publications

Journal Articles

2025

1. Towards high-performance buildings for thermal resilience and health

   Yalin Lu, Nan Ma, Alpha Yacob Arsano, Nathan Brown, Jihoon Chung, Aysegul Demir Dilsiz, Bing Dong, Ellen Franconi, Xu Han, Zixin Jiang, Nathaniel L. Jones, Mili Kyropoulou, Remy Mermelstein, Ulrike Passe, Tarek Rakha, Jialei Shen, Tarek Sherif, Qingqing Sun, Jordan Thompson, Zherui Wang, Youmin Xu, Yunyang Ye, and Xiang Zhang

   Energy and Buildings, 2025

   Abs Website

   Climate disasters and the increasing frequency of extreme weather events significantly challenge the ability of buildings to maintain safe and comfortable indoor environments. High-performance buildings (HPBs) are primarily promoted for their energy efficiency, focusing on minimizing energy consumption and reducing carbon emissions. However, this narrow focus can overshadow the need for thermal resilience and environmental health, leaving building occupants vulnerable to evolving environmental challenges. It is crucial to expand the design focus of HPBs to include these aspects to enhance their sustainability and adaptability to severe weather. To address this gap, we formulated ten critical questions aimed at integrating thermal resilience and health considerations into HPB design. We convened a panel of 23 experts from the U.S. regional affiliate of the International Building Performance Simulation Association (IBPSA-USA) at SimBuild 2024 to effectively explore these questions. This panel included architects, engineers, and researchers from academia, national labs, and industry, who participated in moderated discussions. Their diverse perspectives and expert insights have enriched our understanding and led to a comprehensive examination of how HPBs can be optimized for both sustainability and occupant well-being in a changing climate. This paper presents the consensus and ideas generated from these discussions, providing a multifaceted approach to designing buildings that are both energy-efficient and resilient to climate-induced stressors.

2023

1. A field measurement study of the effects of outdoor pollutants and room volumes on indoor fine particle and ozone concentrations

   Fusuo Xu, Jialei Shen, and Zhi Gao

   Journal of Building Engineering, 2023

   Abs Website

   Air pollution, represented by ozone (O3) and fine particulate matter (PM2.5), threatens the health of urban residents. This study examined 24 residential buildings in Nanjing to investigate the factors that affect indoor ozone and PM2.5 concentrations. Windows closed/open state, room geometry, ventilation rate, and pollutant removal and emission rates are taken as influencing factors. The correlation between influence factors and indoor air quality was analyzed to help residents in Nanjing understand which factors significantly affect indoor air quality. Fitted methods were employed to assess the removal and emission rates of pollutants. It was found that for the bedroom of 10-20 m2 (i.e., 30-60 m3), the air change rate (ACR, h-1) of infiltration is relatively more correlated with the room volume than other room volumes. The increase in indoor ozone concentration due to windows opening is below the indoor air quality standard in China (160 μg/m3) and the USA (70 μg/m3) under the test period in these measured cases. Therefore, when natural ventilation is adopted for residential buildings in Nanjing, outdoor fine particle concentrations should be a priority concern.

2022

1. On the effects of urban-like intersections on ventilation and pollutant dispersion

   Xin Guo, Riccardo Buccolieri, Zhi Gao, Mingjie Zhang, Tong Lyu, Liyan Rui, and Jialei Shen

   Building Simulation, 2022

   Abs Website

   Focusing on the effect of street morphology on the ventilation efficiency, this paper presents 3D computational fluid dynamics (CFD) simulations of airflow and pollutant dispersion within urban-like three-way intersections, four-way intersections and roundabouts. The steady-state Reynolds-averaged Navier-Stokes (RANS) κ-εturbulence model is adopted and eight directions of the approaching wind are considered. The ventilation efficiency is evaluated using the ventilation indices purging flow rate (PFR) and the net escape velocity (NEV). Results show the sensitivity of the ventilation efficiency to the type of intersection, to the wind direction and to the number of branches. Specifically, the ventilation efficiency of the investigated three-way intersections is found to be better than that of the other intersections, especially when the angle between the streets is large, while that of roundabouts is also considerable, even with a similar average wind velocity, among the cases evaluated in this paper. Further, the influence of the wind direction for the three-way and four-way intersections is greater than that on roundabouts. Studies on the ventilation efficiency at urban intersections are not common in the literature and this work may help urban planners to better design such hub nodes of urban traffic, where traffic-related pollutants are not easily dispersed, thus avoiding harm to the health of pedestrians and surrounding residents.

2021

1. Airborne transmission of SARS-CoV-2 in indoor environments: A comprehensive review

   Jialei Shen, Meng Kong, Bing Dong, Michael J. Birnkrant, and Jianshun Zhang

   Science and Technology for the Built Environment, 2021

   Abs PDF Website

   The COVID-19 pandemic has caused millions of deaths and great economic loss globally. There has been substantial evidence supporting the airborne transmission of SARS-CoV-2. Airborne route has been considered as a major transmission pathway, which can spread the disease over a longer distance and time. The viral loads in the respiratory tract of a virus carrier are typically below 109 RNA copies/mL and are related to the emission rate of pathogens. Most particles expelled during respiratory activities are smaller than 1-2 μm in diameter. Viral aerosols can remain infectious for hours under typical indoor conditions. Sunlight contributes greatly to the viability inactivation of SARS-CoV-2. The outbreaks in different scenarios are reviewed based on existing data. Most outbreaks were related to long-term care facilities, K-12 schools, restaurants, retail facilities, and offices. The Wells-Riley model for estimating the risk of airborne transmission is introduced, along with model parameters such as the quanta generation rate, virus-containing particle size distribution, and inactivation rate. The effectiveness of various IAQ control strategies for mitigating the airborne transmission risk is analyzed, including PPE, ventilation strategies, partitions, air cleaning, and disinfection technologies, and occupancy control strategies. Both benefits and costs should be considered in designing the control strategies.

2. Effect of greening on pollutant dispersion and ventilation at urban street intersections

   Xin Guo, Zhi Gao, Riccardo Buccolieri, Mingjie Zhang, and Jialei Shen

   Building and Environment, 2021

   Abs Website

   To improve ventilation efficiency and reduce pollution concentration in urban spaces, eco-strategies, including greening, have been suggested. However, there is still very little evidence to assert the benefits of such greening options, particularly at urban street intersections. Therefore, in this work, air flow and pollutant dispersion within urban-like three-way, four-way, and roundabouts intersections are investigated with three simple and five combined greening layouts. Three-dimensional computational fluid dynamics (CFD) analysis using the Reynolds-averaged Navier-Stokes model was conducted considering multiple wind directions. The ventilation efficiency was evaluated using the ventilation indices purging flow rate (PFR) and net escape velocity (NEV). The investigation of simple greening layouts shows that shrubs alone may enhance increase ventilation (i.e., increase PFR and NEV), and trees could increase the pollutant concentration at the pedestrian level. A comparison of greening layouts combining trees and shrubs shows that the presence of greening reduces ventilation and worsens the pollution condition at street intersections, except for shrubs located in the central zone within roundabouts. Specifically, NEV decreases by 16%-43% at four-way and three-way intersections owing to the presence of greening. Greening layouts with two rows of trees located 2.2 m away from buildings show overall significant negative effects on ventilation, particularly for wind directions φ= 0°, 45°, and 90°. The impact of shrubs and trees on ventilation at the roundabout is less significant, with NEV varying by 4%-11%.

3. A systematic approach to estimating the effectiveness of multi-scale IAQ strategies for reducing the risk of airborne infection of SARS-CoV-2

   Jialei Shen, Meng Kong, Bing Dong, Michael J. Birnkrant, and Jianshun Zhang

   Building and Environment, 2021

   Abs PDF Website

   

   The unprecedented coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made more than 125 million people infected and more than 2.7 million people dead globally. Airborne transmission has been recognized as one of the major transmission routes for SARS-CoV-2. This paper presents a systematic approach for evaluating the effectiveness of multi-scale IAQ control strategies in mitigating the infection risk in different scenarios. The IAQ control strategies across multiple scales from a whole building to rooms, and to cubical and personal microenvironments and breathing zone, are introduced, including elevated outdoor airflow rates, high-efficiency filters, advanced air distribution strategies, standalone air cleaning technologies, personal ventilation and face masks. The effectiveness of these strategies for reducing the risk of COVID-19 infection are evaluated for specific indoor spaces, including long-term care facility, school and college, meat plant, retail stores, hospital, office, correctional facility, hotel, restaurant, casino and transportation spaces like airplane, cruise ship, subway, bus and taxi, where airborne transmission are more likely to occur due to high occupancy densities. The baseline cases of these spaces are established according to the existing standards, guidelines or practices. Several integrated mitigation strategies are recommended and classified based on their relative cost and effort of implementation for each indoor space. They can be applied to help meet the current challenge of ongoing COVID-19, and provide better preparation for other possible epidemics and pandemics of airborne infectious diseases in the future.

4. Urban ventilation of typical residential streets and impact of building form variation

   Yunlong Peng, Zhi Gao, Riccardo Buccolieri, Jialei Shen, and Wowo Ding

   Sustainable Cities and Society, 2021

   Abs Website

   This paper numerically investigates the ventilation of residential streets bounded by buildings of different forms. The aim is to provide suggestions for the design of environmentally sustainable urban streets in residential areas. Four representative building form variations along residential streets in Nanjing, located in the Yangtze River Delta region in China, i.e. ’rotation’, ’stagger’, ’bend’ and ’annex building’, are considered and several idealized models are finally built for the ventilation analysis. The focus is on the most common East-West (EW) and North-South (NS) oriented streets subjected to parallel, perpendicular and inclined wind directions. Results show that, for the investigated wind directions, NS oriented streets experience a better ventilation than EW oriented streets for all wind directions. For EW oriented streets, it is suggested to avoid buildings parallel to the street to prevent poor street ventilation conditions, while bended buildings are found to improve the ventilation. For NS oriented streets, keeping the buildings perpendicular to the street as much as possible is the most effective way to improve the street ventilation. Moreover, the presence of annex buildings, employed for commercial purposes, although reduces the airpath between buildings, for a given wind direction has little effect on street ventilation.

5. Ventilation and Pollutant Concentration for the Pedestrian Zone, the Near-Wall Zone, and the Canopy Layer at Urban Intersections

   Mingjie Zhang, Zhi Gao, Xin Guo, and Jialei Shen

   International Journal of Environmental Research and Public Health, 2021

   Abs Website

   To gain further insight into the ventilation at urban street intersections, this study conducted 3D simulations of the ventilation at right- and oblique-angled intersections under eight wind directions by using the Reynolds-averaged Navier-Stokes (RANS) κ-εturbulence model. The divergent responses of ventilation and pollution concentration for the pedestrian zone (ped), the near-wall zone (nwz), and the canopy layer to the change in intersection typology and wind direction were investigated. The flow characteristics of the intersections, taken as the air flow hub, were explored by employing indices such as the minimum flow ratio (β) between horizontal openings. The results show that oblique wind directions lead to a lower total volumetric flow rate (Qtotal) but a higher βvalue for right-angled intersections. For T-shaped intersections, a larger cross-sectional area for the outflow helps to increase Qtotal. Oblique-angled intersections, for example, the X-shaped intersection, experience a more significant difference in Qtotal but a steady value of βwhen the wind direction changes. The vertical air-exchange rate for the intersection was particularly significant when the wind directions were parallel to the street orientation or when there was no opening in the inflow direction. The spatially averaged normalized pollutant concentration and age of air (τ^*-) for the pedestrian zone and the canopy layer showed similar changing trends for most of the cases, while in some cases, only the \tau_ped^*- or \tau_nwz^*- changed obviously. These findings reveal the impact mechanism of intersection configuration on urban local ventilation and pollutant diffusion.

6. Green Design Studio: A modular-based approach for high-performance building design

   Jialei Shen, Bess Krietemeyer, Amber Bartosh, Zhi Gao, and Jianshun Zhang

   Building Simulation, 2021

   Abs Website

   A modular-based Green Design Studio (GDS) platform has been developed in this study for fast and accurate performance analysis for early stage green building design. The GDS platform aims to simplify the design and analysis process by embedding performance parameters into design elements in modules and employing near-real-time model for whole building performance simulation as well as by providing an easy-to-use and intuitive user interface to assist users without extensive knowledge on building physics. The platform consists of building modules as fundamental building blocks, performance predicting models, and a user interface for visualization and interactive design. In the platform, a whole building is composed of modules organized in a hierarchical structure, including spaces, enclosures, service systems, sustainable resource systems and sites. Both physics-based and data-driven models can be used to simulate the building performance and optimize building systems. A simplified physics-based model, the Resistance-Capacitance (RC) model, has been proposed as a generic simulation model for the flows of heat, air, moisture and pollutants, which is significantly faster than conventional simulation tools such as EnergyPlus, and hence more practical for use in real-time design interaction and optimization. A pilot case study is conducted to illustrate the modular-based design approach using a section of an office building. Compared to conventional building performance analysis tools, the GDS platform can provide fast and reliable feedback on performance prediction for early design. The modular approach makes it easier to modify the building design and evaluate the potentials and contributions of various green design features and technologies.

2019

1. Emission rates of indoor ozone emission devices: A literature review

   Chao Guo, Zhi Gao, and Jialei Shen

   Building and Environment, 2019

   Abs Website

   

   As a strong oxidizing gas, ozone can damage the human respiratory tract and cardiovascular system. Aside from ambient outdoor ozone that enters buildings, indoor ozone emission devices (IOEDs) such as disinfectors, air purifiers, and printing devices are the primary source of indoor ozone. This review briefly presents the types and ozone emission mechanisms of IOEDs, the setups and procedures for measuring the ozone emission rate (OER) of IOEDs, and various equations for analyzing test results. This review also summarizes and compares the OERs of different IOEDs and analyzes the factors affecting the OER. The average OERs of in-duct air cleaners, ozone generators, room air purifiers, photocopiers, laser printers, and other small household devices are 62.8, 76.3, 4.6, 3.3, 0.8, and 0.4 mg/h, respectively. The OERs of in-duct air cleaners and ozone generators are generally larger than those of printing devices. The highest and lowest OERs of room air purifiers in the surveyed literature are 30.5 mg/h and 56 μg/h, respectively, with a difference of approximately 550 times. The ozone emission per unit paper for printing devices and per kilowatt hour for other IOEDs are also calculated and compared. In addition, the effects of the design and working mechanism of IOEDs on the OER are also discussed in detail. Users’ operation and daily maintenance of an IOED and the OER test conditions can also affect the OER. Finally, analytical equations are used to compare the influence of the test result processing method on the OER for the same IOED.

2. Commuter exposure to particulate matters in four common transportation modes in Nanjing

   Jialei Shen, and Zhi Gao

   Building and Environment, 2019

   Abs Website

   Particulate matter (PM) is one of the major air pollutants in China. Traffic-related microenvironments are the typical scenarios exposed to high PM concentrations. This paper investigates the personal exposure to PM during commuting in Nanjing in four transportation modes, i.e. subway, bicycle, bus and walking. The measurements were conducted in a heavy-traffic street during rush hours in summer and winter. The result reveals significant PM concentration differences between various commuting modes. Passengers in subway cabin are exposed to lowest PM1 (38.3 μg/m3) and PM2.5 (54.4 μg/m3) concentrations, while passengers in subway station are exposed to highest PM2.5 (90.5 μg/m3). Pedestrians are exposed to highest PM1 (59.5 μg/m3). Both outdoor and indoor-generated particles contribute a lot to the particles in subway station and 63.4% of the PM2.5 generated in subway station are between 1 μm and 2.5 μm in size. Most particles in subway cabin are from subway station and most particles in bus cabin come from the outdoor air, while indoor sources contribute little. Spatial particle concentration variations were observed in subway station. The particle concentration at a deeper level is usually higher than the concentration at a shallower level. Substantial particles within 1-2.5 μm in size were observed at the platform and the portion within 1-2.5 μm decreased at shallower levels. The PM inhalation during subway trip is lowest while the inhalations during walking and cycling are more than 5 times higher. During a short distance subway trip, the exposure in subway station contributes most of the total particle inhalation during the entire subway trip.

2018

1. Ozone removal on building material surface: A literature review

   Jialei Shen, and Zhi Gao

   Building and Environment, 2018

   Abs Website

   Ozone is a reactive gas that can have negative health effects on human. Building materials can be significant sinks for indoor ozone, owing to the irreversible heterogeneous reactions between ozone and material surfaces. Therefore, the ozone removal on material surfaces is crucial for evaluating indoor ozone concentrations and human exposure. This paper presents a review of previous investigations on ozone removal on building materials. The reaction probabilities of common indoor building materials range from 10^-8 to 10^-4, and depend on the material chemical compounds and surface characteristics. The surface-treated materials are probably more important than the underlying material substrate in determining ozone deposition velocities. Ozone removal on material surface is also associated with the fluid mechanics near the surface. Reactions between ozone and unsaturated organic compounds that constituting or adsorbed on material surfaces may result in oxidized by-products yields, while inorganic materials usually exhibit negligible by-products yields. Besides, the ozone surface removal on building materials under various conditions, i.e. ozone concentrations, air flow conditions, relative humidity and temperature, are discussed. Ozone removal on building materials after short-term and long-term exposure is presented.

2. Ventilation and Air Quality in Student Dormitories in China: A Case Study during Summer in Nanjing

   Zhe Yang, Jialei Shen, and Zhi Gao

   International Journal of Environmental Research and Public Health, 2018

   Abs PDF Website

   The Air quality in student dormitories can have a major impact on the health of millions of students in China. This study aims to investigate the ventilation and air quality in student dormitories. Questionnaire survey was conducted in eight dormitory buildings and field measurements were conducted in one dormitory during the summer in Nanjing. The survey result reveals that most students thought the indoor and outdoor air quality was neutral and the correlation between indoor and outdoor perceived air quality is statistically significant. There are few indoor PM2.5 and ozone sources in dormitories and natural ventilation is the most common form of ventilation. However, there is no statistically significant correlation between window opening behaviors and the perceptions of indoor and outdoor air quality. The field measurement result shows the measured I/O ratios of PM2.5 and ozone over 37 days are in the range of 0.42-0.79 and 0.21-1.00, respectively. The I/O ratios for PM2.5 and ozone are 0.49 ± 0.05 and 0.26 ± 0.05 in the case of the window being closed, and the I/O ratios for PM2.5 and ozone are 0.65 ± 0.08 and 0.50 ± 0.15 in the case of the window being open. The outdoor and indoor ozone concentrations show pronounced diurnal periodic variations, while the PM2.5 concentrations do not. Finally, recommended open/close window strategies are discussed to reduce indoor pollutant levels. Understanding the indoor/outdoor PM2.5 and ozone concentrations in different window patterns can be a guidance to preventing high indoor PM2.5 and ozone exposure in student dormitories.

3. The Impact of Green Space Layouts on Microclimate and Air Quality in Residential Districts of Nanjing, China

   Liyan Rui, Riccardo Buccolieri, Zhi Gao, Wowo Ding, and Jialei Shen

   Forests, 2018

   Abs PDF Website

   

   This study numerically investigates the influence of different vegetation types and layouts on microclimate and air quality in residential districts based on the morphology and green layout of Nanjing, China. Simulations were performed using Computational Fluid Dynamics and the microclimate model ENVI-met. Four green indices, i.e., the green cover ratio, the grass and shrub cover ratio, the ecological landscaping plot ratio and the landscaping isolation index, were combined to evaluate thermal and wind fields, as well as air quality in district models. Results show that under the same green cover ratio (i.e., the same quantity of all types of vegetation), the reduction of grass and shrub cover ratio (i.e., the quantity of grass and shrubs), replaced by trees, has an impact, even though small, on thermal comfort, wind speed and air pollution, and increases the leisure space for occupants. When trees are present, a low ecological landscaping plot ratio (which expresses the weight of carbon dioxide absorption and is larger in the presence of trees) is preferable due to a lower blocking effect on wind and pollutant dispersion. In conjunction with a low landscaping plot ratio, a high landscaping isolation index (which means a distributed structure of vegetation) enhances the capability of local cooling and the general thermal comfort, decreasing the average temperature up to about 0.5 °C and the average predicted mean vote (PMV) up to about 20% compared with the non-green scenario. This paper shows that the relationship vegetation-microclimate-air quality should be analyzed taking into account not only the total area covered by vegetation but also its layout and degree of aggregation.

4. Improving residential building arrangement design by assessing outdoor ventilation efficiency in different regional spaces

   Wei You, Jialei Shen, and Wowo Ding

   Architectural Science Review, 2018

   Abs Website

   Using computational fluid dynamic (CFD) simulations, the correlation between residential building arrangement designs and ventilation efficiency of various outdoor spaces is explored. Three indices-purging flow rate (PFR), visitation frequency (VF) and air residence time (Tp)-are adopted to quantify the ventilation efficiency of regional outdoor spaces. Using these indices, changes in residential building lateral spacing, building length, and stagger size were investigated under the effects of different surrounding building arrays for different wind directions. The simulation results indicated that wind direction is the most important factor for improving the residential wind environment, regardless of the patterns of the surrounding building arrays. When the angle between the wind direction and the building’s main facade orientation is more than 30°, the ventilation of different outdoor spaces improves. Staggered surrounding building arrays lower the spatial ventilation of the studied areas. However, this staggering does not affect the variation trend of spatial ventilation influenced by building arrangement design changes.

2017

1. An investigation on the effect of street morphology to ambient air quality using six real-world cases

   Jialei Shen, Zhi Gao, Wowo Ding, and Ying Yu

   Atmospheric Environment, 2017

   Abs Website

   

   Street canyons are vulnerable to air pollution mainly caused by vehicle emissions, which are therefore closely related to pedestrians’ health. Previous studies have showed that air quality in street canyons is associated with street morphology, though the majority of them have focused on idealized street models. This paper attempts to investigate the relationship of street morphology to air quality for 6 irregular real-world cases selected from America, Europe, and China, i.e. Manhattan, Paris, Barcelona, Berlin, London and Nanjing. Each street is analyzed as a set of slices to propose a couple of morphology indices for quantitatively assessing the actual street morphology. Pollutant transport rate of mean flows and turbulent diffusion, net escape velocity and age of air are obtained from computational fluid dynamics (CFD) simulations to assess the ventilations and pollutant dispersion within street canyons with a parallel approaching wind. The results show that the street morphology characteristics, including the street width, lateral openings and intersections, are closely related to the air flows in street canyons. The air quality improves with a decreasing aspect ratio of central street owing to a larger vertical exchange through the street roof, which suggests an open central street is of better air quality. The lateral openings and intersections of streets have important effects on the air flows in street canyons, and the effects are particularly pronounced when the street widths are similar. The street continuity ratio indicates street continuity. It relates to the openings and the symmetry of a street and impacts on the air flows and pollutant dispersion through the lateral openings of the central street. The street spatial closure ratio is determined by the street continuity ratio and the aspect ratio of the central street. When the aspect ratio of central street is not excessively high, higher values of street continuity ratio and spatial closure ratio can lead to a stronger channel flow in street canyons and improve the air quality. The octagon intersections are favorable for air flowing through the lateral openings and improve the channel flows. The oblique intersections can also greatly improve the street ventilations, mainly due to the enhanced air flows through the lateral openings and the increased turbulent diffusion through the street roofs.

Conference Articles

2025

1. A Computational Framework for Modeling Air Quality Exposure: From Outdoor to Indoor Environments

   Jialei Shen, and Moiz Usmani

   In AGU25 Annual Meeting, 2025

   Abs Poster Website

   People spend nearly 90% of their time indoors, making indoor air pollution a critical factor for human health. Therefore, accurate estimation of indoor air quality (IAQ) exposure is essential. While various modeling tools and computational models have been developed to monitor and predict outdoor (atmospheric) air quality, these tools generally do not extend to estimating indoor exposure. Indoor air quality is influenced by factors such as building envelope characteristics, ventilation strategies, and occupant behavior. In addition to pollutants generated indoors, outdoor (ambient) air pollutants can infiltrate indoor environments through ventilation systems and building leakage, further affecting IAQ and human health. This study aims to develop a computational framework for modeling indoor air quality and human exposure. The framework focuses on estimating the infiltration and natural ventilation of buildings that bring ambient air pollutants indoors. It uses CONTAM, a multizone indoor air quality and ventilation simulation tool developed by the National Institute of Standards and Technology (NIST). Simulation models will be created using GeoJSON files containing Level of Detail (LOD) 1 building data for Birmingham, Alabama, sourced from an open database. These data include a variety of building types, including residential homes, schools, office buildings, restaurants, retail spaces, and other public/commercial facilities. Typical airflow configurations, informed by literature and standard practices, will be assigned to the building enclosures in the simulations. Air exchange rates between indoor and outdoor environments will be calculated based on airflow models, considering ambient wind conditions and temperature differences that drive air movement through the building envelope. The results will be integrated with ambient air quality data and predictions to estimate indoor air quality. Empirical models will then be applied to assess human exposure to indoor air pollutants, based on predicted IAQ levels and typical human activity patterns. Birmingham is used as a case study to demonstrate the framework, but the computational pipeline has the potential to be adapted for other cities with different building types and environmental conditions.

2. Predicting The Impact of a Formaldehyde Selective Metal-Organic Framework Material on Indoor Air Quality

   Zhenlei Liu, Jialei Shen, Rui Zhang, Weihui Liang, Doyun Won, Beverly Guo, Wenfeng Huang, Jianshun Zhang, Nicolas Sadovnik, Marco Daturi, Christian Serre, and Menghao Qin

   In COBEE 2025 - The 6th International Conference on Building Energy and Environment, 2025

   Abs Website

   Metal-Organic Framework (MOF) materials present a promising solution to enhance energy efficiency and improve indoor air quality (IAQ) in buildings. This research examines the ability of a MOF material to passively control formaldehyde - a harmful indoor pollutant - by integrating laboratory testing and predictive IAQ modeling. Laboratory experiments used the microporous Al pyrazole carboxylate, denoted Al-3,5-PDA or MOF-303, that was previously identified as a highly efficient material to capture traces of formaldehyde in air without releasing it before 50°C. The formaldehyde adsorption performance was evaluated in a continuous 28-day small-scale chamber test, followed by a 7-day desorption phase. Tests were performed using an Al-3,5-PDA paper sheet at the formaldehyde concentration of 50 - 500 μg/m3 to assess the material’s adsorption performance. Evaluating of the long-term performance of MOF material in room-scale tests would provide valuable insight into their effectiveness in real-world scenarios. However, due to their high adsorption capacity and the significant cost of experimental specimens, it is too expensive to conduct long-term saturation tests or room-scale implementation. To compensate for the lack of the long-term test data, an IAQ simulation model was developed by integrating the tested adsorption capability via a multizone CONTAM software. This model used the parameters derived from short-term, small-scale tests to simulate large-scale, real-world applications. This model not only can enable more accurate forecasts of effectiveness under various scenarios, but also can reduce the cost to conduct extensive tests. Simulations were carried out at room scale with interior walls coated with the Al-3,5-PDA. The simulation demonstrated a 47% short-term reduction of formaldehyde levels by coating 10 m2 of wall surface in a 30 m3 room at 23 °C and 50% relative humidity. The results confirmed that Al-3,5-PDA’s high formaldehyde adsorption capacity, taking 150 days to reach saturation. These findings highlighted the potential of Al-3,5-PDA to effectively adsorb formaldehyde and reduce ventilation demands, contributing to energy savings and the improvement of IAQ in buildings. This study integrated short-term laboratory data into a scalable IAQ model, providing a cost-effective approach to predict performance of MOF materials in real-world building environments.

2024

1. Method of Experimental Evaluation of MOx Sensors for Real-Time Indoor VOCs Monitoring

   Xin Guo, Bing Beverly Guo, Zhenlei Liu, Jialei Shen, Daniel Love, Peter J. McKinney, and Jianshun Zhang

   In IBPC 2024 - The 9th conference of the International Association of Building Physics, 2024

   Abs PDF Website

   This study is specifically aimed at evaluating commercially available metal oxide (MOx) sensors for real-time monitoring of volatile organic compounds (VOCs) in typical indoor environments. To evaluate MOx sensors’ performance, we used a 50 L environmental chamber system to provide a well-controlled testing environment. The VOC types and test concentrations were based on relevant indoor air quality (IAQ) standards and guides in the literature. Test VOCs included toluene, formaldehyde, m-Xylene, phenol, benzene, naphthalene, acetaldehyde, acetone, dichloromethane, tetrachloroethylene, 1,1,1-trichloroethane. The evaluation tests are categorized into individual VOC tests, mixture VOCs tests, temperature and relative humidity dependence tests, short-term stability tests, and long-term drifting tests to investigate the sensitivity to specific VOC, mixture co-influence under realistic condition, moisture compensation, and reliability. This paper focuses on the procedures and results of the toluene test, identifying necessary improvements in the algorithm through comparisons between raw signals and TVOC readings. Results of this study will help provide guidance on the selection and utilization of MOx VOC sensors for VOC monitoring and IAQ control.

2. ANT: A Multizone Indoor Air Quality (IAQ) and Ventilation Analysis Plug-in for Algorithm Aided Design

   Jialei Shen, William Stuart Dols, and Brian Polidoro

   In SimBuild 2024, 2024

   Best Paper Award Abs PDF Website

   This paper received the Best Application Paper Award at the SimBuild 2024 conference.

   To facilitate the design and analysis related to indoor air quality (IAQ) and ventilation in buildings, a plug-in named ANT (contam-in-ANT) has been developed for Rhino/Grasshopper, an algorithm aided design platform. ANT is a whole-building IAQ and ventilation analysis tool based on CONTAM. ANT can be utilized to perform multizone simulations to assess airborne transmission risks, estimate health impacts due to inhalation exposure, perform parametric analyses, and optimize performance-driven building design and system settings. Cost-effective optimization of IAQ and ventilation for existing buildings is critical to the retrofitting required for these structures to achieve sustainability goals by 2050. A case study of a medium office building is used to demonstrate ANT and the post-processing of simulation results within Rhino/Grasshopper.

2023

1. A CFD approach to reduce the risk of Covid-19 airborne transmission in a typical office

   Yibing Hu, Jialei Shen, Jianshun Jensen Zhang, and Zhi Gao

   In IAQVEC 2023 - The 11th International Conference on Indoor Air Quality, Ventilation & Energy Conservation in Buildings, 2023

   Abs PDF Website

   The Covid-19 virus can spread rapidly in the air and cause the epidemic to rage around the world. This study takes a typical office as the research object and proposes four different partition settings to suppress the spread of the virus in the air based on displacement ventilation. And these strategies are verified by DPM model simulations of two daily situations of indexed person for coughing and talking. This study then employed a modified Wells-Riley model to evaluate the effectiveness of these strategies in mitigating the risk of viral infection. As expected, in the absence of a partition, a susceptible person at the other end of the seat greatly increased the risk of infection. Partitions can significantly reduce the risk of infection (100% -> 20%), while partitions with a full-wrapped structure can reduce the risk of infection to less than 1%. For the instantaneous release scenario of coughing, the barrier can capture a large particle diameter (>50 μm) particles, and the smaller particle diameter can be discharged out of the room with the thermal plume. The strategies provided in this study can provide recommendations for indoor epidemic prevention and control in the context of the Covid-19 pandemic.

2. Performance and Cost of Airborne Infection Mitigation Strategies

   Jialei Shen

   In ASHRAE Annual Conference 2023 - Seminar 12: Balancing Virus Risk Control and Energy Consumption for Better Building Operation, 2023

   Abs Website

   The COVID-19 pandemic has caused devastating loss of life and economy globally. Airborne transmission has been recognized as one of the major transmission routes. Many mitigation strategies have been developed and implemented to address COVID-19 infection risk, including elevated outdoor airflow rates, high-efficiency filters, advanced air distribution strategies, standalone air cleaning technologies, personal ventilation, displacement ventilation, and face masks. The effectiveness and energy consumption of using these strategies for reducing infection risk are investigated based on airborne infection risk and energy estimation models in this study. The potential of risk mitigation and energy use are compared.

2022

1. Estimation of infection risk through airborne transmission in large open spaces with different air distributions

   Jialei Shen, Kaloki Nabutola, Michael J. Birnkrant, Peter J. McKinney, Bing Dong, and Jianshun Zhang

   In ROOMVENT 2022 - The 16th ROOMVENT Conference, 2022

   Best Paper Award Abs PDF Slides Website

   This paper received the Best Paper Award at the ROOMVENT 2022 conference.

   Respiratory diseases such as COVID-19 can be spread through airborne transmission, which is highly dependent on the airflow pattern of the studied room. Indoor air is typically not perfectly mixed even using a mixing ventilation, especially in large spaces. Airflow patterns in large open spaces such as hotel banquet rooms and open plan offices, are of particular concern, as these spaces usually accommodate more occupants and thus have the potential to spread diseases more rapidly leading to outbreaks. Therefore, understanding airflow patterns in large open spaces can help to estimate the detailed infection risk at certain locations in the space, which can prevent the spread of virus and track the potential new infections. This study estimated airflow patterns in a typical banquet room under theatre and banquet scenarios, and a large open plan office using computational fluid dynamics (CFD) simulations. Typical ventilation and air distribution approaches, as well as room layouts and occupant configurations in these scenarios were studied and applied in simulations. According to current results, the air distribution in a typical hotel banquet room with mixing ventilation can be very complicated, particularly for the banquet scenario. For a typical theatre scenario, under typical ventilation design, people sitting in the middle and lateral area were exposed to the highest infection risk. The front rows may be exposed to short-range transmission as well. For a banquet scenario, people sitting on the same table were more likely to be cross contaminated. But cross-table infection was still possible. The results can provide guidance on designing ventilation and air distribution approaches in large spaces with similar settings.

2. Performance of in-duct bipolar ionization devices on pollutant removal and potential byproduct formation in indoor environments

   Jialei Shen, Zhenlei Liu, Daniel Love, Mary Dekold, Beverly Guo, Michael J. Birnkrant, Peter J. McKinney, Bing Dong, and Jianshun Zhang

   In Indoor Air 2022 - The 17th International Conference on Indoor Air Quality and Climate, 2022

   Abs PDF Slides Website

   The COVID-19 pandemic has highlighted the importance of indoor air quality (IAQ) since SARS-CoV-2 may be transmitted through virus-laden aerosols in poorly ventilated spaces. Multiple air cleaning technologies have been developed to mitigate airborne transmission risk and improve IAQ. In-duct bipolar ionization technology is an air cleaning technology that can generate ions for inactivating airborne pathogens and increasing particle deposition and removal while without significant byproducts generated. Many commercial in-duct ionization systems have been developed but their practical performance on pollutant removal and potential formation of byproducts have not been investigated comprehensively. The results in this study showed that the in-duct bipolar ionization technology can significantly improve the particle removal efficiency of the regular filter, while no significant ozone and ion were released to the indoor air.

3. Modeling Secondary Emissions from Indoor Chemical Reactions Initiated by Ozone and Hydroxyl Radicals

   Zhenlei Liu, Jialei Shen, Beverly Guo, and Jianshun Zhang

   In Indoor Air 2022 - The 17th International Conference on Indoor Air Quality and Climate, 2022

   Abs Website

   Volatile organic compounds (VOCs) can be oxidized by ozone (O3) and hydroxyl radicals (OH•) under a series of reactions to produce secondary emissions indoors in addition to primary emissions. A mathematical model that accounts for ventilation, surface adsorption, oxidant generation, ozone and hydroxyl radicals-initiated chemical reactions was developed for evaluating the pollution loads and concentrations in a ventilated space. The model focused on major chemical reactions that were responsible for stable products from secondary emissions as detected in full-scale chamber experiments. The experiments were simulating a realistic ventilated room and how a source of O3 and OH• would affect the concentrations of VOCs. The modeled results were in line with the experimental results. Alpha-pinene and heptanal were selected to illustrate the model prediction results as an example given their relatively high reaction rates with O3 and OH•. Limitations of the model and the needs for further development were also identified.

4. A Comprehensive Approach to Testing Air Cleaning Devices Under Realistic Room Conditions

   Zhenlei Liu, Eloise Parry-Nweye, Yousr Dhaouadi, Xuezheng Wang, Jialei Shen, Beverly Guo, Moises Ramirez, Bhavesh Gupta, Dacheng Ren, Bing Dong, and Jianshun Zhang

   In Indoor Air 2022 - The 17th International Conference on Indoor Air Quality and Climate, 2022

   Abs Website

   The classical decay method for testing air cleaner performance requires high initial challenge concentrations of pollutants and is performed during a transient pollutant concentration period. This does not reflect the device’s usage condition where concentrations are significantly lower and remain relatively constant under a constant ventilation rate. Previous tests are mostly conducted under empty chamber with a single type of challenge pollutants, while different types of pollutants typically co-exist in the real environment. This study proposes a comprehensive approach to test various types of cleaners and pollutants under the realistic condition. A test procedure was developed involving constant injections of target and comparison of the measured concentrations with and without the operation of the device under a condition with realistic ventilation rate, typical interior surfaces, furnishing, and simulated occupancy. Results show that the procedure can effectively measure the performance of different types of air cleaners for removing the target pollutants including VOCs, particles and a virus surrogate (phi6).

2021

1. Effectiveness of multi-scale IAQ strategies for reducing the risk of airborne infection of SARS-CoV-2

   Jialei Shen, Zhenlei Liu, Yibing Hu, Michael J. Birnkrant, Zhi Gao, Bing Dong, and Jianshun Zhang

   In Healthy Buildings 2021 America, 2021

   Slides
2. Effectiveness of IAQ strategies for mitigating the airborne infection risk of SARS-CoV-2

   Jialei Shen, Meng Kong, Bing Dong, Michael J. Birnkrant, and Jianshun Zhang

   In IBPC 2021 - The 8th International Building Physics Conference, 2021

   Slides
3. Ozone Emission Sources and Surface Removal in Indoor Environments

   Jialei Shen

   In ASHRAE Annual Conference 2021 - Seminar 14: Reducing Ozone: A Critical Factor in Improving IAQ, 2021

   Slides

2019

1. An approach to develop a green building technology database for residential buildings

   Jialei Shen, and Jianshun Zhang

   In IAQVEC 2019 - The 10th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, 2019

   Abs PDF Slides Website

   Buildings consume approximately 39% of the total energy used in US, of which 53% is consumed by residential buildings. Besides, indoor air quality (IAQ) have significant impacts on occupant health since people spend on average around 90% of their time indoors. Nowadays, a great number of green building technologies (GBTs) have been developed and implemented in buildings for reducing energy consumption and improving IAQ. This paper proposes an approach to develop a green building technology database for residential buildings including their the technology’s feature and performance for energy saving and IAQ improvement under different building configuration and climate conditions. The GBTs are collected from case study buildings. For each study case, the GBTs are classified by the Virtual Design Studio (VDS) building assessment method. A local reference building is first defined for the region where the case building is constructed. Both forward-step evaluation of a proposed GBT to a reference building and backward-step tracking of the contribution of the technology to the case building are conducted. A scalability analysis is also conducted to understand the practical application of the performance parameters to other cases with different building design. EnergyPlus and CHAMPS-Multizone are used to analyse the energy and IAQ performance for each technology. The approach is verified by a case study of two single-family houses in US.

2017

1. Outdoor and Indoor Ozone Concentration Estimation Based on Artificial Neural Network and Single Zone Mass Balance Model

   Jialei Shen, Jie Chen, Xinyi Zhang, Sicong Zou, and Zhi Gao

   In ISHVAC 2017 - The 10th International Symposium on Heating, Ventilation and Air Conditioning, 2017

   Abs Website

   Both outdoor and indoor ozone concentrations have negative health effects on human. This paper proposes an artificial neural network to estimate the outdoor ozone concentrations and a mass balance model tool to estimate indoor ozone concentrations. The prediction of outdoor and indoor ozone concentration levels is of great significance for people’s health. The estimation models are validated by the measured data selected from the monitoring stations and field measurements in a room in Nanjing, respectively. The accuracy of the estimation models is evaluated. The neural network built in this paper can generally estimate the outdoor ozone concentrations to some extent, while the single zone mass balance model is useful for predicting indoor ozone concentration levels.

2. Commuter Exposure to Particulate Matter of Different Transportation Modes in Nanjing

   Jialei Shen, Jie Chen, Xinyi Zhang, Sicong Zou, and Zhi Gao

   In ISHVAC 2017 - The 10th International Symposium on Heating, Ventilation and Air Conditioning, 2017

   PDF
3. Indoor and Outdoor PM2.5 and Ozone Levels: A Case Study in a College Student Dormitory in Summer

   Jialei Shen, and Zhi Gao

   In ISHVAC 2017 - The 10th International Symposium on Heating, Ventilation and Air Conditioning, 2017

   PDF
4. Study on Relationship of Residential Building Form Variations to Pollutant Dispersion in Streets

   Jialei Shen, Zhi Gao, Wowo Ding, and Wei You

   In Healthy Buildings 2017 Europe, 2017

   PDF
5. Improving wind environment design based on assessing spatial distribution of ventilation efficiency in regional space

   Wei You, Jialei Shen, and Wowo Ding

   In ICAE 2017 - The 9th International Conference on Applied Energy, 2017

   Abs Website

   This paper discusses the influence of design variations on spatial distribution of Ventilation Efficiency (VE) in idealized residential building groups. Series of design cases referring building length and spacing changing are investigated using Computational Fluid Dynamics (CFD) simulation method. Air change rate (ACH) and purging flow rate (PFR) are adopted as evaluation indices of ventilation efficiency. Simulation results indicate that these design changes have evident effects on distribution of spatial ventilation efficiency. Widening building spacing could improve ventilation efficiency of different spaces. However, the benefit is not linear improved as spacing distance increases. When the distance is higher than 15m, improving extent of spatial ventilation efficiency decreases evidently. Variations of building length also has effect on distribution of spatial ventilation efficiency. As building length increase, less wind could reach into space between south and north buildings, which lead to the decrease of wind ventilation for middle residential-unit. Preliminary study indicates that building length should be restricted within 5 residential-unit.

6. Improving Wind Environment of Residential Neighborhoods by Understanding the Relationship between Building Layouts and Ventilation Efficiency

   Wei You, Jialei Shen, and Wowo Ding

   In ICAE 2016 - The 8th International Conference on Applied Energy, 2017

   Abs Website

   This research attempts to probe into the correlation between the residential building layout and ventilation performance of various spaces in an operative level. To quantify the influence of design change on outdoor ventilation, numerical modeling technology is adopted with ANSYS-Fluent as the simulation tool. As to evaluate the ventilation efficiency of exterior space, local mean age of air (L-MAA), which is common used in recent urban form studies, is further discussed for local region’s ventilation efficiency in residential neighborhoods. Using this ventilation index, several cases are calculated and three types of building layout changes (lateral spacing, building lengths and stagger of location) are discussed. The simulation results show that L-MAA is a useful ventilation index to access the design changes on urban space ventilation and these design changes have great effects on exterior space ventilation. Building length has great influence on ventilation efficiency of different spaces, while the influence of lateral spacing and stagger of location changes varies greatly in different local regions.

Book Chapters

2022

1. Managing IAQ at Multiple Scales: From Urban to Personal Microenvironments

   Jianshun Jensen Zhang, Jialei Shen, and Zhi Gao

   In Handbook of Indoor Air Quality, 2022

   Abs PDF Website

   Indoor air quality (IAQ) is vital to human health, comfort, performance, and wellbeing as people typically spend over 80% of their time indoors. The indoor pollutants people are exposed to originate from both indoors and outdoors. In order to devise an energy-efficient and cost-effective approach to improve IAQ, it is necessary to consider strategies across multiple scales-from the outdoor environment around buildings to inside buildings, to rooms, and to the microenvironment around the occupants that directly affect the human exposure and intake of the pollutants. In this chapter, we present a 3-dimensional view of the IAQ engineering: the scales (of environments), the species (of pollutants), and strategies (of IAQ control). The objective is to improve the understanding of and assess the potential and limits of the various source control, ventilation, and air purification strategies across the different scales so that an integrated approach can be developed for managing IAQ. Existing data from previous research on the effectiveness of various IAQ strategies at the different environmental scales are discussed along with an outlook to the future work and challenges.