The Covid pandemic brought to the fore in a compelling way the issues of ventilation of indoor spaces where people gather together. The aim of the current research topic is to investigate the possibilities and control techniques of natural ventilation to improve indoor air quality and by doing so, to limit the spread of airborne infections such as Covid-19. The research focuses on the study and comparative evaluation of alternative natural ventilation scenarios for school buildings with the main objective of removing pathogenic particles and minimizing virus transmission. Due to the high concentration of students the classrooms are of special study interest compared to other gathering places e.g. offices.

The study starts with an overarching presentation of the natural ventilation techniques as well as with an analysis of the special challenges and requirements that the Covid-19 pandemic brought in the context of indoor ventilation design.

In the following, existing international and local standards/recommendations for natural ventilation in educational buildings are presented, followed by international school building cases in which natural ventilation systems and air flow control techniques have been implemented in order to improve indoor air quality.

Our research has simulated and evaluated four alternative natural ventilation scenarios for a typical classroom considering air renewal rate, flow direction and energy consumption as the main performance criteria. To model and simulate the scenarios the DesignBuilder software has been used.  For a more accurate representation of the airflows CFD (Computer Fluid Dynamics) analysis techniques have been additionally applied using the corresponding functionality of the same software tool. The results include 3D airflow as well as age of air (local mean age - LMA) contours.

Based on the analysis of the simulation and CFD results, the best scenario in terms of Covid prevention is the “displacement ventilation” one that creates an effective airflow leveraging temperature differences and the effect of buoyancy. We are presenting the advantages and challenges of the preferred approach and proposing further optimization via dynamic control of flows through sensors. Final target should be the setup of a "smart natural ventilation control strategy" that not only improves air quality and reduces spread of airborne Covid contagion but as well ensures thermal comfort and energy efficiencies.