Investigating the influence of design parameters on the indoor environmental quality and thermal comfort in primary schools in ho chi minh city, vietnam

Department of Architecture and Built Environment INVESTIGATING THE INFLUENCE OF DESIGN PARAMETERS ON THE INDOOR ENVIRONMENTAL QUALITY AND THERMAL COMFORT IN PRIMARY SCHOOLS IN HO CHI

Department of Architecture

and Built Environment

INVESTIGATING THE INFLUENCE OF DESIGN PARAMETERS

ON THE INDOOR ENVIRONMENTAL QUALITY

AND THERMAL COMFORT

IN PRIMARY SCHOOLS IN HO CHI MINH CITY, VIETNAM

ABSTRACT

Indoor environmental quality significantly impacts on comfort levels which affect students’ performance and productivity Currently in Vietnam, very few studies have dealt with the issue, and the current trend is to install energy-intensive air-conditioning in primary schools as this is perceived as more comfortable In this study, indoor comfort and users’ perceptions were investigated in three primary schools in Ho Chi Minh City during the mid-season (September 2015), the hottest season (April 2016) and the coldest season (December 2016 – January 2017) to provide a good overview In-situ spot and long-term measurements were recorded Questionnaires were completed by 4411 children (age range from 8 to 11 years) and 116 teachers to inform the study about their experiences and the extent of their interaction with the buildings in 124 classrooms The results were analysed by correlating the conditions measured and the comfort votes on a seven-point scale

In free-running schools, more than 90% of children were satisfied with the overall indoor conditions, although the classrooms were found to be out of thermal comfort for more than 20% of the school time Furthermore, the classrooms were usually in noisy and dim conditions The conflict between the quantitative and qualitative results shows that the current standards

do not reflect the current expectation in the free running classrooms In the air-conditioned classrooms, the CO2 concentration levels were over 2000ppm and affected children’s alertness

The calculated neutral temperature in the free running classrooms was 31.3oC with the relative humidity of 60% to 70% and an average air velocity of 0.56m/s; and a benchmark of 33°C for overheating calculations was suggested The adjusted neutral temperature with a normal air speed was 29.4oC In this study, an adaptive thermal comfort model for Vietnamese children

in primary schools was proposed The thermal comfort criteria of design parameters for renovation projects and new-built buildings were recommended through parametric and optimisation studies

The findings suggested that air conditioning all year round may be unnecessary from a comfort perspective These findings could help and encourage architects and engineers to design and deliver schools that provide thermal comfort and minimise the use of air conditioning systems The results of this work could inform design standards to deliver high quality, low-energy indoor environmental classrooms in primary schools in Ho Chi Minh City, Vietnam

PUBLICATIONS

VI LE, T H., GILLOTT, M C & RODRIGUES, L T 2016 The case for hybrid ventilated primary schools in Ho Chi Minh City in Vietnam 36th International Conference on Passive and Low Energy Architecture Cities, Buildings, People: Towards Regenerative Environments (PLEA 2016) Los Angeles, USA

LE, T H V., GILLOTT, M C & RODRIGUES, L T 2017 An analysis of thermal comfort in primary schools in Vietnam 16th International Conference on Sustainable Energy Technologies (SET2017) Bologna, Italy

LE, T H V., GILLOTT, M C & RODRIGUES, L T 2017 Children thermal comfort in primary schools in Ho Chi Minh City in Vietnam Passive Low Energy Architecture Design to Thrive (PLEA 2017) Edinburgh, Scotland, UK

Under preparation:

LE, T H V., GILLOTT, M C & RODRIGUES, L T - expected 2021- The impact of indoor environmental quality on children’s productivity in primary schools in Vietnam

ACKNOWLEDGEMENTS

I would like to express my deepest gratitude to my supervisors, Professor Mark Gillott and Dr Lucelia Rodrigues, for their excellent guidance and supervision throughout this research project Without their support, this thesis would not have been possible

The research depends very much on the field study data from various case studies I would like to thank to Mr To Huu Cuong (the headmaster of Binh Quoi Tay Primary School), Ms Pham Thi Thanh Hao (the headmistress of Phu Dong Primary School), Ms Vo Thi Kim Lien (the headmistress of Ha Huy Tap Primary School) and all of teachers and children in three primary schools for their support during the data collection of the project I am also grateful to

my assistance team during the surveys

I also wish to acknowledge the financial support from the Ministry of Education and Training

of Vietnam, the University of Nottingham and the Newton Fund (British Council) Without their funding, this research could not have reached its goal

I am heartily thankful to my colleagues in Ho Chi Minh City University of Architecture for their help and introduction to the case studies Many thanks to all of my friends in SRB, Mark Group House and Nottingham House, as well as in the UK, for spending their invaluable time with

me Thanks also go to Mrs Chau Lam, my closest friend, and her family for their kind-hearted host during my time in the UK Special thanks to Mr and Mrs Peters for their love and care to

me

Last but not the least, I would like to express my deepest appreciation to my family: my parents,

my parents in law, my husband, my sister and especially my son - Benz, for their understanding, encouragement and support throughout the research

TABLE OF CONTENTS

ABSTRACT i

PUBLICATIONS ii

ACKNOWLEDGEMENTS iii

TABLE OF CONTENTS iv

LIST OF FIGURES 9

LIST OF TABLES 18

INTRODUCTION 22

1 THE CONTEXT OF HO CHI MINH CITY – VIETNAM 27

1.1 The climate context 28

1.1.1 Climate classification 29

1.1.2 Climate for building design in Ho Chi Minh City 30

1.1.3 Summary 36

1.2 The socio-economic and urban environmental contexts 36

1.2.1 Socio-economic context 36

1.2.2 Urban environmental context 39

1.2.3 Summary 43

1.3 The context of primary education in Ho Chi Minh City 44

1.3.1 Funding and management of education 45

1.3.2 The architecture of primary schools 48

1.3.3 Summary 54

1.4 Conclusion and discussion 55

2 INDOOR ENVIRONMENTAL QUALITY IN PRIMARY SCHOOLS 57

2.1 Thermal Comfort 58

Heat balance model 58

The adaptive thermal comfort model 61

Vietnamese standards 64

Thermal comfort studies in naturally ventilated primary schools 64

Conclusion 69

2.2 Indoor Air Quality 69

Standards 70

Research 72

2.3 Visual Comfort 74

Maintained illuminance 74

Uniformity 76

Vietnamese standards 76

Research 77

2.4 Acoustic Comfort 77

Standards 78

Research 80

2.5 Indoor environmental quality 81

Standards 81

Research 83

2.6 Conclusions 84

3 PILOT STUDY BINH QUOI TAY PRIMARY SCHOOL 87

3.1 Description 87

3.2 Scope and Method 89

3.3 Results and discussion 92

3.3.1 Spot measurements 93

3.3.2 Long-term monitoring 95

3.4 Conclusions 97

4 CASE STUDY 1 BINH QUOI TAY PRIMARY SCHOOL 99

4.1 Scope and Method 100

4.1.1 Long-term recording 101

4.1.2 Spot measurement 101

4.1.3 Questionnaire survey 102

4.1.4 International and Vietnamese Standards for indoor environmental quality 103

4.2 Results and discussion 103

4.2.1 Thermal comfort 108

4.2.2 Indoor air quality 122

4.2.3 Visual Comfort 124

4.2.4 Acoustic comfort 126

4.2.5 Indoor environmental quality 129

4.2.6 Occupants’ behaviour 131

4.3 Conclusions 133

5 CASE STUDY 2 PHU DONG PRIMARY SCHOOL 135

5.1 Description 136

5.2 Scope and Method 140

5.2.1 Long-term recording 141

5.2.2 Spot measurement 142

5.2.3 Questionnaire survey 142

5.3 Results and Discussion 143

5.3.1 Thermal comfort 147

5.3.2 Indoor air quality 160

5.3.3 Visual Comfort 163

5.3.4 Acoustic comfort 165

5.3.5 Indoor environmental quality 168

5.3.6 Occupants’ behaviour 169

5.4 Conclusions 173

6 CASE STUDY 3 HA HUY TAP PRIMARY SCHOOL 175

6.1 Description 176

6.2 Scope and Method 179

6.2.1 Long-term recording 180

6.2.2 Spot measurement 180

6.2.3 Questionnaire survey 181

6.3 Results and Discussion 181

6.3.1 Thermal comfort 187

6.3.2 Indoor air quality 196

6.3.3 Visual Comfort 198

6.3.4 Acoustic comfort 200

6.3.5 Indoor environmental quality 202

6.3.6 Occupants’ behaviour 203

6.4 Conclusions 205

7 AN ADAPTIVE THERMAL COMFORT MODEL FOR CHILDREN 207

7.1 Case studies 208

7.2 Scope and Method 208

7.2.1 Environmental data collection 209

7.2.2 Questionnaire 209

7.2.3 Analysis 210

7.3 Results and discussion 212

7.3.1 Neutral temperature 214

7.3.2 The relationship between comfort temperature and outdoor climate 222

7.3.3 Overheating occurrence 224

7.3.4 Teachers’ thermal comfort and occupant’s behaviour 227

7.4 Indoor thermal conditions and building elements 227

7.4.1 Shape 228

7.4.2 Fabric 229

7.4.3 Fenestration 230

7.4.4 Ventilation 232

7.4.5 Summary 232

7.5 Conclusion 233

8 SENSITIVITY ANALYSIS OF DESIGN PARAMETERS AND THERMAL COMFORT 235 8.1 Simulation basis 236

8.1.1 Simulation software 236

8.1.2 Simulation model 237

8.1.3 Model calibration 240

8.1.4 Weather data file 242

8.1.5 Base Case 243

8.2 Parametric study 246

8.2.1 Floor-to-ceiling height 246

8.2.2 Window area 248

8.2.3 Window type 250

8.2.4 Exhaust opening area 252

8.2.5 Overhang projection 254

8.2.6 Orientation 256

8.2.7 External wall material 258

8.2.8 Roof system 261

8.2.9 Infiltration 264

8.2.10 Additional natural ventilation 266

8.2.11 Summary 268

8.3 Optimisation study 269

8.3.1 Method 270

8.3.2 Results and discussion 271

8.4 Conclusion 274

9 CONCLUSIONS 277

9.1 Significance and impact of the study 281

9.2 Originality and contribution to knowledge 281

9.3 Recommendations for further work 282

REFERENCES 283

APPENDIX A 295

APPENDIX B 298

APPENDIX C 302

LIST OF FIGURES

Figure 1-1 Ho Chi Minh City at (a) daytime and (b) night time (Long T Nguyen, 2019) 27

Figure 1-2 Administrative map of Socialist Republic of Vietnam (Center of Survey and Mapping Data, 2020) 28

Figure 1-3 Koppen-Geiger map of Asia showing climate type (Aw) of Ho Chi Minh City (Peel et al., 2007) 29

Figure 1-4 Building climate zones in Vietnam (Ministry of Construction, 2009) 30

Figure 1-5 Urban districts (bright shaded) and rural districts (dark shaded) (Google, 2020) 30 Figure 1-6 Monthly mean precipitation of Ho Chi Minh City 31

Figure 1-7 Monthly mean air temperature of Ho Chi Minh City 32

Figure 1-8 Air temperature during typical days of the hottest month (April) and the coldest month (December) in Ho Chi Minh City 32

Figure 1-9 Monthly average relative humidity of Ho Chi Minh City 33

Figure 1-10 Relative humidity during typical days of the hottest month (April) and the coldest month (December) in Ho Chi Minh City 33

Figure 1-11 Wind velocity and main wind direction of Ho Chi Minh City 34

Figure 1-12 Stereographic Diagram of Ho Chi Minh City (Andrew Marsh, 2014) 34

Figure 1-13 Total sunshine hours during a year in Ho Chi Minh City 35

Figure 1-14 Monthly mean global solar radiation on horizontal surfaces in Ho Chi Minh City 35

Figure 1-15 The density of (a) an urban area (District 5) and (b) a rural area (Binh Chanh District) (Google, 2020) 37

Figure 1-16 Population pyramid of Ho Chi Minh City in 2014 (General Statistics Office, 2016a) 38

Figure 1-17 Urban environmental threats from both climate change impacts and urban development patterns (Gravert, 2011) 39

Figure 1-18 Rankings of the most PM2.5 levels across South East Asian countries (IQAir AirVisual, 2018) 42

Figure 1-19 Hourly AQI level in the first quarter during recent years in Ho Chi Minh City 42

Figure 1-20 The national education system in Vietnam (Ministry of Education and Training, 2016) 44

Figure 1-21 State funding for school constructions and the number of new classrooms put into use (Ho Chi Minh City People’s Committee, 2017) 47

Figure 1-22 Timeline of Saigon – Ho Chi Minh City history of development and relationship to Modern Architecture (Truong and Vu, 2018) 49

Figure 1-23 A study group organised by a local tutor in Vietnam in the pre-colonial period (An

An, 2018) 49

Figure 1-24 Pictures of (a) Petrus Ky High School and (b) the classroom organisation (photos: Fernand Nadal) 50

Figure 1-25 Nong Lam University 51

Figure 1-26 The International Primary School (IPS) in District 1, Ho Chi Minh City 52

Figure 1-27 A typical layout of a classroom (Ministry of Construction, 1993, p.2) 54

Figure 2-1 Observed and predicted indoor comfort temperatures from the RP-884 database, for (a) HVAC buildings and (b) naturally ventilated buildings (de Dear and Brager, 2002, p.552) 60

Figure 2-2 Acceptable operative temperature ranges for naturally conditioned spaces (ASHRAE, 2013, p.12) 61

Figure 2-3 Design values for the indoor operative temperature for buildings without mechanical cooling systems as a function of the exponentially weighted running mean of the outdoor temperature (CEN, 2007, p.27) 62

Figure 2-4 Air speed required to offset increased temperature (CEN, 2007, p.30) 63

Figure 2-5 Regression lines of children’s adaptive thermal comfort by Teli et al (2017) and European Standard EN 15251 66

Figure 2-6 Adaptive thermal comfort lines of comfort studies in primary schools 68

Figure 2-7 Carbon dioxide as an indicator of human bioeffluents (CEN, 1998, p.24) 70

Figure 2-8 Typical sources of noise (Canning et al., 2015) 78

Figure 3-1 Coordinates of Binh Quoi Tay Primary School: 10o49’22”N 106o43’59”E (four investigated classrooms are highlighted) 87

Figure 3-2 Views from the courtyard in Binh Quoi Tay Primary School: (a) toward the entrance and (b) toward functional rooms 88

Figure 3-3 Picture of the typical classroom: (a) two doors and two openings and (b) two windows and curtains 88

Figure 3-4 The arrangement of fans and lights in the typical classroom in Binh Quoi Tay Primary School: (a) views toward the teacher’s desk and (b) view toward the children’s desk 89

Figure 3-5 Positions of investigated classrooms: Rooms A, B, C and D 90

Figure 3-6 Grid for spot measurements and the position of NETATMO Weather Station Modules in a typical classroom 91

Figure 3-7 Illuminance distribution map 94

Figure 3-8 Temperature values during the period of 11 May – 11 June 2015 at Binh Quoi Tay Primary School 96

Figure 3-9 Relative humidity values during the period of 11 May – 11 June 2015 at Binh Quoi Tay Primary School 96

Figure 3-10 CO2 concentration level during the period of 11 May – 11 June 2015 at Binh Quoi

Tay Primary School 97Figure 3-11 Sound level during the period of 11 May – 11 June 2015 at Binh Quoi Tay Primary

School 97Figure 4-1 Aerial view of Binh Quoi Tay Primary School (obtained from MAPS) 99Figure 4-2 Position of NETATMO Weather Station Modules and the spot point measurement

grid 101Figure 4-3 Schematic plans of School 1 and investigated classrooms (mid-season) 104Figure 4-4 Schematic plans of School 1 and investigated classrooms (hottest season) 105Figure 4-5 Schematic plans of School 1 and investigated classrooms (coldest season) 107Figure 4-6 Children’s thermal sensation compared with the indoor air temperature in the mid-

season 110Figure 4-7 Temperature profiles during the mid-season in Classroom 3 with the range of the

air temperature (a) from 0oC to 40oC and (b) from 25oC to 37oC 112Figure 4-8 Relative humidity levels during the mid-season in Classroom 3 112Figure 4-9 Children’s thermal sensation compared with the indoor air temperature in School

1 in the hottest season 113Figure 4-10 Relative humidity levels during the hottest season in Classroom 3 114Figure 4-11 Temperature profiles during the hottest season in Classroom 3 with the air

temperature range (a) from 0oC to 40oC and (b) 25oC to 39oC 115Figure 4-12 Thermal comfort and thermal sensation votes in the hottest season in School 1

116Figure 4-13 Thermal comfort and thermal preference votes in the hottest season in School 1

116Figure 4-14 Children’s thermal sensation compared with indoor air temperature in School 1 in

the coldest season 117Figure 4-15 Temperature profiles during the coldest season in Classroom 3 with the air

temperature range (a) from 0oC to 40oC and (b) from 24oC to 34oC 118Figure 4-16 Relative humidity levels during the coldest season in Classroom 3 119Figure 4-17 Thermal sensation and thermal comfort votes in naturally ventilated classrooms

in the coldest season in School 1 119Figure 4-18 Thermal comfort and preference votes in naturally ventilated classrooms in the

coldest season in School 1 120Figure 4-19 Thermal sensation and thermal comfort votes in air-conditioned classrooms in the

coldest season in School 1 121Figure 4-20 Thermal comfort and thermal preference votes in air-conditioned classrooms in

the coldest season in School 1 121

Figure 4-21 Percentage of votes for the odour in the classrooms during the investigation

periods 123Figure 4-22 CO2 concentration level during the investigation periods in Classroom 3: (a) mid-

season, (b) hottest season and (c) coldest season 123Figure 4-23 Children’s visual comfort vote compared with indoor illuminance in School 1 in

(a) mid-season, (b) hottest season and (c) coldest season 125Figure 4-24 Votes of the sound level compared with the indoor sound level in School 1 in (a)

mid-season, (b) hottest season and (c) coldest season 128Figure 4-25 Sound levels during the investigation periods in Classroom 3 in (a) mid-season,

(b) hottest season and (c) coldest season 129Figure 4-26 Users’ control and building elements 133Figure 4-27 The frequency of using building elements 133Figure 5-1 Aerial view of Phu Dong Primary School, including Building A and Building B

(obtained from MAPS) 135Figure 5-2 Phu Dong Primary School including (a) Building A and (b) Building B 136Figure 5-3 Typical cross sections of School 2: (a) Building A and (b) Building B 137Figure 5-4 Typical classroom with (a) windows and (b) doors and openings in Building A 138Figure 5-5 Typical classroom with two air conditioning units in Building A 138Figure 5-6 Temporary playground in Building B (a) in original condition and (b) with overhangs

in use 138Figure 5-7 Typical classroom with (a) wooden windows and (b) glazed door, window and

exhaust openings in Building B 139Figure 5-8 Classroom X (a) without air conditioning and (b) windows at the opposite side in

the hottest season 140Figure 5-9 Classroom X with (a) two air conditioning units and an extractor fan and (b) no

windows at the opposite side in the coldest season 140Figure 5-10 Position of NETATMO Modules and the spot point measurement grid in

Classroom X 142Figure 5-11 Schematic plans of School 2 and investigated classrooms in the hottest season

144Figure 5-12 Schematic plans of School 2 and investigated classrooms in the coldest season

146Figure 5-13 Children’s thermal sensation compared with the indoor air temperature in the

hottest season in School 2 148Figure 5-14 Thermal comfort and thermal sensation votes in naturally ventilated classrooms

in the hottest season in School 2 149Figure 5-15 Thermal comfort and thermal preference votes in the naturally ventilated

classrooms in the hottest season in School 2 149

Figure 5-16 Thermal comfort and thermal sensation votes in air-conditioned classrooms in the

hottest season in School 2 151Figure 5-17 Thermal comfort and thermal preference votes in air-conditioned classrooms in

the hottest season in School 2 152Figure 5-18 Relative humidity levels during the hottest season in Classroom X 153Figure 5-19 Temperature profiles during the hottest season in Classroom X with the air

temperature range (a) from 0oC to 40oC and (b) from 25oC to 37oC 153Figure 5-20 Children’s thermal sensation compared with indoor air temperature in School 2 in

the coldest season 155Figure 5-21 Thermal sensation and thermal comfort votes in naturally ventilated classrooms

in the coldest season in School 2 155Figure 5-22 Thermal comfort and preference in the naturally ventilated classroom in School 2

in the coldest season 156Figure 5-23 Thermal sensation and thermal comfort votes in air-conditioned classrooms in

School 2 in the coldest season 157Figure 5-24 Thermal comfort and preference in air-conditioned classrooms in School 2 in the

coldest season 157Figure 5-25 Temperature profiles during the coldest season in Classroom X with the air

temperature range (a) from 0oC to 40oC and (b) from 23oC to 35oC 158Figure 5-26 Relative humidity levels during the coldest season in Classroom X 159Figure 5-27 Percentage of votes for the odour during the investigation periods 160Figure 5-28 CO2 concentration level during the hottest season in Classroom X (free-running

mode) 161Figure 5-29 CO2 concentration level during the period of August 2016 – October 2016 in

Classroom X 162Figure 5-30 CO2 concentration level during the coldest season in Classroom X (air

conditioning) 163Figure 5-31 Children's visual comfort vote compared with indoor illuminance level in School 2

during the investigation periods: (a) the hottest season and (b) the coldest season 164Figure 5-32 Illuminance distribution map (lux) of Classroom X 165Figure 5-33 Children’s perceptions of the acoustic environment in naturally ventilated and air-

conditioned classrooms in two seasons 166Figure 5-34 Votes of the sound level compared with the indoor sound level in School 2 during

the investigation periods: (a) the hottest season and (b) the coldest season 167Figure 5-35 Sound level during the hottest season in Classroom X 168Figure 5-36 Sound level during the coldest season in Classroom X 168

Figure 5-37 Users’ control and building elements in naturally ventilated and air-conditioned

classrooms 172

Figure 5-38 The frequency of using building elements in naturally ventilated and air-conditioned classrooms 172

Figure 6-1 Aerial view of Ha Huy Tap Primary School (obtained from MAPS) 175

Figure 6-2 Ha Huy Tap Primary School during the investigation periods 2016 - 2017(a) and in 2018 (b) 176

Figure 6-3 Views from the schoolyard in School 3: Block C – Block B (a) and Block B – Block A (b) 177

Figure 6-4 Positions of investigated classrooms in three building blocks in School 2 177

Figure 6-5 A classroom with single side openings in Block A 177

Figure 6-6 A classroom with doors and windows on two sides in Block A 178

Figure 6-7 A typical classroom in Block B 178

Figure 6-8 Classrooms in Block C with single side openings (a), with a tight front corridor (b) and with wooden louvred windows and doors (c) 179

Figure 6-9 Position of NETATMO Weather Station Modules and the spot point measurement grid in Classroom 34 180

Figure 6-10 Schematic plans of School 3 and investigated classrooms in the hottest season 182

Figure 6-11 Schematic plans of School 3 and investigated classrooms in the coldest season 184

Figure 6-12 Children's thermal sensation compared with the indoor air temperature in the hottest season in School 3 188

Figure 6-13 Temperature profiles during the hottest season in Classroom 34 with the air temperature range (a) from 0oC to 40oC and (b) from 25oC to 41oC 190

Figure 6-14 Relative humidity levels during the hottest season in Classroom 34 190

Figure 6-15 Thermal comfort and thermal sensation votes in the hottest season in School 3 191

Figure 6-16 Thermal comfort and thermal preference votes in the hottest season in School 3 191

Figure 6-17 Children’s thermal sensation compared with indoor air temperature in School 3 in the coldest season 192

Figure 6-18 Relative humidity levels during the coldest season in Classroom 34 193

Figure 6-19 Temperature profiles during the coldest season in Classroom 34 with the air temperature range (a) from 0oC to 40oC and (b) from 23oC to 35oC 194

Figure 6-20 Thermal sensation and thermal comfort votes in the coldest season in School 3 194

Figure 6-21 Thermal comfort and preference in the coldest season in School 3 195

Figure 6-22 A typical wooden louvred window 196

Figure 6-23 Main characteristics of investigated classrooms in School 2 196

Figure 6-24 Percentage of votes for the odour in School 3 during the investigation periods 197

Figure 6-25 CO2 concentration level in Classroom 34 during the investigation periods: (a) the hottest season and (b) the coldest season 197

Figure 6-26 Children’s visual comfort vote compared with indoor illuminance in School 3 199 Figure 6-27 Votes of the sound level compared with the indoor sound level in School 3 during the investigation periods: (a) the hottest season and (b) the coldest season 201

Figure 6-28 Sound levels in Classroom 34 during the investigation periods: (a) the hottest season and (b) the coldest season 202

Figure 6-29 Users’ control and building elements in School 3 205

Figure 6-30 The frequency of using building elements in School 3 205

Figure 7-1 Excerpt of thermal comfort questions 210

Figure 7-2 Children’s thermal sensation vote in the hottest and coldest seasons 214

Figure 7-3 Regression of children’s thermal sensation mean vote against the indoor temperature in classrooms in the hottest and coldest seasons 215

Figure 7-4 The percentage of children voting Neutral and Warm-Neutral-Cool in relation to the offset from the comfort temperature in the hottest and coldest seasons 218

Figure 7-5 The percentage of children voting Neutral, Warm-Neutral-Cool and Comfortable in relation to classrooms’ indoor temperature in the hottest and the coldest seasons 219 Figure 7-6 Thermal sensation vote and preference vote in the hottest and the coldest seasons 220

Figure 7-7 Preference and comfort votes in the hottest season and the coldest season 220

Figure 7-8 The percentage of children’s thermal preferences in relation to classrooms’ indoor temperature in the hottest and coldest seasons 221

Figure 7-9 Regression of the thermal preference mean vote against the indoor air temperature in three investigated primary schools 221

Figure 7-10 The relationship between the children’s comfort temperature and the running mean of the outdoor temperature with regression line and comfort lines for comparison 224

Figure 7-11 The indoor air temperature in three primary schools during school time in the hottest and coldest seasons 225

Figure 7-12 Temperature profile of the hottest day in School 3 227

Figure 7-13 Naturally ventilated classrooms with different orientations in three investigated primary schools 229

Figure 7-14 Design parameters that influenced the thermal conditions in Vietnamese primary

schools 232Figure 8-1 The position of the selected classrooms in School 1 for Case 0 and the model of

Case 0 in ModelIT – IES VE 2018 238Figure 8-2 Plan (A) and section (B) of the typical classroom 239Figure 8-3 The correlations between measured and simulated data in a closed condition (A)

and a free-running condition (B) 241Figure 8-4 The measured and simulated temperatures in a closed condition 242Figure 8-5 The measured and simulated temperatures in a free-running condition 242Figure 8-6 The monthly mean temperatures (extracted from the ASHRAE weather data) 243Figure 8-7 The position of three investigated classrooms in further simulations 244Figure 8-8 Typical plan of Base Case model 245Figure 8-9 Indoor temperature ranges for investigated classrooms in the Base Case and

outdoor temperature range 246Figure 8-10 Average indoor air temperature during school time when varying the floor-to-

ceiling height 248Figure 8-11 The percentage of overheating hours during school time when varying the floor-

to-ceiling height 248Figure 8-12 Average indoor air temperature during school time when varying the window area

249Figure 8-13 The percentage of overheating hours during school time when varying the window

area 250Figure 8-14 Average indoor air temperature during school time with different window types

252Figure 8-15 The percentage of overheating hours during school time with different window

types 252Figure 8-16 Exhaust openings in the three case studies: (a) School 1, (b) School 2 and (c)

School 3 253Figure 8-17 Average indoor air temperature during school time when varying the exhaust

opening area 254Figure 8-18 The percentage of overheating hours during school time when varying the

exhaust opening area 254Figure 8-19 Average indoor air temperature during school time when varying the overhang

projection 255Figure 8-20 The percentage of overheating hours during school time when varying the

overhang projection 255Figure 8-21 Average indoor air temperature during school time when changing the windows’

orientation 257

Figure 8-22 The percentage of overheating hours during school time when changing the

windows’ orientation 257Figure 8-23 Wind wheel of Ho Chi Minh City 258Figure 8-24 Average indoor air temperature during school time when changing the external

materials 260Figure 8-25 The percentage of overheating hours during school time when changing the

external wall materials 260Figure 8-26 Average indoor air temperature during school time when changing the roof

system 263Figure 8-27 The percentage of overheating hours during school time when changing the roof

systems 264Figure 8-28 Average indoor air temperature in school time when varying the infiltration rate

265Figure 8-29 The percentage of overheating hours during school time when varying the

infiltration rate 266Figure 8-30 Average indoor air temperature during school time when varying the additional

ventilation rate 267Figure 8-31 The percentage of overheating hours during school time when varying the natural

ventilation rate 268Figure 8-32 The differences of overheating hours in comparison with Base Case for each

parameter 268Figure 8-33 Optimisation process 271Figure 8-34 The percentage of the overheating hours of the Base Case, the Improved Case

from the parametric study and the Optimum Case 273

LIST OF TABLES

Table 1-1 Legal documents about children and primary education 45

Table 1-2 Clothing insulation of school uniforms (based on ASHRAE (2013)) 45

Table 1-3 Number of primary schools in Ho Chi Minh City (Ho Chi Minh City Statistical Office, 2018) 48

Table 1-4 Design standards and guidelines for primary schools 53

Table 2-1 Description of the applicability of the building categories 58

Table 2-2 Seven-point thermal sensation scales (Nicol et al., 2012, p.13) 59

Table 2-3 Predicted Mean Vote and recommended temperature for classrooms according to Building Category (CEN, 2007, p.13) 60

Table 2-4 Average air speed and the increases in upper temperature limits (ASHRAE, 2013, p.13) 63

Table 2-5 Thermal comfort of Vietnamese (Ministry of Construction, 2004, pp.7-8) 64

Table 2-6 Adaptive thermal comfort equations in the studies of primary schools (Singh et al., 2019) 67

Table 2-7 Adaptive thermal comfort equations for hot and humid climates 68

Table 2-8 Recommended design criteria for indoor air quality (CEN, 2007) 71

Table 2-9 The maintained illuminance on the task area and the surrounding area (ISO, 2002, p.4) 75

Table 2-10 Classroom illuminance recommendations in international standard (Tran, 2010, p.99) 75

Table 2-11 Lighting requirements for classrooms (CEN, 2011a, p.39) 75

Table 2-12 Lighting recommendations in primary schools (Ministry of Science and Technology, 2011) 77

Table 2-13 Ventilation system type and noise level limit for classrooms (DfE, 2015, pp.19-22) 79

Table 2-14 Noise limits according to the period of exposure (Ministry of Health, 2016b) 80

Table 2-15 Noise limits according to zones 80

Table 2-16 Indoor environmental quality for classrooms – general requirements (CEN, 2007) 81

Table 2-17 Recommended comfort criteria for teaching spaces in educational buildings (CIBSE, 2015, p.1-10) 82

Table 2-18 Reference values for indoor environmental quality 82

Table 3-1 Typical room's dimensions 89

Table 3-2 Pictures of investigated classrooms and time of measurements 91

Table 3-3 Reference values for indoor environmental quality 92

Table 3-4 Illuminance data (lux) 93

Table 3-5 Temperature values 95

Table 3-6 Relative humidity values from spot measurement 95

Table 3-7 The percentage of the uncomfortable indoor condition in school time 96

Table 4-1 Summary of data collection methods 100

Table 4-2 Recommended criteria for thermal comfort in classrooms (CEN, 2007) 103

Table 4-3 Recommended equations for the acceptable operative temperature in occupant-controlled naturally conditioned spaces (ASHRAE, 2013, ASHRAE, 2017) 103

Table 4-4 Recommended values for indoor air quality, lighting and noise 103

Table 4-5 Environmental parameters and indoor conditions of investigated classrooms in School 1 in the mid-season 104

Table 4-6 Environmental parameters and indoor conditions of investigated classrooms in School 1 in the mid-season (continued) 105

Table 4-7 Environmental parameters and indoor conditions of investigated classrooms in School 1 in the hottest season 106

Table 4-8 Environmental parameters and indoor conditions of investigated classrooms in School 1 in the hottest season (continued) 106

Table 4-9 Environmental parameters and indoor conditions of investigated classrooms in School 1 in the coldest season 107

Table 4-10 Environmental parameters and indoor conditions of investigated classrooms in School 1 in the coldest season (continued) 108

Table 4-11 Overall indoor comfort in School 1 131

Table 4-12 Results from teachers’ questionnaires for all seasons 132

Table 5-1 Typical classroom’s dimensions in Building A 137

Table 5-2 Typical classroom’s dimension in Building B 139

Table 5-3 Summary of data collection methods 141

Table 5-4 Environmental parameters and indoor conditions of investigated classrooms in School 2 in the hottest season 144

Table 5-5 Environmental parameters and indoor conditions of investigated classrooms in School 2 in the hottest season (continued) 145

Table 5-6 Environmental parameters and indoor conditions of investigated classrooms in School 2 in the coldest season 146

Table 5-7 Environmental parameters and indoor conditions of investigated classrooms in

School 2 in the coldest season (continued) 147Table 5-8 Overall indoor comfort in School 2 169Table 5-9 Results from teachers’ questionnaires in naturally ventilated classrooms in School

2 170Table 5-10 Results from teachers’ questionnaires in the air-conditioned classrooms in School

2 171Table 6-1 Classrooms’ dimensions (Block B) 178Table 6-2 Summary of data collection method for School 3 179Table 6-3 Environmental parameters and indoor conditions of investigated classrooms in

School 3 in the hottest season (part 1) 182Table 6-4 Environmental parameters and indoor conditions of investigated classrooms in

School 3 in the hottest season (part 2) 183Table 6-5 Environmental parameters and indoor conditions of investigated classrooms in

School 3 in the hottest season (part 3) 183Table 6-6 Environmental parameters and indoor conditions of investigated classrooms in

School 3 in the coldest season (part 1) 185Table 6-7 Environmental parameters and indoor conditions of investigated classrooms in

School 3 in the coldest season (part 2) 186Table 6-8 Environmental parameters and indoor conditions of investigated classrooms in

School 3 in the coldest season (part 3) 187Table 6-9 Overall indoor comfort in School 3 203Table 6-10 Results from teachers’ questionnaires in School 3 204Table 7-1 The selected periods of the long-term recording in three primary schools for further

analysis 209Table 7-2 Recommended criteria for thermal comfort in classrooms (CEN, 2007) 211Table 7-3 Recommended equations for the acceptable temperature limits in occupant-

controlled naturally conditioned spaces (ASHRAE, 2013, ASHRAE, 2017) 211Table 7-4 Summary of spot point measurements of three primary schools in two seasons

213Table 7-5 Regression equations and neutral temperature for Vietnamese children in

classrooms 216Table 7-6 Regression equations and neutral temperature for Vietnamese children (based on

the individual votes) 216Table 7-7 Adaptive thermal comfort equations and their squared correlation coefficient in

descending 223Table 7-8 Number of hours and the percentage of occupied time during the academic year in

unacceptable thermal conditions 226

Table 7-9 Results from the spot point measurements and surveys 228Table 7-10 External walls and roofs in three investigated primary schools 230Table 7-11 Fenestration details of the typical free-running classrooms in three investigated

primary schools 231Table 8-1 The combination of investigated parameters in Case 0 239Table 8-2 Calibration of the simulation model – validation between measured and simulated

temperatures in a closed condition from 27 June 2016 to 14 August 2016 and a running condition from 9 to 11 June 2018 240Table 8-3 General assumptions for Base Case model 244Table 8-4 The temperatures of the outdoor and indoor conditions of the Base Case during

free-school time 245Table 8-5 Variations of floor-to-ceiling height 247Table 8-6 Variations of window area 249Table 8-7 Variations of window type 251Table 8-8 Variations of exhaust opening area 253Table 8-9 Variations of the overhang projection 255Table 8-10 Variations of the window’s orientation 256Table 8-11 Variations of external wall materials 259Table 8-12 Variations of the pitched roof system 262Table 8-13 Variations of the flat roof system 263Table 8-14 Variations of the infiltration rate 265Table 8-15 Variations of the additional natural ventilation 266Table 8-16 Ranking of the parameters’ sensitivity based on overheating hours within the

defined input range 269Table 8-17 Design parameters for optimisation to minimise overheating in schools 270Table 8-18 Setting for Genetic Algorithm 270Table 8-19 The optimum set for total overheating hours in three investigated classrooms 271Table 8-20 Settings of the Base Case, the Improved Case from the parametric study and the

Optimum Case 272Table 9-1 The optimum set for total overheating hours in three investigated classrooms 281

INTRODUCTION

Indoor environmental quality is an important scientific field, including various factors that considerably influence the health, comfort, and productivity of the occupants and contribute to defining the building’s value Indoor environmental quality is assessed by comfort parameters such as thermal comfort, indoor air quality, visual comfort, and acoustic comfort Indoor environmental quality in Vietnamese public primary schools has been of particular social concern as 25% of the classrooms show degraded conditions and have a number of environmental deficiencies (Dan Tri News, 2019) This is because the shortage of public funding contributes to inadequate operation and maintenance of facilities According to Dan Tri News (2019), the apparent consequences of the degraded environment were identified as overheating, insufficient lighting, poor indoor air quality, or noise These environmental issues affected the occupants’ comfort and productivity, and the teaching and learning activities in the schools

Among these issues, overheating of premises is a typical thermal discomfort issue in Ho Chi Minh City and is made worse by the hot and humid climate Therefore, the cooling demand is significantly high, and there is a trend of using air conditioning for achieving thermal comfort (Tomiyama and Ito, 2018) This leads to excessive energy consumption (EVN, 2018) and environmental problems in the primary schools as well as adverse effects on children’s health and performance in the long term (Seppanen and Fisk, 2002, Qian et al., 2014, Yamaguchi, 2016) Despite this, schools without air conditioning are seen as less ‘fit for purpose’ when compared to the ones with, and this seems based purely on occupants’ perception of comfort

as there were no studies that could back up that claim Furthermore, the payment for air conditioning systems is a burden for low-income parents (Matsumoto and Omata, 2017), and consequently it deepens the gap between the classes in society Therefore, because of these disadvantages, the use of air conditioning systems needs to be considered and revised Besides overheating problems, air and sound pollution and their effect on the indoor environment are of rising concern in a developing city like Ho Chi Minh City Obviously, the fast urbanisation causes not only social but also environmental problems Although there are reports about the issues relating to indoor conditions (WHO, 2009b, Viet Nam News, 2017), the importance of indoor environmental quality for teaching and learning activities remains underestimated

Research to date has shown the strong relationship between the indoor environment, its factors and the children’s health, well-being and academic achievements Any inconveniences – such as overheating problems, polluted air, inadequate indoor lighting or loud background noise – may impact the occupant’s health and discomfort, and cause disruption at work Therefore, the indoor environmental quality in schools for young children is of particular concern due to their effects on the children’s development International standards provide

specific requirements for each of the indoor environmental quality factors However, there is generally a lack of updated standards and locally relevant research on the subject for adults and young children in particular and nothing that is applicable to Vietnam

Therefore, through this work, the author aims to contribute to the delivery of better indoor environmental quality, in particular thermal conditions, in primary schools in Ho Chi Minh City

in Vietnam, and help inform design standards In order to respond to the aim of the research, the objectives of this study were:

• To establish the current indoor environmental conditions, the user’s perceptions and expectations of comfort in primary schools in Ho Chi Minh City;

• To identify the boundaries of indoor thermal comfort conditions in classrooms in primary schools under the local climatic context of Ho Chi Minh City, and use those to set up comfort criteria and update the standards for primary school design; and

• To translate the above comfort criteria into appropriate and tested design responses

to develop design guidelines on thermal conditions for existing and new-built primary schools in Ho Chi Minh City, Vietnam

Qualitative and quantitative methods of research were used to investigate the indoor environmental quality and users’ perceptions in 124 classrooms of three primary schools in

Ho Chi Minh City in Vietnam during three continuous seasons Spot and long-term measurements were recorded, covering a range of environmental parameters such as air temperature, relative humidity, CO2 concentration level, illuminance, and sound level A questionnaire was designed and administered to 4411 children (aged from 8 to 11) to investigate their perceptions of the thermal and visual comfort, indoor air quality, noise and overall comfort in their classrooms (the response rate is 99%) In addition, 116 teachers were asked to inform the study about the experiences and behaviours in the classrooms The results were analysed by cross relating the environmental conditions measured and the comfort vote

on a seven-point scale The methodology and the applied techniques have been summarised

in Figure 1 and are discussed in greater details in further chapters

The thesis was divided into nine chapters The first two introduce the background and context

of primary schools in general and in Vietnam in particular Chapter 3 to 6 present the fieldwork

in all three schools, whilst Chapters 7 and 8 bring the learnings together to develop an adaptive comfort model and design guidelines, before the thesis conclusion As far as the author is aware, this is the first work to use such a significant sample of both classrooms and users in primary schools in one city This is also the first work to develop an updated children-focused comfort model, and the first to relate this to design guidelines

Figure 1 Diagram of thesis structure and applied research methods

The breakdown of chapter contents is as follows:

Chapter 1 presents the overview of the climate, the socio-economic context and the education

in Ho Chi Minh City with a focus on primary education for children and primary schools Chapter 2 reviews the international and Vietnamese standards as well as research to date about the indoor environmental quality in primary schools

Chapter 3 presents the pilot study, which led to the gathering of preliminary evidence showing that the current indoor environmental quality in primary schools in Ho Chi Minh City is below expectations and did not achieve the expected indoor comfort It also demonstrated that thermal comfort was the most crucial problem to be addressed

Chapter 4, Chapter 5 and Chapter 6 present the evaluation of the indoor environmental quality

of Binh Quoi Tay Primary School, Phu Dong Primary School and Ha Huy Tap Primary School Each school has specific features that affected its indoor environmental quality Parameters investigated were air temperature, relative humidity, CO2 concentration level, illuminance level, sound level and comfort vote this was done through spot measurements, long term monitoring and questionnaire The results led to the understanding of the need to develop a model that takes into account the perception and acceptance of the children, which is presented in Chapter 7, and the needs to explore the sensitivity of thermal comfort parameters

to design changes, which is presented in Chapter 8

Chapter 7 presents the findings of the adaptive thermal comfort model for children in Ho Chi Minh City, based on the collected data from investigated primary schools The neutral temperature and adaptive thermal comfort equation were identified The benchmark for overheating assessment was proposed, and the building-related design parameters were recognised the results led to the need to investigate the sensitivity of design parameters on the indoor thermal conditions, which is presented in Chapter 8

Chapter 8 is a computer-based study showing the sensitivity of the design parameters and thermal comfort The parametric and optimisation studies provide the thermal comfort criteria

of the design standards and the design guidelines for the existing and new-built buildings Chapter 9 presents the overall conclusions, discussing these within the limitations of the work, and suggesting further work

1 THE CONTEXT OF HO CHI MINH CITY –

VIETNAM

Ho Chi Minh City has grown rapidly over the last few decades and has become one of the fastest developing cities in South East Asia (Figure 1-1) Besides economic development, two critical issues are investing in people and ensuring climate resilience and environmental sustainability In 2015, Ho Chi Minh City set a goal to be the Child Friendly City where children have the right to survive and thrive in a safe environment, to have quality education, and to participate fully in the society (Ho Chi Minh City People’s Committee, 2017)

(a)

(b)

Figure 1-1 Ho Chi Minh City at (a) daytime and (b) night time (Long T Nguyen, 2019)

Children of primary school age spend most of their daytime in their classrooms, and therefore the indoor environment affects teaching and learning activities From a broader perspective, the indoor conditions are largely influenced by the outdoor climate In addition, the current urban contexts influence children’s education

This chapter clarifies all factors affecting the environment and the children’s education in primary schools in Ho Chi Minh City The background of the climate, the current contexts and the education in Ho Chi Minh City are discussed herein

1.1 The climate context

Vietnam is located in Southeast Asia The country stretches from 23o23’N to 8o27’N and from

102o08′E to 109o28′E; shares borders with Cambodia, Laos and China It also has a long coastal line of 3444km and a total area of 331210km2 The country’s climate is significantly affected by monsoons Furthermore, the fact that three-quarters of Vietnam are mountainous and hilly topography means that the country has several climate types Ho Chi Minh City, also known as Saigon, is located in south-eastern Vietnam at the height of 19m above sea level The city, approximately 1725km away from the capital Ha Noi, settles on Saigon River, at the north of the Mekong Delta, as shown in Figure 1-2 (Ho Chi Minh City People’s Committee, 2017)

Figure 1-2 Administrative map of Socialist Republic of Vietnam (Center of Survey and Mapping Data,

is tropical wet-dry climate (Aw) which consists of high temperature, distinct wet and dry seasons, and precipitation in the summertime

Figure 1-3 Koppen-Geiger map of Asia showing climate type (Aw) of Ho Chi Minh City (Peel et al.,

2007)

The Ministry of Construction issued the Vietnam Building Code (2009) providing climate data for construction in each part of the country According to this Building Code, Vietnam belongs

to the humid tropical monsoon climate area, which is similar to Koppen-Geiger’s classification

In Vietnam, two main climate types (type I and type II) are separated by latitude 16oN, as shown in Figure 1-4

The climate type I in the North is characterised by a cold winter when the average temperature

is low, even in comparison with other areas at the same latitude There are two main seasons based on the monsoon: the cold winter with a lack of rain and the hot summer with heavy rains As shown in Figure 1-4, the region of climate type I is divided into four subtypes, which are different because of the terrains A part of this region, in particular, has a hot and dry climate, which is common along the coast in the centre of Vietnam

Having wet and dry seasons without cold winters are the characteristics of climate type II in the south of Vietnam In this region, there are three climate subtypes, IIa, IIb and IIc, as shown

in Figure 1-4 The area of the subtype IIb is mountainous, and the climate depends on the terrain elevation The coastal area that has the climate type IIc is directly affected by storms,

especially during the rainy season The climate subtype IIc is prevalent in the Southwest of Vietnam, such as Mekong Delta and the adjacent areas

Figure 1-4 Building climate zones in Vietnam (Ministry of Construction, 2009)

1.1.2 Climate for building design in Ho Chi Minh City

Ho Chi Minh City is one of the largest and fastest-growing cities in Vietnam as well as in Southeast Asia Consisting of 19 urban and five rural districts, the city covers an area of around 2095km2 Figure 1-5 illustrates the map of Ho Chi Minh City in which the areas are shaded in bright tone for the urban districts and dark tone for rural districts

Figure 1-5 Urban districts (bright shaded) and rural districts (dark shaded) (Google, 2020)

Ho Chi Minh City is in the area of climate subtype IIc, which is divided into two distinct seasons based on the monsoon season The dry season lasts from November to April and the rainy season begins at the same time as the summer monsoon with significant-high precipitation, lasting from May to October The environmental parameters are detailed in the following part

of this section The climate data of Ho Chi Minh City, which is advised for construction by the Vietnam Building Code (Ministry of Construction, 2009), was collected from the official meteorological station Tan Son Nhat (106.40oE – 10.49oN)

a Precipitation

In Ho Chi Minh City, the total precipitation during the year is 1926mm Figure 1-6 shows that the rainy season lasts six months from May to October and the rainfall accounts for nearly 90% of the total during the year The rainfall distribution differs across the city, where the annual precipitation decreases from northeast to southwest (Khoi and Trang, 2016) Because

of the heavy rainfall during the rainy season, water pooling and leakage is the risk for built environment Therefore, the pitched roofs are highly recommended for building design and construction in Ho Chi Minh City

Figure 1-6 Monthly mean precipitation of Ho Chi Minh City

b Temperature

The climate in Ho Chi Minh City is usually hot due to the considerable effect of solar radiation The annual average temperature is 27.4oC, and the average daily amplitude is 8.6oC during the year As shown in Figure 1-7, the highest and the lowest monthly average temperatures are 29.2oC in April and 26oC in December, respectively The hottest and the coldest periods

of the year occur during the dry season when the annual average maximum temperature is 32.3oC, but the absolute maximum temperatures can rise to 40oC in April The lowest temperature recorded over 20 years is 13.8oC, but the average minimum temperature is higher than 20oC Due to the hot climate, the building design and construction focuses on reducing the effect of solar radiation and enhancing the natural ventilation for cooling purpose

Therefore, shading devices and adequate openings’ size are important to apply for buildings

in Ho Chi Minh City

Figure 1-8 shows the temperatures range during a typical day in the hottest month of April and the coldest month of December The difference in temperatures between both months is up to

5oC The temperatures rise during the daytime and reach a peak in the afternoon, around 13:00-14:00 The temperatures at night are quite stable

Figure 1-7 Monthly mean air temperature of Ho Chi Minh City

Figure 1-8 Air temperature during typical days of the hottest month (April) and the coldest month

(December) in Ho Chi Minh City

During this study, the hottest season is considered from March to May and the coldest season

is from November to January The mid-season is the transition period from the hottest to the coldest season and is considered as the period from July to September

c Relative humidity

Due to the climate and high rate of rainfall, the annual average relative humidity in Ho Chi Minh City is considerably high at about 78% As shown in Figure 1-9, the monthly average relative humidity ranges from 79% to 85% during the wet season and from 70% to 78% during

the dry season The maximum relative humidity can rise to 100% during the rainy season; this suggests that buildings in Ho Chi Minh City should be well ventilated to avoid damp air

As shown in Figure 1-10, the levels of relative humidity in the hottest month of April are lower than in the coldest month of December However, the relative humidity levels in both months are not extreme because they are in the dry season During the daytime, the relative humidity drops to 50%, especially in the afternoon from 12:00 to 16:00

Figure 1-9 Monthly average relative humidity of Ho Chi Minh City

Figure 1-10 Relative humidity during typical days of the hottest month (April) and the coldest month

(December) in Ho Chi Minh City

d Wind speed and wind direction

As shown in Figure 1-11, in Ho Chi Minh City, over the course of 12 months, there are a trade wind and two winds based on monsoons The trade wind flows at 3.1m/s on average from south-southeast from March to May From June to October, the monsoon wind from west-southwest has an average velocity of 2.9m/s The monsoon wind from north-northeast lasts four months from November to February with an average wind speed of 2.4m/s (HCM City People's Committee, 2019)

Heavy rainfall is usually accompanied by the strong wind from the west-southwest during the rainy season Therefore, the buildings in Ho Chi Minh City should have devices to prevent rainwater falling on the southwest surfaces It is recommended that the angle of the pitched roof should be up to 40o to reduce the effects of rainfall and to decrease the wind pressure during the rainy season (Ministry of Construction, 2009)

Figure 1-11 Wind velocity and main wind direction of Ho Chi Minh City

e Solar effects

The sun path diagram of Ho Chi Minh City is shown in Figure 1-12 Because the position of the city is close to the equator, the sunlight distributes on both south and north surfaces The southern facade is still more impacted The buildings receive intensive solar gain and direct sunlight from the east and west, and therefore the shading devices are needed at those orientations to reduce the solar effects Furthermore, the overhang, which is the most popular type of shading devices in Ho Chi Minh City, is considerably effective in preventing the rainwater coming through windows or doors

Figure 1-12 Stereographic Diagram of Ho Chi Minh City (Andrew Marsh, 2014)

Ho Chi Minh City has a high number of sunshine hours during the year, as shown in Figure 1-13 The total sunshine hours of 2489 show the high availability of daylight Therefore, daylighting should be a priority in lighting design in Ho Chi Minh City There are more sunshine hours during the dry season than during the rainy season

Figure 1-13 Total sunshine hours during a year in Ho Chi Minh City

The average daily global solar radiation during the year in Ho Chi Minh City is 5595W/m2; this

is considerably high, as shown in Figure 1-14, because of the equatorial solar condition and the plentiful availability of sunshine hours The intense solar radiation results in high temperatures throughout the year Therefore, solar control is one of the most important issues

in building design On the other hand, solar energy is an abundant renewable energy source which brings remarkable benefit to built environment The highest levels of solar radiation are over 6000W/(m2.day) from February to April Consequently, the temperatures during this period are higher than in the remaining months of the year

Figure 1-14 Monthly mean global solar radiation on horizontal surfaces in Ho Chi Minh City

1.1.3 Summary

Overall, according to the Vietnam Building Code (Ministry of Construction, 2009), the climate

of Ho Chi Minh City is hot and humid with monsoons During the year, there are two distinct periods: rainy and dry seasons In the rainy season, the precipitation is significantly high The hottest and coldest months fall within the dry season The air temperature, solar radiation and the sunshine hours are considerably high throughout the year

Therefore, building design should consider the effect of intense solar radiation carefully in order to reduce the indoor temperature and consequently improve indoor environmental quality In Ho Chi Minh City, the cooling demand is significantly high while there is no heating demand over the year Daylight and wind are plentiful, so it is possible to have natural ventilation and natural lighting in buildings

1.2 The socio-economic and urban environmental contexts

1.2.1 Socio-economic context

Vietnam currently is a lower-middle-income country with rapid economic development In

2016, the GDP per capita in Vietnam reached USD 2185.7; in particular, Ho Chi Minh City accounted for per-capita GDP of USD 5428 As the financial and economic centre of Vietnam,

Ho Chi Minh City accounts for more than 20% of the national GDP The foreign investment and Official Development Assistance (ODA) projects have increased considerably in Ho Chi Minh City despite a reduction generally in the whole country (Ho Chi Minh City People’s Committee, 2017) Therefore, Ho Chi Minh City has a significant role in contributing to the state budget and developing the country

a Population and density

In 2017, the population in Vietnam was 95.54 million people In Ho Chi Minh City, there are 8.64 million people, of which more than 80% live in urban districts The population density of

Ho Chi Minh City is 4126 people/km2 However, the density in urban districts is significantly high at 13910 people/km2, while it is only 1106 person/km2 in rural districts (Ho Chi Minh City Statistical Office, 2018) The population density reflects the compactness of the city Figure 1-15 shows the building density in two typical urban and rural districts in Ho Chi Minh City The population densities are 42985 people/km2 in District 5 (urban area) and 2584 people/km2

in Binh Chanh District (rural area)

As a typical urban area, the population density in Binh Thanh District is significantly high at

23633 people/km2 The study focuses on the schools in the urban area because they are likely

to be more negatively impacted by the environmental conditions For example, there is low potential for wind-driven ventilation in the urban area due to the high density of building blocks Vietnam has 54 ethnic groups living throughout the country All groups have rich culture and traditions In Ho Chi Minh City, there are four main ethnic groups; these are Vietnamese (93.5%), Chinese (5.8%), Khmer (0.34%), and Cham (0.1%) In a report from Ho Chi Minh City People’s Committee (2017), children from the minority ethnic groups had less chance to get a quality education

As seen in Figure 1-16, the population pyramid of Ho Chi Minh City has a narrow base, particularly for the proportion of the population aged 15-19 and younger The report from the General Statistics Office (2016a) explained that Ho Chi Minh City had low birth rates in recent years and the age group from 20-59 accounted for a large proportion of the population due to in-migration

b Migration

People at the labour age of 20-59 moved to Ho Chi Minh City for many reasons such as work, study and family Therefore the population growth in Ho Chi Minh City is strongly related to rapid urbanisation and massive in-migration (Ho Chi Minh City People’s Committee, 2017) The demographic management in Ho Chi Minh City is based on the household registration system People who want to register as permanent residents need to follow some strict requirements set by the 2013 Revised Law on Residence This is an attempt to control rapid

urbanisation and reduce the pressure on infrastructure and social services in Ho Chi Minh City

Figure 1-16 Population pyramid of Ho Chi Minh City in 2014 (General Statistics Office, 2016a)

In 2015, people with short-term or long-term temporary registration, mostly migrants, numbered approximately 2.9million This means that around 36% of people in Ho Chi Minh City have not been able to access quality social services such as healthcare or education (Ho Chi Minh City People’s Committee, 2017) In particular, migrant children account for 86.4% of the total out-of-school children at primary school age in the academic year 2014-2015

In Ho Chi Minh City, in 2017, 5% of children aged 0-16 years were living in or nearly in special circumstances, and more than 23% of children from migrant families lived in temporary household registration This suggests that more than 23 % of children aged 0-16 years are out-of-school or studying in low-quality institutions (Ho Chi Minh City People’s Committee, 2017)

c Poverty

Besides developing the economy, the Vietnamese government has made significant efforts to reduce poverty in the country According to the World Bank (2019), the overall poverty rate reduced from 17.2% in 2010 to 9.8% of the population in 2017 In Ho Chi Minh City, with reference to the national poverty line, the rate was 8.4% of the population, of which 2.79% living in urban areas and 10.34% living in rural areas The differences in poverty are significant between urban and rural areas This is because people in rural districts mainly rely on agriculture production, which brings lower incomes than industrial and commercial activities

do

Although the poverty rate in urban districts of Ho Chi Minh City was generally low, the income gap was significantly different (more than six times) between the highest and the lowest

incomes Ho Chi Minh City People’s Committee (2017) reported that, in 2016, the number of children living in poverty was 67179 for Ho Chi Minh City and an average of 2700 for urban districts This suggests that the opportunities to access quality education and healthcare are limited to a large number of children from low-income families

1.2.2 Urban environmental context

The Megacity Research Project reported that the urban environment in Ho Chi Minh City was significantly influenced by climate change and the rapid urbanisation (Gravert, 2011) Figure 1-17 shows the causes and effects of urban development and climate change on the environment in Ho Chi Minh City

Figure 1-17 Urban environmental threats from both climate change impacts and urban development

patterns (Gravert, 2011)

a Climate change impacts

Climate change has a significant effect on the environment in general, including outdoor and indoor conditions As shown in Figure 1-17, among climate change impacts, the increase in air temperature is noticeable at the building scale It causes increases in greenhouse gas emissions, the urban heat island effect and risk to health A study undertaken by Nicholls et

al (2008) reported that Ho Chi Minh City is one of the top 10 cities in the world with high population exposure and vulnerability to climate change This is mainly because of the rapid urbanisation with a lack of control on migration and urban planning The Asian Development Bank (2010) indicated that the climate change in Ho Chi Minh City has clearly evolved through the increasing occurrence of tropical storms, droughts and floods and the increase of temperature

The tropical storms and typhoons occurred more frequently in the south of Vietnam over the last 60 years and around 10% of those made landfall in Ho Chi Minh City Heavy rains usually