building envelope design for indoor air...

BUILDING ENVELOPE DESIGN FOR INDOOR

AIR TEMPERATURE IN HOT AND DRY

CLIMATE, YEMEN

MOHAMMED SALEM OBAID BAKHLAH

UNIVERSITI SAINS MALAYSIA

2015

BUILDING ENVELOPE DESIGN FOR INDOOR

AIR TEMPERATURE IN HOT AND DRY

CLIMATE, YEMEN

By

MOHAMMED SALEM OBAID BAKHLAH

THESIS SUBMITTED IN FULFILMENT OF THE

REQUIREMENTS FOR THE DEGREE OF DOCTOR OF

PHILOSOPHY

February 2015

ii

ACKNOWLEDGMENTS

Thanks and gratitude to Allah. Without the assistance of Allah, this thesis could not

be completed, who bestowed on me the patience to complete this work. I would like

to express my sincerest gratitude to Professor Dr. Ahmad Sanusi Hassan. I have the

honour to work under his supervision, who guided and provided me with

constructive comments and criticisms. Special thanks to him due to selecting me as a

research assistance.

I would like to greatly thank Sheikh, Engineer: Abdullah Ahmad Bugshan, and I am

highly indebted to him for continuous financial support during my study. Special

thanks also to Hadhramout University of Science and Technology, Faculty of

Environment science and marine Biology special to Dr. Mohammed Al-dohail who

provided me with some environmental equipment. I would like to thank the staff of

meteorology station at Seiyun Airport who provided me with the required weather

data. I would like to thank the dean and all academic lecturers and staff of School of

Housing, Building and Planning for their friendliness.

My heartfelt thanks also go to my beloved parents, wife, kids, brothers and sisters,

for their patience and unwavering support. I also deeply grateful to all the houses

owners who allowed me access to their houses during data collection, and to all my

friends who participated in carrying out data collection namely, Khalil, Saber and

Mutea, Adel Al-Muallem, Dr. Nedhal, Dr. Mand, and Adel Bahfi and everyone who

has contributed to the completion of this thesis.

iii

TABLE OF CONTENTS

ACKNOWLEDGMENTS ................................................................................................ ii

TABLE OF CONTENTS ................................................................................................ iii

LIST OF TABLES .......................................................................................................... xv

LIST OF FIGURES ....................................................................................................... xvi

LIST OF ABBREVIATIONS .................................................................................... xxviii

ABSTRAK ................................................................................................................... xxix

ABSTRACT ................................................................................................................ xxxi

CHAPTER ONE: INTRODUCTION ........................................................................... 1

1.1 INTRODUCTION ......................................................................................... 1

1.2 RESEARCH BACKGROUND ..................................................................... 1

1.3 PREVIOUS RELATED RESEARCH STUDIES ....................................... 11

1.4 PROBLEM STATEMENT .......................................................................... 21

1.5 RESEARCH QUESTIONS ......................................................................... 23

1.6 OBJECTIVES OF THE STUDY ................................................................. 23

1.7 RESEARCH FRAMEWORK ...................................................................... 24

1.8 SCOPE OF THE STUDY ............................................................................ 27

1.9 LIMITATION OF THE STUDY ................................................................. 27

1.9.1 Limitation of Case Study ................................................................. 28

1.9.2 Limitation in Fieldwork ................................................................... 28

1.9.3 Limitation of the Instruments ........................................................... 29

Page

iv

1.10 IMPORTANCE OF THE RESEARCH ....................................................... 29

1.11 RESEARCH PHILOSOPHY for energy saving .......................................... 30

1.12 SUMMARY OF THE CHAPTERS ............................................................ 31

CHAPTER TWO: LITERATURE REVIEW ............................................................ 33

2.1 INTRODUCTION ....................................................................................... 33

2.2 HOT AND DRY CLIMATE ....................................................................... 33

2.2.1 Geographical Area and Climate Studied .......................................... 35

2.2.2 Hot and Dry Climate in Wadi Hadhramout ..................................... 36

2.2.2.1 Temperature ....................................................................... 37

2.2.2.2 Relative humidity ............................................................... 38

2.2.2.3 Solar radiation .................................................................... 40

2.2.2.4 Wind ................................................................................... 41

2.2.2.5 Rain fall .............................................................................. 43

2.3 PASSIVE BUILDING ENVELOPE DESIGN ............................................ 44

2.3.1 Introductions .................................................................................... 44

2.3.2 Definitions ........................................................................................ 45

2.3.2.1 Building envelope .............................................................. 45

2.3.2.2 Passive cooling .................................................................. 46

2.3.2.3 Passive heating ................................................................... 47

2.4 IMPACT OF BUILDING ENVELOPE DESIGN ON INDOOR

THERMAL CONDITION ........................................................................... 48

v

2.4.1 Influence of Wall Design ................................................................. 48

2.4.1.1 Wall as a thermal mass ...................................................... 49

2.4.1.2 Wall thickness .................................................................... 50

2.4.1.3 Wall finishing and external surface colour ........................ 50

2.4.1.4 Wall thermal insulation ...................................................... 52

2.4.2 Influence of Roof Design ................................................................. 53

2.4.2.1 Roof thermal insulation ..................................................... 55

2.4.2.2 Influence of roof colour ..................................................... 55

2.4.2.3 Roof material properties .................................................... 57

2.4.2.4 Roof coating ....................................................................... 58

2.4.3 Influence of Window to Wall Ratio ................................................. 59

2.4.4 Influence of External Shading Devices ............................................ 62

2.4.5 Influence of Orientation ................................................................... 67

2.4.6 Evaporative Cooling ........................................................................ 69

2.4.7 U-Value ............................................................................................ 69

2.4.8 R-Value ............................................................................................ 70

2.4.9 OTTV ............................................................................................... 71

2.4.10 RTTV ............................................................................................... 72

2.4.11 Heat Transfer through Skin .............................................................. 73

2.4.12 Sun Path Diagram ............................................................................ 74

2.5 INDOOR THERMAL ENVIRONMENT ................................................... 76

2.5.1 Thermal Comfort Definition ............................................................ 76

vi

2.5.2 Thermal Comfort Zone .................................................................... 76

2.5.3 Factors of Comfort ........................................................................... 77

2.5.4 Acceptable Thermal Conditions in Naturally Conditioned Space ... 77

2.5.5 Adaptive Comfort Model for Natural Ventilation Spaces ............... 79

2.5.6 Thermal Comfort Previous Studies in Hot and Dry Climate ........... 82

2.6 SUMMARY OF THE CHAPTER ............................................................... 85

CHAPTER THREE: RESEARCH METHODOLOGY ........................................... 86

3.1 INTRODUCTION ....................................................................................... 86

3.2 RESEARCH METHODOLOGY ................................................................ 86

3.2.1 Research Approach .......................................................................... 86

3.2.2 Measurable Factors and Scale .......................................................... 90

3.3 CASE STUDIES: Mud brick houses in Tarim city ..................................... 91

3.3.1 Old and new urban fabric ................................................................. 92

3.3.2 Selection of Case Study ................................................................... 93

3.4 SELECTED CASE STUDIES ..................................................................... 94

3.4.1 Justification of Selected Case Studies .............................................. 95

3.4.2 Case No 1 (Abu Saeed) - Old Urban Fabric .................................... 97

3.4.2.1 Description of building construction ................................. 99

3.4.2.1.1 Wall ................................................................... 99

3.4.2.1.2 Ceiling and roof ............................................... 100

3.4.2.1.3 Window and doors .......................................... 101

3.4.3 Case No 2 (Abu Kamal) – Old Urban Fabric ................................. 102

vii

3.4.3.1 Description of building construction ............................... 105

3.4.3.1.1 Wall ................................................................. 105

3.4.3.1.2 Ceiling and roof ............................................... 105

3.4.3.1.3 Window and doors .......................................... 106

3.4.4 Case No 3 (Barfaid) - New Urban Fabric ...................................... 107


3.4.4.1.1 Wall ................................................................. 109

3.4.4.1.2 Ceiling and roof ............................................... 109

3.4.4.1.3 Window and doors .......................................... 110

3.4.5 Case No 4 (Musaied) – New Urban Fabric .................................... 111


3.4.5.1.1 Wall ................................................................. 113

3.4.5.1.2 Ceiling and roof ............................................... 113

3.4.5.1.3 Window and doors .......................................... 114

3.5 MEASURABLE EQUIPMENTS .............................................................. 115

3.5.1 45170: Hygro-Thermo Anemometer Light Meter ......................... 115

3.5.2 Temperature Humidity Recorder ................................................... 116

3.5.3 Ir60: Infrared Thermometer ........................................................... 116

3.5.4 Wind Direction Indicator ............................................................... 117

3.6 FIELDWORK ............................................................................................ 118

3.6.1 Internal Survey ............................................................................... 119

3.6.2 External Survey .............................................................................. 120

3.6.3 Period of Data Collection ............................................................... 121

3.6.4 Meteorological Data ....................................................................... 124

viii

3.6.5 Calibration of Instruments ............................................................. 125

3.7 LIST OF CHECKLIST FACTOR ............................................................. 125

3.7.1 Wall and Roof ................................................................................ 126

3.7.2 Orientation ..................................................................................... 126

3.7.3 Insulation ........................................................................................ 127

3.7.4 Shading Devices ............................................................................. 127

3.7.5 Window to Wall Ratio ................................................................... 127

3.8 SIMULATION MODEL ........................................................................... 128

3.8.1 Reviews on Simulation Tools ........................................................ 128

3.8.1.1 Autodesk Ecotect ............................................................. 129

3.8.1.2 Energy Plus ...................................................................... 130

3.8.1.3 Energy -10 ........................................................................ 131

3.8.1.4 IES (VE) .......................................................................... 131

3.8.1.5 eQUEST ........................................................................... 132

3.8.2 Selection of Software ..................................................................... 133

3.8.3 Calibration and Validation of the Software Tool ........................... 134

3.8.4 Analysis Methodology of the Fieldwork Data ............................... 138

3.8.5 Analysis Methodology of the Simulation Data .............................. 139

3.8.5.1 Effect of roof .................................................................... 139

3.8.5.2 Effect of wall ................................................................... 140

3.8.5.3 Effect of orientation ......................................................... 140

ix

3.8.5.4 Effect of window to wall ratio (WWR) ........................... 140

3.8.5.5 Effect of shading devices ................................................. 141

3.8.5.6 Effect of ideal strategies .................................................. 141

3.8.6 Required Data ................................................................................ 141

3.8.6.1 Thermal properties ........................................................... 141

3.8.6.2 Weather data .................................................................... 142

3.9 REVIEW OF THE CHAPTER .................................................................. 143

CHAPTER FOUR: RESULT OF THE ANALYSES: FIELDWORK .................. 144

4.1 INTRODUCTION ..................................................................................... 144

4.2 AIR TEMPERATURE DIFFERENCE BETWEEN OLD AND NEW

URBAN FABRIC ...................................................................................... 144

4.3 INDOOR CONDITION DURING SUMMER AND WINTER

PERIOD ..................................................................................................... 146

4.4 CASE NO 1 (ABU SAEED) - OLD URBAN FABRIC ........................... 149

4.4.1 Indoor and Outdoor Air Temperature ............................................ 149

4.4.2 Indoor Air Temperature of All Rooms with Each Other ............... 152

4.4.2.1 Difference between R1 and R2 ........................................ 152






x

4.4.3 Indoor Air Temperature of All Rooms and Outdoor Temperature 158

4.5 CASE NO 2 (ABU KAMAL) – OLD URBAN FABRIC ......................... 161









4.5.3 Indoor air temperature of all rooms and outdoor temperature ....... 170

4.6 CASE NO 3 (BARFAID) - NEW URBAN FABRIC ............................... 173










4.6.4 Effect of Wall Orientation on Surface Temperature ...................... 185

xi

4.6.4.1 Room 1 ............................................................................. 186

4.6.4.1.1 Wall oriented to south (164°) .......................... 186

4.6.4.1.2 Wall oriented to west (254°) ........................... 186

4.6.4.1.3 Roof ................................................................. 186

4.6.4.2 Room 2 ............................................................................. 193

4.6.4.2.1 Wall oriented south (164°) .............................. 193

4.6.4.2.2 Roof ................................................................. 194

4.6.4.3 Room 3 ............................................................................. 196

4.6.4.3.1 Wall oriented to north (344°) .......................... 196

4.6.4.3.2 Wall oriented to west (254°) ........................... 197

4.6.4.3.3 Roof ................................................................. 197

4.6.5 Effect of Roof Colour on Indoor Air Temperature and Surface

Temperature ................................................................................... 203

4.6.6 Effect of Shading Devices on Indoor Air Temperature and

Surface Temperature ...................................................................... 208

4.6.6.1 Effect on indoor air temperature ...................................... 208

4.6.6.2 Effect on surface temperature .......................................... 212

4.7 CASE NO 4 (MUSAIED) – NEW URBAN FABRIC .............................. 217








xii



4.8 SUMMARY OF IMPORTANT FIELDWORK RESULTS ..................... 229


CHAPTER FIVE: RESULT OF THE ANALYSES: BUILDING SIMULATION ... 231

5.1 INTRODUCTION ..................................................................................... 231

5.2 BUILDING MODIFICATION .................................................................. 231

5.2.1 Effect of Roof Modifications on Indoor Air Temperature ............. 232

5.2.1.1 Roof design plan .............................................................. 232

5.2.1.2 Effect on indoor air temperatures .................................... 233

5.2.1.3 Effect on annual thermal comfort hours .......................... 238

5.2.2 Effect of Wall Modification on Indoor Temperature ..................... 240

5.2.2.1 Wall design plan .............................................................. 240

5.2.2.2 Effect of wall thickness on indoor air temperatures ........ 241

5.2.2.3 Effect of lime plaster finishing on indoor air

temperatures ..................................................................... 246

5.2.2.4 Effect of concrete walls on indoor air temperatures ........ 248

5.2.2.5 Performance base on maximum and minimum

temperature ...................................................................... 250

5.2.2.6 Effect on thermal comfort hours ...................................... 251

5.2.3 Effect of Orientation on Indoor Air Temperatures ........................ 253

5.2.3.1 Orientation design plan .................................................... 253

xiii

5.2.3.2 Effect on indoor air temperatures during summer ........... 255


5.2.3.4 Effect on hottest maximum and minimum temperatures . 259

5.2.4 Effect of window to wall ratio on indoor temperature ................... 261

5.2.4.1 Window to wall ratio design plan .................................... 261



5.2.5 Effect of External Shading Devices on Indoor Temperature ......... 267

5.2.5.1 Shading devices design plan ............................................ 267


5.2.5.3 Annual effect on indoor air temperatures ........................ 272


5.2.6 Effect of All Ideal Modification ..................................................... 278

5.2.6.1 Ideal modifications design plan ....................................... 278




CHAPTER SIX: CONCLUSION AND RECOMMENDATION .......................... 286

6.1 INTRODUCTION ..................................................................................... 286

6.2 REVIEW OF THESIS OBJECTIVES AND RESEARCH

QUESTIONS ............................................................................................. 286

6.3 RESEARCH FINDINGS ........................................................................... 288

xiv

6.3.1 Fieldwork Findings for Objective 1 ............................................... 288

6.3.1.1 Impact of orientation ........................................................ 289

6.3.1.2 Impact of surface temperature ......................................... 291

6.3.1.3 Impact of roof colour ....................................................... 292

6.3.1.4 Impact of shading devices ................................................ 292

6.3.2 Simulation Model Findings for Objective 2 .................................. 293

6.3.2.1 Impact of roof .................................................................. 293

6.3.2.2 Impact of wall .................................................................. 294

6.3.2.3 Impact of orientation ........................................................ 295

6.3.2.4 Impact of window to wall ratio ........................................ 295

6.3.2.5 Impact of shading devices ................................................ 296

6.3.2.6 Impact of ideal strategies ................................................. 296

6.4 RECOMMENDATIONS ........................................................................... 297

6.5 ENVELOPE DESIGN METHODS AND RECOMMENDATIONS

FOR RESIDENTIAL BUILDING IN HOT AND DRY CLIMATE

OF YEMEN ............................................................................................... 299

6.6 PROPOSED FUTURE RESEARCH STUDIES ....................................... 300

REFERENCES ........................................................................................................... 302

xv

LIST OF TABLES

Table ‎2.1 OTTV of different climatic regions for Arab countries (Hanna,

2010) ..................................................................................................... 72

Table ‎2.2 Factors influence thermal comfort ........................................................ 77

Table ‎3.1 Measurable factors and scale ................................................................ 90

Table ‎3.2 Table shows comparison between all case studies ............................. 115

Table ‎3.3 Correlation test of outdoor fieldwork measurements and airport

weather station .................................................................................... 124

Table ‎3.4 Difference between fieldwork result and predicted result from

simulation tools ................................................................................... 137

Table ‎3.5 Correlation test of field measurement and simulation tools IES

(VE) and Ecotect ................................................................................. 137

Table ‎3.6 Thermal properties of building materials ............................................ 142

Table ‎5.1 Number of modified parameters and simulated conditions ................ 232

Table ‎5.2 Simulated roofs description and modification .................................... 233

Table ‎5.3 Annual period of thermal comfort of investigated roofs .................... 238

Table ‎5.4 Simulated walls description and modification .................................... 241

Table ‎5.5 Annual period of thermal comfort of investigated walls .................... 252

Table ‎5.6 Annual period of thermal comfort of all investigated orientation ...... 258

Table ‎5.7 Effect of shading devices on annual period of thermal comfort ......... 277

Table ‎5.8 Suggested building envelope designs from combination of ideal

previous modifications. ....................................................................... 278

Table ‎5.9 Annual thermal comfort hours of different suggested designs ........... 284

Table ‎6.1 Summary of the fieldwork measurements between cases................... 289

Page

xvi

LIST OF FIGURES

Figure ‎1.1 Electricity consumption for different sectors GW/H for the year

2004 in Yemen ..................................................................................... 7

Figure ‎1.2 Electricity consumption for different sectors GW/H for the year

1990 in Yemen ..................................................................................... 7

Figure ‎1.3 Electricity consumption for different sectors GW/H in Yemen ........... 8

Figure ‎1.4 Electric consumption for different sectors in Wadi Hadhramout

(kw/h) for the year 1999 ....................................................................... 9

Figure ‎1.5 Electric consumption for different sectors in Wadi Hadhramout

(kw/h) for the year 2004 ....................................................................... 9

Figure ‎1.6 Electric consumption for different sector in Wadi Hadhramout

(kw/h) for year 2009 ........................................................................... 10

Figure ‎1.7 Electricity consumption in Wadi Hadhramout for different

sectors GW/H ..................................................................................... 10

Figure ‎1.8 Research framework ........................................................................... 26

Figure ‎2.1 Map of Yemen governorates .............................................................. 35

Figure ‎2.2 Regional map of Wadi Hadhramout ................................................... 37

Figure ‎2.3 Average annual maximum and minimum air temperature in

Wadi Hadhramout .............................................................................. 38

Figure ‎2.4 Relative humidity in Wadi Hadhramout ............................................ 39

Figure ‎2.5 Sunshine duration in Wadi Hadhramout ............................................ 40

Figure ‎2.6 Solar radiations on horizontal surface ................................................ 41

Figure ‎2.7 Monthly average of wind speed at Wadi Hadhramout ....................... 42

Figure ‎2.8 Percentage of wind direction for Seiyun city ..................................... 43

Page

xvii

Figure ‎2.9 Amount of annual rainfall for Wadi Hadhramout .............................. 44

Figure ‎2.10 Diagram of heat balance on the roof .................................................. 54

Figure ‎2.11 Different designs of external shade devices ....................................... 66

Figure ‎2.12 Sun path diagram of Tarim city Yemen, during the year ................... 75

Figure ‎2.13 Comfort zone of summer and winter for Hadhramout (Hot and

dry climate cities) ............................................................................... 79

Figure ‎2.14 Acceptable operative temperature for natural ventilation

buildings ............................................................................................. 81

Figure ‎3.1 Research methodology diagram ......................................................... 89

Figure ‎3.2 Satellite image of case studies location .............................................. 91

Figure ‎3.3 Satellite urban fabric of Tarim city (A) old urban fabric (B) new

urban fabric......................................................................................... 93

Figure ‎3.4 Location plan shows the location of visited and selected case

studies ................................................................................................. 95

Figure ‎3.5 Location plan shows the location of case study No1 squared ............ 97

Figure ‎3.6 Photos of the case study ..................................................................... 97

Figure ‎3.7 First floor plan shows room 1 and room 2 ......................................... 98

Figure ‎3.8 First floor plan shows room 3 and room 4 ......................................... 98

Figure ‎3.9 Section A-A of the case study No1 .................................................... 99

Figure ‎3.10 Roof construction in case study No1 ................................................ 100

Figure ‎3.11 Windows at case study No 1 ............................................................ 101

Figure ‎3.12 Location plan shows the location of case study No 2 squared ......... 102

Figure ‎3.13 Photo shows case study No 2 ........................................................... 102

xviii

Figure ‎3.14 First floor plan shows room 1 and room 2 ....................................... 103

Figure ‎3.15 Second floor plan shows room 3 and room 4 ................................... 104

Figure ‎3.16 Section B-B of the case study No2 ................................................... 104

Figure ‎3.17 Roof construction in case study No2 ................................................ 106


Figure ‎3.19 Photos of the case study ................................................................... 107

Figure ‎3.20 Floor plan shows the selected spaces ............................................... 108

Figure ‎3.21 Section C-C of the case study........................................................... 108

Figure ‎3.22 Roof construction in case study No 3 ............................................... 110



Figure ‎3.25 Photo shows case study from outside ............................................... 111

Figure ‎3.26 First floor plan shows selected rooms .............................................. 112

Figure ‎3.27 Section D-D of the case study No 4 ................................................. 112

Figure ‎3.28 Roof construction in case study No 4 ............................................... 114


Figure ‎3.30 Hygro-Thermo Anemometer Light Meter ........................................ 117

Figure ‎3.31 CENTER 342 Temperature Humidity Recorder .............................. 117

Figure ‎3.32 Ir60: Infrared Thermometer .............................................................. 117

Figure ‎3.33 TestLink SE342 software interface .................................................. 117

Figure ‎3.34 Wind direction indicator ................................................................... 118

Figure ‎3.35 Direction indicator and ..................................................................... 118

xix

Figure ‎3.36 Equipment set up 1- plan, 2- section ................................................ 120

Figure ‎3.37 Average outdoor temperature of 30 years ........................................ 121

Figure ‎3.38 Hottest period in summer season...................................................... 122

Figure ‎3.39 Coldest period in winter season........................................................ 122

Figure ‎3.40 Sun path diagram of Tarim city Yemen, during the year ................. 123

Figure ‎3.41 Comparison between airport weather station and data collected

from the fieldwork ............................................................................ 124

Figure ‎3.42 Calibration of instruments ................................................................ 125

Figure ‎3.43 Comparison of the field measurement and software tools

prediction measurements .................................................................. 136

Figure ‎3.44 Difference between field measurement and software

measurements ................................................................................... 136

Figure ‎3.45 Simulation weather data worksheet converter.................................. 143

Figure ‎4.1 Comprison between outdoor air temperature of old and new

urban area ......................................................................................... 145

Figure ‎4.2 Temperature difference between new and old urban area ................ 146

Figure ‎4.3 Indoor air temperature during summer period in Tarim city............ 147

Figure ‎4.4 Indoor air temperature during selected two days of summer

period in Tarim city .......................................................................... 148

Figure ‎4.5 Indoor air temperature during winter period in Tarim city .............. 148

Figure ‎4.6 Indoor air temperature during selected two days of winter period ... 149

Figure ‎4.7 Comparison between average indoor air temperature of all

spaces and outdoor air temperature .................................................. 150

xx

Figure ‎4.8 Average indoor air temperature of all spaces and outdoor

temperature for selected day ............................................................. 151

Figure ‎4.9 Difference between indoor and outdoor air temperature and

temperature above upper level of thermal comfort .......................... 151

Figure ‎4.10 Indoor air temperature of room 1 and room 2 .................................. 153


Figure ‎4.12 External wall configuration .............................................................. 154





Figure ‎4.17 Indoor air temperature of all rooms and outdoor air temperature .... 160

Figure ‎4.18 Indoor air temperature for selected day of all rooms and outdoor

air temperature .................................................................................. 160











xxi







air temperature .................................................................................. 172



Figure ‎4.32 Comparison between indoor and outdoor air temperature ............... 174

Figure ‎4.33 Average indoor temperature of all spaces and outdoor

temperature ....................................................................................... 175


between indoor and natural temperature .......................................... 175







Figure ‎4.41 Indoor air temperature of all rooms outdoor air temperature ........... 183


air temperature .................................................................................. 184

xxii


between indoor and natural temperature for room1 ......................... 184


between indoor and natural temperature for all rooms..................... 185

Figure ‎4.45 Indoor and outdoor surface temperature of room1 ........................... 188

Figure ‎4.46 Indoor and outdoor surface temperature of room1 for a selected

day .................................................................................................... 188

Figure ‎4.47 Difference in outdoor surface temperature between south and

west orientation ................................................................................ 191

Figure ‎4.48 Difference in indoor surface temperature between south and

west orientation ................................................................................ 191

Figure ‎4.49 Walls (south and west) and roof indoor surface temperature ........... 192

Figure ‎4.50 Difference in indoor surface temperature roof and walls oriented

to south and west .............................................................................. 192

Figure ‎4.51 Difference in outdoor surface temperature roof and wall oriented

to south and west .............................................................................. 193


Figure ‎4.53 Indoor and outdoor wall and roof surface temperature .................... 195

Figure ‎4.54 Indoor wall and roof surface temperature and indoor air

temperature ....................................................................................... 196


Figure ‎4.56 Average indoor and outdoor surface temperature of room3 ............ 199

Figure ‎4.57 Comparison between indoor and outdoor surface temperature of

wall oriented to west and north ........................................................ 200

xxiii

Figure ‎4.58 Average difference on indoor wall surface temperature between

walls oriented to north and west ....................................................... 200

Figure ‎4.59 Average difference in outdoor wall surface temperature between

walls oriented to north and west ....................................................... 201

Figure ‎4.60 Walls and roof indoor surface temperature ...................................... 201

Figure ‎4.61 Average difference in indoor surface temperature between walls

and roof............................................................................................. 202

Figure ‎4.62 Indoor air temperature and indoor surfaces temperature .................. 202

Figure ‎4.63 Roof colour before painted (A) and roof after painted with

whitewash (B)................................................................................... 205

Figure ‎4.64 Outdoor roof surface temperature and outdoor air temperature

before and after painting................................................................... 206

Figure ‎4.65 All tested parameters before and after painting ................................ 206

Figure ‎4.66 Indoor roof surface temperature and indoor air temperature


Figure ‎4.67 Difference between indoor and outdoor roof surface temperature


Figure ‎4.68 Layout and shading devices location................................................ 208

Figure ‎4.69 Shading projection which was installed on the wall ........................ 208

Figure ‎4.70 Indoor and outdoor air temperature of room1 before and after

installing shading devices ................................................................. 210

Figure ‎4.71 Indoor air temperature of room1 before and after installing

shading devices................................................................................. 211

Figure ‎4.72 Difference (after – before) in indoor and outdoor air temperature

of room1 after and before installing shading devices ....................... 211

xxiv

Figure ‎4.73 Outdoor surface temperature of west wall before and after


Figure ‎4.74 Indoor surface temperature of west wall before and after


Figure ‎4.75 Indoor and outdoor surface temperature of west wall after

installed shading devices .................................................................. 215

Figure ‎4.76 Indoor surface temperature of west wall for R1 with and R3

without shading devices ................................................................... 216

Figure ‎4.77 Indoor surface temperature of west wall of R3 before and after

installing shading devices in R1 ....................................................... 216

Figure ‎4.78 Difference in indoor surface temperature of west wall at R1 and

R3 before and after shading devices................................................. 217














xxv


air temperature .................................................................................. 228



Figure ‎5.1 Effect of difference roof modification on indoor air temperature .... 236

Figure ‎5.2 Temperatures differences between Ti field and several mud

roofs .................................................................................................. 237

Figure ‎5.3 Temperatures differences between Ti field and concrete roofs ........ 237

Figure ‎5.4 Number of hours within thermal comfort of each roof .................... 239

Figure ‎5.5 Difference between the mud roofs (real field) and other roofs ........ 239

Figure ‎5.6 Effect of different mud wall thickness on indoor air temperature ... 243

Figure ‎5.7 Temperatures differences between Ti field (0.50m) and several

mud wall thickness ........................................................................... 244

Figure ‎5.8 Maximum and minimum Ti pattern of different mud wall

thickness ........................................................................................... 245

Figure ‎5.9 Daily range of different mud wall thickness .................................... 245

Figure ‎5.10 Effect of lime plaster finishing on indoor air temperature ............... 247

Figure ‎5.11 Temperatures differences between Ti field (0.50m) and walls

finished by lime plaster .................................................................... 248

Figure ‎5.12 Effect of concrete walls on indoor air temperature .......................... 249

Figure ‎5.13 Temperatures differences between Ti field (0.50m) and concrete

walls.................................................................................................. 250

Figure ‎5.14 Number of hours within thermal comfort of each wall .................... 252

xxvi

Figure ‎5.15 Difference between the wall thickness of 0.50m (real field) and

other walls ........................................................................................ 253

Figure ‎5.16 Eight investigated room orientations ................................................ 254

Figure ‎5.17 Sun path diagram show summer and winter sun position over

investigated orientations ................................................................... 254

Figure ‎5.18 Effect of difference orientation on indoor air temperatures ............. 256

Figure ‎5.19 Temperatures differences between ideal orientation (S) and

other orientations .............................................................................. 257

Figure ‎5.20 Temperatures differences between ideal orientation (S) and

other orientations .............................................................................. 257

Figure ‎5.21 Relation between orientation and Ti during summer and number

of annual hours within thermal comfort ........................................... 259

Figure ‎5.22 Sun path diagram on summer and winter months ............................. 260

Figure ‎5.23 Investigated window wall ratio (WWR) of room2 ........................... 261

Figure ‎5.24 Maximum and minimum Ti during summer period of room2

oriented to south with different WWR ............................................. 262

Figure ‎5.25 Effect of window wall ratio for south orientation on number of

hours within thermal comfort ........................................................... 263

Figure ‎5.26 Relationship between orientation and window to wall ratio at

maximum numbers of hours within thermal comfort ....................... 264

Figure ‎5.27 Difference between Max. and Min. thermal comfort hours of all

investigated WWR ........................................................................... 265

Figure ‎5.28 Effect of west window on number of thermal comfort hours .......... 266

Figure ‎5.29 Effect of one and two sides window on number of thermal

comfort hours ................................................................................... 267

xxvii

Figure ‎5.30 External shading devices used in simulation .................................... 268

Figure ‎5.31 Different between case of no shading devices and other three

cases (horizontal projection, vertical fins and combination of

both).................................................................................................. 270

Figure ‎5.32 Predicted Ti of R1 for combination shading devices with

different projection during summer .................................................. 271

Figure ‎5.33 Different between horizontal projection, vertical fins and

combination of both on indoor air temperature ................................ 273

Figure ‎5.34 Different between case of no shading devices and other three

cases (horizontal projection, vertical fins and combination of

both).................................................................................................. 273

Figure ‎5.35 Effect of different horizontal shading projection on indoor air

temperature ....................................................................................... 274

Figure ‎5.36 Effect of different vertical fins projection on indoor air

temperature ....................................................................................... 274

Figure ‎5.37 Effect of different combination horizontal and vertical fins

projection on indoor air temperature ................................................ 275

Figure ‎5.38 Difference between all shading device types ................................... 275

Figure ‎5.39 Indoor air temperature of different envelope design ........................ 281

Figure ‎5.40 Indoor air temperature difference between field measurements

and difference envelope design D1 – D5 ......................................... 282

Figure ‎5.41 Indoor air temperature difference between field measurements

and difference envelope design D6 – D10 ....................................... 282

Figure ‎5.42 Number of thermal comfort hours in range ...................................... 284

Figure ‎5.43 Difference between the real field condition and the suggested

designs .............................................................................................. 285

xxviii

LIST OF ABBREVIATIONS

Ti Indoor air temperature Ro1 Roof No 1

To Outdoor air temperature Ro2 Roof No 2

Tn Natural temperature Ro3 Roof No 3

R1 Room number one Ro4 Roof No 4

R2 Room number two Ro5 Roof No 5

R3 Room number three Ro6 Roof No 6

R4 Room number four (hall) Ro7 Roof No 7

Ti Ss Indoor south surface temperature Ro8 Roof No 8

To Ss Outdoor south surface temperature W1 Wall No 1

Ti Ws Indoor west surface temperature W2 Wall No 2

To Ws Outdoor west surface temperature W3 Wall No 3

Ti Ns Indoor north surface temperature W4 Wall No 4

To Ns Outdoor north surface temperature W5 Wall No 5

Ti Rs Indoor roof surface temperature W6 Wall No 6

To Rs Outdoor roof surface temperature W7 Wall No 7

Dif Difference W8 Wall No 8

Tis Indoor surface temperature W9 Wall No 9

Tos Outdoor surface temperature W10 Wall No 10

Tc Thermal comfort W11 Wall No 11

WWR Window to wall ratio W12 Wall No 12

N North D1 Design No 1

NE North East D2 Design No 2

E East D3 Design No 3

SE South East D4 Design No 4

S South D5 Design No 5

SW South West D6 Design No 6

W West D7 Design No 7

NW North West D8 Design No 8

Ti max Maximum indoor temperature D9 Design No 9

Ti min Minimum indoor temperature D10 Design No 10

To max Maximum outdoor temperature

To min Minimum outdoor temperature

xxix

REKA BENTUK SAMPUL BANGUNAN UNTUK SUHU UDARA

DALAMAN DI IKLIM PANAS DAN KERING, YAMAN

ABSTRAK

Reka bentuk pasif pada sampul bangunan adalah salah satu kaedah yang paling berkesan

untuk mengurangkan kesan kondisi udara luar yang tinggi, pengurangan penyerapan

haba dan juga untuk penambahbaikan termal dalam bangunan untuk negara beriklim

panas dan kering di Yaman. Tambahan lagi, kurangnya keprihatinan para arkitek

tempatan pada hari ini terhadap reka bentuk sampul bangunan untuk mengurangkan suhu

udara di dalam bangunan. Oleh itu, kajian ini membincangkan hasil kajian eksperimen

dan simulasi untuk mengurangkan suhu udara di dalam bangunan dengan

mengaplikasikan pengubahsuaian terhadap reka bentuk sampul bangunan. Tujuannya

adalah untuk mengurangkan suhu udara di dalam rumah yang dibina daripada batu bata

lumpur untuk iklim panas dan kering di Wadi Hadhramaut, Yaman, serta dapat memberi

rekomendasi kaedah yang efisien untuk reka bentuk sampul bangunan. Kajian ini

dijalankan dalam dua fasa: fasa pertama ialah kerja lapangan di dalam dan luar bangunan

untuk empat kajian kes dalam bandar baru dan lama di Bandar Tarim, Yaman. Beberapa

pengubahsuaian dinding luaran seperti unjuran teduhan dan bumbung dengan warna

putih kapur telah dibuat. Fasa kedua ialah simulasi komputer menggunakan perisian IES

(VE) untuk menganalisa kesan-kesan pengubahsuaian dinding luaran yang berbeza.

Pengubahsuaian ini dilakukan pada bumbung, dinding, orientasi dan nisbah tingkap

dengan dinding bangunan serta tambahan teduhan luaran. Kajian dijalankan pada setiap

parameter dan pada peringkat terakhir, gabungan pengubahsuaian yang ideal dihasilkan.

Hasil kajian menunjukkan dengan penggunaan kombinasi gabungan pada semua

pengubahsuaian, suhu udara di dalam bangunan dapat dikurangkan berbanding suhu

xxx

diukur dalam kerja lapangan. Reka bentuk No. 4 (D4) ialah reka bentuk terbaik dinding

luaran yang mencatatkan perbezaan purata tertinggi (0.76ºC) pada suhu udara dalaman.

Dari segi bilangan jangkamasa keselesaan termal tahunan, reka bentuk No. 3 dan 6 (D3

dan D6) ialah reka bentuk dinding luaran terbaik yang mana ia menambahbaik

jangkamasa keselesaan termal tahunan kepada 7.87%.

xxxi

BUILDING ENVELOPE DESIGN FOR INDOOR AIR

TEMPERATURE IN HOT AND DRY CLIMATE, YEMEN

ABSTRACT

Passive design on building envelope is one of the most effective methods of

minimising the impact of harsh outdoor condition, reducing the heat gain as well as

to improving the indoor thermal condition in hot and dry climate in Yemen. Local

architects of today give less attention to building envelope design to reduce indoor

air temperature. This research discusses the results of the experimental and

simulation studies with the purpose to reduce the indoor air temperature by applying

modifications on the building envelope design. It aims to reduce the indoor air

temperature of residential houses built from mud bricks in hot and dry climate of

Wadi Hadhramout, Yemen, and finds recommendations for efficient method in

building envelope design. The investigation was performed in two phases: first phase

is indoor and outdoor fieldwork measurements in four case studies in old and new

urban area at Tarim city, Yemen. Several modifications on building envelope such as

fix shading projection and painting roof whitewash colour were performed. Second

phase is: computer simulation using IES (VE) software was carried out to investigate

the effects of other different envelope modifications. The modifications were carried

out on the roof, wall, orientation, window to wall ratio and external shading devices.

The investigation was carried out on each parameter and then in the last stage the

combination of all ideal modifications was made. The results showed that by

applying a combination of all ideal modifications, the indoor air temperature was

able to be reduce compared to the fieldwork measurements. Design No.4 (D4) is the

xxxii

best building envelope design which recorded the highest average difference

(0.76ºC) of indoor air temperature. In terms of the number of annual thermal comfort

hours, design No.3 and 6 (D3 and D6) are the best envelope designs in which they

improved the annual number of thermal comfort hours to 7.87%.

1

CHAPTER ONE: INTRODUCTION

1.1 INTRODUCTION

This chapter will briefly explain the key words of this study. Meanwhile, the primary

motivation of this study, in general, will explain what is going on in this study. The

research background, problem statement, previous reviewed research studies,

objectives, importance of the research, research questions and an overview of the

thesis structure will be discussed in this chapter.

1.2 RESEARCH BACKGROUND

This study discusses and focuses on the performance of mud brick house envelope in

hot and dry climate to enhance the indoor air temperature, which is the major

problem during the summer season due to excessive outdoor condition. The

measurable scales of this performance are focused on passive cooling. Houses

selected in this study are traditional and modern mud brick houses in Tarim city at

Wadi Hadhramout, Yemen. The main subjects are: building envelope, indoor air

temperature, hot and dry climate and mud brick.

The abundance and easy availability of mechanical cooling systems help in

propagating the inaccurate idea among common people in such a way that providing

thermal comfort has become just as easy as pressing a button. Another thing that

helps in the growth of this misconception is the lack of awareness of the problems

related to increasing energy use and the benefits of minimised consumption. The

climate responsive building design which incorporates passive features are very good

options for energy conservation (Singh et al., 2011). According to Martin (1980),

2

heating and cooling systems may be used where building design alone cannot

achieve suitable conditions for maintaining thermal comfort.

In this section of research background, can start by briefly define the main keywords

in this study. The first subject is building envelope which is defined by ASHRAE

(2007) as the building elements that separate uncontrolled outdoor environment from

controlled indoor environment. It is one of the most important factors in designing

energy-efficient buildings. Its design strongly affects heating and cooling loads

(ASHRAE, 2007). However, its components include: foundation, walls, roofs, floors,

window and doors (California Energy, 2009; ASHRAE, 2007; Szokolay, 2001a;

Lang, 2004). One of the most basic significant functions of the building envelope is

to control the environmental factors such as heat, air movement, daylight and sound

in order to provide comfort for users with minimal energy consumption (Oral et al.,

2004). It is the most important design parameter among other parameters effecting

indoor thermal comfort (Manioğlu and Yılmaz, 2008). (Lang, 2004).

In terms of building envelope design, Givoni (1998) reported that the appropriate

design is the design aimed at minimising or maximising the impact of solar radiation

depending on the climate and related design objective considering building shape,

orientation, wall, roof, external colour and window shade devices. Envelope design

as a means of improving indoor condition is the integrated design of building

parameters as a total system to obtain comfortable and energy savings (Okba, 2005).

Moreover, Huovila et al. (2007) pointed out, that in relation to how the building

envelope is designed, that it is also how building is located in the local environment:

a building must be designed with taking into account passive solar issues, such as

building orientation and siting, window size and location glazing area, natural

3

lighting and ventilation, as well as shading device strategies. Others such as

Bouchlaghem (2000) addressed the aspect of building envelope in terms of

improving thermal performance saying that there are mainly two types of parameters

affecting the thermal performance of a building. The first type is the fluctuant

climatic factors that the building is subject to, such as solar radiation, air

temperature, relative humidity and wind direction, the second type is under the

control of the architect such as layout and siting, materials properties, window

location and size, shading, insulation and finishing. However, some of these factors

have more influence over the building thermal response than others.

From the energy consumption point of view, the selection of proper material, design

and construction of a building’s facades has a major effect on the building energy

consumption (Hammad and Abu-Hijleh, 2010; Bader, 2010). During the early stages

of the building design process, the solar radiation and the neighbouring buildings

(building surrounding areas) should be determined, and the shape of the building

structure to achieve the self-shaded facades during the hot summer days, the best

selections for building envelop materials and exterior and interior finishes material,

shading devices, window size and glazing should also be identified (Capeluto, 2003).

The second subject is the indoor air temperature, In simple terms, temperature is a

measure of the motion of molecules (Bluyssen, 2009) and it is also defined as ‘‘the

symptom of the presence of heat in a substance‘‘ (Szokolay, 2008). The degree of

heat contained in a body or fluid medium describes the concept of temperature

(Fathy, 1986). In other words, it measures how hot or cold the air is, and it is

measured in Celsius scale, Kelvin scale and Fahrenheit scale. Heat flows from a

higher (hotter) temperature zone (or body) to a lower (colder) temperature one. Such

4

heat flow can take place in three forms (Capehart et al., 2002) (Binggeli, 2003)

(Szokolay, 2008) :

1. Conduction within a body or bodies in contact, by the ‘spread’ of molecular

movement.

2. Convection between a solid body and liquid or gas. The convection heat flow

rate depends on area contact, difference in temperature and convection

coefficient.

3. Radiation from a body with a warmer surface to another which is cooler.

Air temperature is one of the main climatic factors, and dry blub temperature (DBT)

is the variable most generally used to describe climate (Rosenlund, 2000; Groth,

2007). Moreover, air temperature is direct result of solar radiation. According to

Givoni (1976) the rate of heating and cooling of the surface of the earth is the main

factor determining the temperature of the air above it. As is well-known, the indoor

air temperature is influenced by the outdoor air temperature and by the indoor

surface temperature which is also influenced at a high degree by the absorbed heat

from direct exposure to solar radiation and in a small degree by the long wave

radiation from the clear sky.

In terms of human comfort, which is considered the most important requirement for

the indoor environment, air temperature is one of the main parameters affecting

human comfort. It is well-known that maintaining indoor air temperature within

thermal comfort is the key word of saving energy as well as the main purpose of

passive house. Huovila et al. (2007) define passive house as a building which

provides comfortable interior climate for residents without the use of active cooling

or heating system. Generally, from another point of view, passive design is the

5

design that does not require any mechanical system whether for heating or cooling. It

is designed for enhanced comfortable conditions over outside environment without

the use of any electric mechanical systems (Reardon et al., 2008; Yeang, 2006).

These authors noted that a house that takes the advantage of natural climate to

maintain thermal comfort is considered as a passively-designed house. Thus, in

relations to the local climate, passive ideas should be considered from the initial

design stage. Ji and Plainiotis (2006) sited that passive design is not an attachment or

supplement to architectural design, but a design process that is integrated with

architectural design.

From the previous statement, it can be noted that the intricate design of building

envelope will reduce external heat gain, indoor air temperature, increase ventilation,

and day lighting as well as improve indoor thermal comfort, which comes out with

elimination, or at least reduce the requirement of mechanical heating and cooling

systems, which means reducing energy consumption.

The third subject in this study is the hot and dry climate. The indoor environment of

houses is greatly influenced by the climate prevailing in the region. However, hot

and dry climate is the most dominant climate in the world (Peel et al., 2007). It is the

climate which is characterised by summer day time temperature which is very high,

large diurnal (day–night) temperature variation, winter cool or warm, winter night

which is very cold, dry air, with seldom rains of less than 250 mm annual (Meir and

Roaf, 2002; Rosemary and Susan, 2007; Szokolay, 2008; Huddart and Stott, 2010).

Therefore, the house envelope design must take into consideration the indoor thermal

comfort to avoid any negative impact on the occupants thermal comfort sensation.

6

Efficient use of energy has become a key issue for most energy policies.

Papadopoulos and Giama (2007) posited that energy efficient buildings decrease the

quantity of fossil fuels consumed and thus decrease the amount of carbon dioxide

and sulphur dioxide emitted into the atmosphere. Golubchikov and Badyina (2012)

add that generation energy is the major contributor of CO2 emissions and climate

change and it also results in many other forms of environmental pollution. Building

sector energy consumption grew 18% between 2000 and 2010, to reach around one-

third of global final energy use (International Energy Agency, 2013). Buildings are

one of the major sectors that consume energy. According to Yılmaz (2007), buildings

sector consumes more than half of all electricity, in addition to its being responsible

for more than one-third of all greenhouse gas emissions. Moreover, residential

buildings sector in the developing countries consumes more than half of the

electricity distributed (Synnefa et al., 2007). At the present time, climate

consideration in building design has become a necessity to meet this growing energy

demand (Singh et al., 2010).

According to Yemen Government Report (2005) as shown in Figure ‎1.1 residential

buildings consume about 58% of total electrical energy generated in the year 2004,

with an increase of about 12% than 1990 in Figure ‎1.2. Furthermore, Figure ‎1.3

shows that the increase in electric consumption in residential buildings through the

years was very high compared with other sectors where the increase was moderate.

The choices of material, design and construction of a building’s facades have major

impact on the energy consumption of buildings. However, reducing energy

consumption in buildings can be achieved through several ways such as proper urban

planning and landscape design, building layout, orientation, ventilation, shape,

windows, selection of proper materials, finishing, insulation and shading.

7

Figure ‎1.1 Electricity consumption for different sectors GW/H for the year 2004 in

Yemen

Source: Yemen Government Report (2005)

Figure ‎1.2 Electricity consumption for different sectors GW/H for the year 1990 in

Yemen


228

8%

529

18%

454

16%

1692

58%

Industrial

Commercial

Public utility

Residential

202

16%

335

27%

136

11%

565

46%

Industrial

Commercial

Public utility

Residential

8

Figure ‎1.3 Electricity consumption for different sectors GW/H in Yemen


In Wadi Hadhramout particularly, according to a Branch of the Ministry of

Electricity in Wadi Hadhramout (Refer to appendix H), Figure ‎1.4, ‎1.5 and ‎1.6 have

shown that residential buildings consume electricity ranging from 68% to 79% of

total electrical energy generated. Moreover, Figure ‎1.7 has shown remarkable

increase in electric consumption through the past eleven years. The responsibility of

architects and engineers for a passive design presents an important factor. However,

Studies aimed at minimising energy consumption for heating and cooling of these

houses have become a necessity.

0

200

400

600

800

1000

1200

1400

1600

1800

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

GW

/H

Residential Public utility Commercial Industrial

9

Figure ‎1.4 Electric consumption for different sectors in Wadi Hadhramout (kw/h)

for the year 1999

Source: Ministry of Electricity (2010)

Figure ‎1.5 Electric consumption for different sectors in Wadi Hadhramout (kw/h)

for the year 2004


65,886,018

76%

5,185,295

6%

3,504,329

4%

6,792,906

8%

4,860,059

6%

Residential

Commercial

Public utility

Water pumps

Others

112,396,541

79%

10,167,564

7%

14,479,986

10%

2,782,046

2%

3,187,812

2%

Residential

Commercial

Public utility

Water pumps

Others

10

Figure ‎1.6 Electric consumption for different sector in Wadi Hadhramout (kw/h)

for year 2009


Figure ‎1.7 Electricity consumption in Wadi Hadhramout for different

sectors GW/H


177,261,831

68% 15,518,916

6%

57,614,880

22%

5,756,598

2%

6,487,328

2%

Residential

Commercial

Public utility

Water pumps

Others

0

20

40

60

80

100

120

140

160

180

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

GW

/H

Residential Commercial Public utility Water pumps Others

11

This study will focus on the optimization of the indoor air temperature of the modern

houses in Tarim city at Wadi Hadhramout, particularly on the most common houses

in the new city extension. With the assistance of simulation software, the study will

investigate the effects of different building envelope parameters, which have effects

on indoor air temperature, such as roof, wall, window to wall ratio (WWR), external

shading projection, and orientation as a passive cooling technique for the purpose of

minimising dependence on the mechanical system and providing thermal comfort for

the users.

1.3 PREVIOUS RELATED RESEARCH STUDIES

Many studies were conducted in hot and dry climate by a number of researchers

aimed at enhancing indoor condition of residential buildings. They are varied in

addressing this purpose. While some studied the thermal performance of envelope

materials and design, others studied the appropriateness of building design to the

local climate. Other studies focus on means of passive techniques to provide thermal

comfort for occupants, with difference in the number of parameters, while some

studied only one or two parameters of passive techniques such as orientation and

insulation and so on. However, some of these studies are listed and briefly mentioned

below.

a- Saleh (1990)

A study has been conducted by Saleh (1990a) in hot and dry climate in Saudi Arabia.

He investigated the effect of six different wall designs and three different roof

designs on the indoor air temperature and surface temperature as well as the cooling

load generated by the heat flow from walls and roofs. The study also aims at

12

verifying the hypothesis, which says that the mud brick is a thermal regulating

material. The results of six model simulation indicated that the mud brick model, in

terms of space air temperature, performs better than other models except the

insulated one, in terms of indoor surface temperature the mud brick model remained

lower than ambient air temperature for longer periods than that of the other models.

The study noted that the mud brick is classified as not a good heat conductor and

concluded by proving the hypothesis and considered the mud brick as a thermal

regulating material.

b- Algifri et al. ( 1992)

Algifri et al. (1992) conducted a thermal behaviour study on mud brick and concrete

houses in hot and dry climate in Yemen at Seiyun city. The quantitative results of the

analysis indicate the good performance of mud houses, where the inside surface

temperature of concrete house was higher than ambient temperature in comparison

with mud brick house which recorded lower surface temperature than the ambient

temperature. He reported that mud brick is a good construction material for energy

saving.

c- Qadhi and Algifri (2000)

Qadhi and Algifri (2000) carried out a comparative study on the thermal properties of

mud and concrete construction materials. The studies concluded that the local

building material (mud brick) has excellent thermal properties which maintain the

indoor condition within thermal comfort range. However, both studies were not

concerned with any type of passive cooling techniques which enhance indoor air

temperature such as orientation window size etc.

13

d- Alani (2000)

Alani (2000) made an analytical study of the energy of a house built with mud brick

and another one built with concrete conducted by Algifri, in which the results

showed the efficiency of mud house (walls and roof) to maintain the indoor thermal

comfort during summer period. The study also cited some thermal and durability

properties of mud brick.

e- Al-Sanea and Zedan (2002)

Many studies were conducted on the effects of orientation on indoor thermal

comfort. Al-Sanea and Zedan (2002) reported in the study conducted in Riyadh hot

and dry climate during summer season, that the wall orientation has a significant

effect on the heat transfer and on the yearly cooling load.

f- Nahar et al. (2003)

Several studies have been conducted with a focus on roofs. Nahar et al. (2003) tested

the cooling performance of different passive techniques on the roof such as painting

by white cement, roof pond, evaporative cooling, air void thermal insulation, broken

white glazed tile pieces. It has been found that evaporative cooling is the best cooling

technique, but it consumes water. Thus instead of evaporative cooling, the study

recommended the second best technique which was white glazed tiles over the roof

for enhancing comfort condition in arid area.

g- Marsh and Al-Oraier (2005)

A study of traditional mud brick houses was conducted by Marsh and Al-Oraier

(2005) in hot and dry climate. The study was to determine the most effective passive

cooling techniques required to enhance occupant comfort in these buildings.

14

However, the study examined the effect of different parameters on indoor air

temperature. By applying the tested modification on one example model, the study

suggested some strategies to maximise comfort condition, and it concluded that the

application of passive design modification can have a significant effect on internal

comfort levels.

h- Kumar et al. (2005)

Kumar et al. (2005) described the performance evaluation of solar shading insulation

as one of solar passive cooling techniques, and he noticed about 2.5°C to 4.5°C of

reduction in indoor air temperature obtained by solar shading. Further reduction of

4.4°C to 6.8°C in room temperature was obtained when the results was modified

with insulation and controlled air exchange rate. The study suggests that solar

shading with insulation and air exchange is quite useful to maintain indoor air

temperature lower than that in the conventional building.

i- Amer (2006)

Amer (2006) introduced several passive modification to the roof in hot and dry

climate in order to reduce the indoor air temperature, and the result showed a fall in

indoor air temperature from the ambient temperature up to 6ºC when the roof is

painted white, and 3ºC when thermal insulation layer has been added.

j- Al Hamdi and Kaki (2007)

Many studies have been conducted in Saudi Arabia regarding appropriate cooling

techniques in hot and dry climate. Al Hamdi and Kaki (2007) conducted a

comparative study which focused on investigating the thermal performance of the

mud brick old building and modern buildings constructed with concrete. The study

15

was to determine the pattern of change in indoor air temperature and wall surface

temperature as well. The results showed good performance of mud brick house,

where the indoor air temperature of old mud brick house was lower than concrete

block house by about 4°C, and the indoor surface temperature of mud brick house

was cooler than indoor surface temperature of concrete block with about 7.6°C.

k- Al Hamdi (2007)

Al Hamdi (2007), in his study, talks about some of passive cooling techniques such

as wind catcher, water roof pond system, natural ventilation, and some passive

heating techniques such as direct and indirect solar radiation and direct roof soil

coupled system. However, the study noted that the use of passive cooling and heating

strategies contribute in reducing energy consumption, and it also draws some

recommendations regarding the use of these passive techniques.

l- Gutierrez and Labaki (2007)

Another experimental study conducted by (Gutierrez and Labaki, 2007) was about

the thermal performance of fixed exterior shading devices on north and west

orientation. Horizontal louvers, vertical fins and eggcrate typology made of concrete

and wood were the investigated devices. Results showed that the most significant

performance was the horizontal concrete louver on north facade. However, in

relation to materials, the concrete devices obtained the most excellent results, and it

recorded that indoor air temperature lowers the wood, in spite of the good insulation

properties of wood. The study also noted that the facade orientation has great effect

on the performance of shading devices.

16

m- Ghisi and Felipe Massignani (2007)

Ghisi and Felipe Massignani (2007) studied the thermal performance of residential

buildings, and the objective was to compare the thermal performance of eight

unoccupied bedrooms with four different orientation. The assessment includes the

correlation between the indoor air temperature and thermal properties of the wall and

window and drawing the shading on the window. The study concluded that the two

parameters in which show the best correlation with maximum air temperatures and

should be minimised in summer for improved indoor thermal condition are U-value

and facade area. The thermal capacity and thermal time lag are the two parameters

that show the best correlation in winter and should be maximised to improve indoor

thermal condition.

n- Albatici (2009)

In a study conducted by Albatici (2009), aimed to define possible design action to

improve indoor comfort condition, the first three steps were monitoring the indoor

thermal condition of one pilot building; second, modelling and simulating the

thermal behaviour of this pilot building, and then suggestion of changes in some

passive building elements (insulation, material properties, glass area and sun space)

in order to evaluate the best options. The study in the end draw a guideline regarding

the investigated passive elements towards the right design for low energy and with

local techniques and materials.

o- Khalil et al. (2010)

Efforts have been made by Khalil et al. (2010) in hot and dry climate in Egypt to

evaluate the thermal performance of different construction materials (insulated and

non-insulated concrete, double, plant and active concrete covering). The results of

17

this study reported that heat transfer through the material (U-value) plays a major

role. The study also emphasised on the use of insulation which was damping the

thermal stress and maintaining the indoor condition near comfort zone. Natural night

ventilation was recommended to improve the indoor condition. Indoor air

temperature recorded thermal damping of 96%, 90%, 89% and 76% for insulated

concrete, double, planted and non-insulated concrete respectively. More

experimental studies have been carried out in different passive cooling techniques.

However, in terms of insulation there are many studies investigating the performance

of insulation. While some studied the effect of insulation in reducing energy

consumption, others studied the optimum thickness, location in the wall and roof and

tested different kinds of insulation materials (Ozel and Pihtili, 2007; Mishra et al.,

2012; Al-Sanea and Zedan, 2002; Çomakli and Yüksel, 2003; Cabeza et al., 2010;

Fertelli, 2013).

p- Kamal (2010)

A theoretical study by Kamal (2010) discussed different shading strategies that can

be used to shade buildings, thus providing natural cooling and assisting in minimised

energy consumption in buildings. The study also reported the ways and techniques in

which it can shade and protect buildings from direct sunlight. He also mentioned a

number of points that must be taken into account for summer shading as well as a

brief classification of shading devices. Meanwhile, in terms of shading as a simple

method of passive cooling in order to protect buildings from the sun, its use is highly

recommended and their thermal performance and benefits are recognised and

discussed by many researchers (Baker, 2001; Etzion, 2001; Brown and Dekay,

2001). However, many studies have been conducted to determine the performance of

self-shading building envelope and external shading devices as a passive cooling

18

technique and effective element for saving energy and improving indoor thermal

condition (Fadzil and Sia, 2003; Capeluto, 2003; Al-Musaed et al., 2007; Bakhlah et

al., 2008; Laouadi and Galasiu, 2009; Tariq and Jinia, 2012).

q- Al-sudais (2010)

Al-sudais (2010) conducted a study on the effect of window to wall ratio (20%, 50%,

75% and 100%), window with multiple panes (single, duple and triple), and

orientation towards south and west on the performance of indoor thermal condition

of the tested room. By the comparison of these parameters, the study made

recommendations regarding the performance of window to wall ratio on thermal

condition. The main conclusion was in the case of the building oriented to the south

with window to wall ratio of 25%, it is preferable to use window with single pane

glass, because the comparison results show no significant difference between the

three types (single, duple and triple).

r- Khoukhi and Fezzioui (2012)

Khoukhi and Fezzioui (2012) conducted a study on traditional houses in hot and dry

climate in Algeria; and the study evaluated the thermal comfort of modern houses by

conducting comparative analysis with existing traditional houses, in which they

tabulated the percentage of hours within thermal comfort. The study concluded that

the modern houses were inappropriate for hot and dry climate, and there are no other

solutions to ensure thermal comfort in summer apart from the air-conditioned

system.

19

s- Kim et al. (2012)

Kim et al. (2012) conducted a comparative study of external shading devices in

residential houses in terms of energy saving for heating and cooling; and the analysis

by energy simulations programme IES-VE (Integrated Environmental Solution –

Virtual Environment) has shown that the experimental shading device provides the

most efficient performance with different adjustments of the slat angle.

t- Kokogiannakis et al. (2012)

Effects of material surface properties on thermal performance have been observed by

Kokogiannakis et al. (2012). He analysed the energy impact of different external and

internal surface coating. The study concluded that, roof coatings can have a

significant influence on the energy performance of buildings with low insulation

levels in the roof.

u- Hamdani et al. (2012)

Hamdani et al. (2012) conducted a study on the effect of orientation and insulation

on indoor air temperature in hot and dry climate in Algeria. He noted that changing

orientation of buildings has not had a significant impact on interior temperature

especially in hot season. The study noted that the use of high thermal inertia (The

resistance of a material to temperature change) is the key property in controlling

temperature fluctuation.

v- Leskovar and Premrov (2012)

Leskovar and Premrov (2012) conducted a study to determine the ideal windows to

wall ratios in relation to energy efficiency in well-insulated houses with prefabricated

20

timber frame structural. The results point out that the optimal windows area for walls

with lower U-values is slightly smaller than in walls with higher U-values.

w- Sherif et al. (2012)

Sherif et al. (2012) investigated the effect of the depth and perforation configuration

of the external perforated window solar screens on the annual energy load in hot and

dry climate in Egypt. The result proved that the deep perforated solar screens in the

South and West orientations efficiently achieved up to 30% of the total energy load.

However, the study recommended perforation of 80% to 90% and depth/opening

width ratio of 1:1.

x- Bencheikh (2013)

Bencheikh (2013) investigated the performance of passive cooling system by evapo-

reflective roof in buildings for hot arid climates. Result showed reduction in indoor

air temperature up to 6 to 10ºC compared to indoor air temperature of room with

exposed roof. Moreover, by allowing natural ventilation at night, further reduction up

to 3 to 3ºC was obtained.

y- Sedki et al. (2013)

Recent field measurements of indoor air temperature and relative humidity were

conducted by Sedki et al. (2013b) to analyse the effects of orientation on indoor

thermal comfort in hot and dry climate during winter in Egypt. IES-VE (Integrated

Environmental Solution – Virtual Environment) was used after calibration to predict

indoor air temperature. The study concluded that there is no significant effect for the

orientation on improving thermal conditions in this specific week of the survey

period.

21

1.4 PROBLEM STATEMENT

In hot and dry climate, minimising indoor air temperature by passive techniques is

very important, as argued by all worldwide researchers who noted that the building

envelope design has significant effect in reducing heat gain from the outdoor thus

minimising energy consumption. The problems are buildings in developing countries

mostly designed without taking enough consideration of the climate condition

(Rosenlund, 2000). Moreover, most architects ignore the effect of the passive

techniques such as envelope design, orientation, materials, etc. and its importance to

reduce the indoor air temperature. Hence, its contribution in obtaining indoor thermal

comfort, and unfortunately, the resort to using mechanical system for cooling to

provide comfort (Nahar et al., 2003; Koranteng and Abaitey, 2009; Heidari, 2010).

Lack of studies so far is conducted to guide the architecture to the optimal design of

the building envelope of mud brick house in hot and dry climate in Yemen. Few

studies have been conducted to determine how much passive cooling techniques

contribute in reducing the indoor air temperature for naturally ventilated mud brick

houses in hot and dry climate in Wadi Hadhramout, Yemen. Furthermore, there is no

guideline for building envelope design of natural ventilation building and no energy

efficiency codes for the building sector, which are necessary to guide and provide the

designers with necessary information to obtaining thermal comfort condition and

minimising energy consumption.

There is a need of study in Yemen to determine the amount of energy consumption

for cooling in residential buildings. However, a study conducted in Saudi Arabia by

(Elhadidy et al., 2001) reported that air conditioning in residential buildings

consumed about 73% of total electricity; and this excessive consumption of electric

22

energy for just air-conditioning system, makes it necessary to design energy-efficient

buildings (Ahmad, 2004). Residential buildings are now becoming more influenced

by external climate; and energy and thermal comfort were not considered as

important issues in settlements planning (Eliasson, 2000; Johansson, 2006).

The energy sector plays a vital role in the socio-economic development of any

country (Al-Yousfi, 2004). More than 20% of the population in Arab regions suffer

from the lack of electrical energy supplies; and almost the same percentage suffer

from epileptic supply of electric power (UN-ESCWA, 2006; Al-Yousfi, 2004;

Fattouh and El-Katiri, 2012; Abdul Gelil, 2008). Yemen is one of Arab world

countries with the poorest energy services particularly in the field of electricity

access (Fattouh and El-Katiri, 2012). According to Yemeni government report

published in (2005), it was reported that the beneficiaries of the electricity power are

about 36% of total population in the year 2004; and about 39.6% in years 2009 and

2010 (W B, 2013). In Hadhramout state, energy consumption increased rapidly to

reach about 278.25 GW/H in 2010 from 140.07 GW/H in 2001with a growth rate of

about 11% per annum. Yemen still needs to increase electric power generation to

meet needs which means increase in air pollution and CO2 emissions. Thus, any

successful energy-efficiency building design will also have a significant impact in

reducing the negative impact on the environment.

Thus, it is certain that the results of this study will significantly help in understanding

and promoting the use of passive cooling techniques, suggest recommendations for

methods in improving the indoor environment, and consequently contributing to

eliminate or reduce the reliance on active cooling mechanical system.

23

1.5 RESEARCH QUESTIONS

The research questions of this study are as follows:

1- What is the indoor and outdoor thermal condition during summer and winter

in traditional and modern mud brick houses in hot and dry climate of Wadi

Hadhramout? Is it within the thermal comfort zone?

2- How do the building envelope elements affect the indoor condition; and how

does each element affect indoor air temperature in hot and dry climate?

3- Is the existing wall and roof thickness effective; and what is the effective wall

and roof thickness?

4- What is the important element of envelope design which has good

contribution in enhancing indoor thermal condition?

5- What is the new building envelope design which improves the indoor air

temperature in hot and dry climate? Is it achieving comfortable indoor

condition?

1.6 OBJECTIVES OF THE STUDY

The main objectives of this study are to evaluate thermal features of the house

envelope and identify the appropriate methods and means of building envelope

elements to reduce indoor air temperature of hot and dry climate in Tarim, to ensure

thermal comfort level of the users and minimise energy consumption. So the

objectives of the study are:

1- To investigate the existing building envelope elements which affect the

indoor air temperature and thermal comfort of residential buildings.

24

2- To suggest appropriate methods as a recommendation for building envelope

design which reduces indoor air temperature by passive cooling techniques in

hot and dry climate.

1.7 RESEARCH FRAMEWORK

Before starting any research it is essential to draw a clear plan describing the steps

and methods that will be followed to conduct this research correctly. The research

framework of this study (Figure ‎1.8) can be summarised and organised into three

main phases namely: literature review, research methodology and analysis. The first

step contains two parts; the first one is the definition and collecting of sufficient

information and resources such as books, journals and theses related to the research

subject in order to know the background, problems, objective and research questions,

and in the end drawing a clear framework on how to accomplish this research. The

second part is the identification of the climate in the study area; and then, definition

of keywords will be reviewed followed by previous research and studies in similar

contexts of this study especially on the impact of building envelope elements on

indoor thermal condition. Finally, the indoor thermal comfort and the previous

studies in this context will be reviewed.

The second phase is research methodology which consists of the methodology of

survey, simulation and case study. The first step (methodology of survey) will cover

the methodology of data collection from the fieldwork, methodology diagram,

checklist factors and equipments to be used. However, the second step is the

simulation which consists of a review of building simulation software and selection

of software. Model will be calibrated by the real measurements from the field.

Modifications that will be made to the building envelope elements will also be

building envelope design for indoor air...

Documents