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ENHANCING THERMAL COMFORT USING VERTICAL GREENERY SYSTEMS (VGS) IN THE DESIGN OF A SUSTAINABLE MID- RISE ESTATE IN THE HOT DRY CLIMATE OF KANO, NIGERIA
ABSTRACT
In battling some of the most alarming situations the world is facing right now which are the climate change and global warming, architects are saddled with the responsibility of designing buildings that are energy efficient as buildings account for about 40% of the total energy use. About 40-60% is utilized in cooling the institutional building while in residential buildings, cooling accounts for 30% of the total energy use. In order to reduce carbon emissions and decrease urban heat islands, ecofriendly methods must be employed when designing buildings. This research therefore seeks to enhance thermal comfort using Vertical Greenery Systems (VGS) as an architectural strategy in residential buildings in the hot dry climate of Kano that is known to have very high temperatures.
The study entails the use of visual survey and computer simulation. Case studies on VGS application were carried out in Kaduna and Kano and simulation was carried out using Design Builder® and EnergyPlus® as the simulation engine as this is one of the most common, free and validated simulation software. At the end of the simulation analysis to determine the effect of VGS on thermal comfort, it is found that living walls have the highest impact on temperature reduction attaining a maximum of 7°C using 100% coverage ratio on all orientations. A reduction of 5.35°C was attained using indirect green facades. All the temperatures obtained after the VGS was applied fell in the range of ASHRAE standard 55 (22.2°C-26.7°C) which is the benchmark for thermal comfort in hot dry climates A residential estate was then proposed using the findings from the research. The results of the research implied that living walls are suitable for west and east orientations and green facades for the north and south orientations. The research recommends that simulation softwares should integrate green wall modules to enhance research process and further studies should be carried out on other plants and types of
VGS such as the direct green facades.
TABLE OF CONTENTS
Cover Page ………………………………………………………………………………………………………
Fly Leaf ………………………………………………………………………………………………………… 1
Title Page ……………………………………………………………………………………………………… 2
Declaration…………………………………………………………………………………………………. i
Certification………………………………………………………………………………………………. ii
Dedication………………………………………………………………………………………………… iii
Acknowledgement…………………………………………………………………………………….. iv
Abstract…………………………………………………………………………………………………….. v
List of Figures…………………………………………………………………………………………… xi
List of Tables……………………………………………………………………………………………. xii
List of Plates……………………………………………………………………………………………. xiii
List of Appendices……………………………………………………………………………………. xv
Abbreviations and Definition of Terms……………………………………………………. xvii
1.0 INTRODUCTION……………………………………………………………………………. 1
1.1 Background to the Study…………………………………………………………………………. 1
1.2 Problem Statement………………………………………………………………………………….. 3
1.3 Justification…………………………………………………………………………………………….. 3
1.4 Aim and Objectives…………………………………………………………………………………. 4
1.5 Research Questions…………………………………………………………………………………. 4
1.6 Scope………………………………………………………………………………………………………. 4
2.0 LITERATURE REVIEW…………………………………………………………………. 6
2.1 Introduction……………………………………………………………………………………………. 6
2.2 The concept of Vertical Greenery Systems (VGS)…………………………………….. 6
2.2.1 Benefits of VGS in Buildings……………………………………………………………………. 6
2.2.2 Classification of VGS………………………………………………………………………………. 8
2.3 Effects of VGS on thermal comfort…………………………………………………….. 14
2.3.1 Mechanisms through which VGS acts as a passive technique……………………… 14
2.4 Parameters to be considered for the application of VGS………………………. 23
2.4.1 Plant species selection…………………………………………………………………………… 23
2.4.2 Orientation of the façade………………………………………………………………………. 27
2.5 Computer Simulation…………………………………………………………………………….. 28
2.5.1 Simulation softwares……………………………………………………………………………… 28
2.5.2 Validation and Reliability…………………………………………………………………….. 29
2.5.3 Simulating VGS………………………………………………………………………………….. 29
2.6 Mid-rise Housing Design……………………………………………………………………. 30
2.7 Estate Design……………………………………………………………………………………… 30
2.7.1 Guidelines in Midrise estate design……………………………………………………….. 31
2.8 Summary…………………………………………………………………………………………… 32
3.0 RESEARCH METHODOLOGY…………………………………………………….. 35
3.1 Introduction………………………………………………………………………………………….. 35
3.2 Research Design…………………………………………………………………………………….. 35
3.2.1 Case Study Research Design…………………………………………………………………… 35
3.3 Research Variables…………………………………………………………………………….. 36
3.4 Sampling Method………………………………………………………………………………. 36
3.4 Methods and Instruments of Data Collection………………………………………. 36
3.5 Procedure for Data Collection……………………………………………………………. 37
3.6 Simulation…………………………………………………………………………………………. 37
3.7 Data Analysis…………………………………………………………………………………….. 37
4.0 RESULTS AND DISCUSSION……………………………………………………….. 39
4.1 Introduction………………………………………………………………………………………….. 39
4.2 Case Study One (Three Bedroom bungalow)………………………………………. 39
4.2.1 Background………………………………………………………………………………………….. 39
4.2.2 VGS description……………………………………………………………………………………. 39
4.3 Case Study Two (A-two storey building)…………………………………………….. 41
4.3.1 Background………………………………………………………………………………………….. 41
4.3.2 VGS description……………………………………………………………………………………. 41
4.4 Summary of results from case study…………………………………………………… 42
4.5 Simulation Results and Discussion……………………………………………………… 43
4.5.1 Base-case modelling………………………………………………………………………………. 45
4.5.2 Variables to be examined……………………………………………………………………….. 45
4.5.3 Constant variables…………………………………………………………………………………. 46
4.5.4 Comfort profile of the base case……………………………………………………………… 46
4.6 VGS models…………………………………………………………………………………………… 48
4.6.1 Indirect greening façade Modelling………………………………………………………… 48
4.6.2 Indirect Green Façade VGS Model Case…………………………………………………. 49
4.6.3 Modular living wall VGS Model Case…………………………………………………….. 54
4.7 Summary of results from the simulation………………………………………………… 59
5.0 DESIGN PRELIMINARIES………………………………………………………….. 61
5.1 Introduction………………………………………………………………………………………….. 61
5.2 Study Area…………………………………………………………………………………………….. 61
5.2.1 Weather and Climate……………………………………………………………………………… 61
5.2.2 Vegetation……………………………………………………………………………………………. 61
5.3 Site Location…………………………………………………………………………………….. 62
5.4 Site Selection Criteria……………………………………………………………………………. 62
5.4.2 Site 2…………………………………………………………………………………………………… 63
5.4.3 Site 3…………………………………………………………………………………………………… 64
5.5 Site analysis…………………………………………………………………………………………… 65
5.5.1 Site Location…………………………………………………………………………………………. 65
5.5.2 Site Climate………………………………………………………………………………………….. 66
6.0 DESIGN REPORT…………………………………………………………………………. 70
6.1 Brief Development…………………………………………………………………………………. 70
6.3 Design Consideration…………………………………………………………………………. 70
6.3.1 VGS systems………………………………………………………………………………………. 70
6.3.2 Plant selection……………………………………………………………………………………. 71
6.3.3 Orientation…………………………………………………………………………………………. 72
6.3.4 Site planning………………………………………………………………………………………. 72
6.3.5 Services……………………………………………………………………………………………….. 73
6.4 Schedule of accommodation………………………………………………………………….. 73
7.0 SUMMARY, CONCLUSION AND RECOMMENDATIONS……………… 77
7.1 Introduction………………………………………………………………………………………….. 77
7.2 Summary……………………………………………………………………………………………… 77
8.3 Conclusion…………………………………………………………………………………………….. 78
8.4 Contributions to knowledge……………………………………………………………………. 79
8.5 Recommendations………………………………………………………………………………….. 79
References……………………………………………………………………………………………….. 80
Appendices………………………………………………………………………………………………. 86
1.0 INTRODUCTION
1.1 Background to the Study
Over the years researches has been carried out on how to improve thermal comfort within spaces and buildings with emphasis on bioclimatic design principles (Hussaini, 2016), building materials such as double cavity walls (Musa, 2016) and building envelope design (Arowona, 2017), these studies were conducted on institutional typologies such as office buildings, hotels, recreation centers and so on. Previous studies also show a lot of work carried out on thermal comfort in residential typologies, (Akande and Adebamowo, 2010; Adaji and Watkins, 2015; Abdulkareem, Almaiyah and Cook, 2015). However, only little work had been carried out on Vertical Greenery Systems (VGS) in Nigeria which includes the works of Akinwolemiwa and Gwilliam (2015) and (Akinwolemiwa, Bleil de Souza,
De Luca and Gwilliam, 2018) which were carried out in the hot and humid climate of Lagos state. This research therefore is focused on VGS in the hot dry climate of Nigeria to explore and investigate its application in this climate. Furthermore, there is a wide gap in research on the application of Vertical Greenery Systems (VGS) such as green walls to enhance thermal comfort in Nigeria (Akinwolemiwa and Gwilliam, 2015) as most works done are being carried out in Europe, Asia and the United States with climate such as the hot and humid or the temperate region.
The application of plants in buildings has been in existence for years as seen from the hanging gardens of Babylon (Dahanayake and Chow, 2017). As technology progressed, there are more effective and advanced methods of integrating these plants in buildings and thus the concept of Vertical Greenery Systems (VGS) came into being. VGS are structures that allow vegetation to spread over a building façade or an interior wall (Pérez, Cañero, Franco and Egea, 2016). It is mainly categorized into two based on the growing mechanisms which is the carrier and support (Jaafar, Said and Rasidi, 2011) and are also called living walls and green facades (Pérez, et al.,2016).
In battling one of the most alarming situations the world is facing right now which is the climate change and global warming, architects are saddled with the responsibility of designing buildings that are energy efficient as buildings account for about 40% of the total energy use (Perini, Ottelé, Haas and Raiteri, 2011;Raji, Tenpierik and Dobbelsteen, 2014). Most of the energy, about 40-60% is utilized in cooling the institutional building while in residential buildings, cooling accounts for 30% of the total energy use (Federal Ministry of Power, 2016). For architects to contributes their own quota in ensuring the sustainable energy goal of 2030, buildings have to be designed to reduce their energy use and still achieve the desired target.
Plants are known to be excellent in providing microclimate in an environment and have a number of advantages, as such their importance can’t be over-emphasized (Prihatmanti and Taib, 2017) They are adopted in bioclimatic design as landscaping, which is one of its major principles in enhancing thermal comfort. Plants are known to provide shade against solar radiation, serve as wind breakers and cool the environment through evapotranspiration (Afshari, 2017). Research has shown that the application of plants on building façade can cool down the ambient temperature of the immediate environment up to 20°C (Mazzali, Scarpa and Peron, 2014). This is due to the evaporation from the plants and substrate material which is known as evapo-transpiration. In addition, when plants are placed on the interior walls, they improve the indoor temperature and air quality as they filtrate the sorrounding air and are such called biofilters (Raji et al.,2014).
Greening has become one of the fastest solutions in the world where rapid urbanisation is the order of the day,as plants absorb the carbon around and give out oxygen in exchange (Dahanayake and Chow, 2017). Integrating plants in buildings will not only enhance thermal comfort but will render other benefits such as wind and noise breaking, reducing energy consumption, acting as food supply (vertical farming), shading and aesthetics (Prihatmanti and Taib, 2018).
1.2 Problem Statement
Research has shown that Vertical Greenery Systems (VGS) are effective in cutting down the energy used for cooling and enhancing thermal comfort in buildings. Hence, VGS have been applied to various kinds of buildings ranging from institutional to residential, low-rise to high-rise. Previous studies in Nigeria show a lot of work carried out on thermal comfort in residential typologies with emphasis on building envelope, building materials and so on. However, only a few of these works had been carried out on Vertical Greenery Systems (VGS) which was carried out in the hot and humid climate of Lagos state. Most of the studies on VGS were conducted in temperate and fully humid climates, humid subtropical and Mediterranean climates in the developed countries. Little has been done on tropical and arid regions and the developing countries. Due to VGS peculiarity with plants it is important to know how these plants behave under different climatic conditions and as to what plants are suitable for a particular climate, as such results from one climate is not sufficient enough to be applied to another. This is why this research is set to investigate how VGS can enhance thermal comfort in the hot dry climate of Nigeria.
1.3 Justification
There is need to provide a thermally comfortable and conducive environment for residents which can only be achieved by finding techniques to mitigate the effects of climate change and global warming such as urban heat island and pollution. Plants are known to be very effective in providing a micro climate, reducing and cooling the surrounding temperature and even filtrating the air. They are one of the best solutions in mitigating urban heat island. By integrating VGS in buildings, energy consumption is reduced as plants are proven to cool the environment, serve as insulation and provide a means of shading.
In addition, there are very few studies available on VGS for enhancing thermal comfort in Nigeria, not only in residential buildings but the whole built environment (Koc, Alan and Paul, 2018). This research contributes to the body of knowledge in response to the Sustainable Development Goals (SDG’s) and the 2030 agenda for sustainable energy.
1.4 Aim and Objectives
The aim of this study is to enhance thermal comfort using VGS as an architectural strategy through the following objectives:
- To examine the relationship between VGS and indoor thermal comfort in
buildings.
- To evaluate the application of VGS characteristics in selected visual survey and assessments.
- To determine the effects of VGS on thermal comfort in residential building design through computer simulation in the hot dry climate of Nigeria
- To demonstrates the outcome of the study in the design of a midrise housing
estate.
1.5 Research Questions
- What is the relationship between VGS and indoor thermal comfort in buildings?
- What are the effects of VGS on thermal comfort of residents in residential building design in hot dry climates of Nigeria?
- How can the result of the study be best demonstrated in the design of a midrise housing estate?
1.6 Scope
For the purpose of this research, the application of VGS is limited to providing thermal comfort through the shading, evapotranspiration and thermal insulation effects only. The research is limited to kano state which has a hot and dry climate. The issue of maintenance and occupancy behavior is beyond the scope of this study.
ENHANCING THERMAL COMFORT USING VERTICAL GREENERY SYSTEMS (VGS) IN THE DESIGN OF A SUSTAINABLE MID- RISE ESTATE IN THE HOT DRY CLIMATE OF KANO, NIGERIA
