Recently, there has been an increased interest observed in the areas of personal comfort systems and personalized ventilation (PV) systems in enhancing the occupant's personal thermal comfort through localized cooling/heating. Personalized ventilation systems have the ability to provide occupant’s preferred thermal environment as well as higher perceived air quality through a desk-level control mechanism. Several studies on personalized ventilation systems with different ventilation systems including mixing ventilation, displacement ventilation underfloor air distribution, and ceiling-mounted air distribution systems explored widely. There were significant developments took place in the last few years under personally controlled environmental chamber experiments using human subjects and thermal mannequins. Occupant microthermal environment under personalized ventilation (PV) depends mainly on various parameters including background ventilation system, PV supply temperature, flowrate variation, control strategies applied type of air terminal device used, and other physical and airflow characteristics. To accurately assess the PV system performance, it is important to understand the effectiveness of each key variable. Therefore, in this present study, we aimed to evaluate the PV system performance parameters based on PV physical configuration, dynamics of airflow, occupant health and well-being, and energy consumption. This study employs the analytical method to evaluate PV system effectiveness under different scenarios and derive the performance assessment criteria to compare with other PV systems-based studies.

Driven by a substantial demand to save energy, improve thermal comfort, and enhance indoor air quality (IAQ), this research proposes an innovative enhancement to Underfloor Air Distribution (UFAD) systems. This paper presents an experimental analysis of a tree-branch UFAD structure coupled with a wall-mounted Radiant Cooling (RC) panel, designed according to constructal law principles, in a test room simulating an office environment. The RC panel is mounted directly on the inner wall to maximize heat transfer by absorbing thermal radiation from the room via circulating water in the RC tubes, reducing indoor air temperature by convection. As supply air passes over the RC tubes, it is pre-cooled before entering the UFAD plenum. This enhances the cooling capacity and eliminates the need for an Air Handling Unit (AHU). The constructal law-based design of the UFAD structure optimizes indoor air distribution, reducing the power required for airflow. The indoor air velocity and temperature were measured at critical points in the occupied zone to ensure that the integrated UFAD-RC system provides effective cooling and prevents occupant discomfort. Furthermore, the ventilation performance of the integrated system was examined by injecting particles into the room and observing their dispersion behavior to evaluate the system’s capability to remove airborne contaminants from the occupied zone. The findings demonstrate that the vertical air temperature gradient between the ankle and head levels maintained below 0.75 [°C/m] (0.41 [°F/ft]) even for a low airflow rate, meeting the thermal comfort standards set by ASHRAE for seated and standing occupants. Additionally, the particle residence time in the room was significantly decreased at an airflow rate of 139.0 [m³/hr] (82.0 [cfm]), which demonstrates a notable capability of the integrated system to provide adequate IAQ that clears the way for sustainable and high-performance building ventilation solutions.

The thermal comfort of built environments is crucial to occupants’ well-being, health, and work efficiency. In hot climate regions, HVAC systems in buildings consume substantial energy to maintain comfortable indoor conditions. However, occupants’ feedback on their thermal satisfaction often falls short of expectations. This study aims to explain this phenomenon and discuss optimization strategies from the perspective of group thermal preferences.

First, a theoretical framework for group thermal preferences was established, focusing on three key characteristics: group maximum satisfaction, optimal group thermal environmental parameters, and group thermal sensitivity. Subsequently, stochastic simulations were conducted to illustrate the randomness and variability of group thermal preferences in real-world scenarios. The results indicate that a low survey satisfaction rate is not necessarily due to a poor thermal environment.

To improve satisfaction rates and select suitable thermal environment optimization strategies for multi-occupant spaces such as classrooms, open-plan offices, or even sections of parks, it is essential to understand the distinct thermal preferences of the occupant groups in specific venues.

Controlling relative humidity presents significant challenges in the HVAC industry, especially in hot and humid climates. Inadequate relative humidity management can lead to occupant discomfort, mold growth, and excessive energy use. Various methods exist to manage relative humidity and prevent mold, including constant volume, constant air temperature systems, variable air volume systems (VFD), and face and bypass dampers. This paper presents a case study of an existing residential building in Dharan, Saudi Arabia, where high relative humidity levels and mold growth were experienced. Several strategies were evaluated to better assess their potential in controlling relative humidity with careful consideration of energy consumption and carbon footprints. The study identified the optimal solution, which is the face and bypass damper, as it significantly reduced the relative humidity with energy savings of 20,000 kWh which will correspond in reducing carbon emission by 15 tons annually. In addition, it allows continuous fan operation which provides ventilation, filtration, uniform mixing of the space temperature.