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1. Using Building Energy and Smart Thermostat Data to Evaluate Indoor Ultrafine Particle Source and Loss Processes in a Net-Zero Energy House

   https://doi.org/10.1021/acsestengg.1c00002  

   Jiang, Jinglin; Jung, Nusrat; Boor, Brandon E. (January 2021, ACS ES&T Engineering)

   null (Ed.)

   The integration of Internet of Things (IoT)-enabled sensors and building energy management systems (BEMS) into smart buildings offers a platform for real-time monitoring of myriad factors that shape indoor air quality. This study explores the application of building energy and smart thermostat data to evaluate indoor ultrafine particle dynamics (UFP, diameter ≤ 100 nm). A new framework is developed whereby a cloud-based BEMS and smart thermostats are integrated with real time UFP sensing and a material balance model to characterize UFP source and loss processes. The data-driven framework was evaluated through a field campaign conducted in an occupied net-zero energy building—the Purdue Retrofit Net-zero: Energy, Water, and Waste (ReNEWW) House. Indoor UFP source events were identified through time-resolved electrical kitchen appliance energy use profiles derived from BEMS data. This enabled determination of kitchen appliance-resolved UFP source rates and time-averaged concentrations and size distributions. BEMS and smart thermostat data were used to identify the operational mode and runtime profiles of the air handling unit and energy recovery ventilator, from which UFP source and loss rates were estimated for each mode. The framework demonstrates that equipment-level energy use data can be used to understand how occupant activities and building systems affect indoor air quality. 

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2. Spatiotemporal Variations in Ozone and Carbon Dioxide Concentrations in an HVAC System of a LEED-Certified Office Building

   https://doi.org/10.1016/j.buildenv.2025.112651  

   Jiang, Jinglin; Huang, Junkai; Jung, Nusrat; Boor, Brandon E (April 2025, Building and Environment)

   Indoor air quality (IAQ) is crucial for the health, well-being, and productivity of office occupants. IAQ is strongly influenced by occupancy and the operational mode of the heating, ventilation, and air conditioning (HVAC) system. This study investigates the spatiotemporal variations in ozone (O3) and carbon dioxide (CO2) concentrations throughout the HVAC system of a LEED-certified office building. A four-month field measurement campaign was conducted at the Ray W. Herrick Laboratories, employing an automated multi-point sampling system to monitor O3 and CO2 at eight locations throughout the HVAC system. The objectives of this study are to characterize the spatiotemporal distribution of these gases under different ventilation modes and occupancy levels, and to identify O3 loss mechanisms in the office and its HVAC system. Spatiotemporal variations in O3 and CO2 concentrations were observed throughout the HVAC system. Results indicate that outdoor air exchange rates (AERs) significantly impact indoor O3 levels, with higher AERs resulting in increased indoor O3 but reduced CO2 concentrations. Measurements reveal that HVAC filters and ducts contribute to O3 loss, with up to 18% O3 removal observed in the longest HVAC duct segment. Additionally, occupancy influences O3 deposition onto human skin and clothing surfaces. This research underscores the limitations of ventilation standards that focus only on CO2, highlighting the need for ventilation strategies that consider the effects of occupancy and outdoor AERs on different gases. By integrating multi-point gas sampling into building automation systems, more effective control strategies can be developed to enhance IAQ and occupant health while reducing energy consumption. 

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3. Modern buildings act as a dynamic source and sink for urban air pollutants

   https://doi.org/10.1016/j.crsus.2024.100103  

   Wu, Tianren; Tasoglou, Antonios; Wagner, Danielle N; Jiang, Jinglin; Huber, Heinz J; Stevens, Philip S; Jung, Nusrat; Boor, Brandon E (May 2024, Cell Reports Sustainability)

   Science for Society Buildings account for a significant fraction of the land area in cities and actively exchange air with their proximate outdoor environments via mechanical ventilation systems. However, the direct impact of buildings on urban air pollution remains poorly characterized. Due to reductions in traffic-associated emissions of volatile organic compounds (VOCs), volatile chemical products, which are widely used inside buildings, have become a major VOC source in urban areas. Indoor-generated VOCs are likely to be an important contributor to the VOC burden of the urban atmosphere, and ventilation systems provide a pathway for VOCs to be released outdoors. Here, we show how modern buildings act as significant emission sources of VOCs for the outdoor environment. Our results demonstrate that future air quality monitoring efforts in cities need to account for direct VOC discharge from buildings in order to capture emerging sources of environmental pollution that can impact the climate and human health. Summary Urban air undergoes transformations as it is actively circulated throughout buildings via ventilation systems. However, the influence of air exchange between outdoor and indoor atmospheres on urban air pollution is not well understood. Here, we quantify how buildings behave as a dynamic source and sink for urban air pollutants via high-resolution online mass spectrometry measurements. During our field campaign in a high-performance office building, we observed that the building continually released volatile organic compounds (VOCs) into the urban air and removed outdoor ozone and fine particulate matter. VOC emissions from people, their activities, and surface reservoirs result in significant VOC discharge from the building to the outdoors. Per unit area, building emissions of VOCs are comparable to traffic, industrial, and biogenic emissions. The building source-sink behavior changed dynamically with occupancy and ventilation conditions. Our results demonstrate that buildings can directly influence urban air quality due to substantial outdoor-indoor air exchange. 

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4. A longitudinal study of IAQ metrics and the efficacy of default HVAC ventilation

   https://doi.org/10.1016/j.buildenv.2024.111353  

   Pahlavikhah_Varnosfaderani, Mahsa; Heydarian, Arsalan; Jazizadeh, Farrokh (April 2024, Building and Environment)

   People spend approximately 90% of their time indoors, making effective indoor air quality (IAQ) monitoring crucial for occupants’ well-being. Traditional IAQ monitoring primarily focuses on carbon dioxide ( ) levels to inform the operation of Heating, Ventilation, and Air Conditioning (HVAC) systems. However, HVAC systems often overlook other critical IAQ metrics, such as volatile organic compounds (VOC), which may correspond better to occupant activities in some cases. This naturalistic study, conducted over four months at the University of Virginia, addresses this significant gap by observing changes in VOC and levels across various times, events, and spaces, including conference rooms, single occupancy offices, and common open-space areas. We aimed to determine whether can be the only representative of IAQ for dynamically adjusting the ventilation rates within this testbed. A key focus was on poor IAQ instances where levels were below the recommended levels, but VOC concentrations exceeded them, potentially impacting occupants’ health and well-being. Our results revealed that in the studied conference room, poor IAQ conditions prevailed 71% of the time during occupancy, in contrast to lower rates in single occupancy offices (11%, 7%, and 16%). Notably, while social events influenced levels less, VOC levels significantly increased in all open-space areas. These findings challenge the conventional reliance on monitoring for IAQ management, highlighting the necessity of incorporating comprehensive IAQ metrics in HVAC systems. The study underscores the critical need for dynamic HVAC systems that adapt to real-time IAQ conditions, a vital step towards enhancing indoor environmental quality in various settings. 

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5. What drives our behaviors in buildings? A review on occupant interactions with building systems from the lens of behavioral theories

   https://doi.org/10.1016/j.buildenv.2020.106928  

   Arsalan Heydarian, Claire McIlvennie (July 2020, Building and environment)

   Occupant behavior has a significant impact on building systems’ operations and efficiency. As a result, several innovative approaches have been introduced to quantify the dynamics of occupants within indoor environments, such as interactions with different building systems and the impact of various feedback and interventions to reduce the building energy consumption. To achieve this, researchers have highlighted the importance of reducing energy consumption without impacting occupant comfort. As a result, there is an increasing body of research evaluating how different theories of behavior across a variety of disciplines can explain occupant interactions with building systems. Future progress in this area calls for an in-depth understanding of behavioral theories in explaining occupant interactions with different building systems. In this paper, we have used a structured literature review approach to investigate how different psychological, sociological, and economic theories have been applied to explain occupant interactions with heating and cooling (HVAC systems), opening windows and ventilation, lighting and shading, electronic appliances, domestic hot water, as well as energy conservation behaviors. Throughout the paper, we identify the most common theories and methodologies applied within the existing research, general findings related to how occupants interact with different building systems, as well as a number of identified gaps within the literature. Finally, we provide a discussion on directions for future research studies in this area under each building system. 

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