Energy implications of meeting indoor air quality and thermal comfort standards in Mediterranean schools using natural and mechanical ventilation strategies

Educational buildings often face significant challenges with indoor air quality and thermal comfort, mainly due to a lack of mechanical ventilation and air conditioning systems. Research has demonstrated that these issues negatively affect students' learning. The main objective of this paper was to assess compliance with indoor air quality and thermal comfort standards in educational buildings, by quantifying HVAC energy implications under natural and mechanical ventilation strategies. For this purpose, an educational building model that has 4 classrooms occupied by students from different age groups was simulated in 11 Mediterranean climate zones, for 4 ventilation strategies, and with 2 building orientations. The results reveal that natural ventilation is effective only in mild Mediterranean climates, with air quality non-compliance ranging from 0 % to 2 % and thermal comfort non-compliance between 2 % and 5 %. As expected, mechanical ventilation always ensures acceptable indoor air quality and thermal comfort. It achieves average HVAC energy savings of 80 % compared to natural ventilation. When considering that students' CO2 generation rates vary depending on the age, systems with CO2 sensors further reduce HVAC demand (8 %), while maintaining comfort levels. Building orientation was found to have a significant impact for naturally ventilated buildings. South-facing orientations can reduce HVAC energy demand by up to 42 % (1,989 kWh/m2 & sdot;year), whereas mechanically ventilated buildings show minimal sensitivity to orientation (up to 36 kWh/m2 & sdot;year). This research will help public authorities of the educational community and architecture and engineering sectors when they are planning, designing and retrofitting educational buildings. Educational building managers will also benefit from this research by being able to optimise building ventilation through the effective management of existing resources.