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Public Summary

Poor indoor air quality in schools can impair students' cognitive abilities. The Dutch government has taken several steps to combat this issue, including establishing the LCVS team (Landelijk Co枚rdinatieteam Ventilatie in Scholen), allocating funding through the SUVIS (Specifieke uitkering ventilatie in scholen) program, and equipping schools with low-cost CO2 meters. The ECoS-IAQ project is a part of that program, which aims to improve indoor air quality (IAQ) in schools by proposing new strategies for improving performance of ventilation systems in Dutch schools.

This study explores the concept of ventilation effectiveness as a strategy to improve IAQ in classrooms. It demonstrates the potential of improving ventilation effectiveness rather than merely increasing airflow rates to meet indoor air quality needs. Taking the concept of ventilation effectiveness to define relevant performance indicators for the assessment of the effectiveness, the research compares two major room ventilation strategies that can be applied to address the IAQ in classrooms, displacement, and mixing ventilation. Computational Fluid Dynamics (CFD) simulation is used to analyse these strategies, based on a selection of the placement of supply and exhaust in the classroom.

The findings reveal that displacement ventilation systems create a more uniform air distribution horizontally, at head level, reducing the need for a multi-zone approach. However, the mixing ventilation systems showed a clear division of the classroom into two main zones. One zone was located near the ventilation units, and the other was on the opposite side of the room. The zone near the ventilation units had a longer mean age of the air, indicating a less efficient circulation of fresh air compared to the displacement ventilation systems. The outcomes are sensitive to the supply conditions in the case of applying a mixing ventilation solution. It emphasizes the importance of considering a multi-zone concept when designing mixing ventilation systems, avoiding the design of single supplies to achieve a mixing situation.

The research underscores the impact of external temperatures on the age of air within the room for the displacement concept, especially in areas close to windows. This is particularly crucial in areas near cold surfaces, such as windows in the winter.

Apart from the ventilation effectiveness, thermal comfort needs to be achieved, in this case mainly focused on the draught rate as this can significantly affect the comfort and well-being of students seated in areas where draught or large temperature gradients result from the ventilation concept applied.

The research also investigates the concept of multizone demand control based on air quality. For mixing ventilation, it suggests that, through the distribution of supplies, different ventilation rates could be applied in the identified zones. This approach could enhance indoor air quality and potentially reduce energy consumption.

However, the study has limitations, as only an extremely limited number of cases could be investigated. Furthermore, the modelling requires several assumptions and simplifications that depart from reality. These notions have to be taken into account when analysing the outcomes and design guidance, however, can be extended by analysing more cases, and parameters within the case, through the method as applied.The findings of this thesis contribute to the ECoS-IAQ project, which aims to arrive at effective solutions to address the complex IAQ problem in Dutch schools and provide a design guidance for ventilation engineers and designers.

Funded by: TKI & Eindhoven Engine: 鈥淓fficient Comfortable School Indoor Air Quality (ECoS-IAQ)鈥�