AN EXPERIMENTAL SETUP TO EVALUATE THE DAYLIGHTING PERFORMANCE OF AN ADVANCED OPTICAL LIGHT PIPE FOR DEEP-PLAN OFFICE BUILDINGS A Thesis by BETINA GISELA MARTINS MOGO DE NADAL Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 2005 Major Subject: Architecture AN EXPERIMENTAL SETUP TO EVALUATE THE DAYLIGHTING PERFORMANCE OF AN ADVANCED OPTICAL LIGHT PIPE FOR DEEP-PLAN OFFICE BUILDINGS A Thesis by BETINA GISELA MARTINS MOGO DE NADAL Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved by: Chair of Committee, Liliana O. Beltrán Committee Members, Ergun Akleman John Leggett Head of Department, Phillip Tabb August 2005 Major Subject: Architecture iii ABSTRACT An Experimental Setup to Evaluate the Daylighting Performance of an Advanced Optical Light Pipe for Deep-Plan Office Buildings. (August 2005) Betina Gisela Martins Mogo de Nadal, Dip. in Arch., Universidad Nacional de Rosario Chair of Advisory Committee: Dr. Liliana O. Beltrán This research focuses on an advanced optical light pipe daylighting system as a means to deliver natural light at the back of deep-plan office buildings (15ft to 30ft), using optimized geometry and high reflective materials. The light pipe configurations follow a previous study at the Lawrence Berkeley National Laboratory (Beltrán et al., 1997). The current system is designed for College Station, TX (lat: 30° 36‘N), with predominantly mostly sunny sky conditions. This work consists of the monitoring of two scale models simulating a portion of a multi-story office building with open-plan configuration, with interior dimensions 30ft x 20ft x 10ft, built at 1:4 of its real scale, one of the models being the reference case and the other the test case where the light pipe system is placed. The main objectives of this thesis are (a) to examine this daylighting system comparative to the reference case, taking measurements for longer periods than the study at LBNL, as well as to collect detailed data of its performance under different weather conditions and with different materials; (b) to evaluate the visual comfort and possible glare problems of the light pipe system through photographic evaluation and the conduction of a survey that provides people’s opinions and suggestions about the daylighting system. The light pipe system demonstrated a higher performance than the reference case in terms of appropriate levels of light and people’s preferences. The illuminance at the workplane level showed to be adequate with any of the two different diffusing materials used to spread the light into the room. The light pipe without a diffuser was the other iv condition observed to further understand the bounces of the sunbeam inside the reflective chamber and its consequences on the lighting output. Recommended standards for office spaces with VDT screens together with the analysis of the daylight system, led to preliminary suggestions on how to integrate the light pipe system in an open-plan office configuration. Further study is indicated to reach the complete potential of this advanced optical light pipe that ties illuminance quality with energy savings through the integration of daylight and electric light systems. v DEDICATION To my daughter Sofía, who gave me the strength to complete this thesis vi ACKNOWLEDGMENTS The pursuit of this thesis has taught me many valuable things: that everything is possible if you are determined and believe in what you are doing, and, that some periods on the timeline of a person’s life can be so crowded and complicated that you think you will never complete them, but eventually you will. I would like to express my gratitude to all the people who helped me during this time. Without their generosity, I would never have been able to finish this work. I would like to extend my deepest thanks to Dr. Liliana Beltran, chair of my advisory committee, for her support, her precious guidance, and her encouragement during the entire process of this study. My sincere gratitude goes out to Dr. Ergun Akleman and Dr. John Leggett, members of my advisory committee, for their time and valuable advice on this research. I would also like to thank Chuck Tedrick and all the student workers at the Woodshop who helped me to build the models. I greatly appreciate the collaboration of Dr. Jeff Haberl, who generously provided me with the shadow band necessary for this study. I would like to extend special thanks to Kelly Millican and Jim Sweeny for their help and advice on setting up the equipment for the experiment. I would also like to acknowledge the collaboration of Dr. Richard Furuta and two of his students, Ray Evans and Joshua Edwards, on their study of the datalogger’s software and development of a remote access and retrieval of data. Finally, I am deeply indebted to my family from close and afar for their encouragement and help. My special thanks to my “Longhorn” husband who many times played the roll of single Daddy, taking care of Sofia. To my lovely daughter Sofia, who patiently waited for her Mommy to finish this thesis so there would be more “Mommy time” for her. The most particular gratitude to my two moms: Norma, my mom, and Marta, my mom-in-law, who left their homes in Argentina for long periods to take care of Sofia, and to their husbands, my dads, to let them come. Furthermore, particular thanks to Alicia, my substitute mom in the US, for taking care of Sofia so many times. Thanks to all of them for being close to me when I needed it the most. vii TABLE OF CONTENTS Page ABSTRACT................................................................................................................. iii DEDICATION............................................................................................................. v ACKNOWLEDGMENTS............................................................................................ vi TABLE OF CONTENTS............................................................................................. vii LIST OF TABLES....................................................................................................... x LIST OF FIGURES...................................................................................................... xi CHAPTER I INTRODUCTION............................................................................................ 1 1.1. Background.............................................................................................. 1 1.2. Statement of the Problem and Research Purpose.................................... 2 1.3. Objectives................................................................................................ 3 1.4. Research Design...................................................................................... 3 1.5. Significance of the Proposed Study......................................................... 3 1.6. Scope of Research.................................................................................... 4 1.7. Organization of the Thesis....................................................................... 5 II LITERATURE REVIEW................................................................................. 6 2.1. Daylight in Offices................................................................................... 6 2.1.1. Use of daylight in office buildings................................................ 6 2.1.2. Effects of daylight in building occupants...................................... 10 2.2. Advanced Daylight Systems.................................................................... 12 2.2.1. Introduction and classification...................................................... 12 2.2.2. Light guides................................................................................... 13 2.2.2.1. Remote lighting................................................................ 13 2.2.2.2. Vertical light pipes........................................................... 14 2.2.2.3. Horizontal light pipes....................................................... 15 2.3. Daylight Evaluation................................................................................. 17 2.3.1. Scaled models................................................................................ 17 viii CHAPTER Page 2.3.2. Photometric evaluation.................................................................. 18 2.3.3. Lighting quality and visual comfort evaluation............................ 19 2.3.4. Visual observation......................................................................... 20 III METHODOLOGY........................................................................................... 22 3.1. Construction of Physical Scale Models................................................... 22 3.1.1. Scale models: design and construction.......................................... 22 3.1.2. Light pipe prototypes: materials, design and construction............ 27 3.2. Evaluation Methods................................................................................. 33 3.2.1. Data collection with a datalogger and photometric sensors.......... 33 3.2.2. Visual assessment.......................................................................... 36 3.2.2.1. The use of luminance ratios and photographic documentation for visual comfort evaluation.................. 36 3.2.2.2. Survey for human response evaluation............................ 37 IV DATA ANALYSIS.......................................................................................... 38 4.1. Measurements under Clear Sky Conditions............................................. 38 4.2. Raytracing with Time-Lapse Images....................................................... 54 4.3. Measurements under Overcast Sky Conditions....................................... 55 4.4. Analysis of Visual Comfort and Glare Analysis..................................... 58 4.4.1. Photographic documentation with HDR images and luminance ratios ............................................................................................. 58 4.4.2. Analysis of survey for human response evaluation....................... 61 V CONCLUSIONS AND FUTURE WORK...................................................... 69 5.1. Conclusions about the Use of Light Pipes as a Means to Illuminate Deep Plans............................................................................................... 69 5.1.1. Conclusions about illuminance values.......................................... 69 5.1.2. Conclusions about design and materials used............................... 70 5.1.3. Conclusions about visual comfort and people acceptance............ 70 5.2. Future Work............................................................................................ 71 REFERENCES............................................................................................................. 73 APPENDIX A.............................................................................................................. 78 ix Page APPENDIX B.............................................................................................................. 81 APPENDIX C.............................................................................................................. 83 APPENDIX D.............................................................................................................. 85 APPENDIX E............................................................................................................... 90 APPENDIX F............................................................................................................... 94 APPENDIX G.............................................................................................................. 103 APPENDIX H.............................................................................................................. 105 APPENDIX I................................................................................................................ 120 APPENDIX J................................................................................................................ 125 VITA............................................................................................................................ 129 x LIST OF TABLES TABLE Page 1 Determination of illuminance categories .................................................... 8 2 Floor, ceiling, walls, and furniture reflectances........................................... 23 3 Annual cloudiness for Austin, TX, with 54 years of data collected............ 32 4 Cloudiness for College Station, TX, for the year 2003 only....................... 32 5 Cloud Cover categories according to sunlight probability data bins by Robbins, 1996................................................................................. 33 6 Workplane illuminance (lux) of the three light pipe conditions at 24 ft, with lower window contribution.................................................... 39 7 Average illuminance at the half-front (max.) and half-back of the space (min.) and the resulting illuminance contrast gradient (ICG) for two light pipe conditions compared to the reference case..................... 42 8 Maximum and minimum workplane illuminance (lux) and illuminance contrast gradient (ICG) across the 15-30 ft area for the three light pipe conditions without lower window...................................... 53 9 Maximum and minimum workplane illuminance (lux) and illuminance contrast gradient (ICG) across the 15-30 ft area for the three light pipe conditions with lower window contribution....................... 53 10 Information of people who attended the survey on 02/03/2005 and 02/04/2005............................................................................................ 62 11 Working environment and lighting preferences of people who attended the survey...................................................................................... 62