Zhiqiang John Zhai
University of Colorado at Boulder
1111 Engineering Dr, ECOT441
Boulder, CO 80309-0428
United States
3034924699
Region:
Honorarium:
Languages Spoken:
Dr. Zhiqiang (John) Zhai is a full Professor and the Program Coordinator of the Architectural Engineering Program in the Department of Civil, Environmental and Architectural Engineering (CEAE) at the University of Colorado at Boulder (CU), and the Site Director of the US NSF Building Energy Smart Technologies (BEST) Center. He has a unique and integrated background in both Architecture and Engineering with a Ph.D. degree in Mechanics (Tsinghua University, 1999) and a Ph.D. degree in Architecture (MIT, 2003). Dr. Zhai’s research and teaching interests and expertise include: integrated building systems; indoor and outdoor environmental quality; sustainable building and urban.
Dr. Zhai is the Fulbright US Scholar of the US Department of State and the International Leader Fellow of Royal Society of New Zealand. Dr. Zhai is a Fellow of The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), The International Society of Indoor Air Quality and Climate (ISIAQ), and The International Building Performance Simulation Association (IBPSA). Dr. Zhai is a PI/Co-PI for over 70 projects and published over 250 technical papers and was ranked as the World’s Top 2% Scientists by Stanford University (2021-2024).
Dr. Zhai was a Senior Fellow and Manager at Rocky Mountain Institute (RMI) and a Fellow of The Japan Society for the Promotion of Science (JSPS). He was a Visiting Scientist at Lawrence Berkeley National Laboratory and Hong Kong University, and a Visiting Professor at a dozen of universities such as University of Canterbury, University of Malaya, Gadjah Mada University, Shanghai Jiaotong University, and Tianjin University etc.
Dr. Zhai has served as Conference Chairs, Advisory/Scientific Committee Members, Track and Session Chairs for many building, energy and environment related conferences and symposiums; and he has delivered over 250 talks globally. Dr. Zhai is an Editor, Guest Editor and Editorial Board Member for a few important journals in the field, such as, Energy and Buildings, Science and Technology for the Built Environment, Sustainable Cities and Society, Building and Environment, Buildings, Building Simulation: An International Journal, and Indoor and Built Environment etc.
Dr. Zhai has been serving as Program Coordinator and Faculty Director of the Architectural Engineering (AREN) Program and the Executive Committee of CEAE, and the First Level Review Committee for tenure and promotion of the Engineering College at CU. He was granted numerous academic and service awards including the most prestigious “Changjiang Scholar” Chair Professorship Award by the Ministry of Education of China (2016), the Distinguished Service Award (2010) and the Distinguished Lectureship (2014) by ASHRAE, and the Gold Award of New Product & Technology (one of the ten) by the 2016 World Internet of Things (IoT) Conference and Exposition (2016). Dr. Zhai was the Invited Participant for the most prominent US Frontiers of Engineering (US FOE) 2010 Symposium and the Invited Organizer (one of the eight) for the 2011 Symposium by National Academy of Engineering of US.
Dr. Zhai is an active and renowned consultant for a few companies, such as, Marriot, Carrier, AprilAire, The Wharf, The Clinton Foundation, Red Star Macalline, and The World Bank (IFC) etc. Examples of his consulted projects include the Chicago Botanic Garden, the National Museum of African American History & Culture, and the wharf of Suzhou International Financial Center, etc.
Dr. Zhai has taught a variety of core courses since he joined CU, of which six are newly developed and two with significant revision. The courses vary significantly in scope and content, from fundamental undergraduate courses (i.e., Thermodynamics, Fluid Mechanics and Heat Transfer, and Energy Efficient Buildings) to advanced graduate courses (i.e., Building Energy Systems, Building Science and Engineering II, and Sustainable Building Design), from laboratory (i.e., Building Energy Laboratory) to computer simulation course (i.e., Computational Fluid Dynamics Analysis for Built and Natural Environment), from theoretical (i.e., Building Systems Modeling and Simulation) to design practice (i.e., Sustainable Building Practices in Developed and Developing Countries). Besides course teaching, Dr. Zhai has been closely supervising research of individual graduate and undergraduate students, including, 14 Ph.D. students (10 graduated), 35 M.S. students (31 graduated), 17 B.S. students, and 35 visiting scholars (including 6 visiting Ph.D. students – 5 graduated).
Topic
CFD for Indoor Environment Study
This talk presents a review of the applications of Computational Fluid Dynamics (CFD) to indoor environment design and studies, introducing the most popular CFD models used in both design and research practices. Although CFD is a powerful tool, a standard procedure must be followed to validate both the program and the user so that the results can be trusted. To this end, the ASHRAE standard procedure for conducting a CFD study is introduced and demonstrated with a few case studies. The presentation confirms that through proper and incremental exercises, the user and the CFD program can produce reliable results for indoor environment design and studies.
Inverse Design Method for Indoor HVAC Systems
Optimizing indoor flow distributions with specific design goals requires systematic evaluation and prediction of the influences of critical flow control conditions, such as flow inlet temperature and velocity. While the conventional approach involves simulating a large number of flow scenarios with different boundary conditions for comparison, this talk presents an innovative approach that can efficiently design HVAC system specifications in a confined space to meet multiple design goals, including thermal comfort, IAQ, and energy efficiency. A number of practical cases are presented to demonstrate the application of this method, including examples from an office building and an aircraft cabin.
The Short-term and Urgent Impact of AI on the Architectural Engineering Major
The impact of AI will be profound and comprehensive; while its long-term effects are still debated and specific domain impacts are in the early exploration stage, the short-term influence on the industry is gradually emerging and requires immediate response strategies. This report explores the possible impact of AI technology on the Architectural Engineering profession. It specifically focuses on the urgent, near-term effects of AI on professional direction, curriculum settings, teaching modes, and talent development, while proposing corresponding countermeasures.
Role of CFD in Building Design
Computational Fluid Dynamics (CFD), as the most sophisticated airflow modeling method, can simultaneously predict airflow, heat transfer, and contaminant transportation in and around buildings. This talk introduces the roles of CFD in building design, demonstrating its typical applications in designing a thermally comfortable, healthy, and energy-efficient building. It discusses the primary challenges of using CFD in building modeling and design practice. Furthermore, the talk analyzes developing trends in applying CFD to building design by thoroughly reviewing literature from the proceedings of the International Conference on Building Simulation, one of the most influential symposiums in the field.
Innovation from Convention: Inspiration from ASHRAE Research Projects
This report introduces the development and assessment processes of various standards and research projects by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The presentation focuses on the entire research process and major findings of two specific ASHRAE projects: the simulation of natural ventilation in public buildings and the study of ventilation in hospital operating rooms. Through these research cases, the report attempts to analyze the relationship between research originality and traditional practices, as well as how they extend into new innovations.
Post-Pandemic Thoughts on Ventilation and Air Conditioning Systems in Public Buildings
This talk discusses the challenges posed by COVID-19 to the indoor environment of commercial and public buildings, with a focus on air conditioning strategies such as ventilation and cleaning. Potential improvement strategies and solutions are presented for the design and operation of several vulnerable building types, including hospitals, hotels, and schools. Inspired by research outcomes during the pandemic, the talk highlights trends for building and system design, operation, and research in response to post-pandemic building development. It concludes that the holistic consideration of building health, comfort, energy-saving, and economy through integrated design is the sole approach to developing future public buildings.
Energy Performance of Active Chilled Beam System
Chilled beams are used to help cool a space evenly and efficiently through the process of conduction and convection. The use of water-based heat transfer gives the system an inherent efficiency boost when compared with air transfer technologies such as conventional fan-powered forced-air systems. This presentation introduces the principles of active chilled beam (ACB) systems along with relevant design and test standards. It provides first-hand knowledge of the thermal and energy performance of selected chilled beam systems characterized in both a full-scale laboratory and a computer-simulated environment. These findings can enhance the foundation and quality of current design guidelines. Additionally, the talk compares and evaluates the modeling capacities of current building simulation tools for ACB to guide the proper design of these systems for various building configurations.
Indoor Environmental Quality: The Practical Challenges and Solutions
This talk presents the practical significance and challenges in managing comfortable and healthy building environments. Through two engineering projects – one commercial building and one residential building – existing and new ventilation strategies are compared quantitatively. The CFD technique is utilized for system performance evaluation, and the talk summarizes general recommendations for engineering-level solutions. Additionally, challenges in modeling-based design are discussed, along with practical tips for implementation.
Energy Performance and Modeling of Naturally Ventilated Buildings
Proper simulation tools are highly desired to ensure acceptable thermal performance and to assist in the design and optimization of naturally ventilated buildings. This talk aims to advance the use of natural and hybrid ventilation concepts in building design by assessing the accuracy and usability of current thermal-ventilation models. It reviews existing network models available for design and investigates the capability and accuracy of four prevalent network airflow models in simulating a wide range of natural ventilation scenarios, with varying combinations of geometry and driving forces. The presentation indicates the need for improvements in network airflow models and evaluates the prevalent airflow-thermal modeling program, EnergyPlus, by simulating three real buildings with detailed data. These case studies reveal significant functional limitations of the simulation model, leading to a discussion on the building and measurement data critical for more accurate validation of thermal-ventilation models.
Better Buildings: Comfortable, Healthy, Efficient, and Safe
This talk provides an overview of primary research interests and projects conducted by Dr. Zhai over the past 20 years. It is organized into three categories: indoor environment, building envelopes, and urban environment. Both passive and active building systems, such as natural ventilation, displacement ventilation, thermal storage walls, and building-integrated PVT systems, are discussed with shared experiences and lessons learned. The presentation topics range from micro-scale virus movement in mission-critical spaces, such as aircraft cabins and hospital operating rooms, to urban-scale pollution impact analysis and energy demand prediction. Examples are provided to stimulate discussions on proper approaches for improving research and application in each category.
Uncertainty in Building Engineering Modeling: Significance and Impact
This talk starts by establishing the necessity of applying building engineering modeling in the design, construction, operation, and retrofit processes. It clarifies the distinction between uncertainty and error, subsequently discussing simulation uncertainty from various sources, including weather, human behavior, materials and construction, boundaries, building stock, and climate change. The significance and impact of this induced uncertainty on building performance modeling are illustrated, and the talk concludes by defining acceptable uncertainty ranges for different applications.
Air Distribution and Contaminant Dispersion in Hospital Operating Rooms
Effective ventilation is critical to the successful prevention of surgical site infections (SSI) in hospital operating rooms (OR). ASHRAE Standard 170 provides specific requirements for the design of hospital operating room ventilation systems, including specifications for air change rates, supply air face velocity, room pressurization, diffuser coverage area, return grille locations, and air filtration systems39. This talk reviews and compares various current OR design guidelines, with a focus on verifying and enhancing current practices by conducting on-site field experiments, full-scale laboratory experiments, and computational modeling. Results from field measurements of typical OR conditions and wound temperatures are presented. Key findings regarding air and contaminant distributions in a controlled full-scale laboratory are reported and compared against CFD modeling results, concluding with a discussion on potential improvement solutions for OR ventilation.
Natural Ventilation: Concept and Design
Natural ventilation is a traditional, cost-effective technique used to cool and ventilate buildings. This talk introduces the fundamental principles of natural ventilation (NV), including cross-ventilation, single-sided ventilation, wind-driven ventilation, and buoyancy-driven ventilation. It presents various design approaches and tools, ranging from simple rules-of-thumb to sophisticated computer modeling. Furthermore, advanced NV design concepts, such as hybrid ventilation and night cooling, are demonstrated through a significant number of case studies. The general procedure for designing a naturally ventilated building is introduced using practical industry guidelines, followed by a discussion on the challenges associated with designing and operating these systems.
Integrated Building Energy and CFD Simulations
Energy simulation (ES) and computational fluid dynamics (CFD) play important roles in building design by providing complementary information on building performance. Since separate applications often fail to accurately predict thermal and flow behaviors due to inherent assumptions, an integration of ES and CFD can eliminate many of these assumptions. This talk describes efficient approaches to integrating these tools to bridge the discontinuities of timescale, spatial resolution, and computing speed. It discusses the potential building and environmental characteristics that determine the necessity and effectiveness of applying a coupled simulation. These characteristics and accuracy requirements determine whether a coupled simulation is needed, and which method provides the best compromise between accuracy and efficiency. Finally, a sensitivity analysis of potential influential factors is provided, and case studies are demonstrated using coupled EnergyPlus and CFD simulations.
Building Energy and Environment: Challenges in Different Scales
This report introduces current research dynamics and challenges in the field of building energy and environment in the United States. It primarily shares the research progress of the author's team, focusing on micro-physical research and macro-predictive analysis of building environments and energy. The content covers the underlying mechanisms of pollutant propagation, the mechanisms, optimization, and application of novel building materials, material aging research, and the simulation, optimization, and control of integrated energy systems at the urban scale.
Identification of Indoor Airborne Contaminant Sources with Inverse Modeling Methods
Indoor air quality (IAQ) has received growing attention recently due to the extended time people spend indoors and increasing reports of health problems related to poor environments. Alarms regarding potential terrorist attacks with airborne chemical and biological agents have further highlighted research needs regarding building vulnerability and protection. To maintain a healthy and safe indoor environment, it is crucial to identify contaminant source locations, strengths, and release histories so that sources can be quickly removed and contaminated spaces effectively isolated and cleaned. This talk reviews various source identification approaches and introduces a probability-based prediction method that can track potential indoor airborne contaminant sources with limited sensor outputs. It describes the general modeling algorithm and procedure implementable with current CFD or multi-zone airflow models, demonstrates the method in realistic environments, and verifies its feasibility and accuracy through numerical and physical experiments.
Thermal Comfort Driven Studies on Building Energy and Environmental Systems
This talk reviews and looks forward to the hotspots and development trends of building energy and environmental system research that is driven by human thermal comfort, in combination with predictions from AI models. By sharing the research progress of the authors and collaborators in the fields of indoor and outdoor thermal comfort, the presentation discusses the microphysical difficulties and macroscopic application bottlenecks of building energy and environmental system research aimed at thermal comfort. The talk covers a wide range of topics, including personalized thermal comfort systems, advanced materials and technologies, climate-responsive design, outdoor thermal comfort innovations, extreme climate resilience, IoT monitoring, and sustainable energy solutions.
Cost of Engineering Indoor Air: Implications and Pathways to Net-Zero-Energy
This talk discusses the energy implications and costs associated with conditioning indoor air, including heating, cooling, ventilation, and purification. Both simple estimates and complex energy simulation solutions are presented, revealing the significance of air conditioning cost. Approaches to reducing these costs—and consequently carbon emissions—are explored, ranging from improving building envelopes to applying on-site renewables and using portable HVAC and cleaning devices. Several general observations and suggestions are obtained, such as the effectiveness of local solutions, the practicality of simple adjustments, and the importance of considering source energy and life-cycle costs.
