Hybrid ventilation feasibility in Finnish schools - Case studies and outlook

Abstract

Hybrid ventilation is uncommon in Finnish buildings, particularly in schools, owing to the cold climate and the predominance of mechanical ventilation systems. This study evaluates the indoor air quality (IAQ) and ventilation performance, as well as the feasibility of hybrid ventilation, in a selected classroom of four mechanically ventilated Finnish schools in Espoo, using a measurement-driven analytical framework. A year-long dataset of IAQ sensor data from the case schools and outdoor climate data were analysed, together with classroom and ventilation schedules, to estimate the Natural Ventilation Opportunity Index (NVOI) for each school. The findings indicate that hybrid ventilation was not necessarily needed to improve IAQ, as all classrooms recorded only a negligible period during which CO2 levels exceeded 1000 ppm. However, Natural Ventilation Opportunity (NVO) based on outdoor climate triggers yielded 16.6%-18.7% potential air handling unit (AHU) fan-energy savings for the year across all four classrooms. The study concludes that integrating smart hybrid ventilation could reduce energy consumption in Finnish educational buildings. The study concludes with an outlook on the practical implications of adopting artificial intelligence (AI) hybrid ventilation control strategies in cold-climate educational buildings.