Thermal Comfort in Naturally-Ventilated and Air-Conditioned Classrooms in the Tropics
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Thermal Comfort in Naturally-Ventilated and Air-Conditioned Classrooms in the Tropics by Alison Grace Kwok B.A. (Knox College) 1977 M.Ed. (University of Hawaii at Manoa) 1980 M.Arch. (University of California, Berkeley) 1990 Submitted in partial satisfaction of the requirements of the requirements for the degree of Doctor of Philosophy in Architecture in the GRADUATE DIVISION of the UNIVERSITY of CALIFORNIA at BERKELEY Committee in charge: Professor Charles C. Benton, Chair Professor Edward A. Arens Professor Gail S. Brager Professor Robert C. Spear Spring 1997 PhD Dissertation, Dept. of Architecture, UC Berkeley 1997 1 https://escholarship.org/uc/item/65d3k1jt PhD Dissertation, Dept. of Architecture, UC Berkeley 1997 2 https://escholarship.org/uc/item/65d3k1jt Thermal Comfort in Naturally-Ventilated and Air-Conditioned Classrooms in the Tropics © 1997 by Alison Grace Kwok PhD Dissertation, Dept. of Architecture, UC Berkeley 1997 3 https://escholarship.org/uc/item/65d3k1jt Abstract Thermal Comfort in Naturally-Ventilated and Air-Conditioned Classrooms in the Tropics by Alison Grace Kwok Doctor of Philosophy in Architecture University of California, Berkeley Professor Charles C. Benton, Chair Designers use thermal comfort standards, such as Thermal Environmental Conditions for Human Occupancy by the American Society of Heating Refrigeration, and Air-conditioning (ASHRAE Standard 55-1992) and Moderate Thermal Environments - Determination of PMV and PPD Indices and Specification of the Conditions for Thermal Comfort by the International Standards Organizations (ISO 7730-1994), to design systems to provide a physical environment appropriate for thermal comfort. This thesis examines the comfort criteria of ASHRAE Standard 55-1992 for their applicability in tropical classrooms. The Standard specifies exact physical criteria for producing acceptable thermal environments: minimum and maximum limits for temperature, air speeds, and humidity that are often difficult to apply, particularly in hot and humid tropical climates. The Standard’s requirements are based in part on climate-controlled, laboratory experiments in temperate climates. The primary questions here ask: Are laboratory-based air-conditioning standards applicable in tropical climates? Does a different set of criteria exist for people accustomed to hot and humid climates than for those living in temperate climates? Preference for, or acceptance of, thermal factors beyond the prescriptions of the standard might suggest wider latitude for environmental control and air-conditioning set points. Borrowing primarily from previous thermal comfort studies in office buildings and adapting them for the school setting, I used a variety of methods to collect the data: survey questionnaires, physical measurements, interviews, behavioral observations, and statistical analysis techniques. Hawaii serves as a case study where 3,544 students and teachers completed questionnaires in 29 naturally-ventilated and air-conditioned PhD Dissertation, Dept. of Architecture, UC Berkeley 1997 4 https://escholarship.org/uc/item/65d3k1jt classrooms in 6 schools. Concurrent measurements of the physical environment were made during each class visit. The majority of classrooms failed to meet the physical specifications of the ASHRAE Standard 55-1992 comfort zone. Analysis of subjective responses using the thermal sensation, preference, and other scales and environmental indices, found votes of more than 80% acceptability by both naturally-ventilated and air-conditioned occupants whether in or out of the comfort zone. Responses from these two school populations, suggest not only a basis for separate comfort standards, but energy conservation opportunities through raising thermostat set points and certainly by choosing to design optimized naturally-ventilated environments. PhD Dissertation, Dept. of Architecture, UC Berkeley 1997 5 https://escholarship.org/uc/item/65d3k1jt Thermal Comfort in Naturally Ventilated and Air-Conditioned Classrooms in the Tropics CONTENTS Table of Contents ............................................................................................................... iv List of Figures ................................................................................................................... vii List of Tables ..................................................................................................................... ix CHAPTER 1: INTRODUCTION 1.1 Introduction .......................................................................................................... 1 1.2 Codes and Standards in Design ............................................................................ 2 1.3 The Tropical Context ........................................................................................... 4 1.4 Hawaii Schools as a Case Study .......................................................................... 5 1.5 Objectives ............................................................................................................. 6 1.6 Approach .............................................................................................................. 7 1.7 Organization of the Dissertation .......................................................................... 8 CHAPTER: OVERVIEW OF PREVIOUS RESEARCH 2.1 The Thermal Environment ................................................................................. 10 2.1.1 A Definition for Thermal Comfort 11 2.2 Standard 55 History ............................................................................................ 13 2.2.1 Acclimatization, adaptation, expectation 17 2.3 Thermal Comfort Studies in the Tropics ............................................................ 21 2.4 Thermal Comfort Studies in Schools ................................................................. 24 2.5 Ventilation Studies ............................................................................................. 27 2.6 Summary ............................................................................................................ 29 CHAPTER 3: SCHOOL DESIGN AND THE PHYSICAL ENVIRONMENT 3.1 Introduction ................................................................................................................. 35 3.2 1800 - 1900 One-Room Schools to the Schoolhouse ................................................. 36 3.2.1 Pedagogy and Design 36 3.2.2 Conditions and Standards 39 3.3 1900 - 1950 Humanistic Approach ............................................................................ 42 3.3.1 Pedagogy and Design 42 3.3.2 Conditions and Standards 46 3.4 1950 - Present .............................................................................................................. 49 iv PhD Dissertation, Dept. of Architecture, UC Berkeley 1997 6 https://escholarship.org/uc/item/65d3k1jt 3.4.1 Pedagogy and Design 49 3.4.2 Conditions and Standards 52 3.5 Future .......................................................................................................................... 56 3.5.1 Pedagogy and Design 56 3.5.2 Conditions and Standards 57 3.6 Summary ..................................................................................................................... 57 CHAPTER 4: RESEARCH METHODS AND EQUIPMENT 4.1 Introduction ........................................................................................................ 61 4.2 Climate of Hawaii .............................................................................................. 62 4.3 School Buildings and Classroom Descriptions .................................................. 63 4.4 Subjects .............................................................................................................. 64 4.4.1 Recruitment Method 64 4.5 Indoor Climate Measurements and Equipment .................................................. 66 4.6 Concurrent Outdoor Climatological Measurements .......................................... 71 4.7 Standardized Questionnaire (Subjective Survey) ............................................... 73 4.8 Indices and Scales .............................................................................................. 75 4.9 Measurement Protocol ........................................................................................ 78 4.10 Data Processing .................................................................................................. 79 4.11 Summary ............................................................................................................ 82 CHAPTER 5: RESULTS 5.1 Introduction ........................................................................................................ 85 5.2 Descriptive Measures ......................................................................................... 86 5.2.1 Sample Size 86 5.2.2 Gender and Age 86 5.2.3 Length of Residence in Tropics 87 5.2.4 Clothing and Metabolic Factors 88 5.2.5 Use of Home/Car Air-Conditioning 90 5.3 Thermal - Physical ............................................................................................. 92 5.3.1 Measured Thermal Variables 93 5.3.2 Indoor Climate Indices 93 5.3.3 Comparisons to the Comfort Zone 94 5.4 Thermal - Subjective .......................................................................................... 97 5.4.1 Observed Measurements and Calculations 98 5.4.1.1 Thermal Sensation 98 5.4.1.2 Thermal Preference 102 5.4.1.3 General Comfort 105 5.4.1.4 Thermal Acceptability 105 5.4.1.5