Natural Ventilation in Building Design: Dynamic Performance Metrics and Interactive Modeling The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Yoon, Nari. 2019. Natural Ventilation in Building Design: Dynamic Performance Metrics and Interactive Modeling. Doctoral dissertation, Harvard Graduate School of Design. Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:41021630 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA Natural Ventilation in Building Design: dynamic performance metrics and interactive modeling A dissertation presented by Nari Yoon MDesS, Harvard University, 2012 B.Arch, Hongik University, 2010 to The Harvard Graduate School of Design in partial fulfillment of the requirements for the degree of Doctor of Design Harvard University Cambridge,Massachusetts January 2019 Copyright c 2019 by Nari Yoon. All rights reserved. Advisors: Author: Nari Yoon Professor Ali Malkawi Professor Holly W. Samuelson Professor Leslie K. Norford Natural Ventilation in Building Design: dynamic performance metrics and interactive modeling Abstract This study proposes a new method to evaluate natural ventilation performance in the early design phase by introducing dynamic performance metrics of natural ventilation and devel- oping an interactive tool that applies the metrics. The tool will help understand how a given design utilizes natural ventilation and which spatial variances could improve the effectiveness of natural ventilation. It also looks into important design aspects, including materials, thermal mass, aperture configurations, occupancy etc. These factors influence whether or not natural ventilation might be effective for the given design. There are four sub-topics: natural ventilation metrics, thermal mass and window con- trols, validation, and tool implementation. These sub-topics, in this order, structure the thesis. First, it introduces dynamic metrics that gauge the degree of cooling power that is achieved through natural ventilation. The metrics will be first developed under steady-state conditions, and be demonstrated in a feasibility study using an interactive design platform. Second, once metrics for steady-state are established, the effect of thermal mass and window controls are considered. Thermal mass interacts with its environment through time in a dynamic way which must be explored to refine the natural ventilation metrics. Therefore, this part will analyze the temperature change through time, examine the impact of different window operations, and further suggest efficient ventilation routines. Third, the process of calculating the dynamic metrics is validated with experiments. This ensures that the proposed method works as intended. Lastly, an interactive design procedure that utilizes the dynamic performance metrics is demonstrated in the 3D modeling environment. This study contributes to early-staged building design in three ways. First, quick simu- lation time and interactivity will provide users with rapid feedback on different design possi- bilities. Second, natural ventilation performance is estimated for a customized building design, albeit with some limitations, as opposed to a general box model. The tool may yield different results for buildings with different sizes, features, and construction conditions. By yielding metrics for a specific design, it will help users to alter the design to enhance performance. Third, the tool helps designers understand that the thermal environment is influenced by im- portant factors including window operation, thermal mass, and internal heat gains. Users will be able to learn the sensitivity of the thermal environment to various construction materials and thermal masses, which is pedagogically important. ii Acknowledgements Thank you, Prof. Malkawi, Prof. Samuelson, and Prof. Norford, for sharing your invaluable insights, guidance, and care. I am forever indebted to you. Thank you, Christoph Reinhart, Joyce Rosenthal, Alejandra Menchaca, and Yuya Ando, for showing confidence in me and supporting my doctoral journey. Thank you, my colleagues at the GSD and the CGBC, for inspiring me with your talents and encouraging me with your sympathy. Special thanks to Bin for your kindness and support that goes beyond colleagueship. Thank you, my friends in Korea, USA and anywhere on the globe, for laughing, grumbling, and singing with me. A special shout-out to Jung Min and Jung Hyun for our countless coffee breaks. Thank you, Min Ju, for taking the seat next to me on this roller coaster of life. I am thrilled for more to come. \mÐ Ä신 가q들, 감¬X고 ¬랑i니다. Contents Abstract i Acknowledgements iii List of Tables xi List of Figures xiii 1 Introduction 1 1.1 Research statement....................................1 1.2 Research objectives....................................2 1.3 Research methodology..................................4 1.3.1 Natural ventilation performance metrics...................4 1.3.2 Natural ventilation performance assisted by additional passive design strategies......................................4 1.3.3 Software selection for tool implementation..................5 1.3.4 Validation with the HouseZero project....................6 1.4 Structure of dissertation.................................6 2 Literature Review7 2.1 Natural ventilation in Architecture...........................7 2.1.1 Natural ventilation and energy savings....................7 2.1.2 Natural ventilation and thermal mass.....................9 2.1.3 Controls for natural ventilation and energy savings............. 11 2.2 Evaluation of natural ventilation............................ 12 2.2.1 Common metrics used in natural ventilation evaluation.......... 12 Contents 2.2.2 Customized indices used in natural ventilation evaluation......... 14 2.3 Natural ventilation modeling in design processes.................. 18 2.3.1 Site evaluation and conceptual design phase................. 19 2.3.2 Design development phase........................... 23 3 Dynamic metrics for interactive modeling 29 3.1 Metrics of natural ventilation performance...................... 30 3.1.1 Static and dynamic metrics of natural ventilation.............. 30 3.1.2 Terminology.................................... 31 3.2 Dynamic performance metrics for natural ventilation................ 35 3.2.1 Design natural ventilation cooling effectiveness (dNVCE)......... 35 3.2.2 Climate Potential Utilization Rate (CPUR).................. 39 3.2.3 Understanding dNVCE and CPUR together................. 39 3.2.4 Framework for dNVCE and CPUR....................... 40 3.3 Feasibility study for interactive modeling....................... 42 3.3.1 Study description................................. 42 3.3.2 Geometry..................................... 42 3.3.3 Climate natural ventilation effectiveness (cNVCE).............. 43 3.3.4 Pressure coefficient (cp) and available cooling power............ 44 3.3.5 Ideal cooling capacity.............................. 45 3.3.6 Initial results and testing more design alternatives............. 46 3.3.7 Results....................................... 47 3.3.8 Discussions.................................... 47 4 Thermal mass, dynamic window controls, and natural ventilation 51 4.1 Multi-zone thermal mass solution........................... 52 4.1.1 Single-zone model................................ 52 4.1.2 Multi-zone model: two-zone problem..................... 56 4.1.3 Multi-zone: more than two zones....................... 60 4.1.4 Implications of the multi-zone solution.................... 62 4.2 Model verification: with windows closed....................... 63 4.2.1 Objective of verification............................. 63 vi Contents 4.2.2 Verification methods............................... 64 4.2.3 Single-zone model setting: with windows closed.............. 65 4.2.4 Single-zone model verification results: with windows closed....... 66 4.2.5 Multi-zone model setting: with windows closed............... 67 4.2.6 Multi-zone model verification results: with windows closed........ 69 4.3 Model verification: with windows open........................ 70 4.3.1 Model assumptions with natural ventilation................. 70 4.3.2 Model settings for natural ventilation..................... 70 4.3.3 Single-zone verification results: with windows open............ 72 4.3.4 Multi-zone verification results: with windows open............. 74 4.3.5 Conclusion from the verification........................ 75 4.4 Thermal mass and dynamic window operation.................... 75 4.5 Calculation of dNVCE in a transient state....................... 77 4.5.1 Available cooling power (qavail) in a transient state............. 77 4.5.2 Ideal cooling power (qideal) in a transient state................ 78 4.5.3 Design natural ventilation cooling effectiveness (dNVCE) in a transient state........................................ 78 4.6 Discussion......................................... 80 4.6.1 Impact of thermal mass and window controls on dNVCE......... 80 4.6.2 Impact of thermal mass and window controls on CPUR.......... 81 4.7 Limitations......................................... 81 4.7.1 Geometry..................................... 81 4.7.2 Zoning for natural ventilation......................... 82 4.7.3 Thickness of thermal mass..........................