A comparative study of the indoor environmental quality in renovated and non-renovated classrooms

This paper reports on a comparative study of the indoor environment in two adjacent classrooms, one renovated, and the other non-renovated. The aim of the study was to investigate the positive consequences of renovating classrooms, but also to disclose unanticipated side-effects.
The non-renovated classroom was without mechanical ventilation, fitted with woodwool ceiling plates for acoustics and lighting fixtures with horizontal illuminances of 200-300 lux on the tables.
The renovated classroom was retrofitted with a new acoustic ceiling made from perforated gypsum tiles and suspended lighting fixtures and mechanical ventilation via decentral room unit mounted below the ceiling. The ventilation air was supplied in the void above the acoustic ceiling, which distributes air through perforations and joints in the ceiling to the occupied zone – a concept often referred to as diffuse ventilation. In this setup, the acoustic ceiling also acted as silencer for the ventilation inlet.
Different indoor environmental parameters were comparatively measured in each classroom, including longterm CO₂-concentration, temperature and noise levels as well as reverberation time and technical noise from the ventilation equipment. In all respects, the objective measurements improved in the renovated classroom.
Interviews with pupils and questionnaire surveys were conducted, and – while showing less evidence of the improvements than expected – did indicate increased user satisfaction with the retrofit.