Conference Agenda

Thermal comfort and indoor air quality (IAQ) are essential for maximising learning and productivity in university classrooms. In India, split air-conditioned (SAC) buildings typically operate in a manual changeover mixed-mode system, switching between air conditioning during hot seasons and natural ventilation in the cold season to maintain comfortable indoor conditions. To examine thermal comfort perceptions and air quality in these spaces, an experimental study was conducted in an Indian university classroom with 18 students during the summer of 2024. Unlike centralised HVAC systems, SAC units lack mechanical ventilation and rely on natural ventilation and air infiltration for fresh air. In high-occupancy settings, this can lead to elevated CO2 levels degrading IAQ. Thermal comfort perception was assessed using regression analysis and probit analysis, with results compared to the ASHRAE PMV model. Regression models were developed to relate the Mean Thermal Sensation Vote (MTSV) to operative temperature and Predicted Mean Vote (PMV). The analysis revealed a neutral temperature and thermal preference of approximately 28°C(82.4°F), notably higher than the National Building Code of India, with a comfort range of 24–26°C(75.2°F- 78.8°F). Furthermore, findings suggest that ceiling fans significantly improve comfort, whereas fluctuations of humidity levels are restricted due to the split AC’s dehumidifying effect. Throughout the study, PM2.5 and CO2 levels were monitored. CO2 levels peaked at around 2400 ppm, with an average of about 1570 ppm, indicating an inadequate fresh air supply in the studied classroom. PM2.5 levels were often above 50 µg/m³, exceeding the safe limits set by international agencies, further highlighting the lack of adequate ventilation and filtration. This study provides valuable insights into acceptable temperature ranges and air quality standards for university classrooms with SAC systems, offering guidance for future building design and operation strategies to enhance thermal comfort and IAQ in educational settings in India.

Given civilization's diverse and often divisive responses to the past several years of a pandemic, Legionella outbreaks, and climate changes with consequence, the global collective of building professionals would benefit from a retooling starting with a deeper understanding of the implied meanings of indoor environmental quality (IEQ) and heating, ventilation and air conditioning (HVAC). Additionally, it would benefit from newer and modernized systems to facilitate compliance with evolving IEQ standards and mitigate the indoor environmental challenges brought to public awareness through circumstances affecting all citizens. From a practitioner's perspective, this paper presents an application-based explanation for key terms and identifies potential operational conflicts between ASHRAE Standards 62.1, 62.2, 241 and Standard 55 created due to inadequate understanding of these terms within industry and society. It addresses IEQ/HVAC operational incompatibilities found within single-purpose systems. It introduces one potential solution illustrating hydronic-based hybrid HVAC systems with domestic water heat-interface units to enable healthier indoor environments, specifically for the quality of air, thermal comfort and potable hot water.

We proposed a novel ventilation strategy for double-loaded affordable apartments to improve indoor natural ventilation especially for the leeward side of the building, and constructed a full-scale experimental house in Indonesia in 2020. The previous study presented the results of field measurements to confirm ventilation performance of the proposed ventilation strategy. This paper presents the results of indoor thermal comfort evaluation in the same experimental house through field measurements conducted in October 2022. The experimental house has a total floor area of approximately 2000 m2, comprising 12 units. A vertical-closed void (2.85 m width) was designed between the rows of units. A pilotis was provided on the ground floor and a wind fin was attached to the bottom of the vertical void. The results showed that during full-day ventilation, indoor air temperature in the units closely followed the outdoors. Indoor wind speeds were averaged at approximately 0.55 m/s even in the leeward units primarily due to the effects of vertical void. Thus, full-day ventilation was found to be a better option than the other ventilation strategies including night ventilation. Even when the outdoor temperature reached 32-33°C, SET* was as low as 28-29°C in the windward units and 26-29°C in the leeward units. Compared with the typical double-loaded apartment without a vertical void, the proposed void-induced ventilation strategy would be able to provide sufficient indoor thermal comfort without relying on air-conditioning on both sides of double-loaded apartment buildings by improving cross-ventilation under the hot and humid climates.

In this study, the indoor environmental performance and energy-saving performance of a newly developed air-conditioning system designed for office use was evaluated in an experimental chamber. The air-conditioning system is a combined floor radiant cooling system and floor-blown air conditioning. This system primarily provides task/ambient air-conditioning that can create a localized indoor environment customized to the individual preferences of office workers while promoting energy efficiency. The floor radiant cooling system tends to release heat not only to the upper side of the floor, but also into the underfloor plenum. Small fans, changing the direction of airflow, circulate air from the room into the underfloor plenum and back into the room. Within the plenum, the air is cooled by the floor radiant cooling system. This cooled air is then returned to the room, ensuring efficient utilization of the cooling energy stored in the underfloor space. We constructed a prototype of this air-conditioning system with a variable air supply direction in the experimental chamber, allowing for controlled airflow between the room and underfloor plenum. Performance testing was conducted to evaluate the system’s effectiveness in regulating the thermal environment, its energy-saving performance, and the optimal operation strategies for such a system. The results indicated that at 100% fan power output, the cooled air reached the ceiling level, approximately 2,400 mm above the floor. At 50% fan output, the cooled air reached 1,700 mm from the floor level. These findings demonstrate that by adjusting the fan power, the range of local air-conditioning can be controlled. Additionally, we confirmed that the air circulation between the rooms enhances the thermal efficiency of the radiant cooling system.

Energy-efficient building renovation is a key priority in the face of today's climate challenges. Among the most critical elements, windows play a decisive role in the energy performance of buildings. In their original state, traditional windows are often poorly airtight, resulting in significant energy losses. This poor airtightness contributes to excessive heating consumption, worsening the building's carbon footprint, but also affects the comfort of occupants, notably through draughts, temperature variations and acoustic weakness.

To meet these challenges, this paper presents and illustrates an in-situ test method for windows airtightness inspired by the Blower Door test. This device enables air leakage to be measured precisely at element level, offering a practical and reliable alternative for assessing window performance before and after renovation.

The article presents the application of this method to various case studies, with a specific attention paid to testing conditions, including variations in temperature and relative humidity, as well as the presence or absence of a shutter. Although it is normally an in-situ test method, some tests were conducted in laboratory in complement with HAMSTER-equipment in order to study the impact of climatic conditions on airtightness performances.

The results show that this test offers good accuracy in detecting and quantifying air leaks. It can also be used to assess the impact of renovation work on windows, both from an environmental point of view, by reducing energy consumption, and in terms of occupant comfort. This paper goes one step further in quantifying the impact of windows airtightness in user-oriented criteria (e.g., energy bill or draught discomfort).