Atiye Jarrahi

Natural ventilation could be established as an effective passive design strategy for increasing air changes per hour in a built environment. Modern air conditioning systems often fail to provide sufficient fresh air, potentially causing health issues for occupants. In contrast, natural ventilation offers an effective alternative for maintaining sufficient indoor air quality in buildings. This study explores the application of grouped airfoil arrays on building façades as an innovative passive design to enhance the air change rate. Numerical simulations were conducted to analyze various airfoil configurations, determining the most effective design for building a façade. Three groups, including symmetrical, semi-symmetrical, and flat-bottomed grouped airfoils, were selected according to their aerodynamic properties and potential impacts on airflow dynamics. For this purpose, a typical high-rise residential building was selected as a case study for field measurement and CFD simulation. The results indicated that symmetrical airfoil arrays could increase the air changes per hour (ACH) up to 23 times per hour with a wind velocity of 0.37 m/s at 10 m above ground, whereas their bidirectional performance ensured stable airflow regardless of wind direction. Although semi-symmetrical airfoil arrays maximize air capture and induce beneficial turbulence, the ACH within a residential unit was boosted up to 16 times per hour under the same outdoor wind velocity conditions. The ACH was 14 times per hour for the flat-bottom airfoils, serving as a comparative baseline and providing insights into the performance advantages of more complex designs.

The indoor environmental quality of a library greatly affects the comfort and productivity of its users while preserving the materials. Despite the high energy consumption of HVACs in libraries, achieving acceptable thermal conditions, acceptable acoustics, and sufficient daylight levels for users remains a challenge. There are limited studies on the IEQ of educational buildings, especially regarding the current situation of libraries. It is important to conduct further studies to define design guidelines promoting indoor environmental conditions. The main objectives of this study were to investigate the IEQ of a campus library to recommend retrofitting strategies. The IEQ parameters in the rare collection room, which houses special collections, and in the library hall were assessed using a full-scale measurement, with eight HOBO data loggers and sensors deployed in various locations to monitor IEQ. A comparison of the results with the standards revealed that rare collection room was unsuitable for maintaining rare collections, as the average indoor air temperature exceeded 21.2 °C, which is beyond the threshold limit. Additionally, the relative humidity ranged from 51.3% to 55.8%, which is marginally high. To provide acceptable indoor conditions, this study recommends retrofitting strategies for the exterior walls, such as using cement plaster with a low thermal conductivity. In the library hall, the reading zone was found to be thermally uncomfortable. The air velocity was below the range of 0.15 ms⁻¹ to 0.50 ms⁻¹ recommended by MS 1525. The average CO₂ level was 479.5 ppm, with some points registering an increase of up to 588 ppm. The noise level in the library hall ranged between 43 dB(A) and 61 dB(A), while the light intensity was below 300 lux in the reading area, which is not within the acceptable range. This study suggests improvement solutions, such as implementing an air temperature between 24.5 and 26.5 °C for higher thermal comfort and increasing the window-to-wall ratio to utilize natural daylight. These findings provide insights into the design of new libraries and the renovation of existing ones, ensuring that libraries continue to serve as vibrant centers of knowledge and learning for generations to come.