 Conclusions 5.4.4 Evaluation of the model

57 57 60 60 61 63 64 65 65 66 68 72 72 73 75 76 76 77 79 80

6. Faรงade criteria (conclusions)

83 83 85 87 87 88 88 89 91 92

7. Implementation in Architecture (recommendations)

93 93 95 96

6.1. 6.2. 6.3. 6.3.1 6.3.2 6.3.3 6.3.4. 6.4. 6.5.

50 50 51 51 53 53 53 54 54 56

7.1. 7.2. 7.3.

Comparison systems on sustainability Criteria from sustainable aspects Principle details Faรงade division Implementation of systems Water and dirt Implementation sustainable aspects Influence on the building design Evaluation

Final design Choice of the living faรงade system Implementation of the faรงade

Literature Pictures, diagrams and tables

99 105

A. Building systems Hort Park, Singapore

111

B. Leaf characteristics

113

C. Building volumes

115

D. Climate calculation model

116

E. Faรงade details

129

F. Final design

155

1. Introduction 1.1. Background

In the design project for the SADD studio Architecture of the Delft University of Technology a design was made for the fictitious United Nations Environmental Council. This organisation was conceived as a guide for governments and citizens all around the world to a more sustainable world through environmental topics. It could be a merger of different environmental and ecological programs that are already established by the UN. The merged organisation could function as an authority on ecological knowledge. The main idea of the project was to house this combination of organisations in a new annex to the UN headquarters in New York. The new building ought to be a sustainable icon that spreads a message of a greener future. The preliminary design for this building is an object formed like a landscape, which is constructed from a vegetated glass covering. This covering consists of a steel construction that holds glass panes and supports a growing medium that is positioned on the glazing beads. This growing medium could be planted with vegetation that greens the building. This form of vegetated façades or roofs will be called living façades or living roofs in this research. The aim of the project is not to create a gimmick, but to really achieve the creation of a sustainable building. For the design of this UN Environmental Headquarters it is interesting to know whether the living façade and roof really contribute to the building’s sustainable performance. This research explores the sustainable aspects of the plants to answer that question.

1.2. Problem

On the one hand, the plants on the façade create a green image for the building and seem to be an ecology-friendly measure. On the other hand,however, it is unclear whether the plants really have sustainable properties and what those are. Besides, the possible impact its sustainable benefits have, are completely unclear. Therefore, a comparison between a planted façade and a regular glass façade would have to be made in order to understand the benefit of the plants.

1.3. Research question

What is the absolute contribution of façade planting around the glass of a glass façade compared to a regular glass façade?

1.4. Goals

The goal of the research is to find out whether façade planting on glass façades has its effect on the sustainable qualities of the façade and, if so, how much planting is needed in order to sustain all the employees working in it. The ‘absolute contribution’ of this question should be found in quantities such as energy and temperature, which can be measured, calculated and compared to a normal façade. The aim of this report is to find those quantities that can define the proportions of vegetation and glazing on the façade and that can be used in the further design process. In this way, the understanding of the benefits of the plants can contribute to the design of the most optimal façade in terms of sustainability. The output of this report can give the architect an idea of the quantities of

planting, the systems that could be used or implemented and the efficiency of different types of façade division.

1.5. Sub-questions

Sub-questions are formulated to define several sustainable aspects that can be derived from the properties of a plant as found in the Precedents of this research (see chapter three).The investigation to the water cycle (question 2) leads to the influence on Urban Heat Island Effect (question 8). Next to these aspects of the plant itself, the mode of implementation and the systems for buildings have to be investigated (questions 1 and 11). Sub questions: 1. What living façade systems can be used for the assembly of the living façade and how do they compare? 2. How do plants influence the air composition and how can this be optimized? 3. How does the façade influence rainwater run off and the water cycle and how can this be optimized? 4. How do plants influence the soil composition and how can this be optimized? 5. Can the façade be used to grow agricultural crops for food supply? 6. How does the appearance of the plants on the façade influence people? 7. What is the effect in noise reduction by the green façade and how can this be optimized? 8. Does the façade contribute to the preservation of the local biodiversity? 9. What is the effect of the façade on the temperature of the surroundings in view of the Urban Heat Island Effect and how can this be optimized? 10. What temperature difference does the planting of the system cause, compared to a normal glass façade and how can this be optimized? 11. How can the plants be implemented best, in order to maximize their sustainable properties and how does this influence the technical aspects of the façade?

1.6. Method

Sub-question 1 is a literature study on the systems invented to assemble a living façade. This is a broad study that categorises and defines the existent systems for living façades. (These systems will be called ‘vertical greening systems’ in this report.) With the information of this inventory, a comparison on the different kinds of systems can be made. This can lead to conclusions on the usability, efforts and shortcomings of the different systems. The sustainable features (questions 2-10) can also be studied in literature. These issues will need to be assessed on useful numbers that can be used to determine percentages of vegetation, vegetation density and amount of glass in the façade. Where possible, the information should be focussed on the conditions in Manhattan. Data will be converted to usable figures for the building and, if possible, its location. Question 10 will need extra physical calculations, in order to understand the influence of the shape of the building on the cooling properties of the plants. This question is of extra importance, because the planting in the given façade

system provides shading and evaporation , which will influence the thermal behaviour of the building. This behaviour is not an add-up of the glass and the green surface, but a synthesis of both of the parts. Moreover, this topic is more important, because the main function of a façade is controlling the interior climate of a building.

Figure 1.1: Building sections

To allow calculations on building scale, four standard sections are defined for the building shape (A to E). To keep the relation with the design project, all volumes should be 100.000m3 .We define the building as a 100m extrusion of a square (A, 32m x 32m); a standing or lying slab (B&C, 18m x 55m); a half circle arc (D, radius = 25m) and a trapezium (E) which is 50m wide at the bottom, 22,5m wide at the top and 27,5m high. These four typologies should give a view of the influence of the building shape on the investigated properties of the green façade. (See also appendix C)

1.7. Structure

The research will first look into the Architectural project that preceded in chapter 2. The architectural design and its appearance created a need for further knowledge on living façades as well as information that can be used to develop the architectural design. This information can be used to understand the criteria and the purpose of the living façade in its architectural context. After this introduction, the research focuses on precedents that are of importance for the research on the façade itself in chapter 3. The first part contains knowledge about plants, the most important ingredient of a living façade. This part of the research can lead to indications of the potential of the plants, which will define the research field. Next to the knowledge about plants, knowledge about vertical greening systems and their properties is needed, in order to understand how the plants can be implemented on the façade. Then there is also a need for knowledge on the climate in New York, to make a calculation of the interior climate. The main body of the research (chapter 4 and 5) consists of the sustainable aspects and possibilities of plants on a façade. The research looks into all impacts that the plants could have on their environment, the building and the users of the building. For reasons of usability of this research, the climate and properties of New York are used as much as possible. In chapter 5 the research looks deeper into the effect on heat. This chapter focuses on plants installed in combination with a glass façade. The combination of plants and glass leads to special thermal behaviour, which will be studied in this chapter.

After these important aspects, criteria for the faรงade design are formulated in chapter 6. All sustainable aspects lead to knowledge about the systems that could be used best, of the impact of the plants and how this can be optimized in the faรงade. With these properties, technical detail drawings of the faรงade are made. In chapter 7 the implementation of these criteria, principals and proposals is evaluated on the basis of the design process executed with the knowledge from this report. This chapter aims to investigate their usability and value and evaluate this research report in terms of value for the architecture. The structure for the report is derived from the structure of the project that consists of many different aspects. Below, these aspects are visualised in a tree scheme that shows the origin of the aspects that are treated in this report.

Figure 1.2: Research structure

The project comprises four broad main themes: the building design itself; the theory of green cities, in which nature is implemented in the urban space; sustainability, as a theme for both the organisation that houses in the building, and as a condition for the total design; and the political goals on sustainability and on a greener earth, for which the project functions as a statement. On the building scale, four important sub-topics are defined. Of course, the most important topic is the architecture of the building. The architecture itself is largely defined by the living façade, a second topic, which is largely influenced by the main ‘green city’ theme and that relates to the topic of site ecology, which is also influenced by the green city ideas. The last important theme on the building scale is the sustainable solutions that give the building the sustainable character that fits the project. The living façade is the main topic for this research report. For the façade there are three important subjects: its form, which is partly defined by architecture and partly by the optimisation of its sustainable aspects; the sustainable impact of the plants, which forms a part of the sustainable solutions on the building scale; and the technical detailing, that will define the way the façade will be assembled. This report will focus on the creation of a program of requirement and principle detailing for the façade, through the research of the sustainable aspects of the plants on the living façade. This program of requirements should give a suggestion on the most optimal system for and proportion of the façade. It is influenced by the architectural demands and limited by the technical detailing of façade greening systems. All in all, this scheme gives the structure for the information that preceded this research and the topics that will be discussed in this report.

2. Architectural concept

In this chapter the architectural ideas and constraints for the building preceding this report will be discussed. They give an impression of the intentions of the architecture by which a more focussed program of requirements can be formulated in this report.

2.1. Political goals

The architectural project on the UN Environmental Council is itself a political statement for a more sustainable world. It was founded on ideas about sustainability from the UN itself. In 1983 The United Nations convened the Brundtland Commission to address growing concern “about the accelerating deterioration of the human environment and natural resources and the consequences of that deterioration for ecnomic and social development.” (DESA 1987) The outcome was the report ‘Our common future’ , which targets sustainable development. This laid the groundwork for the policy on sustainable development for the UN. In 2007 the UN ratified ‘The Triple bottom line’ (people, planet and prosperity) approach and it became the dominant criterion for measuring organizational success. (Sustainability and business 2008) While the people and planet aspect of the triple bottom line are well addressed in the Economic and Social council, the Security Council and the Court of Justice; the Planet aspect is only taken care of in programs and sub-organisations (like UNEP). This project was born out feelings of frustration in relation to environmental issues and the lack of a leading actor. Climate and waste issues are easily trivialized or underestimated by a large audience. Earlier this year United Nations organ IPCC was publicly criticized for publishing untrue facts, which convinced even more people to believe environmental problems are not to be taken seriously. The initiative calls for an empowerment of the environmental and development programs at the UN, which could be a global and objective stakeholder in the creation of a sustainable world. The design project aims to improve the image of the ecological programs by making an Environmental Council housed in the United Nations Headquarters for Sustainability. The initiative proposes a reform within the United Nations institution that wishes to detach organs that have environmental issues as a main objective. A new combined council should be formed , which represents the third pillar of the triple bottom line for sustainable development ‘planet’, next to the already existing economic and social pillars. This new institution, like all other councils, would still function in symbiosis with the United Nations and should have as main target the propagation of a clear, condensed message to the public. Whereas few people know about the IPCC the United Nations Environmental Council should be a force to be reckoned with: it has a clear image and profound authority to safeguard and control environmental sustainability all over the planet. (The image below shows the new structure of the UN after this interference.)

Figure 2.1: new UN structure 16

2.2. Architectural appearance

The location for the UN headquarters for Sustainability is situated right next to the UN headquarters in East-midtown, Manhattan, New York. As a strategy for the realization of an icon, the choice has been made to deal with the problem of biodiversity in the middle of Manhattan by keeping the location on which the icon will be built as green a space as possible. As vegetation is scarce in Manhattan, it is extremely important to try and create new nature. The realization of a building that supports nature in the middle of Manhattan can be an aesthetically strong gesture.

Figure 2.2: Design sketch

Form study shows that the building distinguishes itself best from the surrounding blocks when the shape is more organic and horizontal. This led to the concept of a landscape-like building perforated by architectonic boxes. The total building is covered with vegetation to enforce the perception of the hill shape. This is the basis for the living faรงades and roofs design. The landscape element in this sketch is the roof and faรงade structure that contains most public functions and spaces. To light these spaces, this faรงade should be partly translucent, opaque or transparent. This is an important criterion for the faรงade and roof. An impression of the faรงade and the architectonic volumes inside the building is displayed the picture below. The architectural shape is located on the north side of the location. In this way, it forms a boundary to the International Territories of the UN Headquarters on the north. Also, the view from First Ave on the East River at the west side of the location is preserved in this way. At the south side of the location a space is kept free to make a north entrance to the existent United Nations Building. In the image below the red rectangle is the footprint of the building; the horizontal arrow shows the line of sight and path to the East River; the vertical arrow shows the new entrance path to the General Assembly building of the United Nations Headquarters. Figure 2.3: Interior landscape reference

2.3. Sustainability and the green city

The concept for the architecture is based on the concept of a ‘green city’. This is the aspiration for an urban landscape in which nature is reintegrated and buildings and surfaces are vegetated as much as possible. This idea largely influences the design for the UN Environmental Council and is the root of the concept for the living façade and the roof structure that are implemented in this design. The discussion about integration of nature in the city can be overruled by the

Figure 2.4: Site plan

critique that planned greenery is not real nature and should therefore not be craved for as such. This comment often leads to the conclusion that we should not bother to facilitate a place for nature in our buildings or building materials, for ‘the city is the city and nature is nature’. This would lead to the conclusion that a living façade is a gimmick; a costly interference without use. This argument can be argued upon if we look at the map below, on which we see the human influence index on global scale: In this map we can see that there are few areas in the world that are totally unaffected by human activities. The only areas on which humans do not have any influence, are mainly located within the polar circle, in the Amazon, central Australia, the Himalaya and the Sahara. The natural areas as we perceive them in Europe and the United states, are in fact heavily influenced by human activity. This brings us to a quote about nature from the point of view of the city planner:

“The decision ‘to leave nature be’ can also be considered a human production of nature as there is no solely ‘natural’ matter outside human reach or impact on the surface of the earth.” (Swyngedouw, Kaika en Heynen 2006) The fact that pure nature, uninfluenced by human actions, does not exist, cancels the discussion about nature as a pure entity. As nature in the Western world seems to be interconnected with human planning, we can therefore consider whether to plan with the factor ‘nature’ or not, depending on the circumstances.

While more and more land is used for planned activities, the decrease of nature is often still ignored. Nature should therefore be reconsidered in architectural and urban theories. The design of the UN Environmental headquarters is inspired on Louis le Roy’s concept of giving the city back to nature (see picture of his ‘eco-cathedral’ below). In this view, the building can be the key point from which nature could reclaim the city. (Roy 2010) By giving building sites back to nature

Figure 2.5: Map of human footprint on the world

after the building process and by planning space for reciprocation by nature the city can be made green again. “The skin of the city can be transformed into a living landscape”. (Newton 2004) In this report the sustainable aspects of living façades are explored in order to determine their value for the building and the city and to leave the conceptual discussion about nature as a definition. This can at least help to revalue the presence of plants in the built environment and thereby also revalue the living façade as a building investment instead of a mere philosophical discussion.

2.4. Faรงade

In the architectural project, a living faรงade is implemented in the design derived from the green city concept. The faรงade surface forms an extra expansion space for nature when it can be overgrown. This adds another important function to the faรงade next to controlling the buildingโ s interior climate. The design combines the glass faรงade with plants in order to merge with the park landscape around the building. Sustainable criteria should be used to further shape this faรงade and the relation between glass and plants and their

Figure 2.6: The eco-cathedral of Louis le Roy

quantities. In this way, the faรงade can be designed as a sustainable tool instead of a gadget. The appearance for the living faรงade is defined in the picture below. Overall, it is defined by a straight grid of glass panes that is sometimes interrupted by a closed vegetated area. The criteria for this faรงade from the preliminary design are that the faรงade can be used as an umbrella for the functions below. It is a hill-like shape that shades volumes and spaces underneath it. This means that it should be able to function both for different slopes and for horizontal or vertical planes. This might mean different techniques to detail the living faรงade may be necessary to realise the design.

3. Precedents

Before the report looks into the sustainable aspects of plants and how to optimize them on the façade it will look into plants, living façade systems and the climate in New York first. The consideration of plants can lead to the various sustainable aspects of these organisms , which can help structuring chapter four. By investigating what living façade systems are already available the optimization can be rendered to technical details for the façade. The preceding research on the climate in New York gives a lead for the thermal calculations in chapter five.

3.1. Plants

Plants are the most important ingredient for a living façade. Therefore, the term plant should be understood and defined very precisely. In this paragraph, the word plant will be defined and the different aspects of plants will be described. The definition of the word ‘plant’ can be found in biology. According to this science, a plant is an organism belonging to the kingdom of ‘plantae’. In the family of plantae many species exist, varying from herbs and trees to mosses and algae. Within this family, there are three concepts of plants: ‘plantae sensu strictissimo’, ‘plantae senso stricto’ and ‘plantae sensu lato’. The last two groups Figure 2.7: Appearance of the living façade include water plants and algae and will not be discussed in this report. The land plants defined in the ‘sensu strictissimo’ form the group that can be applied on the architectural concept in the project described. Plants are classified in the APGIII system for plant taxonomy, in which 350.000 species have been identified as land plants. All these 350.000 species could be implemented on a living façade. A typical plant has one or more roots that are mostly located under the soil surface. With these roots, the plant absorbs water and inorganic nutrients. They also help to anchor the plant to the earth and store food and nutrients. Above the soil surface, the plant has one or more stems with leaves. Most plants (260.000 species) have special stems for reproduction that we call flowers. Land plants, with few exceptions, live and grow by photosynthesis from carbon dioxide. For this process, sunlight is absorbed to add energy to a chemical process with the nutrients that the roots of the plant absorb. In the photosynthesis reaction, a chlorophyll molecule is used to absorb light from the ultraviolet and infrared range, which causes the plants to look green. A plant does not strictly require soil to live. It only needs water with dissolved minerals, light and carbon dioxide to live and grow. The way to grow plants without soil is

called hydroponics and uses an mineral nutrient solution without a solid growing medium or with an inert medium such as gravel or mineral wool. Over half of the plant species reproduce by seeds. A seed is an embryonic plant enclosed in a seed cover that usually also contains food. Some seeds are enclosed with a hard or fleshy structure called fruit. Other means for reproduction of plant species are spores, rhizomes, corms, tubers, bulbs, cuttings, grafts, bulbs and buds. Many of these fruits are a food source for humans and animals.

3.1.1. Sustainable aspects of plants From this description of land plants we can derive the influences plants can have on humans around them and the environment they live in. We know that they react with air, water, light and nutrients in the soil in order to keep themselves alive, grow and reproduce. This means the plants play an active role in the chemical composition of air and soil. By these chemical processes, they grow and form seeds and fruits that can function as food for humans. In a passive way, the plants form green objects that, like any other object or material, influence sight, sound and warmth. Next to these properties, the plant itself is present in city ecology. This adds the topic ‘biodiversity’ to the passive influences. Influence on the human environment: Active: Passive: ■■ Air composition ■ Appearance ■■ Water ■ Sound ■■ Soil composition ■ Warmth ■■ Food production ■ Biodiversity ■■ Light These aspects and their influence will be further investigated in chapter four to determine their sustainable potential. Warmth will be investigated in more detail in chapter five. Figure 3.1: Influences of plants

3.2. Vertical Greening Systems

In the current building industry, several different types of living façades are used, of which the most used ones can be described in four categories. First is the modular green container, which uses panels with a growing medium mounted on a construction frame. Second is the industrial felts systems which uses felts as a growing medium and is mounted directly on the façade. Then there are façade greening systems that use climber plants that grow over the façade. The last category are the vegetative tiles or stony surfaces, which consist of rough stone materials that allow plants to grow in holes and cracks. These are four significantly differing façades that all have their specific properties. There are also many other options when making a living façade, but most of them can be described as hybrids or derivatives of these four. For the cause of clearness in the report only these four categories will be compared. This chapter will give a description of all these types of façades in order to be able to compare them and understand the influence the systems have on the sustainable aspects described in this research.

3.2.1 Modular green container This is a container filled with a growing medium, often just natural soil, that is attached to a construction frame on the wall of a building. The containers generally have slats inclined in an angle that hold the soil. Some systems make use of a foil over the containers to keep the soil in place. There are several standard sizes and systems to be found on the market. Usually these panels are square in measures as 30x30, 50x50 or 60x60 cm. Custom sizes can often also be delivered. The system is quite heavy due to the soil and weighs about 200 to 300 kg/ m2 (Gerhardt en Vale 2010). Before installation, the plants have to grow several weeks in horizontal position to strengthen their roots. After this period the panels can easily be attached to the construction frame, often with a customized quick-fastener system. The plants can be watered by hand, naturally, or by an extra irrigation system. For steep surfaces the last solution is recommended. The plants are prevented from overwatering by little holes in the sides of the container that let the surplus of rainwater out.

Figure 3.2: Construction frame for G-sky containers

As the soil gets depleted by the plants over time, the soil will need to be replaced after a few years.

Figure 3.3: ELT living wall panel

Alternatives for this system are, for example, frames with planter pots, or frames clad with sacks of soil. One could think up many solutions to add an amount of soil to a frame.

Figure 3.4: Vegetated living wall panel

Figure 3.5 Habitile system

Figure 3.6: Mosstikapanel

Figure 3.7: Schiavello

3.2.2 Industrial Felts This system is based on the idea that plants only need water and nutrients and therefore soil could be left out of the system. In this system, the plants root into a fibrous material. For exterior façade cladding many building projects use Felts. The material is mounted directly on a waterproofed façade. The entire living wall system has a depth of 40 mm and weighs roughly 30 kg/m². (Gerhardt en Vale 2010)

Figure 3.8: 3D section felts system

Before assembly, the waterproofed façade is first clad with two or more layers of a fibrous growing medium. Through this growing medium, an irrigation system of plastic tubes is mounted. The plants are planted in this system by making incisions in the upper layer(-s) and placing the roots of the plant in the cut. The plants are provided with water and nutrients by the irrigation system, which keeps the layers of fabrics, and thereby the roots of the plants, moist. This system thereby prevents the plants from dehydration. The irrigation system is often made up out of little plastic tubes that can also be found in aquarium installations. This part of the system is most crucial for the façade, because it determines the fertility of the system.

Figure 3.9: Vegetated felts detail drawing

Plants can last long in this system, because of the artificial nutrition, but there is little chance of spontaneous vegetation due to the lack of soil. Coconut fibre mats or Rockwool can be used as an alternative for the felts. There are also solutions with different growing media on the market such as facades with Aquadyne blocks. Often these solutions are made from more artificial and less flexible media than felts. This report therefore uses felts as the best example of an artificial growing medium.

Figure 3.10: Technical drawing felts system

3.2.3 Façade Greening A façade greening system consists of a trellis structure that is attached to the side of a house or building, which allows plants to grow from the ground up or from planter boxes. This means that the plants are not really growing on the building, but over the building. The height of the façade that can be covered with this system is dependent on the used climber plant. The most used plant for these systems is the Hedera Helix (ivy), which can grow 20 to 30 meter high, with an average of 1 to 2 meters per year. A choice for a suitable climbing plant can be made from a wide range however, with plants varying in average height from 1 to 25m. (Zimmermann 2008) In general, this system is very light. A steel trellis structure weights only 1 to 3kg/m2. The plants adds a little weight to this, depending on the size and species. The total is much lighter than the previous two systems. To ‘green’ the building with this system, a construction for the trellis structure is added to the façade. Then the trellis, often a steel net or steel cables, is mounted on this construction. Climber plants are then planted on the ground or distributed in planter boxes over the façade. Most climber plants, like Ivy or grapevines, do not need a lot of water. Most systems are therefore implemented without irrigation.

Figure 3.12: Facade greening

Figure 3.11: Section trellis structure

Figure 3.13: Hedera Helix

Figure 3.14: Moss on concrete

Figure 3.15: Gabion wall as river bank

3.2.4 Vegetative tiles or stony surfaces A wide range of mosses can grow on nearly every surface that is a little bit porous or rough, provided that there is enough moisture around to keep these plants alive. These plants do not have roots but a kind of cellular anchors to keep themselves attached to a surface. A system in this category is the so-called gabion: a metal cage with stones loosely piled in it. The cages can be used as large blocks to make a wall. Over time, plants can root in between the rocks thanks to dust, water and compost that accumulate in between the rocks. In this way the system grows green over time. The gabion system is capable of sustaining more plants, because of the possibility for the roots of plants to grow through the staple of rocks. It is so flexible that even trees may grow on it. This is a risk however, because the large roots might destroy the system in time, although this takes decades. The wall preferably has to be in the shade to avoid dehydration of the plants on the surface. A system that sprinkles water on the surfaces can improve the process. (Schenk 2004)

Figure 3.16: Gabion

3.2.5 Comparison of the systems On the basis of the given technical properties a comparison between the different systems can be made. The systems will be compared as far as weight, vegetation density, maintenance, installation, complexity and water use is concerned. The comparison is made on the basis of economic advantages and expediency to vegetate a faรงade since the benefits in terms of sustainability are yet to be researched. In terms of weight a lightweight system will be judged as more positive than a heavyweight since it will require less construction and less transport and will thereby cost less (--= heavy; ++=light). Vegetation density will be judged more positively when more plants grow on a system per square meter, as it is assumed that the aim of a system is to facilitate plants as much as possible (--=not dense; ++= very dense). Maintenance will be judged more positively when the system requires less care, since this will be more convenient for the building user and will cost less after the building process (--= requires a lot; ++= requires nothing). Installation will be judged more positively when the system can be applied more easily, since this will lead to lower installation costs (--= difficult; ++= easy). Complexity will be judged as more positive when a system is less complex, since it is assumed that a system can be assembled more easily and will therefore cost less effort to make (--= very complex; ++= very simple). Water use will be judged as more positive when the system uses less water since more water will lead to more costs for the irrigation system and the water itself (--= uses a lot of water; ++= water saving). The comparison:

Weight Vegetation diversity Maintenance Installation Complexity Water use

Modular green system

Industrial felts system

Faรงade greening

++ -0 +

+ + + ---

++ 0 ++ + ++

Vegetative tiles or stony surfaces -++ 0 ++ -

In terms of weight, the faรงade greening system is most favourable. This system only needs a trellis structure to support the plants that can grow from the ground up. In this way, it cancels out the growing medium that is present in all the other systems. Only if a building gets a lot higher than 30 meters does the growing range of the plants not suffice. This is only the case if the building shape of a standing rectangle is chosen in the architectural design. In that case, a row of hanging planter boxes halfway the faรงade will be needed. This is still less added weight to the building than the other systems would need. The industrial felts system is the second lightest system. The felts or other artificial growing mediums are very light in weight. However, they do need a supporting structure of a plate material and an irrigation system over the whole surface , which makes them heavier than the faรงade greening. The modular green system is heavier, because of the use of soil and a steel

frame to mount the containers on. This system can be combined with irrigation to lower the maintenance burden , which makes it even heavier. The vegetative tiles or stony surfaces systems are rated as the heaviest system and as such, it rules out every option to make a light building. The system needs the heavy stones, tiles, or concrete by definition and therefore has a lot of mass. The vegetation diversity is most optimal in the modular green system. It can sustain almost every plant form, because of the use of soil. Only the slope of the façade influences the system on this point, because some plants are not capable of growing on a vertical surface, even after they are full-grown. The industrial felts system is also suitable for many different plants, but not every plant is able to form aerial roots. Moreover, just as in the case of the modular green system, the slope of the façade also limits the choice of the plants. The façade greening system supports only climbing plants, but this is still a large plant group. The planter boxes at the foot or halfway of the façade can also support other plant forms. The vegetative tiles or stony surfaces systems supports mosses, which make up a very large plant group with approximately 12.000 species. Systems like the gabion system can support even more species if they get filled with humus over time. The normal stony surfaces, even if they are irrigated, are very fragile though. They cannot be exposed to normal amounts of sunlight, because of the risk of dehydration of the surface and the plants by evaporation. This makes the system less likely to support a lot of plants and therefore the score for these systems is also the lowest. This may not be totally true for the gabion system, especially not after the first decade of its lifetime. The vegetative tiles or stony surfaces do get a good score, as far as maintenance is concerned. Because the wall is less likely to be overgrown the vegetation needs less care. Again, the gabion system is an exception to this rule, because the plants in this system, especially trees, can damage it over time. The first decade of its existence it is likely to be maintenance free, though, and overall, the periods between maintenance can be long. The maintenance of the industrial felts system also scores high. This system keeps the plants moist and feeds them continuously with nutrients , which lowers the chance of plants that dying and having to be replaced for aesthetical causes, provided that the irrigation system works well and keeps the total felts system moist. However, in practice the irrigation systems behind the system’s panels are shown to fail a lot and therefore the system needs some maintenance over time. The climber plants of the façade greening systems tend to overgrow total façades. If the façade is not maintained and the plants are not pruned enough, their stems could get into places in which they do not belong and damage the façade. This makes it a maintenance intensive façade. The modular green system scores worst on maintenance. Main causes are the biodiversity and the soil in this system. The system can support many species of plants, but some of them are not wanted, because they get too big, for instance, and have to be pruned or removed from the façade. Besides, in a system without the optional irrigation the soil gets exhausted after a certain period and has to be replaced. This is a very arduous operation , which makes it the most

maintenance intensive façade. This can be improved by installing an irrigation system that provides the soil with new nutrients and extra water. As far as installation is concerned, the façade greening system scores best. This is partly caused by its low weight. Furthermore, it is a really low-tech system, which only needs a trellis structure, provided that the planter boxes can be installed on the ground around the building. Most façade designs can easily be adjusted to attach the cable nets that can function as a trellis structure. The only negative point could be the installation of the plants themselves: it takes a while before they grow over the full building. The average growing speed is about 2 meters per year , which can be increased a little by using a strong fertilizer. The score for the vegetative tiles or stony surfaces is set to neutral. If the building design already has an outer surface of stone or concrete, only an extra irrigation system would be recommended. This does not take a lot of extra installation work. If, however, the total façade has to be clad with an extra material, this is not an easy system. For instance, the gabions are not easy to combine with the glass façade in the preliminary design preceding this report. In a design with a concrete outer wall in the shades, however, it will not take very much extra effort to turn it into a living façade. In that case simply spraying some water over the façade is enough. The modular green façade scores a minus, for it is a system that needs an extra steel frame installed to attach the containers to. An irrigation system can make this system even more complicated. In this case, a more precise system is necessary that feeds every plant in every container. The felts system is the least easy system to install. Firstly, the irrigation system behind the panels is very delicate and has to be very precise to keep the whole façade moist enough to prevent the plants from dehydration. Secondly, the plants have to be inserted into the felts one by one to green the façade. The installation problems make the industrial felts system a very complicated system. Next to the irrigation pipes, it also needs a pump and water with nutrients flowing through it. Also, the felts (growing medium) need to be a high tech material that cannot rot. Altogether, this system is highly complicated and is hard to design and assemble. The score for the modular green system is neutral, because the steel frame and containers are relatively low-tech and easy to make and assemble, but an irrigation system can make this system much more complicated. The façade greening system is less complicated with only a simple steel cable net attached to the façade and some planter boxes on the ground or somewhere halfway the building. The tile or stony systems are even simpler, since only a surface and a simple irrigation system for moisture would be necessary. As for water use: the industrial felts system is totally dependent on extra water. If water (with some nutrients for the growing process) is not provided, the roots of the plants will dehydrate and die , which will cause the plant to die as well. The vegetative tiles need less extra water, but do need some, especially in a dry place like Manhattan in summer time. Both the façade greening and the modular green system need even less extra water. The first is the most economical, because the climber plants in general do not need a lot of water. The containers of these systems have the advantage that they can store some rainwater. This causes both to have a positive score.

3.2.6 Conclusion on vertical greening systems Of all the systems, the façade greening system has most advantages. It is light, it is simple and low-tech, it is easy to install and it does not need a lot of water. It is a system with a lot of economic advantages and it is very efficient in making the appearance of the buildings look green. It does, however, have two disadvantages. The first is the amount of maintenance the façade needs. Especially when the façade slopes, the plants can tend to leave the trellis net and hang onto the façade. The plants can then creep over the façade and reach unwanted places and might even do damage by blocking ventilation mechanisms, growing into cavities or polluting windows. This is less of a problem when the façade slope is more or less vertical. The second disadvantage is the fact that only climber plants can grow on this system. This conflicts with the idea of nature reclaiming the city, because nature can reclaim the systems containers that are on the ground and might even be here and there on the façade; but nature cannot reclaim the façade itself. Only the climber plants can grow there and otherwise there is still no plant life possible on the façade. If this ‘green city’ idea is more important than anything else, the modular green system would be a better choice. For the simple reason that the system uses soil and is, thereby, able to cover the fragile roots and seeds of plants. This is also the case for the industrial felts system with its growing medium and artificial moist but to a lesser extent. The modular green system is less complex and easier to install than the industrial felts system. Only disadvantages here are maintenance and weight. The 244kg/m2 mass needs quite a big construction and maintenance is burdensome. This last aspect can be eased by making an irrigation system. However, even then, the façade would still need pruning twice a year or even more. The industrial felts system is a better option when a hightech, and thereby more expensive, project is not a problem. It would need less maintenance and the construction can be slimmer thanks to its 30 kg/m² mass. Altogether the choice should be made between really making space for nature in the city and only creating a green image. In the first case, a lot of effort would have to be made to give nature a place and this can result in very complex and water demanding system or a very heavy and maintenance demanding system. The other option is an easy system , which will be quite easy to realise and will provide the building with leaf coverage.

3.3. Climate New York

In order to be able to make calculations for thermal behaviour for the façade some data on the climate in New York are needed. These data are also usable for decisions on irrigation of the plants or to estimate the suitability of the city for plants. In general, this information gives a better view of the circumstances in New York. Measured at: Latitude: +40.71417 (40°42’51.012”N) Longitude: -74.00639 (74°00’23.004”W) (National Weather Service 2010) Manhattan is located at +40.7° latitude , which means the sun will be maximally at 72.7° above the horizon in summer and 25.7° above the horizon in winter. The climate in New York is approximately the same as in the Netherlands, but it is a little more extreme. Temperatures are higher and lower, there is more precipitation and there is a higher wind speed, as can be seen in the tables on the left. The warmest month in Manhattan is July with a daily mean temperature of 24.7°C, an average high of 29°C by day and an average low of 20.4°C by night. The temperature record for this month is as high as 41°C. The coldest month in Manhattan is January with a daily mean temperature of 0.1°C, an average high of 3.3°C by day and an average low of -3.2°C by night. Temperature records for this month are as high as 22°C and as low as -21°C. Throughout the year 1262.1mm precipitation can be expected with an equal spread over the year, which implies about 110mm of precipitation every month. This precipitation is spread over an average of 120.7 precipitation days. In winter months

snowfall can be added to this. The average snowfall is 713.7mm per year on an average of 10.9 snowy days. Throughout the year about 35% of the days is clouded, 35% is partly cloudy and 30% of the days is clear of clouds. October is the only month that these percentages drop by 5 to 10% and there are more cloudy days. Sunshine fluctuates between 50% in wintertime and 65% in summertime. The wind speeds can be as high as 5.0m/s in winter and 4m/s in winter. Humidity is about 70% throughout the year. For the plants these data are an important factor. Temperatures in summer cause the risk of wilting, while the temperature fluctuations in spring may cause the plants to grow or flower too early. The most important factors for plants however, are quite stable. These are sunshine and rain. Over the year the plants are ensured of enough water and enough rain. This implies that Manhattan, besides being a crowded bourough, can be a good place for plants after all.

4. Sustainable aspects 4.1. Urban agriculture

As observed in chapter 3.1 plants can provide food for humans. In this paragraph we will take a look at the possibilities to use the living façade as a food supply. The urge to plant crops in alternative places is present. “The world population is expected to reach 9.2-billion in 2050, which is approximately 3-billion more mouths to feed than there are today. Already 80% of the land suitable for growing crops is being used and the jury is still out on how much of that land will remain arable as climate change sweeps the globe.” (Sky’s the limit 2009) This means we will have to invent new ways and new places to grow our crops. One way is the urban farm: the integration of farm land in our urban landscape. In this way, we eliminate the transportation between producer and consumer and optimize our urban environment. Living façades can play a role in this problem as a system to grow our crops on. One way of doing this, is to create a double skin façade with vegetables inside the cavity planted on hydroponics. The double skin façade in this system can reduce energy costs of the building by 30%. The glass cavity works as a greenhouse for the plants and can be an efficient farming installation. (Arup Engineers 2009)(See picture on the right)

Figure 4.1: Cavity farming

Another possibility is to grow the crops on the façade, as it is done in ‘The farmer’ project. It is stated in this project that the target market for such a system would be food enthusiasts that form 14% of the American market and mainly live in metropolitan areas. The vertical farm here is an investment to reduce costs on shipping and farm footprints. The output would be fresh crops and community presence. (Greene 2009) Another project in this range is the Eathouse by ‘de Stuurlui’ and ‘Atelier Figure 4.2: Eathouse GRAS!’, an experimental vertical farm that is made to seduce visitors of the garden it is placed in (see picture on the right). Looking at the modern agricultural industry, efficiency is key however. Crops have to grow fast, be planted and harvested mechanically, and they are fertilized and irrigated with scientific precision. However, if crops are planted on a façade,

the planting and harvesting becomes a very delicate process , which cannot be done mechanically. Also, insolation of the crops will not be optimal. This constant labour on the façade can cause nuisance and discomfort to the user of the building. This makes farming on the building façade suboptimal. In most reports, the conclusion that efficiency is key, leads to urban farming towers that can deal with the crops most efficiently. These towers could provide food for large amounts of people. “Current research profiles a possible enterprise to feed up to 50.000 people based on a caloric intake of 2,200 people, a staple built up from the Centre for Nutrition Policy and Promotion’s dietary requirements and 19 floors on a 250.000 square foot area, Figure 4.3: Efficient farming or 43 floors on a 90.000 square foot area. This would include the growing of (the most nutritious fish) Tilapia in tanks, and breeding chickens for mainly egg production.” (Bosschaert 2008) These amounts of square feet equal an amount of 360.000 - 440.000 m2 in total; or an amount of 7,2 – 8,8 m2 per person. For the 600 people working in the UN environmental council an amount of 4.300 – 5.300 m2 would equal such a system, provided that the efficiency of the tower can be maintained. It is unlikely that this efficiency can be achieved on the façade of the building. Also, at least half of the façade surface would then be needed as urban farm. 4.1.1 Conclusion Compared to a glass façade, a living façade could make an extra effort in food production. Crops can be grown in a hydroponics system, such as the industrial felts system, which can be optimized for certain crops. A modular green system would also be suitable, as it can function as traditional farming land. However, this system has a bigger chance of depletion, because the nutrients in the soil are hard to refresh. Other systems are less sufficient for agriculture. Still, also in the containers of the modular green system, the planting and harvesting process is quite delicate and cannot be done mechanically. All together, the façade is not very suitable for agriculture, because of the need for efficiency that this aspect entails. It would be best to design another solution in terms of an urban farming tower. In that case, an amount of 7,2 to 8,8 m2 per person would suffice for 600 people. On the façade, the amount is likely to get a lot bigger and to take up at least half of the surface of the building volume. The aspect ‘Urban Agriculture’ will therefore get a low priority in chapter 6.2.

4.2. Bio-filtration

One of the most important sustainable influences of plants is bio-filtration. The natural environment has all kinds of mechanisms to deal with pollution. Research shows that “the removal and disposal of hazardous waste is eliminated through a completely natural method” by the micro-organisms living between the roots of the plants. (Livingwall pdf 2004) The plant absorbs water and in this way transports liquefied pollutants to its roots where microorganisms break them down to nutrients that the plants can use for growth. This process is called phytoremediation and degrades or eliminates all kinds of solvents, pesticides, metals, oil and other contaminants. By this mechanism, the plants can function as a bio filter in a living façade. In the phytoremediation process a range of processes by the plants is distinguished: Phytoextraction: uptake of substances in the plant biomass ■■ Phytostabilization: reducing the mobility of substances in the environment ■■ Phytotransformation: modification of the substances by the plant metabolism ■■ Phytostimulation: degradation of contaminants by enhancement of soil microbial activity, typically associated with roots ■■ Phytovolatilization: removal from soil or water and release into the air ■■ Rhyzofiltration: filtering water by a mass of roots; the pollutants remain absorbed in or to the roots ■■

This cleansing function can be used in a system for biological treatment for waste water. By implementing such a system, the amount of waste water from a building can be brought back to near zero. A bio-filtration system consists of a basin with plants, in which all grey and black water from the building flows. The principal components are pre-treatment grasses, woody and herbaceous plant species, a surface mulch layer, a planting soil medium and a sand layer with under drainage in a gravel bed. (Schundler 2010) The water filtration system can be implemented with water flowing horizontally or vertically (see pictures below). A horizontal system needs 3-10m2 per person with a depth of 60-80cm; a vertical system needs 1,5-5m2 per person with a depth of 80-120cm. Minimum measures suffice for grey water, maximum for black water. (Hegger 2008) Figure 4.4: Filtration systems

The moistier the soil is, the more pollutants are dissolved and the more effective this process is. This makes wetlands the most effective bio filters. Implemented in New York, the bio filters can treat the enormous amounts of waste water of the city. “Currently, the city throws 5.3 billion litres of treated waste water into the rivers each day” (New York news and features 2007)The total consumption of safe drinking water in New York city is 4,9 billion litres per day from 19 reservoirs and three lakes outside the city. (DEP 2007) Together with the run-off from rain and snow and the consumption of products such as bottled water and other drinks this forms a waste water flow. The usage of drinking water can be limited by treating and reusing this waste water on site. A system to treat waste water can be implemented in planter boxes on the façade or on larger areas on the roof. The planter boxes on the façade can be especially suitable for the horizontal system with the waste water flowing along the façade. The system on the roof or on more horizontal surfaces is more suitable for a vertical filtration system. The area available for the bio filtration system is larger on the horizontal planes than on the vertical planes, because the planter boxes cannot be very broad, due to the loads they will add to the façade. The grey water from the building is not the only pollution that the plants can filter. Rainwater also washes away many pollutants present in the city. Thereby, they are directly flushed into rivers and seas. By implementing more green surfaces in cities, plants can deal with these pollutants in rainwater. Over 95% of cadmium, copper and lead can be taken out of rainwater and 16% of zinc. Nitrogen levels also fall dramatically. (Johnston en Newton 2004) These numbers can apply to every living façade that has the possibility of absorbing rainwater for treatment by the plants and the micro-organisms amongst their roots. Overall, the implementation of plants seems to lead to all kinds of possibilities for the break down or capture of contaminants that are unwanted in the city. Therefore, the phytoremediation is an argument to implement a living façade. Making this living façade capable of filtration of grey water is an extra step to maximize its function. 4.2.1 Conclusion For the 600 people working in the Environmental Council we would need an area of 3.000 to 6.000 m2 for filtering grey water. A vertical system can be made on the roof and a horizontal system can be made along the façade. For the treatment of soil and rainwater flush-off the amount of plants in the area should be maximized. It is most important that the rainwater can be absorbed in a growing medium. This makes the modular green system most suitable. The vertical greening system can also be suitable if the growing containers form a trench around the building that can intercept the rainwater run-off from the façade

4.3. Air quality

Next to the cleansing of water, plants are also capable of cleansing air. In this process, fine particles from the air are captured on the leaves. The interaction of the plant with the air around it will be discussed in this paragraph. 4.3.1 Urban air pollutants Urban air pollution arises mainly from the burning of fossil fuels. Primary emissions include: oxides of carbon (CO2 and CO), nitrogen (NOx), sulphur (SOx), Benzene, Toluene, Ethylbenzene, Xylene, ‘PAHs’ (polyaromatic hydrocarbons) and metals and ‘fine particulates’. All these emissions have a proven negative effect on human health. Secondary products are also formed after further photochemical reactions in sunlight. These include ozone (O3), peroxyacetyl nitrate (PAN) and ‘smog/haze’ (from the mixture). In the drawing to the right we can see the causes and effects: (1) greenhouse effect, (2) particulate contamination, (3) increased UV radiation, (4) acid rain, (5) increased ground level ozone concentration and (6) increased levels of nitrogen oxides. Figure 4.5: Air pollution The short-term health risks of this air pollution include asthma, strokes, heart attacks, and sudden infant death syndrome. Longer-term effects include low birth weights, some cancers, cardiovascular problems, and schizophrenia and other mental illnesses. 4.3.2 Air filtration by plants Plants have been shown to absorb and degrade all types of urban air pollutants, thereby reducing air pollution levels. A single tree with a trunk circumference 67cm, for instance, removes 90kg of carbon dioxide, 0,5kg of ozone, and 0,9kg of sulphur dioxide and nitrogen dioxide particulates every year. (Nowak en Rowntree 1994) Research shows that trees in a parkland setting can filter out up to 85% of suspended particulates. The percentage is reduced to approximately 40% in the absence of foliage on deciduous trees in winter. The leaves of climbing plants provide a large surface area capable of filtering out dust (see picture below), pollutants and possibly even viruses. (Johnston en Newton 2004) Every plant has these abilities of cleansing air. The amounts of pollutants that can be taken from the air depend on the plant species, leaf size, metabolism and the texture of the leaves. Overall, plants with hairy leaves prove to be better in capturing fine particulates and metals from the air. These particulates are eventually washed away from the plants by rain or compost into the ground when the leaf dies. The particulates are then taken care of in the biofiltration process that was described in the previous chapter.

39 Figure 4.6: Pollution accumulating on plant leaf

In the images to the left we can see the average concentrations particulate matter with an aerodynamic diameter of less than 2.5 micrometres (PM2.5), the concentration Sulphur dioxide (SO2) and the concentration Nitrogen dioxide (NO2) in Manhattan for the winter of 2008-2009. (Concentrations in winter are usually higher and therefore of more importance in relation to public health) The figures show variations in concentration of two times or greater dependent on building, population and traffic density. (Department of health 2009) Figure 4.7: Particulate matter NY

Figure 4.8: Sulphur oxide NY

40 Figure 4.9: Nitrogen dioxide NY

It is certain that an increase of vegetation in Manhattan would partly solve this problem. Exact calculation of the amount of greenery needed, would require a complex dynamic model that includes factors such as wind, spread of greenery, spread of concentrations and dry deposition kinetics. Such an exact model seems not have been made yet. What is known about air filtering and its effectiveness, is that the air flows can bend around the green obstacle and thereby do not flow through the plants. The filtering effect can be maximized by making thin strips of greenery perpendicular to the wind direction to allow flows through them. (Schildwacht 2008) With this form more air will flow through the plants and more air will be cleansed.

4.3.2 Oxygen production Not only is it important to have clean air, but also are our lives dependent on oxygen, a gas produced by plants. Oxygen is formed in the photosynthesis process in which plants use sun energy to make glucose from CO2 and H2O: (CO2 + H2O → C6H12O6 + O2) (White 2006) Solar energy is used to split the H2O molecules. It is about 2% of the incident radiation to be trapped and used in photosynthesis. (White 2006) The reaction then continues as a ‘dark reaction’ in the so-called Calvin cycle in which the plant binds CO2 and produces its food. In this process, the plant makes an oxygen molecule for every combination of a CO2 molecule and an H2O molecule. According to American Forests, an average-sized tree releases enough oxygen throughout one day to keep a family of four breathing. (Moll en Young 1992)

Figure 4.10: photosynthesis process

4.3.3 CO2 reduction We can also notice that in the process of photosynthesis CO2, a greenhouse gas, is removed from the air. Quantities vary with the intensity of photosynthesis in the plant. For moss this is about 20gr CO2 per square meter per day, for example. In comparison: a busy road produces 14gr CO2 per square meter per day (Hunk Design 2009). For an average plant, the daily 10g growth of dry matter per m2 uses 1g of nutrients, 80-90g of water and about 14g of CO2. Water is a relatively large component in this process and limits the capacity of plants to bind CO2. (Kravcík, et al. 2007) The New York citizen produces approximately 11 tons of CO2 each year per person. (New York Energy Portal 2005) Half of this amount is produced by transportation only. To compensate for this amount each citizen would need 122 trees, 785700 average sized plants or 550.000 m2 of moss (21,75 times the site surface). 4.3.4 Conclusions For the filtration of particles of air pollution, the amount of green preferably has to be maximized. With the current knowledge it is, however, not possible to determine the exact amount of living façade needed. In terms of oxygen generation, an average-sized tree releases enough oxygen throughout one day to keep a family of four breathing. Plants should be especially present near busy roads to capture the car emissions that are hazardous to our health. A total of 150 trees or 100.000 plants or 190.000 m2 of moss would be needed to generate oxygen for all of the building users. Each citizen needs 122 trees, 785.700 average plants or 550.000 m2 of moss to compensate for CO2 pollution. The site is hence 13.000 times too small to compensate for the people working inside. Maximisation is therefore preferred on this aspect. 41

4.4. Noise reduction

Plants can absorb, reflect and diffract noise and thereby make the built environment more comfortable. On an urban scale, vegetation is often used as a sound barrier. “Shrubs, trees and berms are often used as natural noise blockers.” (ATCO 2001) The effect appears to be dependent on the plant type, planting density, location and sound frequency. 4.4.1 Indoor plants The absorption coefficients have been defined for a number of indoor plants by experiments in a reverberation chamber by Costa. These numbers include a pot with a diameter of 350mm and a height of 350mm and are averaged for multiple tests. (Costa, Constructive Use of Vegetation in Office Buildings 1995) Absorptions by Vegetation 125 to 4k Hz Plant Ficus Benjamina Howea Forsteriana Dracaena Fragrans Spathiphyllum Dracaena Marginata Schefflera Arboricola Philodendron Bark mulch

Hz m3 0,149 0,144 0,127 0,057 0,139 0,139 0,149 1 m2

125

250

500

0,050 0,120 0,1 0,085 0,105 0,05

0,120 0,093 0,1 0,07 0,045 0,13 0,23 0,16

0,180 0,050 0,09 0,065 0,09 0,06 0,22 0,26

0,210 0,133 0,105 0,095 0,065 0,22 0,29 0,46

0,230 0,130 0,145 0,16 0,11 0,23 0,34 0,73

0,360 0,263 0,165 0,305 0,305 0,47 0,72 0,88

It is shown in the table that plants absorb more sound at the higher frequency ranges, which is a common phenomenom for materials in acoustics. The absorption coefficients are calculated with an estimation of plant volume, which does not describe the plants used very accurately. It is likely that these numbers were calculated using Sabines formula on an imaginary cilinder or box volume around the plants, but unfortunately the calculation method is not described in the research paper. Furthermore, Costa measures single plants in a pot, instead of living façades. The measurements do show that large differences in absorption can exist between different plant species.

Figure 4.11: Indoor plants in table order

4.4.2 Living walls (Singapore) There has been research that measures acoustics of living faรงades by the National University of Singapore. (Wong en Tana, Acoustics evaluation of vertical greenery systems for building walls 2010) These scientists worked on measuring the insertion loss and sound absorption coefficient of eight different building systems. (See appendix A for their descriptions)

Figure 4.12: Test mounting

Figure 4.13: Calculation of insertion loss

The insertion loss was measured by microphones 1.5 meters above the ground 1m in front and 2m behind the walls. The results for the three microphones behind the wall were averaged to tone down diffraction differences. The plants were tested on a frequency range of 63-10kHz. Results, or insertion losses, were calculated from the subtraction of noise passing the test case walls from the noise passing a bare concrete wall without vegetation and thereby the noise reduction is obtained. (see picture above) The insertion loss of the plants is defined as follows:

Figure 4.14: Insertion loss results

The results are divided in four frequency zones: A, B, C and D. In the results, we see that some of the systems perform better in the A and B regions and others perform better in the C and D regions. System 2 has the best peak performance of all systems, a 9.9dB loss at 700Hz, which is strange, because this system is the vertical greenery system with greenery growing on a trellis. The explanation for this could be that the plants are growing in quite big pots of 0.61m thick, placed on the ground. System 4 has mostly plants with small leaves and moderate density, resulting in almost zero insertion loss. System five has an air gap between the system and the concrete wall resulting in more insertion loss with a peak of 7dB. Some of the systems show a negative insertion loss of up to 5dB in the results. The authors do not give an explanation for these negative losses. These could be explained by the fact that sound can bend around the walls through diffraction. However, this hypothesis cannot be confirmed with the given results, in which the measurements of the separate microphones are not included. When planting is equally distributed on the wall to cover it completely, performance of the system is better. Biggest insertion loss is mostly measured around the 700Hz band. The substrate in the systems is concluded to do most of the absorption. In the same research there was also a test performed on a greenery system in a reverberation chamber. Nephrolepis Exaltata (Boston Fern) was used for this experiment and was placed in pots on wooden racks. (see picture on the left) 140 pots of plants were defined as covering 100% of the wall with plant. 100 and 60 plants were defined as 71% and 43% cover. With the results of this reverberation experiment the sound absorption coefficient for this living wall was calculated and compared to other building materials:

Figure 4.15: Reveberation chamber

Figure 4.16: Absorption coefficients

The living wall specifically absorbs sound in the range of 500Hz – 2KHz. There is more difference in absorbance between the different covering percentages at higher frequencies. The soil performs well at low frequencies and forms the basis for the absorption coefficients in the lower ranges and the plants perform better at high frequencies. Compared to other building materials these absorption coefficients for high frequencies are very good. 4.4.3 Living walls (Delft) In 2011, Roby van Praag researched the absorption of living walls at Delft University of Technology. She performed tests on two living façade systems and several types of plants in pots with different kinds of growing media. (Praag 2011) The two systems that were tested are shown on the left. The first (Zuidkoop) is a wooden system that is a fully closed façade. The second is a system with aluminium containers (Zeger Reyers). Both are meant for indoor usage.

Figure 4.17: Zuidkoop & Zeger Reyers systems

In this research the sound absorption is determined in a reverberation test like the one in the reverberation chamber in Singapore. The test room is displayed on the left. The absorption of the two systems was defined as follows: system Zuidkoop Zeger Reyers

posititon corner length width length

125 0,22 0,31 0,02 0,02

250 0,46 0,58 0,11 0,03

500 0,71 0,85 0,23 0,2

1k 0,78 0,76 0,52 0,44

2k 0,53 0,66 0,41 0,5

4k 0,59 0,63 0,32 0,39

The wooden system performs a lot better than the aluminium, because it forms a closed wall, and the aluminium system has opening between the containers. The report concludes that the exposure of growing media forms a large influence on the absorption performance of the systems. Another interesting outcome from this report of the tests on growing media is the sound absorption of natural soil which appears to be performing a lot better at the 500 Hz band than other growing media. In general the tested growing media (soil, hydro grain, seramis) are concluded to be good sound absorbers.

Figure 4.18: Test mounting Delft

4.4.4 Comparison Tests with indoor plants show that all plants perform better in the higher frequency bands. Results fluctuate between plant types. The measurements in Singapore show that the soil has a big influence, which is also shown in the results in Delft. The systems in Singapore show the best results in the 4k Hz band, the systems in Delft in the 1k Hz band. Compared to a glass façade, the absorption of plants makes a large difference. Below the acoustic performance of a single pane of glass is displayed:

Absorption coefficient

125 0,10

250 0,04

500 0,03

1k 0,02

2k 0,02

4k 0,02

(DGMR 2005) This table shows that the absorption coefficient of a single pane of glass is a lot lower than the performance of a living façade. Where the living façade performs best in the higher bands with up to 80% absorption, the glass performs best in the 125Hz band with only 10% absorption and less in the higher bands. The living façade thus performs a lot better on sound absorption. If we look at sound insulation, the results in Singapore show only 5dB extra insertion loss through the wall, if a living façade is added to the concrete slab. If we look at performance of a single pane of glass or the effect of extra insulation on the façade, we can compare this improvement of maximum 5dB around the 700Hz band:

Single glass Single glas Double glass Double glass Gas filled double glass

4 mm 8 mm 4-6-4 mm 4-100-4 mm 5-9-8 mm

R- totaal 27 29 26 36 30

125 19 23 22 24 24

250 22 26 23 32 22

500 26 30 23 40 32

1000 30 32 32 48 39

2000 32 28 35 50 39

(Kennisbank Bouwfysica 2009) The difference between single glass of 4 or 8mm in the 500 band is only 4dB and in the 1000 Hz band 2dB. If gas-filled double glass is applied the difference is enlarged to 6dB and 9dB. For this little difference a lot of extra material and expense are made. However, the results from the experiment in Singapore cannot be understood understood totally with the given results. Another distinction should be made on these conclusions in sense of the openness of the wall. The sound insulation of the vegetation depends on the density of the vegetation. More vegetation means more sound insulation and inverse. For sound insulation the correlation between these two parameters is logarithmic. (see picture on the right) Therefore a little amount of openings in a material can cause large insulation losses. This effect can cause large fluctuations in the insulation of vegetation. For glass panes, which are fully closed, this effect of openings does not apply.

Figure 4.19: Logarithmic scale

4.4.5 Conclusions The living faรงade can absorb, reflect and diffract sound. The absorption coefficient of a living faรงade system could be as high as 0,85, as is shown in the research in Delft. The growing medium of the system has a big influence on the performance of the living wall. Soil seems to perform very well around the 500 Hz band, other growing media seem to perform best around 700 Hz. On the urban level, the absorption coefficient can make a large difference compared to the hard city materials. Compared to glass the plants have a very good overall performance. On the building scale, the plants can add an average of 5dB around 700 Hz to the sound isoltation of the faรงade. This is a great improvement compared to the differences that can be made by the choice of glass. Results used are not complete enough to fully understand all the effects of the faรงade, but do help to understand that the plants have a large influence on the acoustic performance of the faรงade. It is also expected that these amounts of insulation are heavily influenced by vegetation density.

4.5. Biodiversity

Worldwide, around 17.000 of the 48.000 assessed species are threatened with extinction. (IUCN 2009) This is a strong indication that biodiversity worldwide should get serious attention. Overall, it can be seen that there is also a decrease of species in cities. However, there is a group of species that grows due to adaption to the city environment. Also, alien species immigrate to cities from all over the world and flourish. This leads to new ecotypes in cities that contain new subspecies. (Wittig 2004) The creation of more green surfaces will help this process. In this way, a living façade can contribute to the biodiversity of our cities. Biodiversity is important to a city. “Ecosystems provide three kinds of services to the city: provisioning, regulating and enriching.” (UNEP & UN Habitat 2005) Provision that biodiversity offers, includes aspects such as food and clean water (see chapter 4.1 & 4.7); regulating functions of city ecosystems include water cycles and climate stabilization (see chapter 4.7, 4.8 & 5); enriching functions include aesthetic and spiritual terms (see chapter 4.6)

Figure 4.20: Bird Richness

In terms of provision the living façade creates a possibility for local plants to grow. Thus, the façade can enforce local ecology. The NYFA (New York Flora Association) has compiled a list that contains all flora in the state of New York. Distinction is made between native and imported plants. According to this source, some 482 different species of flora are known to grow in the state of New York. (New York Flora Atlas sd) These can be given the opportunity to grow in the ever growing cities by implementing them on living walls. Besides plants, the façade might be able to house animals as well. In Manhattan there is no wildlife, except for some bird species. According to the Federation of New York State Bird Clubs there are now as many as 455 species representing 19 orders and 62 families of birds in the entire State of New York. In Manhattan there are less than sixteen species. (New York State Biodiversity Project 2001) Studies show that this biodiversity is influenced by changes to green areas and green structures. For example, the density of house sparrows in residential areas is roughly three times greater in situations where gardens are present. “The model used predicts a drastic fall in the abundance of house sparrows if even a small area of private gardens becomes one of uninterrupted building.” (Wener en Zahner 2009)

Overall, two things are important to support wildlife. First is providing food sources, either directly in the form of berries, nectar, nuts or seeds or indirectly as a result of encouraging invertebrates. Figure 4.21: Food source

Figure 4.22: Shelter

The second is to provide shelter , which is necessary for wildlife to feed, hide, mate and breed. Usually it is native species that are of most value, because they have evolved together with the animals that depend on them. Shrubs with flowers can provide nectar for butterflies; climbing plants can provide nesting possibilities for wrens, blackbirds, song thrushes and house sparrow; Particular species such as cotoneaster, ivy, climbing roses and some honeysuckles produce berries enjoyed by birds as cold weather food. (Johnston en Newton 2004)

The provision of these plants and animal species by the living façade is important to the stabilization of the urban eco-system itself. “Ecosystems are important for regulating pests and vector borne diseases that attack plants, animals and people. Ecosystems regulate pests and diseases through the activities of predators and parasites. Birds, bats, flies, wasps, frogs and fungi all act as natural controls.” (TEEB 2010) Protection against these pests and diseases is a large issue in Manhattan. The whole population has problems with so-called ‘bedbugs’ nowadays. “Tiny blood-sucking bedbugs have become an epidemic in New York City. The little pests have invaded even the cleanest and most expensive apartments in neighbourhoods around New York.” (Skillings 2010) NYC’s Community Health Survey (2009) found 6.7% of adults reported bed bugs in their homes in the past 12 months. A regulating city eco-system would thus be very welcome for this problem. 4.5.1 Conclusion Biodiversity in city ecology is important, because of its provisioning, regulating and enriching functions. For the city ecology itself, the regulation of pests and diseases is an important function. A healthy city environment can solve problems such as the current bed-bug nuisance. The living façade can house plants and thereby also provide food and shelter for animals. In this way, the façade contributes to a rich ecology.

4.6. Social and psychological improvements

The plants also have a direct impact on people: people seem to feel better in a green environment. This theory is called biophilia and suggests that people feel better next to all that is alive and vital. It is a feeling of a bond between humans and other live forms that comes from “the connections that human beings subconsciously seek with the rest of life.” (Wilson 1984) Scientific studies show the effects that plants have on human health. For instance, it is established that visiting a botanical garden lowers blood pressure and reduces heart rate. (Owen 1994) Other studies show that the presence of vegetation will speed recovery from stress. (Ulrich 1991) Also, research shows that in an office space the score sum of symptoms of discomfort was 23% lower during the period when subjects had plants in their offices compared to the control period. (Fjeld 1998) Houses can even gain up to six percent extra value due to a good tree cover in the surroundings. (Morales 1980) A part of the bond that is named in the Biophilia hypothesis could be explained by the fact that our eyes are more sensitive to green light than to other colours. The retina of the eye consists of cones and rods: the rod cells function at low light intensities, as in night situations; the cone cells are less sensitive and used in day situations and allow us to perceive the wavelength of light passing our eye. There are three types of cone cells, each with a sensitivity peak at a different light wavelength. According to this sensitivity, we can determine the colour of the light. (Cyckowski en Grobstein 2009) If we combine the sensitivity of the three types of cones, a peak occurs at 555 nanometres: a yellowish green colour. (Robinson 1984) This means we react more to the colour green than to other colours. Below two diagrams are shown: the first shows the sensitivity of the three types of cones. The second shows the total sensitivity of the three cones combined.

Figure 4.23: Sensitivity per cone

Figure 4.24: Combined sensitivity

4.6.1 Conclusion Studies show that plants have a positive effect on humans. The hypothesis that people feel better in a green environment is called the Biophilia hypothesis. This effect may be explained by our sensitivity to the colour green. There is, however, not enough knowledge on this topic to quantify an amount of plants for the façade.

4.7. Water

Living walls contribute to the water cycle by creating the possibility of evaporation. This is important, because, on a global scale, evaporation of water is the largest and most important component for the conversion of solar radiation. It is also the largest hydrological component together with precipitation; only water that evaporates causes rainfall. Attention for these cycles is necessary, because of the major interests that are involved. According to the United Nations, 50 million people are at risk of displacement due to desertification over the next ten years and two billion people are potential victims of the creeping effect in the future. (United Nations University 2007) Figure 4.25: Water cycle In this chapter we will discuss these effects of the living façade on the water cycle. 4.7.1 The water cycle Evaporation creates a large and a small water cycle of condensation and precipitation. (Schmidt 2006) We will explain here what these cycles are and what the effects of water in these cycles are, to understand their importance. There are around 1400 million cubic kilometres of water on this earth , which we can divide in four environments: ‘in the oceans’, ‘on land’, ‘in the atmosphere’ and ‘in the biota’. (Kravcík, et al. 2007) ■■

■■

The oceans cover 70.8% of the surface of the earth and contain 97.25% of all water. Their temperature is a key to the regulation of temperatures on the planet. Water on land would be mostly associated with rivers (0.0001% of all water volume) and lakes (0.01% of all water volume), but a bigger part is formed by water in solid state such as glaciers or snow that contains 2.05% of volume of all water and up to 70% of the reserves of fresh water. Apart from this solid water, groundwater and soil moisture represent 0.685% of all water, exceeding the volume of rivers and lakes. The volume of water in the atmosphere is around 0.001% and has a key role in local thermoregulation, fluctuating in concentration from 1-4% (CO2=0.0383%). Water in living organisms forms 0.00004% of the volume of all water on earth. On land vegetation has an important role in maintaining thermal stability by evaporation.

Reservoir Oceans and seas Icebergs and glaciers Groundwater Lakes Soil moisture Atmosphere Rivers Biosphere Total global reservoir of water

V (mln. km3) 1370 29 9.5 0.125 0.065 0.013 0.0017 0.0006

Percentage 97.25 2.05 0.68 0.01 0.005 0.001 0.0001 0.00004

1408.7053

100

Solar radiation falling on the earth causes water from all environments to evaporate and the evaporation of each water molecule cools the surface of the earth. The water vapour rises into the atmosphere where it condenses under the influence of cold air and thus releases thermal energy. Also, the water vapour in the form of clouds shields solar radiation. In this repeating process, water works as a cooling mechanism for our planet. In this process, we can see a large cycle in which 86% of vapour evaporates from the seas and 14% from land while 26% of all the precipitation falls over land. In the small cycle, water moves in a closed circulation over the same terrestrial environment , which forms 57%of all precipitation over land. This means we should ensure evaporation over land, if we want to have stable precipitation. In this process, plants fulfil the role of valves that protect the ground from overheating and drying out and that optimize the amount of evaporation by transpiration by which they can regulate the temperature of the air. If there is disruption of vegetation by, for example, deforestation, agricultural activities or urbanization, solar energy is turned into heat and temperature differences increase. Figure 4.26: Large and small cycle

4.7.2 Importance of the water cycle The sun sends 180.000 TW of energy to Earth every year. In comparison, humanity only uses 14 TW for its economy. Of this energy, about 30% is reflected back into space, 47% becomes thermal radiation and 23% used in the water cycle for evaporation. The maximum amount of radiation reaching the surface of the earth, can be as much as 3.000 KWh/m2, but in our geographical surroundings it reaches an average value of 1.100 KWh/m2. The exact amount of energy depends on the weather and the time of year. (NASA, Surface meteorology and Solar Energy 2010) The fate of this radiation depends on the amount of water in an ecosystem , which distributes the radiation over sensible heat (an increase of temperature), and latent heat (due to the vaporization of water). The specific latent heat of water at a temperature of 25°C and under normal pressure is 2.243,7 KJ/ kg, which is the amount of energy used to evaporate a litre of water without increasing the temperature. If water is not present on land, solar radiation is directly turned into sensible heat. In dehydrated areas about 60% of solar radiation is turned into sensible heat, whereas, in areas saturated with water, about 80% of solar radiation is turned Figure 4.27: Global radiation into latent heat. 4.7.3 Rainwater In addition to the latent heat effect, the infiltration of water in living façades leads to a more equal burdening of the city drainage system. The paved surfaces in the city lead to rapid run-off of rainwater. Cities normally drain this rainwater away from the territory as quickly as possible, leading to dehydration of a piece of land. This can lead to a higher risk of flooding in other areas or in sewage systems, but also to a lack of latent heat in the urban area. This contributes to the Urban Heat Island Effect as described in the next paragraph. “Average green roofs absorb 75% of precipitation that falls on them so that immediate discharge is reduced to 25% of normal levels”. (Newton 2004) This means that sewers are better able to cope with run-off from the streets and other hard surfaces and that the risk of flooding is considerably reduced.” (Johnston en Newton 2004) In this way, these façades contribute to the small water cycle by keeping water in the city. This will prevent water run-off to the oceans and thereby scarcity of water on land in many parts of the world. This could be a future horror as predicted by the UN. (UNDP 2006) 4.7.4 Conclusions For the conservation of the water cycles, as many plants as possible are desirable on a site. This especially holds true for an overheated city like New York. A façade that can capture more water would be preferable. However, most important is that the plants are present and provide evaporation. To enlarge the effect on the heating of the city, the greenery on the site should be maximized.

4.8. Heat island effect

Plants are shown to have an effect on The Urban Heat Island Effect (IHIE). This effect is the result of two main properties of urban areas. First, buildings, roads and paved surfaces store heat during the day, which is then released slowly over the evening due to the thermal properties of the surface materials and the building geometry, which trap the heat stored during the day. This problem is connected to the climatic principles described in paragraph 4.7.1. The second contributing factor to the UHIE is due to the artificial heat released into the urban atmosphere by combustive processes from vehicles, industrial activity and the heat that escapes from commercial and domestic air conditioning. (Urban Heat Islands and Climate Change 2006) It is measured that during the summer months the daily minimum temperature in the city is on average 4째C warmer than surrounding suburban and rural areas. (New York City regional heat island initiative 2006) 4.8.1 Absorption of heat The first aspect, the absorption of solar radiation and release of heat, relies on the properties of the materials used in the city, such as asphalt, brick and concrete and various kinds of roof materials. These often stony and dark materials absorb most of the solar radiation resulting in an increase of sensible heat in the city. These surfaces can cause cities to be averagely 5째C warmer than a meadow at noon on a summer day.

Figure 4.28: Heat island

It is obvious that this is an unwanted effect our buildings and infrastructure have on our living environment. Solutions to this problem can be found in both reflecting solar radiation in a way that the heat is turned away from the city, and in creating a way to turn the solar radiation into latent heat. Surfaces can reflect heat by their colour. Most roofs in cities are now coated with black EPDM, which absorbs all solar radiation. If these surfaces are changed from black to white, a lot more solar energy is reflected back into space and thereby the surroundings get cooler. The next images show a relation between the temperature and vegetation in Manhattan. In Manhattan, about 64% of the surfaces are dark and absorb solar radiation. (NASA, making of Urban heat island 2009)

54 Figure 4.29: Temperature

Figure 4.30: Vegetation

The temperature differences of New York compared to its surroundings is 4°C on average. (New York City regional heat island initiative 2006) As we can see in the image on the previous page, green spaces have a large effect on the cooling of the city, as described in the previous chapter. This is caused by all the water the plants in these green spaces evaporate. “For each gram of evaporated water plants absorb 633 calories”. (VEJA 2009) This is as much as 2648,5 kJ/kg, a little bit more than the latent heat of water. Living walls can improve the city by offering more surfaces that evaporate water. Also, unlike a stony surface, the living wall does not store heat, whereby it does not contribute to the Heat Island Effect. A model of the climate in New York (MM5) made by Gaffin, shows weighted average near-surface air temperature reductions for selected mitigation scenarios. These scenarios are averaged over all times of the day and at 3 PM, and assume implementation in 100% of the available area of Manhattan. (New York City regional heat island initiative 2006)

In this table we can see again that especially in Manhattan, roofs and surfaces have a large influence compared to the other areas. The biggest advantage can be gained by a combination of urban forestry and light roofs. By implementing urban forestry and light roofs, we reverse the disappearance of vegetation from the city and reintroduce the evaporation process of these plants, while the dark surfaces that absorb solar radiation are made reflective and thereby cooler. According to Gaffin, about 17% of Manhattans surface can be planted with trees. 14% of all the dark surfaces is formed by roofs. Other surfaces are roads, pavements and of course: façades. Implementation of living façades can help eliminate one of these three remaining categories. Living walls deal with this effect by the transpiration of the plants, in which solar radiation is turned into latent heat, which prevents the rising of sensible heat.

4.8.2 Addition of heat Another part of the problem is the energy use and heat from machines, installations, cars and industry. In Manhattan, a big part of this is heat released by air conditioning. In the image on the next page the energy use in New York is shown, which suddenly rises as temperatures get higher than 18°C (61°F). This increase in energy use is mainly caused by the demand in air cooling. (New York City regional heat island initiative 2006) The problem is paradoxical. On the one hand the heat in the city leads to increasing energy demand for air-conditioning; on the other hand the air-conditioning heats the city even more. In the graph we can see the increase in energy demand of about 100 to 150 GWh caused by a temperature increase of 10 degrees. The air conditioning machines deliver this energy back to the city in the form of extra heat. This is a very unwanted effect, in which a lot of energy is wasted and the actual problem only becomes worse. Figure 4.31: Energy demand

4.8.3 Conclusion By maximizing the amount of planting on the site, the effect on the Urban Heat Island Effect can also be maximized. Preferably, the materials in the applied living façade have as less warmth absorbing surface exposed to solar radiation as possible. If there are parts of the façade that are not covered by greenery, they should have a light colour. By upholding this aspect the energy use of the entire city can be lowered in the future.

5. Heat

As we have seen in the previous chapter plants have an influence on climate and temperature by their capability of evaporation. Just as in the case of the Urban Heat Island Effect (on city level) the plant’s capabilities can be used on a building scale as well. In this chapter a focus on the thermal influence on a building scale is given. The aim of the thermal calculations is to make an equation by which the amount of living façade, plants and glass can be determined for the façade of the building , which can give grip on the design project and lead to a better façade.

5.1. Thermal influence

The plants on the living façade can improve thermal insulation for the building for a number of reasons. In this paragraph a description of the important factors for these aspects will be given to provide a basic understanding which can help to make calculations with heat. There are several ways in which the plants improve thermal insulation for the building: ■■ ■■ ■■ ■■ ■■

Air in-between the leaves insulates Wind is curbed Wind speed around the building lowers Leaves provide shades Leaves provide cooling by water evaporation

An important factor for the magnitude of the thermal impact is the kind of plant that grows on the façade of the building. Each kind of plant has its own properties , which can make quite a difference in the thermal behaviour of the façade. In the various kinds of vegetation, plants can be chosen on the basis of several requirements , which will be explained below: (Lesiuk 2000) ■■ ■■ ■■ ■■

Deciduous vs. Evergreen Complete vs. incomplete canopies Leaf angle distribution: vertically hanging leaves through to horizontal leaves Transpiration capabilities: high transpiring plants vs. low transpiring plants.

The deciduous plants lose their leaves in winter and can thereby be helpful in getting more sunlight and energy into the building in winter, while they can shade the building in summer. With their leaves, the plants also lose their thermal capabilities for insulating the building. In places where there is a lot of wind, this might be a problem, because the façade will thus get less insulated in winter, when most insulation is needed. Deciduous plants can therefore be used best in cases where sunlight is the most important factor to apply the plants. The evergreen plants keep their leaves in all seasons and are green the whole year, which explains this term. These plants therefore keep their influence on the thermal and daylight entry properties of the building in winter. This is especially useful for the limitation of convection by wind , which lowers the heat loss in a winter situation. The leaves create extra insulating capabilities for the building façade, by locking an extra layer of air around the building , which reduces the heat flow through the façade.

Deciduous plants can be stimulated by keeping the soil or growing medium moist, since evergreen species grow better on drier grounds than deciduous species. (Atwell, Kriedemann en Turnbull 1999) Strictly speaking, the canopy of a plant is the part of the plant that grows aboveground. In this list of requirements for plants, the canopy of a plant refers to the outer layer of leaves of a plant that forms a plane over the living faĂ§ade. Plants that have complete canopies form a closed plane while plants that have incomplete canopies leave gaps in the vegetation , which causes the rear structure to be visible and exposed to sun and wind. If plants with a full canopy are planted on the living wall, the sunlight will be shaded more and the wind will be blocked better. The canopy of a plant is not only dependent on the amount of leaves but also on the leaf shape, disposition and margin. Some plants have leaves with a shape or margin that cannot easily form a closed layer; other plants have a disposition of leaves that is too spread to make a closed layer. (see also appendix B for leaf characteristics) A way to express the amount of leaves and their coverage is the Leaf Area Index (LAI). This is the ratio of the total upper leaf surface of vegetation divided by the surface area on which the vegetation grows. Bare ground has a LAI of 0 and dense forest a LAI of 6. A high LAI does not strictly mean that there is a more closed canopy. A tall plants with the same LAI as a smaller plant forms a less closed layer. However, for the average plant the canopy will be more closed if the LAI is higher. In the picture below the LAI of three plants is shown; the growing area is defined by the dotted rectangle.

Figure 5.1: LAI

The leaf angle distribution (LAD) of a plant is a mathematical description of the angular orientation of its leaves on the basis of the zenith and azimuth. For example, grasses have an erectophile (vertical) LAD and oaks have a planophile (horizontal) LAD. Some plants have a more erectophile LAD at the top and a more planophile LAD at the bottom , which might be caused by the plantâ&#x20AC;&#x2122;s strategy not to shade itself. The leaf angle distribution affects the completeness of the canopy and thereby the shading of sunlight and the blocking of wind. Plants, growing on a vertical surface, provide better shading if they have a more erectophile LAD; plants on a horizontal surface provide better shading with a planophile LAD (See picture below).

Figure 5.2: Use of LAD

The transpiration capabilities of plants differ per kind and are also related to the amount of sunlight that shines on the plant. Plants tend to cool themselves by evaporation in order to maintain their internal temperature, which is necessary for the chemical and biological processes in the leaves. The plants respond to the air temperature, as well as to the heat of the sunlight shining on their leaves, and to the heat released in the photosynthesis process. The transpiration rate of the plant determines the amount of cooling. If the transpiration rate is higher than the moisture absorption rate of the roots, the plant runs the risk of wilting. This makes the transpiration capacity also dependent on the humidity of the soil or planting medium. Besides, plants that live in a more moist growing medium are shown to wilt with a higher moisture content. (Moinat 1932) This means that the amount of cooling is limited and an optimum can be found Figure 5.3: Transpiration between growing medium moisture and transpiration. The plants on the living faรงade have to be chosen on the basis of these four requirements. As shown, the requirements can have various consequences for the warmth of the building. In order to be able to make a choice, the thermal properties have to be determined first. This can lead to conclusions on the requirements for the plants. The only factor that influences the choice for a specific system is the transpiration capability. If the transpiration capabilities should be high, a more moist system would be needed, but this is accompanied by a high risk of wilting. If this risk has to be lowered to prevent the green living faรงade from turning into a brown living faรงade, a system should be chosen that is less moist, representing a system with soil that is not irrigated too much. This results in lower transpiration rates.

5.2. Calculations on thermal behaviour

Now that the most important factors for thermal behaviour entry are clearer, a calculation can be performed with the properties of the living façade. In this paragraph, the thermal influence will be quantified to express its influence.

Figure 5.4: Stec’s calculation model

5.2.1 Model In the report “Modelling the double skin façade with plants” (Stec, Paassen en Maziarz 2004) a model is made of a double skin façade (see picture on the left). In this model a heat flow in a cavity with plants is described. The heat flow passes, from left to right: an outer glass pane, a first half of a cavity, plants (Hedera Helix), a second half of a cavity and an insulated wall. In this report a mathematical model is given that simulates the heat flow through these layers. Eight thermal knots are defined to express the radiation, convection and transmission in the cavity. Radiation from the environment is not considered in this model. The right part of this model can be used to simulate plants that are on the outside of a glass façade. Such a model can look like the model on the left. Radiation falls on (qsun) and through (αr1) the plants and warms the plants and glass. Part of this heat forms a convection flow (αc2; αc3) through the cavity. The outside temperature influences the model by another convection flow coupled to these two (αc1). A part of the heat of the plant is made into Latent Heat (LH) by the transpiration process. The heat in the glass is transmitted from T1 to T2.

An important difference between this model and the model of Stec is the air Figure 5.5: Moderation of Stec’s model flow in the cavity: the wind will pass through the plants and exchange heat (z1) with the outdoor air (Tout), so the cavity will be heated less than in the Stec model. This influence of the wind is not completely certain though: “In experiments in Germany no air movement was detected in the space behind a 50cm thick growth of ivy.” (Johnston en Newton 2004) This means that there has to be a very thick layer of leaves before wind is eliminated. It is therefore assumed that a wind flow through the leaves does

occur. The thermal knots derived from Stec are useful to indicate the parts of the thermal process. The three convection flows, the radiation flow, the Latent Heat, solar radiation and wind will influence the glass façade that is covered by plants. We will use these factors to investigate the properties of the façade further. 5.2.2 Leaf coefficients The total heat flow through the plants in this model is qtotal= qtransmission + qradiation + qconvection [W/m2]. A simple calculation of these heat flows can be made by using standard coefficients for reflection, transmission, convection, absorption and solar energy used (for photosynthesis) for leaves (Krusche, et al. 1982). We use the minimum and maximum coefficients of a single leave to make a minimum model (1) in which most of the solar energy passes the plant to the glass of the building and a maximum model (2) in which most of the energy is reflected, used for photosynthesis, or converted into Latent Heat and the least energy passes to the glass façade behind the plant. For the calculation qsun= 600W/m2 is used. This represents the amount of solar energy on a typical summer day on a south orientated (vertical) façade. The typical characteristics of HE++ glass are defined as d=23mm (4-15-4); M= 20kg/ m2; U=1.62W/m2K; G (passing heat) = 0.60; L (passing light) = 0,75. The heat flow on the glass of the façade is influenced by the plant via reflection (5-30%), energy used for photosynthesis (5-20%) and absorption by evaporation (20-40%). Model 1 is calculated with the highest coefficients for energy passing the plant and model 2 is calculated with the lowest coefficients for energy passing the plant in order to form the minimum and maximum model of energy that can pass the living façade, which shows the influence of the plant. Both models are expressed in the table below: Plant Reflection Transmission Convection Photosynthesis Latent heat On façade:

min% 5 10 10 5 20

max% 30 50 50 20 40

model 1 5 40 30 5 20 100%

[W/m2] 30 240 180 30 120 420

model2 25 10 10 20 35 100%

[W/m2] 150 60 60 120 210 120

In both of the models, the amount of heat that passes the plant is formed by the sum of the transmission and the convection flows. For model 1 this is 420W/m2 and for model two this is 120W/m2 as shown in this table. In model 1 about 420W/m2 passes the plant in the most extreme case, without taking into account the heat convection flows directed away from building instead of going to the façade. In reality the value will be closer to 240W/m2, because not all convection energy flows toward the façade. This is even more probable when wind is also taken into account. The convection heat flow with average wind is 19 to 20 W/m2K and with strong wind 100 W/m2K. If wind has an influence on the space behind the plant as was presumed before, the heat flow to the façade will thus be smaller.

In model 2 there is a maximum amount of passing heat of 120W/m2. This amount will also most likely be closer to 60W/m2 as explained for model 1; this is a reduction in the heat flow from solar radiation of almost 90% compared to a glass faรงade without plants growing in front of the glass. This is a very high percentage and more likely, the heat flow will be somewhere in between 60 and 400 W/m2; in which the lower limit of 60 W/m2 is a bit unrealistic. Theoretically however, there must be a reduction in the amount of sunlight passing, compared to the normal situation, because a part of the light will always be blocked by a leaf. As we can see in the figure below this is an improvement on the heat load on the glass of the faรงade, as the plants function as added blinding to the faรงade.

Figure 5.6: Plants as blinds

This effect on heat flow (like blinds against the sun) can also be seen in the results of experiments of Stec with plants and blinds in a double skin faรงade. The results in temperature are shown in the table below.

We see in this table that the plants and the blinds result in a lower temperature on the wall. This is, of course, because they shade a part of this wall. The plants cool the wall even more than the blinds , which can only be ascribed to the extra energy used in photosynthesis and absorbed in the transpiration process , which turns the heat energy into latent heat.

The calculation used above is not very precise, however, not only because typical percentages are used, but also, because these percentages are derived from a single leaf and not a total plant. In case of a total plant we must take into account that a plant has a distinct leaf growth density that affects the canopy of leaves on the living façade. We can take the properties of a specific plant into account by looking at the Leaf Area Index and the Leaf angle distribution of a plant. Both LAI and LAD vary for every plant kind and therefore the thermal behaviour of plants differs a lot. Even the size and age of a plant count in this matter. A plant that is not full-grown will have fewer and smaller leaves. This lowers the LAI and therefore the chance is higher that sunlight can pass the leaves. The shade of the plant leaves can be generalised in a simple formula that describes the amount of passing sunlight. Of the 600W/m2 solar radiation in the previous calculation, a maximum of 420W/m2 passes a single leaf. This amount is more likely to be lower than the amount of 120W/m2 which model 2 showed. In this report we will estimate the amount of sunlight to decrease to an average of 330 W/m2. This means that 0.55 times the radiation passes the plant. Every next leaf will multiply this amount by another 0.55 part. This means that the relation between the LAI and the amount of passing sunlight can be described as qpassing= q*0,55^LAI. With this relation we can be more specific about the influence of the canopy of a plant on the thermal properties of the façade. For example, a full-grown plant can have a LAI of 5 or even much higher, depending on the species. In that case, the heat load on the façade will decrease by a power of five , which results in a heat flow of qpassing= q*0,55^5= 30 W/m2 reaching the façade. This indicates the influence of plant choice and lifetime on the behaviour of the façade. If the light just passes the plants, the two models based on behaviour of leaves in sunlight do not apply and the glass of the façade gets a full 600W/m2 solar radiation. This will definitely increase the heat load on the building. To be more precise in calculations, it would be smart to calculate with parts that are not covered by plants and parts that are covered by plants with a given Leaf Area Index. 5.2.3 Ambient temperature of the leaves Looking at the research of Wong on the thermal influence of living walls there is a temperature influence of the wall that affects all surrounding air. The ambient temperature around the living wall can be about 3°C lower in summer, even at a distance of 30cm from the living façade. (Wong, Tan, et al. 2009) This cooling effect from the evaporation of the plants influences the temperature difference between in- an outside and thereby influences the heat flows through the façade. If, for example, the in- and outside temperatures are 25°C, there is no convection heat flow through the façade, because there is no temperature difference between in- and outside. The plants cause the ambient temperature around the living façade to be 22°C by their evaporation. This temperature difference will start a convection heat flow from the interior of the building to the cooler plants. Now the building cools down compared to the ‘normal’ situation.

On a typical summer day with a solar radiation of qsun= 600W/m2 on the south orientated façade, the convection heat flow through the glass will be q=U* ΔT= 1.62W/m2K*3°C = 4.86W/m2; a cooling capacity of almost 5W per square meter of living façade.

This also means that the convection flows from the leaves, as defined in models 1 & 2 in the previous paragraph, will flow away from the façade and that the total heat flow from the sun to the façade is limited to 60- 240W/ m2, which is only the light transmitted trough the leaves. Of course this is only the case if the LAI of the plants in front of the glass is at least 1. Also, if the outer temperature is higher than the inner temperature, the convection heat flow has to be calculated with q=U* ΔT= 1.67 [W/m2] * (Tout-3-Tin) in order to determine the heat flow. Figure 5.8: Heat flow from glass to plant

5.2.4 Winter situation In winter the plants can contribute to the building by means of insulating the façade from the cold outside air and by decreasing the influence of the wind. “In winter, evergreen species offer a degree of insulation by trapping a layer of air against the façade and reducing convectional heat loss. An insulating effect of up to 30% has been recorded, although such a high percentage is only likely when temperatures fall close to freezing” (Johnston en Newton 2004). Again, for this effect the canopy has an enormous influence on the real insulation value, since it defines the capability of the plant to enclose a layer of air between itself and the building. However, these results count especially for old buildings with a lack of thermal insulation. The insulating effects are not expected to greatly influence the façade as defined in the preliminary design, because the plants will not grow dense enough, especially not in front of the glass. Also, the insulation from a new well-insulated façade is expected to be much higher than the insulation from the air between the plants. Therefore the capacities of insulation by trapping air will not be discussed further.

5.3. Interior climate

In this paragraph a focus on the interior climate will be given to define the amount of solar energy needed or unwanted. This can help to make a statement on the desired shading and insulating properties of the faĂ§ade . In this way, the proportion and density of the greenery on the faĂ§ade can be determined with the knowledge on heat reduction from the previous paragraph. First all important factors of the thermal calculation will be explained. Successively these are defined as the comfort temperature of the indoor climate, the convection flows in summer and winter, solar radiation, internal heat loads, thermal mass, ventilation, influence of greenery and the warming of the air. Together these factor will be used in an Excel model that will be explained in the last part of this paragraph. 5.3.1 Comfort temperature In order to be able to define the amount of greenery on the building, the most sustainable solution for the interior climate of the building is defined. This would be the situation in which the comfort temperature in the building can be maintained with heating by gaining solar energy, cooling with ventilation and without adding any other energy source. The standard temperature for all United Nations buildings in Manhattan is set at 21Â°C. In terms of comfort, this temperature can be higher in summer and lower in winter. In the graphs below the comfort temperature is placed as a graph of the outdoor temperature:

Figure 5.9: Comfort temperature without openable windows

Figure 5.10: Comfort temperature with openable windows

In buildings with windows that can be opened, the indoor temperature can be higher in summer than in a building without such windows. For the design for the United Nations it will be assumed that the windows cannot be opened. Most influential to the interior temperature are the hottest and the coldest month of the year, which will be normative for the thermal calculations. In New York, January is the coldest month with a daily mean temperature of 0.1°C, an average daily high of 3.3°C and an average daily low of -3.2°C; July is the hottest month with a daily mean of 24.7°C , an average daily high of 29°C and an average daily low of 20,4°C. A high ambition for the comfort level will be set to meet the American expectations of the building and in view of the American habits of climate control and air-conditioning. Therefore, the acceptance level of the indoor temperature will have to be higher than 90% to give comfort to most of its users. According to the previous graphs, the comfort temperatures for the extreme summer and winter conditions will be at least 20.5°C and at the most 23°C in January; and at least 22°C and at the most 25°C in July. This indicates that, in terms of comfort, the temperature may differ from the 21°C target that is set by the UN. This variation can help to allow more solar radiation into the building and thus make a more open façade. 5.3.2 Heat transfer through the façade The first important aspect of the indoor temperature is the heat transfer through the façade. This heat flow is caused by the temperature difference between the outdoor temperature and the indoor temperature, which influences the amount of heat in the building and thereby the indoor temperature. For calculations of the heat flow through a façade, the heat transfer coefficient (U) of the façade is determinative, together with the temperature difference (ΔT ) between indoor and outdoor climate according to the formula q=U*ΔT. In this formula U is expressed

in Watts per square meter degree Kelvin (W/m2K) and ΔT in degrees (°C =°K) which results in a value q in Watts (W/m2). The value ΔT is defined as ΔT=Tout-Tin, which means that a positive flow is directed into the building and a negative flow is directed out of the building. The total amount of energy can be determined by multiplying the heat flow (q) by the amount of façade surface (A) according to Q=q*A, which results in an amount of heat (Q) in Watts (W). In the Excel model this amount of heat per hour can be converted to Joule, on the understanding that 1W=1J/s. This means that an amount Q[W]*t[s]=Q[J] or 3.600 seconds * [J/s] = 3.6[KJ] energy flows into the building in one hour.

building A: building B: building C: building D: building E:

Façade (m2) 11.648 14.780 11.080 9.817,5 10.392,9

Figure 5.11: Building shapes

For the glass façade an U value of 1.62 W/m2K has been defined (see paragraph 5.2.2). The outdoor temperatures in New York were also given previously (in paragraph 3.3). The total amount of façade can be determined with the dimensions of the 5 building variants. These are given on the right (for calculation see appendix C). Note that the façade surface of shape B is 150% of the façade of building D. To show the influence of the convection flow through the façade, the flows for summer and winter situations will be calculated. Based on an indoor temperature of 21°C and the average daily high temperatures that occur in the daytime in January, the temperature difference between the exterior and the interior temperature in winter will be ΔT=Tout-Tin=3.3-21=-17.7°C. The heat flow through the glass will then be q=U* ΔT =1.62*-17.7= -28.67W/m2, which is a heat loss. In July, the temperature difference ΔT= Tout-Tin =29-21= 8°C. This means the heat flow will be directed from the outside in, through the glass, and the heat flow q=U* ΔT = 1.62*8= 12.96W/m2, which means the building warms. With these flows and the façade surfaces (see appendix C) the amount of energy for an hour can be calculated in MJ: (in summer situation the flow is directed into the building, in winter it is going out of the building)

A: B: C: D: E:

Surface (m2) 11.648 14.780 11.080 9.817,5 10.392,9

Summer Heat flow (W/m2) 12,96 12,96 12,96 12,96 12,96

Heat (MJ) 543 690 517 458 485

Winter Heat flow (W/m2) 28,67 28,67 28,67 28,67 28,67

Heat (MJ) 1202 1525 1144 1013 1073

We can see that in summer, the amount of energy that enters the building as a heat transfer is about a hundred times smaller than the amount of energy that flows out of the building in winter. This situation is only true at the beginning of our calculations, though. Because of the heat transfer the indoor temperature Tin will rise in summer and fall in winter, causing Î&#x201D;T= Tout-Tin to become smaller. In order to be able to (statically) calculate the situation of the building without ignoring this effect, the situation will be calculated per hour. 5.3.3 Solar radiation Another large influence on the buildingâ&#x20AC;&#x2122;s indoor temperature is the amount of solar radiation that falls on the faĂ§ade. Especially in summer, this radiation can cause the building to heat up extremely. This should be prevented, particular in light of the amounts of energy used for airco systems in Manhattan and the share that this energy has in the Urban Heat Island Effect (as described in paragraph 4.9.2). For the calculation of the solar energy that falls on the building, the solar radiation [W/m2] in normal direction will be used. Because a model with intervals of an hour is made, the solar radiation will also have to be defined per hour. For that reason the data available for the Netherlands will be projected on Manhattan. The values of 15th December with the least radiation and of 15th June with the most radiation are given in the table below: (Van der Linden 2005) 6:00

7:00

8:00

9:00

10:00

11:00

12:00

13:00

14:00

15:00

16:00

17:00

18:00

19:00

20:00

5:00 Solar radiation Summer (W/m2) Winter (W/m2)

129

327

624

732

798 10

838 324

862 507

874 587

876 597

867 544

848 401

813 117

758

665

506

239

The amount of solar energy that falls on a façade surface is not only dependent on the solar radiation but also on the direction of that façade in comparison to the sun. A square meter façade that is directed in the normal plane of the radiation, catches more solar energy than a square meter of façade that makes an angle of 45° with this radiation.

Figure 5.12: Direction of the facade

To define this direction, the place of the sun has to be defined. This position can be described with the azimuth (A) and the elevation (h). The azimuth describes the position of the sun on the horizontal plane as an angle measuring from the North direction. The elevation describes the angle between the direction of the solar rays and the horizontal plane. With these two angles, the position of the sun in the sky can be described from a certain point. Figure 5.13: Postition of the sun

To make variations on the building volume easier, the calculation will use sunlight that only comes from the south. In this way, the orientation of the sun only depends on the elevation and the radiation only falls on the south façade and roof of the building. The elevations through the day on 15th December and 15th January are given in the table below: (US naval observatory 2011)

19:00

20:00

18:00

17:00