Energy efficient window opening for air quality control in classrooms

The aim of the present work was to study how to maximize indoor environmental quality and energy performance in classrooms, when having different ventilation alternatives combined with a visual CO2 feedback. In this effort, in heating and cooling seasons, field experiments were carried out in pairs of naturally and mechanically ventilated classrooms during normal school hours with and without CO2 sensors that provided a green/yellow/red visual indication.

At the end of each week children reported their perceptions and symptoms using a questionnaire. The classroom temperature, humidity and CO2 levels were continuously measured together with the outdoor conditions. Magnetic sensors recorded opening of windows and classrooms energy usage was recorded by the meters installed on water-based radiators.

An energy simulation model was created in IDA-ICE-4 to reproduce and compare energy demands/performance. With the CO2 feedback more windows were open and the levels of CO2 were reduced, as expected. As a consequence of more windows opened in this condition the energy use for heating in winter was increased and for cooling in summer reduced.

Results show that split-cooling in summer can have negative effects on air quality when no CO2 feedback is installed, as less windows are opened then suggesting temperature as the main factor causing window opening. Children reported that they liked to use the CO2 feedback, with their perceptions and symptoms somewhat improved when feedback was installed but the results did not reach statistical significance.

To improve indoor air quality in schools, CO2 feedback was shown to be an effective tool in naturally ventilated classrooms.