Indoor Temperature and CO2 in Educational Buildings during a Pandemic Winter in Spain

Schools had covered special attention in the last year, due to their importance to organize daily work as well as since most of the children were still not vaccinated. Under this circumstance, the importance of air renewal to reduce the probability of COVID-19 contagion inside buildings was highlighted. 
In Spain, educational buildings usually lack mechanical ventilation systems, so renovation of air is generated through the direct opening of windows. In such a way that its effectiveness can be analysed under winter conditions by the measurement of indoor CO2 concentration and temperature. The work presented analyses both parameters: temperature and CO2 data, monitored in 66 classrooms of 27 educational buildings in different climatic regions in Spain, during the winter of 2020-2021. According to the results, a modification of the thermal comfort conditions was observed with the increase of ventilation rates. The latter caused a decrease of CO2 concentration and indoor temperatures, but also an increase of the energy demand that heating systems could not meet.  
This paper provides an analysis of the data recorded during this difficult period in these classrooms, with the aim of highlighting the need for renovation of these buildings, which have enormous potential for improving their resilience, energy efficiency and indoor environmental quality.