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Study of Building Material Emissions and Indoor Air Quality ROTCK Study of Building Material Emissions and Indoor Air Quality by Xudong Yang M.E., Thermal Energy Engineering Tsinghua University, 1993 Submitted to the Department of Architecture on August 6, 1999 in partial fulfillment of the requirements for the Degree of Doctor of Philosophy in the field of Architecture: Building Technology at the Massachusetts Institute of Technology September 1999 @ 1999 Massachusetts Institute of Technology. All rights reserved. Signature of Author Department of Architecture August 6, 1999 Certified by _ Qingyan Chen Associate Professor of Building Technology Thesis supervisor Accepted by Stanford Anderson Chairman, Departmental Committee on Graduate Students Head, Department of Architecture ROTCK Thesis Committee: Leon R. Glicksman, Professor of Building Technology and Mechanical Engineering Ain A. Sonin, Professor of Mechanical Engineering Leslie K. Norford, Associate Professor of Building Technology Study of Building Material Emissions and Indoor Air Quality by Xudong Yang Submitted to the Department of Architecture on August 6, 1999 in partial fulfillment of the requirements for the Degree of Doctor of Philosophy in the field of Architecture: Building Technology ABSTRACT Building materials and furnishings emit a wide variety of indoor pollutants, such as volatile organic compounds (VOCs). At present, no accurate models are available to characterize material emissions and sorption under realistic indoor conditions. The objective of this thesis is to fill that gap. Using the emission data measured in small-scale and full-scale environmental chambers, this investigation has developed a numerical model for simulating emissions of "wet" materials applied to porous substrates. This model considers VOC mass transfer processes in the air, material-air interface, material film, and the substrate. The model can predict "wet" material emissions under different environmental conditions (i.e., temperature, velocity, turbulence, and VOC concentration in the air) with reasonable accuracy. We developed two models for simulating VOC emissions from dry materials. One is a numerical model for short-term predictions, the other is an analytical model for long-term predictions. The models have been successfully used to examine the VOC emissions from two particleboard samples and a polypropene Styrene-Butadiene Rubber (SBR) carpet. A VOC sorption model has also been developed to analytically solve the VOC sorption rate as a function of air-phase concentrations. The model has been validated using an analytical solution as well as data obtained from sorption experiments. The emission and sorption models that we developed have been further used to study indoor air quality (IAQ) in a small office with different ventilation systems. The results show that displacement ventilation may not provide better IAQ than mixing systems if the VOC sources are from the floor. Further, our study shows sink effects from internal walls of gypsum board. Thesis Supervisor: Qingyan Chen Title: Associate Professor of Building Technology ACKNOWLEDGEMENTS I would like to thank my supervisor, Professor Qingyan (Yan) Chen. For the past three years, he has been a constant source of guidance and support. His insightful comments and helpful discussions are invaluable to this work. I am especially grateful for his understanding, support, and encouragement when I face difficulties and failure. With his high standards in research, teaching, and personal integrity, Yan has been a role model for me. My thanks also extend to the members of my thesis committee, Professors Leon Glicksman, Ain Sonin, and Leslie Norford. They give me valuable comments and insightful feedback in every phase of my research. I am also grateful to the National Research Council (NRC) of Canada for allowing me to use their test facilities. Special thanks are given to Dr. Jianshun Zhang, Dr. John Shaw, Dr. Jie Zeng, Mr. Gang Nong, Dr. Jiping Zhu, Mr. Bob Magee, Ms. Ewa Lusztyk, Dr. Yan An, and Dr. Awad Bodalal for their cooperation, assistance, and helpful discussions. My sincere thanks are also given to Professor Yi Jiang of Tsinghua University, Professor Shuzo Murakami of University of Tokyo, Professor John Spengler of Harvard School of Public Health, Drs. John Chang and Zhishi Guo of U.S. Environmental Protection Agency, Dr. Xiaoxiong (John) Yuan of Applied Materials, Inc., and Dr. Philomena Bluyssen of TNO (the Netherlands) for their advise, encouragement, and helpful discussions. I would also like to express my appreciation to all staff members and colleagues of the Building Technology Program for their help and support. Especially, I want to thank Dorrit Schuchter, Kathleen Ross, Chunxin Yang, Jelena Srebric, Weiran Xu, Wei Zhang, Shiping (George) Hu, Junjie Liu, and Yi Jiang. Finally, I am deeply indebted to my parents, my wife, and my brothers for their love, support, and encouragement all the time. DEDICATION To my parents, Yong Yang and Shuxian Zhang and To my wife, Qing Shi CONTENTS Abstract 3 Acknowledgements 4 Dedication 5 Contents 6 1. Introduction 8 1.1 Overview of Problems Associated with Indoor Air Quality 8 1.2 Methods for Measuring Building Material Emissions 10 1.3 Methods for Modeling Building Material Emissions 13 1.4 Aim of the Present Work 16 2. Measurements of VOC Emissions from "Wet" Coating Materials 18 2.1 Introduction 18 2.2 Experimental Method 19 2.3 Results and Discussion 29 2.4 Conclusions 43 3. Modeling of VOC Emissions from "Wet" Coating Materials Applied to Porous Substrates 44 3.1 Introduction 44 3.2 The Emission Mechanisms 45 3.3 The Mathematical Model 47 3.4 Numerical Method 59 3.5 Determination of Material Properties for Numerical Simulation 68 3.6 Results and Discussion 71 3.7 Conclusions 107 4. Modeling of VOC Emissions from Dry Materials 108 4.1 Introduction 108 4.2 The Numerical Method for Short-term Predictions 109 4.3 Development of a Long-term Model for Dry Materials 135 4.4 Conclusions 142 5. Modeling of VOC Sorption on Building Materials 143 5.1 Introduction 143 5.2 Development of a New Sorption Model 147 5.3 Validation of the New Sorption Model Using an Analytical Solution 153 5.4 Experimental Validation of the Sorption Model 158 5.5 Conclusions 164 6. Study of Indoor Air Quality (IAQ) in a Room with Different Ventilation Systems 165 6.1 Introduction 165 6.2 Model for IAQ Studies 167 6.3 Case Study 170 6.4 Conclusions 194 7. Conclusions and Recommendations 196 7.1 Experimental Approach 196 7.2 Modeling Approach 197 7.3 Model Applications 199 7.4 Limitations of the Current Work 200 7.5 Future Perspectives 200 References 201 Appendix 211 Nomenclature 214 Chapter 1 Introduction Indoor air quality (IAQ) is currently of great public concern. This chapter reviews the problems associated with IAQ and current methodology in measuring and modeling the volatile organic compound (VOC) emissions from various building materials and furnishings. The review indicates a need for developing advanced models to fully characterize building material emissions and their impact on IAQ, which comprises the major objective of this thesis. 1.1 Overview of Problems Associated with Indoor Air Quality Every day we breathe 10 m3 of air. This amount is equivalent to 10 housefuls a year, yet this number can increase a factor of 10 via physical activities. This partly explains why people have been extremely concerned about air quality since ancient times. For a long time, however, the concern was almost exclusively with air quality in ambient air. Although some hygienists studied indoor air in 1800's (e.g., Pettenkofer, 1872), concern about the effects of indoor air on human health arose in the past 20 years. Today, indoor air pollution has been identified by the U.S. Environmental Protection Agency (EPA) and World Health Organization (WHO) as one of the top environmental risks to the nations' health (WHO, 1989; US EPA, 1990). The high risk from exposure to indoor pollution reflects the elevated concentration of indoor contaminants, the large number of people exposed to indoor air pollution, and the amount of time spent indoors. The causes of elevated indoor contaminant concentrations are mainly due to two reasons. First, with the advancement of modern technology, the types and amounts of contaminants released into the indoor environment have increased dramatically. New buildings contain many synthetic building materials and furnishings from walls to carpets to air conditioning systems. Use of these new materials and furnishings have resulted in a large number of new indoor pollutants in greater concentrations (van der Wal et al., 1991; Brown et al., 1994). On the other hand, in order to save energy, the air tightness of buildings has been improved and the supply of fresh air (by either natural or mechanical ventilation) has been reduced (Maga and Gammage, 1985; Esmen, 1985). The effects of these two factors combined have increased the indoor air pollutant levels significantly. Studies indicate that indoor air is far more polluted than outdoor air. As evidence, a series of long-term EPA studies of human exposure to air pollutants indicated that indoor levels of many pollutants may be 25 times, and occasionally more than 100 times, higher than outdoor levels (US EPA, 1988). As a result of deteriorated IAQ, numerous cases of health complaints among employees in office buildings have been lodged with federal and state agencies. An EPA report (1991) suggested that up to 30 percent of new and remodeled buildings worldwide have been the subject of a significant number of complaints related to IAQ. The complaints can be divided into two categories: sick building syndrome (SBS) and multiple chemical sensitivity (MCS) (Ashford, 1991). SBS is said to affect otherwise healthy persons whose adverse symptoms are related to time spent in a particular building and which wane when the affected persons leave a suspected problematic indoor air environment. MCS sufferers exhibit similar symptoms, but they are not restricted to a single environment and they manifest as symptoms of continuous discomfort and illness.
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