GREEN ROOF AS AN ELEMENT OF BIOPHILIC ARCHITECTURE by Mekhika G Mohan

GREEN ROOF AS AN ELEMENT OF BIOPHILIC ARCHITECTURE

Submitted by Mekhika G Mohan A dissertation submitted in partial fulfilment of the requirements For the Degree of Bachelor of Architecture

Holy Crescent College of Architecture

Mahatma Gandhi University Kottayam 2019

Holy Crescent College of Architecture, S.Vazhakulam, Alwaye

CERTIFICATE

This is to certify that the dissertation work titled ―Green roof as an element of biophilic architecture‖ is a bonafide work of Mekhika G Mohan, under my guidance, submitted as Semester VII & VIII subject for the award of ―Degree of Bachelor in Architecture‖ during the term of 2018 to 2019 through Mahatma Gandhi University, Kottayam.

Prof. (Ar. Sriparvathy Unni)

Director (Ar. Pratheek Sudhakaran)

Holy Crescent College of Architecture, S.Vazhakulam, Alwaye

DECLARATION

I, Mekhika G Mohan, hereby declare that this dissertation entitled â&#x20AC;&#x153;Green roof as an element of biophilic architectureâ&#x20AC;? is the outcome of my own research study undertaken under the guidance of Ar. Sriparvathy Unni, Professor at Holy Crescent College of Architecture, Cochin. It has not previously formed the basis for the award of any degree, diploma, or certificate of this Institute or of any other institute or university. I have duly acknowledged all the sources used by me in the preparation of this dissertation.

Name of the student: Mekhika G Mohan Date: 20/05/2019 Place: Alwaye

III

ACKNOWLEDGEMENTS First of all, I thank The Almighty God for blessing with his profound grace, without which this dissertation would not have been a success. I would like to express my deep sense of gratitude towards my guide Ar. Sriparvathy Unni for giving me her valuable suggestions and guiding me, throughout the course of my research. I would like to extend my heartfelt gratitude to the Faculty members of the Department of Architecture for their constructive support and cooperation at each and every juncture of the research. Finally, I express my heartfelt gratitude towards my parents and friends for the mental support they had offered me and for their immense encouragement throughout my years of study and towards the successful completion of the work .

ABSTRACT The increased urbanisation, urban heat island effect, global warming are affecting humans badly so that they are more conscious about their built environment. Thus, the innate connection between humans and nature is increasing which leads to the increased practice of biophilic architecture. Green roofs are yet to develop in countries like India and are gradually gaining popularity. Green roofs are being practised in metropolitan cities and becoming an interesting sustainable building design element. People are more demanding than ever in the residential segment due to increased competition and increased marketing budgets of the builders. Mainly in countries like India where the temperature is high, green roof serves greater energy savings compared to other roofs. Through shading, insulation, evapotranspiration and thermal mass, green roofs help to improve the thermal performance of a building. This research gives a brief idea about green roof, its types, its components, specification of materials and about how green roof help to improve the thermal performance of a residential building. The primary and secondary datas are being collected from literature reviews and case studies. Conducted interviews with renowned architects in Kerala about how green roof helps in cooling buildings. The findings from the primary and secondary survey show that how effective green roof system is in reducing problems like pollutions, urban heat island effect, solar albedo effect etc. This report contains various comparative analysis taking into account various parameters that affect the energy performance of buildings. This study mainly gives a brief idea about how green roof can improve the energy performance of a residential building and also concludes about how well green roof can be used as a biophilic architecture element in todayâ&#x20AC;&#x2DC;s scenario.

KEYWORDS Sustainable, Human Comfort Scale, Extensive Green Roof, Intensive Green Roof, Ecotect Analysis, Ecosystem Benefits, Urban Heat Island

LIST OF TABLES Table 1: : Structure of the report ................................................................................................ 6 Table 2: Research methodology................................................................................................. 7 Table 3: Methodology ................................................................................................................ 8 Table 4: Drainage Type P ........................................................................................................ 21 Table 5: Installation of Drainage type G.................................................................................. 23 Table 6: Installation of Drainage type M ................................................................................. 25 Table 7: Estimated annual conductive heat gain through unit roof area ................................. 28 Table 8: Estimated Annual Storm-water runoff from different roofs ..................................... 28 Table 9: Comparison of types of green roof ........................................................................... 29 Table 10: Load of the green roof with respect to the substrate ............................................... 29 Table 11: Comparison of different roofing element with their surface albedo value .............. 31 Table 12: Green roof material specifications ........................................................................... 32 Table 13: Cost of components of green roof .......................................................................... 33 Table 14: Green roof configurations for intensive green roof ................................................ 34 Table 15: Green roof configurations for extensive green roof ............................................... 34 Table 16: Types of plants used ............................................................................................... 50 Table 17: Comparative analysis .............................................................................................. 51

LIST OF FIGURES Figure 1: Temperature vs. time graph showing todayâ&#x20AC;&#x2DC;s scenario ............................................. 1 Figure 2: Global and regional maps showing the location of urban agglomerations ................ 3 Figure 3: Global and regional maps showing the location of urban agglomerations ................ 3 Figure 4: Extensive green roof ................................................................................................. 9 Figure 5: Intensive green roof .................................................................................................. 10 Figure 6: Semi- intensive green roof ...................................................................................... 11 Figure 7: Classification of green roofs..................................................................................... 11 Figure 8: Modular System ...................................................................................................... 12 Figure 9: Loose Laid/Built-Up systems .................................................................................. 12 Figure 10: Section of green roof ............................................................................................. 13 Figure 11: Shading and evapotranspiration ............................................................................. 18 Figure 12: Systems of green roof based on drainage .............................................................. 19 Figure 13: Green Roof Systems .............................................................................................. 20 Figure 14: Installation of Drainage type P .............................................................................. 21 Figure 15: Installation of Drainage type P .............................................................................. 22 Figure 16: Installation of Drainage type G ............................................................................. 24 Figure 17: Installation of drainage type M ............................................................................. 26 Figure 18: Section of green roof ............................................................................................. 27 Figure 20: maximum temperature fluctuation of a typical flat conventional roof .................. 30 Figure 19: Runoff vs. water retention capacities ..................................................................... 30 Figure 21: Anti-slip cleats clipped to anti-sip mesh ................................................................ 32 Figure 22: Anti-slip tees .......................................................................................................... 33 Figure 23: Figure: 3D view of Green House Residence ......................................................... 35 Figure 24: Section of green roof ............................................................................................. 36 Figure 25: Sectional view of Green House Residence ............................................................ 36 Figure 26: Earth Cube residence ............................................................................................. 37 Figure 27: Details about context and site ................................................................................. 38 Figure 29: Zoning of different spaces in the site and the residence......................................... 39 Figure 30: Earth Cube Residence ........................................................................................... 39 Figure 28: Zoning of plan ....................................................................................................... 39 Figure 31: View of the residence from the site ........................................................................ 40 Figure 32: Analysis of each green space in the residence ....................................................... 40 Figure 33: Visual axis of spaces .............................................................................................. 40 Figure 34: Zoning of site plan and floor plans ......................................................................... 41 Figure 35: Section of green roof .............................................................................................. 41 Figure 36: Malabar Headquarters ........................................................................................... 42

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Figure 37: Area statement ....................................................................................................... 42 Figure 38: Site plan of Malabar Headquarters ......................................................................... 43 Figure 39: First basement plan ................................................................................................ 44 Figure 40: Second basement plan ........................................................................................... 44 Figure 41: Third and Fourth basement plan ............................................................................. 45 Figure 42: Ground floor plan ................................................................................................... 46 Figure 43: First floor plan ........................................................................................................ 46 Figure 44: Second floor plan.................................................................................................... 47 Figure 45: Third floor plan ..................................................................................................... 47 Figure 46: Fourth floor plan .................................................................................................... 48 Figure 47: Terrace plan ........................................................................................................... 48 Figure 48: Section .................................................................................................................... 49 Figure 49: Section of green roof ............................................................................................. 50

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TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................. III ABSTRACT ........................................................................................................................... IV LIST OF TABLES .................................................................................................................. V LIST OF FIGURES .............................................................................................................. VI CHAPTER 1 ............................................................................................................................. 1 INTRODUCTION.................................................................................................................... 1 1.1 BACKGROUND OF THE STUDY ................................................................................. 1 1.1.1 GAP IN THE RESEARCH ........................................................................................ 3 1.2 NEED FOR THE STUDY ................................................................................................ 3 1.3 HYPOTHESIS .................................................................................................................. 4 1.4 AIM .................................................................................................................................. 4 1.5 OBJECTIVES ................................................................................................................... 5 1.6 SCOPE AND LIMITATIONS ......................................................................................... 5 1.7 STRUCTURE OF THE REPORT .................................................................................... 6 1.8 RESEARCH QUESTIONS AND METHODOLOGY .................................................... 7 CHAPTER 2 ............................................................................................................................. 9 LITERATURE REVIEW ....................................................................................................... 9 2.1 INTRODUCTION ............................................................................................................ 9 2.2 TYPES OF GREENROOF ............................................................................................... 9 2.3 GREEN ROOF SYSTEMS ............................................................................................ 11 2.4 TYPES OF PLANTS USED .......................................................................................... 12 2.5 BASIC CHARACTERISTICS OF GREEN ROOF PLANTS ....................................... 13 2.6 BENEFITS OF GREEN ROOF: .................................................................................... 15 2.7 DISADVANTAGES OF GREEN ROOF ...................................................................... 17 2.8 HOW GREEN ROOF REDUCE URBAN HEAT ISLAND: ........................................ 17 2.9 INSTALLATION AND MAINTENANCE OF GREEN ROOF: .................................. 18 2.10 GREEN ROOF POTENTIAL ANALYSIS FOR INDIAN CITIES: DISCUSSION (Dubey) ................................................................................................................................. 28

CHAPTER 3 ........................................................................................................................... 29 STUDY/RESEARCH............................................................................................................. 29 3.1 TYPES OF GREEN ROOFS AND ITS SPECIFICATIONS ........................................ 29 3.2 HOW GREEN ROOF HELPS IN PREVENTING ALBEDO EFFECT ....................... 30 3.3 GREEN ROOF MATERIAL SPECIFICATIONS ......................................................... 31 3.4 GREEN ROOF CONFIGURATIONS ........................................................................... 34 CHAPTER 4 ........................................................................................................................... 35 CASE STUDIES ..................................................................................................................... 35 4.1 LITERATURE CASE STUDY ...................................................................................... 35 4.1.1 GREEN HOUSE RESIDENCE ............................................................................... 35 4.2 LIVE CASE STUDY...................................................................................................... 37 4.2.1 EARTH CUBE RESIDENCE .................................................................................. 37 4.2.2 MALABAR HEADQUARTERS ............................................................................. 42 CHAPTER 5 ........................................................................................................................... 52 RECOMMENDATIONS AND CONCLUSIONS ............................................................... 52 5.1 CONCLUSIONS ............................................................................................................ 52 5.2 RECOMMENDATIONS................................................................................................ 52

CHAPTER 1 INTRODUCTION 1.1 BACKGROUND OF THE STUDY Mainly contemporary cities experience more stressful life while the built environments show increasing problems like air and water pollution, greenhouse effect, urban heat island effect, solar albedo effect etc. By considering these problems, a new design strategy is to be established where nature needs to play a significant role which is known as biophilic architecture. This design approach creates an innate connection with nature that helps to make buildings more effective human abodes. One of the biophilic design approaches for ‗sustainable building practice‘ in cities is green roofs. Today, building occupants are more conscious of their built environment and demand for green spaces in the form of green terraces for spending their leisure time has increased. Green terraces are becoming a trend in nowadays in residential segment too. Almost 75 lakh upto 2 crore is being spent on it. The durability of these roofs is no less than three to five decades and sometimes even more. The application of green roof on residential buildings in Kerala is limited and is mainly concentrated on metropolitan areas. Main ecosystem services of a green roof include improved storm-water management, regulation of building temperature, reduced urban heat-island effect and increased green spaces. A green roof is defined as a kind of roof that is completely or partially covered with vegetation, planted over a waterproof membrane. Its main components are its layers like root barrier and drainage layer and irrigation system. It is also known as eco-roofs, vegetated roofs or living roofs.

Figure 1: Temperature vs. time graph showing today‘s scenario (Solar responsive India July 2018 pdf)

Planting vegetation on a building is being practised thousands of years ago. Earlier, it was done for aesthetic purposes but now it is used to cure problems in todayâ&#x20AC;&#x2DC;s environment. The oldest green roof appears to be the ziggurat of ancient Mesopotamia, built from the fourth millennium until 600 B.C.E. located in the courtyards of temples in major cities (Green Roofs and Their Implementations in Architecture The obstacle and challenges in Erbil city, 2015). Ancient known green roof is the Hanging Garden of Babylon, constructed in 500 BC. These gardens consisted of many stone

arches and

they are waterproofed using a combination of reeds and tar. Trees and plants are being planted over it. Sod was used in green roof construction in more recent history and it provides insulation for houses, built of natural materials. Now the trend in green roof technology has been changed dramatically but the principles of green roof technology is same since these times. Germany was the first to adopt modern green roof technology and it was begun in the early seventies and it was marketed on a large scale at that time. Then in the late eighties began the emergence of extensive green roof. The reason is that to create lighter and cheaper systems which could be applied even to flat roofs. The main reason for the practice of green roof was to attain biophilic architecture thereby restoration of nature and protection of the roof membranes from the elements and temperature fluctuations. Green roofs provide many benefits for communities, neighbourhoods and individual property owners by protecting and restoring local watersheds. Green roofs can help reduce the total amount of storm water runoff as well as the sudden surges of runoff by filtering, absorbing, and detaining rainwater. Green roof filters the rain water falling on it and it absorbs the pollutants thus reduce the volume of pollutant entering nearby water bodies and improve the quality of water. As an element of biophilic architecture, green roof attracts bees, birds and creatures and provides a habitat of living for wildlife. Due to population pressures in urban areas since the Renaissance period, steeply terraced gardens were commonly seen in Italy. In contemporary architecture, Le Corbusier and Frank Lloyd Wright made extensive use of green roofs. This was due to the arising concerns about the nature quality and rapid decline of green space in intensely developed areas. Le Corbusier and Frank Lloyd Wright were the modern architects who used the concept of green roof and Le Corbusier encouraged rooftops as another location for urban green space, and Wright used green roofs as a tool to integrate his buildings more closely with the landscape (Green Roofs and Their Implementations in Architecture The obstacle and challenges in Erbil city, 2015).

Figure 2: Global and regional maps showing the location of urban agglomerations with 750000-plus inhabitants in 1950. Source:Revi et al(2014)

Figure 3: Global and regional maps showing the location of urban agglomerations with 750000-plus inhabitants projected for2025. Source:Revi et al (2014)

1.1.1 GAP IN THE RESEARCH: Often, guidelines for green roof system, its benefits is been researched whereas the method of implementing it even in residential buildings is not been researched. My study focuses on the benefits of green roof in the residential buildings and how well it can be used for temperature control and as an effective replacement of open space even in residential buildings.

1.2 NEED FOR THE STUDY ď&#x201A;ˇ

Green roofs can extend the lifespan of a roof by protecting the waterproofing layer from weather and temperature changes.

ď&#x201A;ˇ

They can provide sound insulation, reduce the heating and cooling requirements

and slow storm water runoff, alleviate the urban heat island effects, capture gaseous and particulate pollutants and improve air quality. 

The structures can support local biodiversity, create a new open space for recreation, growing food and support the inhabitants‘ physical and mental health.



There is more scope for biophilic architecture due to drastic changes in climate and due to increasing urbanization problems.

1.3 HYPOTHESIS ―Better living for all and future generations‖ is the main desire and need of the universe. Due to urbanization, natural resources are being utilized without any proper planning and limit. This results in unsustainable development. If this situation continues for a longer term, it will cause disruption and revolt. Mainly, coming generations are being affected due to lack of sufficient natural resources. Thus the desire of universe to have a better living condition will get shattered if the situation is not healed properly. So nature‘s main basic rule is to be followed. i.e.,‖ Reduce, reuse and recycle‖. Focusing on energy efficiency or sustainable buildings, the need for green buildings emerged and biophilic architecture emerged. Green roofs or terrace gardens are popular in trend as they add to the aesthetics and also they have many benefits like they can facilitate water harvesting system, prevent green house effect etc Green roofs benefit biodiversity, storm water management and reduce the heat island effect. Green roofs act as a sponge by soaking up rainwater which would otherwise run off, contributing to erosion and increasing pressure on sewer systems. As a basic cooling mechanism, plants absorb water and then gradually released through transpiration, cooling the air above the humid mass of planting medium and plants adds insulation to the building below thereby reducing the need for air-conditioning. Green roofs can be built everywhere. Anyone who has observed vegetation flourishing on abandoned rooftops, dry- stone walls or gravel road sides can testify that the right plant will find its way into the most inhospitable-looking place.

1.4 AIM The study aims at assessing the benefit of green roofs on residential buildings in India.

1.5 OBJECTIVES 

Research about green roof technology in residential building.



Identify the best solutions that green roof technology can offer to improve energy efficiency.



Survey the possibility of transforming the normal roof to the green roof systems.



Survey the effects of green roof on thermal behaviour inside the buildings.

1.6 SCOPE AND LIMITATIONS SCOPE 

The study helps in finding the best tool for designing solar responsive building.



It helps in understanding the methods to create a healthy sustainable environment.



It also gives a brief about climate responsive features of the roofing system and helps in preventing solar albedo effect, urban heat island effect etc.



As a professional, the future of architecture and construction will be ecological and sustainable.



The demand for green products and solutions are also increasing which is creating a great opportunity for architects and builders who are prepared to deliver high performance.



Today, biophilic architecture is being a trend due to the increase in urbanisation problems and loss of biodiversity and habitat.

LIMITATIONS 

My study focuses on green roof of residential buildings.



This study is limited to the benefits of green roofing system as an element of biophilic architecture.



It also focuses on aesthetics and sustainability without addressing other factors.

1.7 STRUCTURE OF THE REPORT The dissertation is divided into 5 chapters: Chapter 1: It include general introduction which include aim, objective, scope, limitations and methodology of the report. And also the background study, history of green roof, need for the study, research questions are being dealt in chapter 1. Chapter 2: It consists of the background study of the research where topics such as the evolution of green roof and its relevance are discussed along with an in-depth study. The data collection of the relevant topic is being included in this chapter. Chapter 3: It deals with the concept of green roof as an element of aesthetic, detailed information about different types and systems of green roof, their benefits to humans and selection of appropriate materials. Chapter 4: It deals with live, literature case studies of green roof system. Green roof of different projects are being taken and being analysed. Chapter 5: It deals with general comparative analysis, inference and conclusion. And overall summary of the dissertation is also given. The whole report gives an analysis and conclusion about the topic, ―Green roof as an element of biophilic architecture‖.

CHAPTER 1

CHAPTER 2

CHAPTER 3

CHAPTER 4

CHAPTER 5

• INTRODUCTION - Background study, Classification, History and Evolution, Aim, Objective, Scope, Limitations, Methodology, Research question and need for the study

• LITERATURE REVIEW - Data collection

• STUDY/RESEARCH - Specifications of materials, cost

• CASE STUDIES - Live and Literature case studies with inference

• CONCLUSION - Comparative analysis, inference, conclusion and recommendations

Table 1: : Structure of the report (Author)

1.8 RESEARCH QUESTIONS AND METHODOLOGY RESEARCH QUESTIONS 

Which type of green roof is proper for residential buildings



How does green roof affect the thermal behaviour of buildings



How is the irrigation of green roof done



What are the plant species proper for green roofing



Will green roof help to prevent problems like global warming, albedo effect, urban heat island etc

OBJECTIVES

Understanding

RESEARCH

QUESTIONS

METHODOLOGY

the How

buildings Study of present scenario

environmental problems are caused by the buildings.

nature?

To find various issues What that affect nature.

affecting using

net

case

study,

journels, articles are

the Study of climatic problems

environmental

through articles

problems in the present scenario? Understanding

the What

are

the Analysis of climatic factors

climatic factors in warm factors that affect and humid region

the

climatic

variation

warm and humid region? To

explore

the Effectiveness of Live,

possibility of designing presently biophilic

Literature

using studies and analysis.

environment biophilic

using green roof

architecture elements Table 2: Research methodology (Author)

case

METHODOLOGY IDENTIFY DIFFERENT TPES OF GREEN ROOFS AND THE TECHNIQUES OF INSTALLING IT ON ROOF.

IDENTIFY THE MATERIALS USED IN THE LAYERS OF GREEN ROOF, COST

CASE STUDY REVIEW OF

PRACTICAL

RESEARCH

GREEN ROOF BUILDINGS

ANALYSIS/

DIFFERENT

ANALYSIS

TIME

FROM

SURVEY

PERIODS

DATA

LITERATURE

LIVE

CASE STUDY -

STUDY-

DOCUMENTS

THE

INFORMATION,

STUDY

INTERVIEWING

REGARDING

PARAMETERS

SKETCHES,

BUILDINGS

THE

GREEN ROOF

INVOLVED

WITH GREEN

INHABITANTS

ROOF

OF THE GREEN

CASE

FROM THE

ROOF TABLES

RESIDENTIAL

LIST

OUT

AND

BUILDING

BUILDING RELATED

CLIMATE, RAINFALL, LOAD etc

PHOTOGRAPHS

DEVELOPMENT OF ROOF

GRAPHS

COLLECTED

AND GRAPHS

THE GENERATING

ESPECIALLY

GREEN SYSTEM

THROUGH BOOKS,

PDFs,

RESEARCH PAPER etc

COMPARATIVE ANALYSIS OF ALL THE DATAS AND PROVING THE GREEN ROOF AS AN ACCEPTABLE PROPOSITION FOR RESIDENTIAL BUILDING

Table 3: Methodology (Author) â&#x20AC;&#x201C;

CHAPTER 2 LITERATURE REVIEW This chapter explores the current theories and literature about green roof. It begins with an overall understanding about green roof and methods of installing it on roof.

2.1 INTRODUCTION Green roofs provide cool and clean air by allowing the air to get filtered. Air-borne particles such as smog and carbon dioxide are being taken by leaves of the plants and get filtered. Green roof also helps in preventing environmental impacts like urban heat island effect, global warming, green house effect etc. On a hot day, an urban area can be 10 degrees hotter than the surrounding area due to human activities; green roofs stay substantially cooler (up to 40 – 50 degrees cooler) than conventional roofs helping to reduce the surrounding air temperature. This practice may also increase property values and reduce property maintenance fees. Other than these, green roof has so many energy saving benefits. The life of green roof can be increased by green roof as it is an additional layer that helps to protect roof from ultraviolet rays and thermal stress. Green roofs also provide an extra layer of insulation that helps to reduce heating and cooling costs. So by installing a green roof, you can help protect the environment and conserve water resources.

2.2 TYPES OF GREENROOF 1. Shallow green roof system, also known as extensive green roof system. It includes: 

Modular tray systems i.e., growing medium and vegetation in ‗modules‘ or trays.



Modular continuous systems i.e., roll of growing medium and vegetation.

Figure 4: Extensive green roof at Whistler Daycare Centre ( BCIT Commons)

Characteristics of extensive green roofs are ( BCIT Commons): 

3- 6″ of light weight growing medium.



Low-maintenance ground-cover plants.



Ideal for large flat-roof buildings and apartments.



Suitable for low-sloped residential roofs and retrofits.



Desert grasses and succulent plants.



After one year, they do not require watering.



Annual spring weeding of tree seedlings & weeds, brought in by birds and wind.

2. Deeper green roof systems or green roof gardens (also referred to as ‗intensive‘ green roofs).

Figure 5: Intensive green roof at Chicago city hall ( BCIT Commons)

Characteristics of intensive green roofs are ( BCIT Commons): 

8-12 inches, or more, of growing medium.



Fully landscaped roof top garden.



Require regular maintenance -similar to an at-grade garden.



Diverse plants and trees can be planted (avoid plants with invasive root systems).



Walkways, railings and lighting.



Parks, playgrounds or vegetable gardens are possible.

3. Semi-intensive green roofs– It‘s a combination of both extensive and intensive green roofs.

Figure 6: Semi- intensive green roof at Vancouver Public Library ( BCIT Commons)

Figure 7: Classification of green roofs according to type of usage, construction factors and maintenance requirements. (Babak Raji, 2015)

2.3 GREEN ROOF SYSTEMS Green roofs can be of either in modular (trays or continuous mat) or loose laid/built up. 1. Modular systems: Modular systems is made up of readymade flexible (vegetative mats into a woven fabric) or firm (metal or recycled plastic) trays or modules (POLE CHOOBI). Modules have the main components of the green roof system already combined (except the

irrigation process), including: Drainage, Growing medium, Root barrier, Borders, Plants.

Figure 8: Modular System (POLE CHOOBI)

2. Loose Laid/Built-Up Systems: They are separate installations of green roof components. So it increases design opportunities, biodiversity and experience.

Figure 9: Loose Laid/Built-Up systems (ALPHA ROOFING SERVICES LTD)

2.4 TYPES OF PLANTS USED Extensive green roof: 

Mat forming species of sedum, sempervium and moss



Ferns could be used in dry shady conditions.

Semi extensive green roof: 

Dry habitat perennials and ornamental grasses and even bulbs.

Intensive green roof: 

Drought tolerant plants are used as they tend to be both sun and wind tolerant.



Intensive green roofs have deeper growing media, which allows them to incorporate larger plants, including shrubs, bushes, and trees, in their design (Tolderlund).

2.5 BASIC CHARACTERISTICS OF GREEN ROOF PLANTS (Tolderlund): 

Lasting, thriving or active throughout the year and throughout the seasons or through many years (perennial plants).



Lateral and adaptable root system (ﬁbrous or woody root system, without a deep tap root).



Low nutritional requirements.



Low maintenance.



Light weight at maturity.



Drought resistant in both cold dry winters and hot dry summers.



Wind resistant.



Non invasive.



Low, compact, spreading growth habit.



Low dry matter content to alleviate ﬁre safety concerns.

Basic components of green roof are:

Figure 10: Section of green roof (green-roofing-construction)



The primary organic matter of the light weight engineered growing medium may or may not be the soil and they have good water retention property without water-logging the plants.



The growing medium and the roof may have same time of durability. Basically, the growing medium contains at least 80 percent of lightweight inorganic materials and 20 percent of organic material like topsoil (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA).



Plants of the extensive green roofs will have growing medium of height, 6

inches (15 cm) and plants of intensive green roofs will have growing medium of 8 inches (20 cm) or more (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA). 

A filter membrane layer of the green roof may be a geotextile that allows excess water from the growing medium to flow out and also prevents the fine particles from washing away and clogging the roof drain.



A drainage layer of the green roof helps in preventing overloading of the roof and provide a good balance of air-moisture in the growing medium. Drainage layer may be in the form of egg crates which allows the storage of some water.



A root barrier helps in preventing leakages by not allowing the aggressive roots of the plant to penetrate.



A waterproofing/roofing membrane protects the building from water leakages or penetrations. Any roofing membrane can be used in green roofs, although single-ply waterproofing membranes are generally thicker and more durable on green roofs than on conventional ones (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA).



A cover board of a green roof is a thin, semi-rigid board that acts as a protective shield or separation and also support for a roofing membrane. .



A vapour barrier layer of the green roof is may be a plastic or foil sheet that prevents the entry of moisture content through the ceiling.

Building and roof structural support: Green roof components weigh more than normal roofing so extra panels or load bearing supports should be added. Main weighing element of the green roof will be the growing medium and the plants. An extensive roof weighs from 15-30 pounds per square foot and it will depend on the depth of the growing medium and other site-specific factors. Other maintenance activities including: 

Fertilize: Once in a year, the owner should add fertilizer to the green roof to avoid acidity.



Irrigate: Natural irrigation is ideal for all plants so an ideal green roof should have natural irrigation. Irrigation depends on local climate and it helps in reducing fire risks and increases evaporative cooling in green roofs. Intensive and semi-intensive green roofs always needs better irrigation due to the presence

of variety of plants whereas extensive green roof requires only less irrigation. For time-saving and less labour cost, owners of the green roof install drip irrigation system. 

Replant: After some time, replantation or addition of the growing medium is necessary for the better growth of plants.



Fire Safety: Sometimes green roofs may catch fire if it is not saturated with water. So during summer, it‘s better to water the green roof daily. The most common ways to increase fire safety are to:

a) Use plants and grasses that don‘t get dried during summer and use fire resistant plants like sedums and a growing medium that is low in organic content (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA). b) Construct fire breaks on the roof— 2-foot (0.6 m) widths of concrete or gravel at 130-foot (40 m) intervals (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA).

2.6 BENEFITS OF GREEN ROOF: Green roofs offer many benefits to urban areas especially where there is lack of habitat. While some of the benefits can be quantified and assigned financial values, other benefits are intangible and their values are difficult to quantify objectively (Joseph). This section of the dissertation report summarizes the major benefits of green roofs regardless of when, to whom, or with what value the benefit accrues.

Individual Benefits: 

Energy efficiency - A green roof increase the energy efficiency of the building and also reduces a building‘s energy demand on space conditioning by preventing greenhouse gas emissions, through direct shading of the roof, evapotranspiration and improved insulation values. Green roofs prevent heat entry into the building during summer. The plants in the green roof shade and cool the roof. Both plants and growing medium provides insulation. Water in the plants and the growing medium evaporates thus cools the roof. The growing medium acts as a thermal mass by storing solar energy.



Urban agriculture - Green roofs can be used for agricultural purpose by providing opportunities for owners to have their own farm.



Roof durability - Green roofs are less likely to crack because they maintain temperature.



Fire retardation - Compared to conventional roofs, green roofs have a much lower burning heat.



Reduction in electromagnetic radiation - Green roofs are known to reduce the electromagnetic radiation from wireless devices by 99.4% (Herman 2003).



Noise reduction - Green roof have excellent noise attenuation thus reduces noise penetration by up to 40 decibels.



Enhanced marketability - Green roof have increased market value since it became one of the most used feature of biophilic architecture.

Public Benefits: 

Biodiversity and Habitat Preservation - Urban sprawl has badly affected the ecological balance and biodiversity. Green roofs can act as a transitional space or an intermediate space by connecting nature and buildings. Potential for biodiversity or habitat increases with plant height, growing medium depth etc.



Aesthetics and New Amenity - Green roofs not only provide recreational green space for city dwellers and living space for birds and insects; they often improve the architectural aesthetic of the building. Green roofs also encourage a more thoughtful approach to city planning by increasing amenity and green space, encouraging community gardens and food production and extending commercial and recreational space and it has been known that green roof reduces stress and patient recovery time, thus increases property value (Joseph).



Waste diversion - By prolonging the service of the HVAC equipment through decreased use (Joseph).



Storm Water Management – The percentage of permeable surfaces are getting lower due to urbanization so large volume of storm water is sent through various management components such as pipes, ditches and tunnels that leads to water bodies. This increase of runoff causes pollution in rivers and streams. Green roofs can convert impervious rooftops into pervious surfaces by absorbing water and then release it slowly over a period of time. Some water is taken up by the plants and released back to the atmosphere through evapotranspiration and excess water is discharged from the green roof system to the roof drain.

 Reduce urban heat island effect - The urban heat island (UHI) refers to the increase in temperature in the city centre compared to the surrounding natural landscape. Lack of habitat and natural landscape causes less evaporative cooling thus increases the surrounding temperature. Dark building materials on rooftops and pavements further absorb and trap solar heat and these factors combine to cause increase in the urban heat island effect. The implementation of green roofs can reduce UHI by introducing vegetation onto the surfaces prone to excess heat in urban areas (Joseph). Temperature can be reduced by means of evapotranspiration and simply covering the roof with less absorbing surfaces. 

Improved Air Quality - Plants remove airborne particles by absorbing them and purifies air. The particles get washed off by the leaves into the growing substrate during rain.

2.7 DISADVANTAGES OF GREEN ROOF 

Green roof has a higher initial cost.



Maintenance will depend on the type of green roof.



Green roofs require stronger supports for carrying the load of the layers of the green roof, mostly the soil.



Green roof plants that suits with the local climate should be planted otherwise it will not grow well.

2.8 HOW GREEN ROOF REDUCE URBAN HEAT ISLAND Green roof prevents urban heat island effect by shading and evapotranspiration. 

Shading: Roof membrane is protected by the green roof as the plants of the green roof and the associated growing medium, a specially engineered soil block the sunlight. All green roofs don‘t have trees and vines, so green roof indicates how other vegetation shade surfaces below them. For instance, the amount of sunlight transmitted through the canopy of a tree will vary by species (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA). During summer, only 10 to 30 percent of the sun‘s energy reaches the area below a tree and the remaining portion will be absorbed by the leaves which are used for the

process of photosynthesis. Some are being reflected back into the atmosphere. During winter, the amount of sunlight transmitted through a tree is much larger. It is almost 10 to 80 percent because evergreen and deciduous trees have different wintertime foliage, with deciduous trees losing the leaves and allowing more sunlight to enter (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA). Shading reduces temperature of the surface below the plants and these cooler surfaces, in turn, reduce the heat transmitted into buildings or re-emitted into the atmosphere. For instance, a multi-month study measured maximum surface temperature reductions due to shade trees ranging from 20 to 45ºF (11-25º C) for walls and roofs at two buildings.7 Another study examined the effects of vines on wall temperatures, and found reductions of up to 36ºF (20ºC) (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA). The growing medium of a green roof protects the underlying layers from exposure to wind and UV radiation. 

Evapotranspiration: Water is being absorbed by plants through their roots and emits it through their leaves and it‘s known as the process of transpiration. The conversion of water from a liquid to a gas, evaporation, also occurs from the surfaces of plants and the surrounding growing medium in a green roof. Both process of transpiration and evaporation, together, known as evapotranspiration. So the process of evapotranspiration cools the air by using the heat from the air to evaporate water.

Figure 11: Shading and evapotranspiration (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA)

2.9 INSTALLATION AND MAINTENANCE OF GREEN ROOF For all types of green roofs like extensive, Intensive or semi-intensive green roof, the

main factors that should be taken into account are: Vegetation: The main factors that determine type of vegetation are: 

Type of roof (extensive or intensive),



Building design,



Local climate,



Available sunlight,



Irrigation requirements,



Anticipated roof use

Extensive green roof plants are typically hardy perennials having shallow-rooting. They are self generating plants that spread rapidly and require minimal nutrients. They should tolerate sun, wind, and extreme temperature fluctuations and succulents, such as sedums, are well adapted for green roofs because they are drought-resistant and their high water content makes them fire resistant (Reducing Urban Heat Islands: Compendium of Strategies-Green roofs-EPA). Drainage system: By categorizing green roof systems based on type of drainage and thickness of growing media, one can determine the load, slope, rainwater retention characteristics and type of vegetation.

Figure 12: Systems of green roof based on drainage (Laguna, 2011)



Drainage Type P: Drainage Type P uses drainage plates; waffled plastic sheets and it store water

above and drain water below. Drainage plates are lightweight and are easy to install. They are available in 2 sizes to meet the drainage and water storage requirements of almost any type of green roof. ď&#x201A;ˇ

Drainage Type G: Drainage Type G uses a lightweight, porous inorganic granular media and it is embedded with slotted plastic triangular drainage conduit. Granular media is heavier and is more labour-intensive to install when compared to drainage plates. It helps in plant root growth by providing a superior environment.

ď&#x201A;ˇ

Drainage Type M: Drainage Type M uses a drainage mat, a multi-layer fabric mat which combines soil separation, drainage, and protection functions into 1 unit. When compared to other systems, this system is the fastest to install and also the thinnest and lightest one. Since its water storage and drainage capacity is limited, it is mainly used for sloped roofs.

Figure 13: Green Roof Systems based on thickness of the growing media (Laguna, 2011)

Drainage Type P:

System Designation

Thickness Type 1

Thickness Type 2

Thickness

[P1]

[P2]

Type 3 [P3]

Sedum

Perennials

Herbs

Typical plants

Perennials

Grasses Shrubs

Thickness Type 4 [P4]

Grasses Shrubs Trees

Extensive soil mix

3â&#x20AC;&#x2013;

5â&#x20AC;&#x2013;

Intensive soil mix

8â&#x20AC;&#x2013;

12â&#x20AC;&#x2013;

Separation fabric

1/8â&#x20AC;&#x2013;

Drainage plate

1â&#x20AC;&#x2013;

1-1/2â&#x20AC;&#x2013;

Protection mat

1/4â&#x20AC;&#x2013;

4â&#x20AC;&#x2013;

7â&#x20AC;&#x2013;

10â&#x20AC;&#x2013;

14â&#x20AC;&#x2013;

Dry weight

13 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

21 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

34 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

51 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

Saturated weight

21 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

34 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

53 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

78 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

Minimum slope

1/4:12

Maximum slope

1:12

Water retention

50%

60%

70%

80%

Nominal thickness

Table 4: Drainage Type P

Installation of Drainage Type P (Laguna, 2011): ď&#x201A;ˇ

Lay protection mat: First apply a root barrier membrane. Then unroll Standard Protection

Mat,

overlapping

adjacent

sheets at least 6â&#x20AC;&#x2013;, and cut openings for roof drains. ď&#x201A;ˇ

Install drain access boxes: Position Drain Access Boxes over roof drains, adding sidewall elements as needed to match the system thickness.

ď&#x201A;ˇ

Install retaining edge: Retaining Edge should be installed on extensive green Figure 14: Installation of Drainage type P roofs approximately 30â&#x20AC;&#x2013; from roof edges

(Laguna, 2011)

with roof drains and 18‖ from other edges. If there will be a gravel perimeter, the retaining edge will separate the soil and gravel and does not need to be attached. If there will be no gravel perimeter, the retaining edge should be attached to the waterproofing membrane or the protection mat so it will stay in place. 

Lay drain plates: Lay Drain Plates in a staggered pattern. The plates should fit tightly but are not

overlapped.

thicknesses match

are

Two available

drainage

and

water

storage requirements:

25mm

(1‖) and 40mm (1.5‖). 

Lay

separation

fabric:

Separation Fabric is engineered to retain soil without clogging while allowing plant roots to easily penetrate to reach water in the

drain

plates.

Unroll

Separation Fabric over the drain plates,

overlapping

adjacent

sheets at least 6‖.

Trim the

fabric carefully at the edges. 

Spread Spread

gravel

perimeter:

well-washed

screened

3/8‖

particle

size.

gravel minimum

Whenever

possible, the gravel should be dispensed suspended minimize

from from the

super

sacks

cranes potential

15: Installation of Drainage type P (Laguna, to Figure 2011)

for

damage. 

Spread soil: For extensive roofs, spread Extensive Green Roof Soil at a minimum rate of one cubic yard per 100 square feet (3‖). For intensive roofs,

spread Intensive Green Roof Soil as needed to obtain the required system thickness. Where possible, the media should be dispensed from super sacks suspended from cranes to minimize the potential for damage. ď&#x201A;ˇ

Plant: Insert green roof plants in a random pattern, two per square foot. Water thoroughly after installation, and during extended dry periods for the first two years. Broadcast Slow Release Fertilizer twice yearly on extensive roofs.

Drainage Type G: System Designation

Thickness Type 1

Thickness Type 2

Thickness

Thickness Type 4

[G1]

[G2]

Type 3 [G3]

[G4]

Sedum

Perennials

Grasses

Herbs

Extensive soil mix

2â&#x20AC;&#x2013;

4â&#x20AC;&#x2013;

Intensive soil mix

6â&#x20AC;&#x2013;

9â&#x20AC;&#x2013;

Separation fabric

1/8â&#x20AC;&#x2013;

2â&#x20AC;&#x2013;

4â&#x20AC;&#x2013;

5â&#x20AC;&#x2013;

1/4â&#x20AC;&#x2013;

4â&#x20AC;&#x2013;

6â&#x20AC;&#x2013;

10â&#x20AC;&#x2013;

14â&#x20AC;&#x2013;

Dry weight

16 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

24 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

40 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

56 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

Saturated weight

23 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

36 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

58 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

82 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

Minimum slope

0:12

Maximum slope

1:12

Water retention

50%

60%

70%

80%

Typical plants

Granular drainage Protection mat Nominal thickness

Grasses

Shrubs

Table 5: Installation of Drainage type G (Laguna, 2011)

Installation of Drainage Type G (Laguna, 2011): ď&#x201A;ˇ

Lay protection mat: If the primary roof waterproofing is not root resistant, first apply a root barrier membrane. Then unroll a protection mat with water-storage capacity, overlapping adjacent sheets at least 6â&#x20AC;&#x2013;, and cut openings for roof drains. Use Standard Protection Mat, or for optimal performance use Capillary Protection Mat for extensive roofs and Heavy-Duty Protection Mat for intensive roofs.



Install drainage system: Position Drain Access Boxes over roof drains, adding sidewall elements as needed to match the system thickness. Construct drainage ―trees‖ using triangular drainage channels and tees. For optimum performance, any point on the roof should be within two channel lengths of the closest point of the drainage tree: this will be achieved if the ―branches‖ of each drainage tree are laid four channel lengths (4 meters or 13 feet) apart.



. Install retaining edge: Retaining Edge should be

installed

extensive

green

roofs

approximately 30‖ from roof edges with roof drains and 18‖ from other edges. If there will be a gravel perimeter, the retaining edge will separate the soil and gravel and does not need to be attached. If there will be no gravel perimeter, the retaining

edge

should

attached

the

waterproofing membrane or the protection mat so it will stay in place. 

Spread

granular

media:

Spread

Granular

Drainage Media or other free-draining inorganic media with well-graded particle size and neutral pH. Apply a minimum of one cubic yard per 150 square feet (2‖) for extensive or semi-intensive roofs and one cubic yard per 75 square feet (4‖) for intensive roofs. If feasible, the media should be dispensed from super sacks suspended from cranes to minimize the potential for damage. 

Lay separation fabric: Separation Fabric is Figure 16: Installation of Drainage engineered to retain soil without clogging while

type G (Laguna, 2011)

allowing plant roots to easily penetrate to reach water in the granular media and protection mat. Unroll Separation Fabric over the granular media, overlapping adjacent sheets at least six inches. Trim the fabric carefully at the edges.

ď&#x201A;ˇ

Spread gravel perimeter: Spread well-washed gravel screened to 3/8â&#x20AC;&#x2013; minimum particle size. If feasible, the gravel should be dispensed from super sacks suspended from cranes to minimize the potential for damage.

ď&#x201A;ˇ

Spread soil: For extensive roofs, spread Extensive Green Roof Soil at a minimum rate of one cubic yard per 150 square feet (2â&#x20AC;&#x2013;). For intensive roofs, spread Intensive Green Roof Soil as needed to obtain the required system thickness. Where possible, the media should be dispensed from super sacks suspended from cranes to minimize the potential for damage.

ď&#x201A;ˇ

Plant: Insert green roof plants in a random pattern, 2 per square foot. Water thoroughly after installation, and during extended dry periods for the first two years. Broadcast Slow Release Fertilizer twice yearly on extensive roofs.

Drainage Type M: System Designation Typical plants

Thickness Type 1 [M1]

Thickness Type 2 [M2]

Sedum

Herbs

Herbs Perennials

3â&#x20AC;&#x2013;

5â&#x20AC;&#x2013;

3/8â&#x20AC;&#x2013;

Thickness Type 1 [M1]

Thickness Type 2 [M2]

Protection mat

Nominal thickness

3â&#x20AC;&#x2013;

5â&#x20AC;&#x2013;

Dry weight

13 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

21 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

Saturated weight

20 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

32 lbs/đ?&#x2018;&#x201C;đ?&#x2018;Ą 2

Minimum slope

1:12

Maximum slope

3:12

Water retention

50%

60%

Extensive soil mix

Drainage mat System Designation

Table 6: Installation of Drainage type M (Laguna, 2011)

*Protection mat only used at the edges

Installation of Drainage Type M (Laguna, 2011): 

Lay protection mat: First apply a root barrier

membrane.

Then

unroll

protection mat around the roof perimeter and cut

openings

for roof drains.

Although Standard Protection Mat is suitable for the sides and top of the roof, Capillary Protection Mat is preferred for the base of the roof to prevent water accumulation. 

Install drain access boxes: Position Drain Access Boxes over roof drains. On sloped roofs that use scuppers instead of roof drains, Drain Access Boxes are not required.



Install Edge

retaining

edge:

Retaining

should

installed

approximately 30‖ from roof edges with roof drains and 18‖ from other edges.

If there will be a gravel

perimeter, the retaining edge will separate the soil and gravel and does not need to be attached. If there will be no gravel perimeter, the retaining edge

must

waterproofing protection mat.

attached

membrane

the

If there will be no

gravel perimeter, the Retaining Edge should

waterproofing

attached membrane

to or

the the

protection mat so it will stay in place. 

Lay drainage mat: Unroll Drainage Mat, overlapping adjacent sheets at Figure 17: Installation of drainage type M (Laguna, 2011)

least six inches. This mat combines the functions of protection, water storage, and drainage in one product. 

Spread gravel perimeter: spread well-washed gravel screened to 3/8‖ minimum particle size. If feasible, the gravel should be dispensed from super sacks suspended from cranes to minimize the potential for damage.



Spread soil: Spread Extensive Green Roof Soil at a minimum rate of one cubic yard per 100 square feet (3‖). Where possible, the media should be dispensed from super sacks suspended from cranes to minimize the potential for damage.



Cost (paragx): Costs for the green roof system can range from Rs.5500/- Sq.m. to Rs.6900/- Sq.m. or more. Cost per square meter depends on the following factors: i) The size and slope of the roof. ii) Depth and complexity of the system. iii) Height and accessibility from the ground. iv) Cost of labour and need for specialized elements, such as drains, railings, pavers, slope stabilization measure, etc.

Vegetation

Drainage pipe

Figure 18: Section of green roof which has local materials as its layers (paragx)

2.10 GREEN ROOF POTENTIAL ANALYSIS FOR INDIAN CITIES: DISCUSSION (Dubey) Thermal performance of green roof: Annual conductive heat gain through unit roof area of green roofs and normal roof is being calculated and being compared in order to analyse the thermal performance of green roofs. City

Annual

Base case, KWh

cooling

Extensive

green

roof,KWh

Intensive

green

roof,

KWh

degree Kolkata

35592

126.78

25.90

11.31

Mumbai

37791

134.61

27.50

12.01

Chennai

44343

157.95

32.26

14.09

New

42516

151.44

30.93

13.51

Delhi Table 7: Estimated annual conductive heat gain through unit roof area for 3 scenarios (Source: USAID ECO-III PROJECT, 2010)

Sustainable Urban Drainage: Green-roof is an important element of sustainable urban drainage system as it can shift peak discharge by 20â&#x20AC;&#x201C;30 min thus reduces the runoff volume. Calculation is based on the assumptions that a 114 mm thick green roof can retain 55 % of annual average water precipitation and the 365 mm thick intensive green roof can retain 70 % and using average rain data (for the period 1981â&#x20AC;&#x201C; 2005) collected from the National Data Centre of India Meteorological Department based in Pune, India (Dubey). City

Annual rainfall, mm

Base case, mm

Extensive green roof, mm

Intensive green roof, mm

55%

70%

Kolkata

1765.1

1756.27

794.30

529.53

Mumbai

2334.6

2322.93

1050.57

700.38

Chennai

1549.9

1542.15

697.46

464.97

New Delhi

755.4

751.62

339.93

226.62

Annual average storm water retention rate

Table 8: Estimated Annual Storm-water runoff from different roofs (Source: USAID ECO-III PROJECT, 2010)

CHAPTER 3 STUDY/RESEARCH 3.1 TYPES OF GREEN ROOFS AND ITS SPECIFICATIONS TYPES OF GREEN

EXTENSIVE

BIODIVERSE

INTENSIVE

ROOF

(MODULAR)

(BUILT UP)

Smaller

Larger projects

Specific

Roof- garden in

projects like

like multi storeyed

objective

restaurants,

residences,

residences, high

small shops

rise buildings etc

80-90 mm

70-120 mm

70-200 mm

150-1500 mm

64.5 kg/sq.m

80-125 kg/sq.m

90-225

200 kg/sq.m

PICTORIAL REPRESENTATION

SUITABLE FOR

BUILT UP

houses etc

HEIGHT WEIGHT

kg/sq.m MAINTENANCE

Minimal

Regular

IRRIGATION

No, unless

Regular

specified specified Table 9: Comparison of types of green roof (Green Roofs and Their Implementations in Architecture The obstacle and challenges in Erbil city, 2015)

SUBSTRATE Top soil with mineral and organic

LOAD PER 1â&#x20AC;? DEPTH(lbs/đ?&#x2019;&#x2021;đ?&#x2019;&#x2022;đ?&#x;? ) 8-10

content Mineral substrate with high organic

5-7

content Mineral substrate with low organic

5-7

content Expanded clay or slate Recycled aggregates(broken bricks)

3,5-4 5-7

Expanded clay or slate 3,5-4 Table 10: Load of the green roof with respect to the substrate (Joseph)

Figure 19: Runoff vs. water retention capacities of extensive green roofs at 1", 2.5" and 4" depths (Source: A.Dott, 1995, adapted with permission)

Maximum temperature fluctuations for a conventional roof and a green roof

Figure 20: In the graph on the left, the arrow shows the maximum temperature fluctuation of a typical flat conventional roof, up to 60°C (140 F) in a single day, and up to 100°C during the year. The graph on the right shows a significantly lower temperature fluctuations :

3.2 HOW GREEN ROOF HELPS IN PREVENTING ALBEDO EFFECT Albedo is the quantity of solar radiation reflected from an object or surface (Cousineau). One method to increase the albedo of the roof is to plant vegetation. Other materials like white paint and highly refective roof have also high albedo value but they doesn‘t cool roof as green roof does. MATERIAL

SURFACE ALBEDO VALUE

Highly reflective roof

0.60-0.70

White paint

0.50-0.90

Grass

0.25-0.30

31 Brick/Stone

0.20-0.40

Coloured paint

0.15-0.35

Trees

0.15-0.18

Red/Brown tile

0.10-0.35

Concrete

0.10-0.35

Corrugated roof

0.10-0.16

Tar and gravel

0.08-0.18

Asphalt

0.05-0.20

Table 11: Comparison of different roofing element with their surface albedo value

3.3 GREEN ROOF MATERIAL SPECIFICATIONS

Separation Fabric is a non-woven geotextile made from recycled polypropylene. Since it is significantly less likely to clog than common filter fabrics, it is ideal for separating green roof soils from underlying drainage media or drainage plates. Separation Fabric weighs approximately 200 g/m2. (Rolls measure 2m x 25m (6‘8‖ x 82‘) and cover approximately 500 square feet of roof with a 15 cm (6‖) overlap. Standard Protection Mat is a non-woven geotextile made from recycled polypropylene. It is puncture resistant and has a water storage capacity of 4 l/m2, making it ideal for protection and supplemental water storage under plastic drainage plates. Standard Protection Mat weighs 500 g/m2. Rolls measure 2m x 25m (6‘8‖ x 82‘) and cover approximately 500 square feet of roof with a 15cm (6‖) overlap. Heavy-Duty Protection Mat is a non-woven geotextile made from recycled polypropylene. It is extremely puncture resistant and has a water storage capacity of 6 l/m2, making it ideal for protection and supplemental water storage under granular drainage media. Heavy-Duty Protection Mat weighs 900 g/m2. Rolls measure 2m x 15m (6‘8‖ x 49‘) and cover approximately 300 square feet of roof with a 15cm (6‖) overlap. Capillary Protection Mat is a non-woven geotextile made from a blend of rayon and recycled polypropylene.

It has an exceptional water

storage capacity of 9 l/m2 and can wick water and distribute it evenly, making it ideal for use under granular drainage media on extensive roofs. Capillary Protection Mat weighs 900 g/m2; rolls measure 2m x 15m (6‘8‖ x 49‘) and cover 300 square feet of roof a 15cm (6‖) overlap.

32 Drainage Mat is a multi-layer fabric mat made from a blend of polypropylene and acrylic. It acts as a separation fabric, protection mat, and drainage system into one product with a water storage capacity of 6 l/ m2. It is ideal for use on extensive roofs with slopes from 1:12 to 3:12. Drainage Mat weighs 800 g/m2 (24 oz/yd2); rolls measure 2m x 10m (6‘8‖ x 33‘) and cover 200 square feet of roof with a 15cm (6‖) overlap. 25mm (1‖) Drainage Plate is a waffled plastic sheet made of recycled polypropylene. The upper side of the sheet stores 5 l/m2 water and the lower space serves as a high-volume drainage passageway. Water only fills to the midpoint of the sheet, leaving an air gap under the separation fabric. Sheets measure 1m x 2m (40‖ x 80‘) and cover approximately 21.5 square feet of roof, or 20 square feet of roof with a minimal overlap. 40mm (1-1/2‖) Drainage Plate is a waffled plastic sheet made of recycled polypropylene. The upper side of the sheet stores 7 l/m2 water and the lower space serves as a high-volume drainage passageway. Water only fills to the midpoint of the sheet, leaving an air gap under the separation fabric. Sheets measure 1m x 2m (40‖ x 80‘) and cover approximately 21.5 square feet of roof, or 20 square feet of roof with a minimal overlap. Aluminum Edge is made from a 1.5mm (0.060‖) tempered aluminum alloy, used to retain soil and at roof edges or to separate soil from gravel and pavers. Holes on the vertical leg provide ample drainage while retaining soil. It is available in 2m lengths in heights of 100mm, and 150mm, both with extra-wide 150mm bases punched with large holes to permit taping or welding to underlying membranes.

Table 12: Green roof material specifications (Laguna, 2011)

When the roof slope is 2:12 or 10°, special precautions should be taken to avoid sliding of soil and independent root barriers or floating membranes are not recommended. So 2 types of components are being used- 1 system transfers soil loads up the roof and other transfers soil loads down the roof. 1.Anti-slip cleats and mesh: Anti-Slip Cleats are black recycled ABS plastic soil retaining elements used with Anti-Slip Mesh(extraordinarily

strong

structural

plastic mesh used Anti-Slip Cleats) to Figure 21: Anti-slip cleats clipped to anti-sip prevent soil from sliding down sloped green

mesh (Laguna, 2011)

roofs by transferring soil loads to the top of the roof. Rows of cleats are spaced 10‖ to

50‖, depending on the roof slope. 2. Anti-slip tees:

In contrast with the

cleat/mesh system, the Anti-Slip Tee system transfers soil load down the roof to a structural parapet or fascia at the bottom of the roof slope. The system consists of two interlocking T-shaped plastic extrusions: the lower one follows the slope of the roof and

Figure 22: Anti-slip tees (Laguna, 2011)

the upper one crosses the slope of the roof. The lower tees are spaced approximately one meter (40‖) apart and the spacing of the upper tees varies from 10‖ to 50‖ depending on the roof slope. Cost of materials (paragx): Material

Cost

Unit

Waterproofing (0.01m)

Rs. 100/-

Sq.m.

Pumice stone (0.02m)

Rs. 175/-

Sq.m.

Material

Cost

Unit

Shingle (0.05m)

Rs. 500/-

Sq.m.

Soil (0.08m)

Rs. 50/-

Sq.m.

Elephanta Lawn (0.02m)

Rs. 270/-

Sq.m.

P.V.C. pipe 0.02 m(diameter)

Rs. 20/-

L.S.

Plants

Rs. 80/-

Nos.

ray

Rs. 1200/-

Nos.

Rs. 2400/-

Sq.m

Total = Labour 10%

Rs. 240/-

Transport 5%

Rs. 120/-

Overhead 5%

Rs. 120/Total =

Rs. 2880/- Approximately Rs 3000/-

Table 13: Cost of components of green roof (paragx)

Sq.m

3.4 GREEN ROOF CONFIGURATIONS Configuration 1

Intensive green roofs

Flat roofs soft or hard landscaping

Configuration 2

Flat roofs soft or hard landscaping

Configuration 3

Sloped roofs soft landscaping

Configuration 4

Drainage only for soft landscaping

Substrate and Vegetation

Filter Layer

Water Storage/Drainage layer Protection Layer

Separation Layer

Table 14: Green roof configurations for intensive green roof (Green Roof Design Guides and Considerations) Configuration 1

Extensive green roofs

XF301 sedum blanket system

Configuration 2

Plug planted or wildflower blanket

Configuration 3

Biodiverse

Configuration 4

Seeded roof

Substrate and Vegetation

Filter Layer

Water Storage/Drainage layer

Protection Layer

Not required

Separation Layer

Not required

Table 15: Green roof configurations for extensive green roof (Green Roof Design Guides and Considerations)

CHAPTER 4 CASE STUDIES 4.1 LITERATURE CASE STUDY 4.1.1 GREEN HOUSE RESIDENCE

Figure 23: Figure: 3D view of Green House Residence (Saieh, 2010)

Project: Residence Location: WestKadungallur Architects: Lijo Reny architects Built up Area: 4,500 Sqft Macro climate: Kerala belongs to the tropical monsoon climate with south west monsoon winds and the prevailing winds. The climate is generally warm-humid with ample rainfall in the monsoon season. Micro climate: Annual mean temperature is 29.4°C. Maximum rainfall is in June which is 783 mm and minimum rainfall is in January which is 11 mm. Orientation: The building is oriented along east-west direction ―The ‗green roof was not just a statement here, but a thoughtfully crafted design strategy. It was meant to keep the building cool and breathing along with the help of several open to sky courtyards trapped internally. This Residence has broken all so called ‗sacred architectural rules‘ that strangulates the field of design in Kerala. The design doesn‘t carry forward the ‗visual‘ context as the architects felt the need to demonstrate a different design possibility for the Tropical Climate of Kerala along with the urge to discourage the practice of pseudo- traditionalism in design‖ (Saieh, 2010). Plant used: Buffalo grass

Figure 24: Section of green roof (Author)

Figure 25: Sectional view of Green House Residence (Saieh, 2010)

Only buffalo grass is used as vegetation for the green roof and so the green roof is extensive green roof. The temperature inside the green roof residence is 5Â° C lesser when compared to normal residences. Extensive roofing is less costly than intensive and also it is easy to maintain. The courtyard and the green roof of this building act as a sustainable element for reducing heat and provide passive cooling. The whole green roof area is almost 5000 Sq.ft and the green roof grass roll cost will be 10 Rs per Sq.ft. So the total cost of green roof will be 50000 Rs. Inference: Simple extensive green roof which is apt for residential buildings and it is of low cost and maintenance. The vast spread of the vegetation over the roof provides thermal insulation and cooling for all rooms.

4.2 LIVE CASE STUDY 4.2.1 EARTH CUBE RESIDENCE

Figure 26: Earth Cube residence (Cw, 2014)

Project: Residence Location: Perumbavoor Architects: Ar. Niranjan, Ego design studio Built up Area: 210sqm 3bhk residence Cost: 42 lakhs for built form, interiors & landscape The cost is reduced by 25% than normal construction rates near by Thermal quality: 5-7 degree C temperature lesser than the houses near by Macro climate: Kerala belongs to the tropical monsoon climate with south west monsoon winds and the prevailing winds. The climate is generally warm-humid with

ample rainfall in the monsoon season. Micro climate: Annual mean temperature is 29.4°C. Maximum rainfall is in June which is 783 mm and minimum rainfall is in January which is 11 mm. ―Site: The site is located far from the main road, in a purely residential area, with no designed houses around. The site though little far away from main road was chosen due to the presence of brothers and sisters living nearby so as, to have the same togetherness which they once cherished in a joint family. The site faces relatively young teak plantation, a seasonal space – fresh and green during monsoons and dry and dull in summers. The back side of the site is barren land (Cw, 2014).‖ Process: Using the idea of the roof garden to create thermal comfort. Reusing the top soil for the roof garden and using local plants for the roof garden. It was designed using the traditional ideas of verandas and courtyards for ventilation. Locally available plants and landscape materials are been used. Using less mechanical ventilation and lighting systems. Experimented with new methods to interpret previously researched spaces and volumes retracing from the tradition. Instead of a closed boundary wall, porous exterior wall is being used. Adopted new method of landscaping using local plants and sacks.

Figure 27: Details about context and site (Cw, 2014)



Orientation: The building is oriented along east-west direction



Walls : Laterite



Furniture : Mostly built in furniture used



WINDOWS and DOORS: Steel



ROOF GARDEN: Local plants/ karuka/ buffalo grass



CUPBOARDS: Ply wood/ MDF



PERGOLA / HANDRAIL: Stainless steel pipes

Sustainability factors: 

Buffer rooms on South West sides



Verandas all around to reduce heat gain through green house effect.



Local cost effective materials "Laterite" used for walls.



No wood has been used.



Temperature 5-7 degrees reduced.



FAN only in 2 rooms.



Electricity completely through solar Figure 28: Zoning of plan (Cw, 2014) panels.



Top soil and local planting excavated reused for roof garden.



White wall surfaces reduce the use of lights in interiors.

Figure 29: Zoning of different spaces in the site and the residence (Cw, 2014)

The design programme and volumetric stacking was derived from the study of the client‘s ancestral home which was a NALUKETTU. It supported a joint family of about 20-25 members with guests almost every time of the year.

Figure 30: Earth Cube Residence (Cw, 2014)

―The building has an extremely stunning flexibility and thermal quality which made it a purely experiential space which catered to almost all functional purposes‖ (Cw, 2014)

Figure 31: View of the residence from the site (Cw, 2014)

Figure 32: Analysis of each green space in the residence (Cw, 2014)

Spaces and innovations

Figure 33: Visual axis of spaces (Cw, 2014)

Continuous spaces: Volumes for family interaction - seamless interiors for large rooms which could afford a SADYA or a family meeting, enclosed external courts which can offer spaces for family functions. Sustainable ideas: Orientation of spaces, creating verandas outside major Windows to

reduce heat gain, creating buffer rooms on south west sides, green roofing uses local plants, raising the south western side to shade the open courts for evening outside spaces, using local building materials and plants. Client specific spaces: creating calm volumes for spiritually inspiring spaces, white and seamless, bringing in maximum external light through openings skylights and the white colour theme, heat is reduced by about 5-7degrees with respect to nearby houses during summers which makes majority of interior spaces well ventilated and comfortable without fan or AC.

Figure 34: Zoning of site plan and floor plans (Cw, 2014)

Buffalo grass Growing medium 4 inch Tarpaulin sheet with drainage Roof slab Figure 35: Section of green roof (Author)

Inference: The residence is designed in a sustainable way by reusing the top soil for the roof garden and using local plants for the roof garden and also using the traditional ideas of verandas and courtyards for ventilation. Locally available plants and landscape materials are been used.

4.2.2 MALABAR HEADQUARTERS

Figure 36: Malabar Headquarters (Author)

Project: Corporate office Location: Calicut Architects: Stapati architects Site area: 366.346 Ares (36634.66m2) Building area (Sqm): 18323.75m2 Total height of building: 23.43 Metre Thermal quality: Surveyed the temperature and found that it is 8 degree C lesser than the houses nearby. Macro climate: Kerala belongs to the tropical monsoon climate with south west monsoon winds and the prevailing winds. The climate is generally warm-humid with ample rainfall in the monsoon season. Micro climate: Annual mean temperature is 27.3Â°C. Maximum rainfall is in July which is 847 mm and minimum rainfall is in January which is 4 mm. Site: The site is located at a distance of 1.5 km from kuttikattoor junction in Calicut. Since the site is a contour site, the whole building is built in 2 levels. 2 blocks of the building is been connected with cantileverd passages. The whole building is designed by incorporating nature so that it lies in harmony with the surrounding.

Figure 37: Area statement (Author)

SITE PLAN

Figure 38: Site plan of Malabar Headquarters (MHQ)

FIRST BASEMENT PLAN

Figure 39: First basement plan (MHQ)

SECOND BASEMENT PLAN

Figure 40: Second basement plan (MHQ)

THIRD & FOURTH BASEMENT PLAN

Figure 41: Third and Fourth basement plan (MHQ)

GROUND FLOOR PLAN

Figure 42: Ground floor plan (MHQ)

FIRST FLOOR PLAN

Figure 43: First floor plan (MHQ)

SECOND FLOOR PLAN

Figure 44: Second floor plan (MHQ)

THIRD FLOOR PLAN

Figure 45: Third floor plan (MHQ)

FOURTH FLOOR PLAN

Figure 46: Fourth floor plan (MHQ)

TERRACE FLOOR PLAN

Figure 47: Terrace plan (MHQ)

SECTION

Figure 48: Section (MHQ)

Plants used BIRD OF PARADISE

Plant height: 5 - 9 inches Plant spread: 4 - 8 inches Sunlight: Full to partial sunlight Cost: 300 Rs It is being planted in the planter pot Depth: 5 inch depth growing medium

FERNS

Plant height: 5 - 9 inches Plant spread: 4 - 8 inches Sunlight: Part shade Cost: 450 Rs It is also planted in the planter pot Depth: 5 inch depth growing medium

SPIDER LILY

Plant height: 5 - 9 inches Plant spread: 4 - 6 inches Sunlight: Full sun to part shade Cost: 299 Rs It is also planted in the planter pot. Depth: 5 inch depth growing medium

PLUMERIA

Plant height: 15 - 23 inches Plant spread: 4 - 6 inches Sunlight: Plumerias do best in full sun It is also planted in the planter pot. Depth: 5 inch depth growing medium Cost: 489 Rs

BUFFALO GRASS

Cost: Cost will be 10 Rs per sqft. It is being planted on the roof.

Table 16: Types of plants used (Author)

Vegetation

Growing media Drainage layer EPDM, TPO or PVC membrane Figure 49: Section of green roof (Author)

Total cost of roof is around 8 lakh as almost 50000Rs will be spent for the growing medium. Plants used are drought tolerant, ferns and sedums which are mainly used in extensive

building. Vertical green walls are being done using plastic trays whereas green roof is done in its usual method.

Inference: Sustainable building using modern technology and roof terrace is well utilized using green spaces and solar panels.

Comparative analysis:

PROJECT

TECHNIQUE

THERMAL

NAME

AND TYPE

QUALITY

Extensive roof

5°C temperature

Almost

using

lesser than the surrounding

GREEN

HOUSE

RESIDENCE

buffalo

grass

COST

INFERENCE

USER

CLIMATIC

COMFORT

ZONE

Cost effective

Green house

Tropical

Used drainage

50,000

method,

Residence

monsoon

layer, EPDM

Efficient

serves

climate with

technology

functions-

29.4°C

membrane

one to hide

mean

the view and

temperature

buildings.

other

MATERIALS

PVC

reduce

the

temperature. MALABAR

Intensive green

8°C temperature

Almost

Cost effective,

As it is a

Tropical

Used drainage

HEADQUARTERS

roof

lesser than the

2 lakhs

Aesthetically

workspace,

monsoon

layer, EPDM

surrounding

beautiful,

the

climate with

buildings.

Needs

roof act as a

27.3°C

membrane

cooling

mean

care

more and

maintenance

green

and

aesthetically

PVC

temperature

refreshing element

the building. EARTHCUBE

Extensive

5°C

RESIDENCE

green roof

7°C

Cost

Cost effective,

The

temperature

reduced

Simple method

roof

lesser than the

,Simple

harmony

surrounding

percenta

method, Good

with

buildings.

for

surroundings

mean

and

temperature

original cost

climate

kerala

green is

the

also

reduces heat effect.

Table 17: Comparative analysis (Author)

Tropical

Used tarpaulin

monsoon

sheet,

climate with

waterproofing

29.4°C

layer

CHAPTER 5 RECOMMENDATIONS AND CONCLUSIONS This chapter explains an overview of the entire research process and the importance of green roof in design. By comparing the advantages and disadvantages of green roof, the recommendations for architects and engineers to increase the use of green roof are suggested. The possible ways for finding the efficient method of cooling system is suggested and finally it discusses about the scope of extending the study in future.

5.1 CONCLUSIONS This research has critically explored the importance of green roof as a design element. By conducting interviews and surveys with practising architects and users shared their insights about the utility of installing green roof on buildings. The interviews mainly focused on the pros and cons of installing green roof on buildings. Finally, by criticizing the existing development of green roof system in the current scenario gives the conclusion. Green roof require proper attention at the earlier stage so that the plant species get adapted to the conditions of the roof. The structure of the building should be affordable for the green roof. Proper waterproofing should be done while installing green roof. 

Green roof is a sustainable method of improving the quality of life in urban areas by mitigating urban issues.



They help to maintain the natural habitat by providing a space for both residents and wildlife.



Green roof technology is an ideal architectural combination of aesthetics, economy and ecology.



The reduction in usage of energy by green roof contributes to a greener planet by reducing harmful emission of gases.

5.2 RECOMMENDATIONS Recommendations for better green roofing system: For architects and engineers: 

Appropriate plant species that is adaptable to the climatic zone should be selected while installing green roof.



Better waterproofing or an extra water proofing membrane should be installed on the roof for green roofing systems.



The load of the green roofing system should not affect the structure of the building.



New methods with low cost should be developed so that future scope for this technology increases.



Converting terraces into open spaces with the help of green roof installation should be promoted.



Horticulture using green roof system promotes the use of green roof in residential buildings.



When compared to office spaces, people spend most of their time in residences, so green roof in residential buildings promote the scope of this technique.



With the green roofing system, the increasing climatic problems and environmental problems can be eliminated.



Due to the increased benefits of green roof, effort should be taken among the researchers to conduct more research on green roof technology.

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