Conference Agenda

The evolution of residential building characteristics challenges policymakers and standard setters to adopt frameworks that ensure energy efficiency, indoor air quality, and sustainability. A recent update to the 1997 collection of dwellings representing the U.S. housing stock, as documented in a recent National Institute of Standards and Technology publication, highlights significant trends that may necessitate reevaluating current policies and standards. This paper describes the update, incorporating findings from the latest U.S. Department of Energy’s Residential Energy Consumption Survey and the U.S. Department of Housing and Urban Development's American Housing Survey, addressing previously identified gaps and introducing a more representative sample of contemporary dwellings.

Our analysis underscores the continuing emphasis on energy efficiency and the shift towards more sustainable building in codes and regulations as pivotal trends with mixed impacts on the building stock. The updated collection serves as a critical tool for the detailed study of indoor airflow and contaminant dispersion, as well as the coupled modeling of the energy implications of various ventilation strategies nationwide. Such insights are critical for developing building codes, standards, and practices that align with the evolving nature of the U.S. housing stock and that have tenable real-world impacts.

The paper argues for continuously refining the dwelling collection to reflect emerging trends, technological advancements, and in situ building testing. It emphasizes the importance of such updates in maintaining the relevance and utility of this collection for supporting the design and evaluation of buildings. As policymakers and industry professionals grapple with the implications of these findings, our contribution aims to spark a dialogue on the dynamic nature of the housing sector and the need for refining policies and standards to ensure healthier, more sustainable residential environments.

To advance human-centric sensing and environmental control strategies in office environments, this study examines the relationship between environmental conditions, physiological responses, and subjective perceptions of indoor air quality (IAQ) and thermal comfort. Controlled experiments were conducted in a climate chamber by establishing six environmental conditions, combining three air temperature levels (20˚C, 24˚C, 28˚C) and two IAQ levels (4 air changes per hour (ACH) vs. 0.2 ACH, the latter with emissions from newly painted wood particleboards). Eighteen participants (eight males and ten females) were exposed to each condition in 3.5-hour sessions on three separate days while engaging in a cognitive task (language learning on Duolingo) to simulate office-related cognitive load. Data collection included micro-environmental measurements around participants (termed “inhalation exposure”), physiological responses, and subjective evaluations of thermal comfort and perceived IAQ. Results indicated that exposure measurements were the only variables to show statistically significant differences related to IAQ variations. In contrast, both survey responses and physiological parameters were significantly related to changes in thermal conditions rather than changes in IAQ conditions.

In recent years, bathroom designs have evolved considerably, with unit baths becoming standard in most Japanese households over the past 30 years. This trend is expected to grow as unit baths, which dominate the Japanese market, continue to gain popularity globally. More recently, highly insulated bathtubs designed to maintain water temperature have become popular for their energy-saving benefits. However, the prolonged heat retention in these bathtubs raises concerns that the environment inside the bathtub apron (exterior panel of bathtub) may become even more favorable for mold growth due to sustained high temperature and humidity levels. While there has been extensive research into mold causes and prevention, limited attention has been given to the specific temperature and humidity conditions within the bathtub apron. This gap in research highlights the need for focused studies in this area. Preliminary results from single-day measurements taken during summer (August) and winter (February) in an actual home revealed that the bathtub apron’s interior is strongly affected by the bathtub’s heat and surrounding pipework, creating an environment even more favorable for mold growth especially in summer. To gain a comprehensive understanding of the temperature and humidity conditions within the apron, year-round measurements were conducted across multiple seasons, including summer, winter, the rainy season (June and July), and autumn (October and November). This study aims to monitor and analyze temperature and humidity levels around the bathroom, particularly within the bathtub apron, to correlate these conditions with mold growth patterns. By examining seasonal variations, the study identifies trends in temperature and humidity across the year, providing insights into the thermal environment’s influence on mold development. By identifying the specific seasonal conditions that promote mold growth within the bathtub apron, homeowners can adopt targeted cleaning and ventilation strategies, particularly during high-risk periods such as summer and the rainy season.

Although significant progress has been made in the development and implementation of low-carbon buildings, the critical role of occupant experiences and behaviors in this transition has received little attention. Understanding occupant experience and perceptions is essential to ensure that low-carbon features meet occupant needs and satisfaction. This knowledge can drive end-user adoption of these technologies, contributing to broader decarbonization goals, such as California’s goal to achieve net-zero greenhouse gas emissions by 2045. Lower carbon buildings typically focus on electrifying end-uses that are otherwise gas-powered, like space and water heating. As lower carbon housing gains prominence, disseminating information about structural and technical benefits can facilitate industry adoption of advanced energy practices, but the lack of metrics to assess occupant experience may overlook diverse socio-cultural understandings and behaviors which limit end-user adoption.

This study examines occupant perceptions in several multifamily affordable housing communities and one single-family market-rate community in California that varied based on location, technologies, and size. Through surveys and interviews, the satisfaction rating, perceptions, and experiences with advanced energy home features and low-carbon technologies were explored – providing an overall comprehensive view of occupant attitudes and perceptions of their homes and the end-use technologies installed. Findings indicate varying levels of satisfaction with their homes, with 100% of respondents in one multifamily community reporting being “very satisfied” with their overall home. However, satisfaction was lower in the community that received Packaged Terminal Air Conditioners as opposed to all the other homes that received centralized space conditioning, with only 43% reporting being “very satisfied” with their overall home. These results highlight both the successes and areas for improvement in low-carbon housing. Learnings indicate that lower-carbon housing can meet occupant expectations and comfort levels, with opportunities for further engagement through education and outreach to increase adoption and support the broader clean energy transition.

This study focuses on a comprehensive analysis of indoor air quality (IAQ) in a real dwelling by using data collected from six indoor and one outdoor low-cost sensors. The primary variables under scrutiny include temperature, relative humidity, indoor CO2 and particles concentrations, and outdoor NO2 concentration. The dataset, gathered at a high temporal resolution with a 10-second timestep over a one-month period encompassing both holidays and workdays, provides a good understanding of IAQ dynamics. To enhance the contextual understanding, a log file documenting key household activity such as cooking, showering, sleeping, and the open/close status of indoor doors has been maintained. This investigation aims to evaluate from these measurements parameters of interest to better understand the exposure of occupants such as outdoor pollution, room airflow rates, indoor particles sources and deposition to indoor surfaces. Results show that low-cost sensors can provide enough information to evaluate those parameters with accuracy if complementary information such as open/close door status and sleeping time are known.

Residential buildings in cold climates face specific challenges related to maintaining IAQ, because not only do people spend more time indoors, but they also tend to live in more efficient, airtight homes that can trap excess moisture and pollutants indoors if not properly ventilated, leading to problems for both the building structure and occupant health. Ventilating such buildings is important to maintain appropriate indoor air quality (IAQ) but strategies that are currently available can be very energy consumptive. Therefore, alternative measures need to be researched that would reduce ventilation requirements and at the same time optimize IAQ in residential buildings located in cold climates. This study evaluates the impact of ventilation and filtration measures on IAQ and energy efficiency in residential buildings in cold climates. Specifically, the study compares the performance of the selected strategies in forced air systems and radiant floor systems in two houses located in a cold climate in terms of maintaining appropriate IAQ. The study addresses several key questions: 1) What is the impact of heating, ventilating and air-conditioning (HVAC) system characteristics on resultant particulate matter (PM) levels in the house? 2) What is the impact of high-performance filters when operating in conjunction with the two HVAC system types? Results indicate that PM levels are significantly lower in the house installed with hydronic system than the house installed with the forced air system, and high-performance filters are more effective in reducing air pollutants when utilized together with a forced air system than when utilized with the hydronic system.

Recently, innovative modular retrofits incorporating heat pumps and heat exchangers have been designed to enhance the thermal performance of building envelopes. These systems, characterized by their lateral air-conditioning operation, lead to significant variations in temperature and airflow velocity at different locations within a space. This paper examines the thermal environment in an office space equipped with Building Envelope-Integrated HVAC Systems that introduce side air conditioning. Our study includes both experimental observations and Computational Fluid Dynamics (CFD) simulations. Experiments were conducted in a real-time office setting where variations in air velocity, temperature, and thermal radiation were recorded at different occupant locations. The findings reveal that occupants near the air inlet experience colder conditions, while those further away encounter a more temperate environment.

CFD simulations further analyzed thermal imbalances across various diffuser outlet configurations to optimize thermal comfort in occupant-centered control (OCC) systems. Results from four case studies indicate that horizontally elongated diffusers with multiple outlets significantly reduce temperature disparities among occupants, achieving enhanced thermal comfort.

Our combined experimental and simulation results confirm that the indoor thermal imbalance caused by the morphological characteristics of Building Envelope-Integrated HVAC Systems significantly affects occupant thermal comfort. Moreover, we observed that modifying the diffuser's shape can improve thermal imbalance, enhancing comfort levels. These findings highlight the importance of diffuser design in mitigating thermal imbalances and optimizing indoor environments in spaces utilizing lateral air-conditioning systems integrated into the building envelope.

In the Dutch P3venti program, particle measurements were conducted to assess how ventilation influences exposure to airborne aerosols (particles (< 4 µm)) in long-term healthcare facilities. A method was developed to investigate particle distribution behavior and exposure risk in long-term healthcare facility living rooms under realistic, operational conditions. This method was validated in a controlled mock-up environment (9.9 x 6.7 x 3.0 m) for different ventilation rates and ventilation set-ups. Furthermore, a first step was made to identify the most optimal ventilation set-up in the room to reduce particle exposure.

The exposure to airborne particles was measured at 18 different positions using particle counters and particle emission took place at three different locations. Each measurement cycle consists of determining the baseline of particle concentrations (5 minutes), starting particle emission until a steady state condition is achieved (+/- 50 min), switching off emission (15 min) and cleaning the room to return to baseline concentration. Outcome parameters are a ventilation map of particle concentrations in the room, the 100-fold increase time, the 100-fold recovery time, tdelay and the local air change rate.

Results showed that heat sources impact the particle distribution at both low (1 ACH) and high (3 ACH) ventilation rates. Additionally, the particle speed during emission has an impact on the particle distribution in the room. Furthermore, when the incoming ventilation rate is low (< 1 ACH) the positioning of the ventilation vents becomes inferior compared to the ventilation rate. These measurements highlight the distribution of particle concentration around an emitting source in various conditions, contributing to insights into effective ventilation strategies for airborne particle control in long-term healthcare settings.

Achieving energy efficiency while ensuring optimal indoor environmental quality (IEQ) in residential buildings is critical, particularly in the face of increasing global temperatures and rising energy costs. This study investigates the potential of demand-controlled ventilation and smart home systems to improve energy efficiency and ensure overheating prevention in apartment buildings, particularly accounting of these factors in energy calculation and the validity of an updated Estonian energy calculation methodology based on dynamic simulation. Through the analysis of measured data collected from a 4-room apartment, we assess the effectiveness of these systems in responding to real-time occupancy patterns and indoor conditions. The research methodology includes continuous monitoring of indoor parameters such as temperature, humidity, CO₂ levels, and energy consumption in an occupied apartment. Demand-controlled ventilation implemented with a CO2 and RH sensor in the ventilation unit, and alternatively with sensors in the living room, bedrooms and bathroom will be simulated. A calibrated energy simulation model is used to assess the accuracy of energy prediction with the updated Estonian energy calculation method including new input data. Preliminary results suggest that smart home systems including demand-controlled ventilation and accurate room thermostats can significantly improve energy performance in residential buildings, with potential savings up to 20% while maintaining thermal comfort. The findings of this study provide valuable insights into the feasibility and performance of smart ventilation solutions and their treatment in energy calculation methods.

With a global shift towards sustainability, the fashion and textile industries are under pressure to adopt eco-friendly practices due to their significant energy and water usage and environmental impact. One strategy is the renewed focus on natural materials. Understanding the relationship between natural fiber clothing and human thermal sensation has become crucial, as natural fibers like cotton, linen, silk, and wool are often considered less harmful to the environment and human health. However, they also present challenges, such as high water and pesticide requirements in production and animal welfare issues. Natural fibers are known for their unique properties, including high moisture absorption and release and breathability, which are often absent in synthetic alternatives. This study investigates how differences in clothing materials specifically linen, cotton, and polyester affect skin temperature and thermal sensation under conditions of light perspiration. In the experimental setting, we measured participants’ skin temperature and evaluated the thermal sensations during a foot bath to assess the impact of natural fibers on subjective thermal comfort. Additionally, we examined the moisture absorption and release capabilities of each natural fibric, further clarifying the distinctions between natural and synthetic fibers. The findings can contribute to clarify the benefits of natural fibers, contributing to sustainable clothing design and material selection. Additionally, with understood these properties, the use of natural fibers can enhance the comfort and health. As a result, this study can provide the insights into developing clothing that balances environmental considerations with thermal comfort.