Archetypes of public secondary schools in Mediterranean climate. Indoor air quality and comfort field studies

Climate change is a growing global concern and building stock, in particular, is responsible for the emission of greenhouse gases, largely due to its poor energy efficiency. This problem is especially serious in educational buildings, where it is necessary to encourage energy efficient retrofitting under the parameters of nearly Zero Energy Building (nZEB), an objective which in Europe has been set for 2050. This is expected to produce economic, energy saving, hygrothermal comfort and health-safety benefits. In addition, the recent COVID-19 pandemic has shown the advisability of adding to the retrofit aims, ensuring good indoor air quality in spaces with high occupancy density and long stays, not only as a health and hygiene measure but also to minimize the socio-economic and labor repercussions associated with disruption to face-to-face teaching activity. 
In recent years, field studies focused on environmental and energy conditions in educational centers have intensified. However, the selection of the study sample does not usually respond to statistical considerations. The first and principal objective of this work is to develop a database of public Secondary Education Centers (school ages between 14-18 years) in Andalusia, a large region covering the southern Spanish area of the Mediterranean zone, and to identify the archetypes that should be included in the study sample. The second main objective is to carry out a field study, in winter conditions, in a selection of the centers that conform to these archetypes, in order to ascertain the conditions of hygrothermal comfort and indoor air quality in the current pandemic situation. 
In order to meet the first objective, a multi-parametric statistical analysis has been carried out which includes typological, constructive and operational characteristics as well as climate zoning. To achieve the second objective, several variables of environmental comfort and indoor air quality are monitored in the classrooms of the schools selected. Multifunction measurement equipment with sensors is used for indoor air temperature, indoor relative humidity, levels of CO2 and particulate matter (PM). 
The analysis of the database shows that approximately 41% of the public Secondary Education Centers in Andalusia were built before 1979, prior to the implementation of the first regulations on energy efficiency in Spain, while 53 % were built between 1979 and 2006, with regulations that are far from the nZEB requirements. The solution used in 95 % of the centers is natural ventilation, failing to comply with current regulations in Spain and compromising the air quality inside the classrooms when thermal comfort conditions cannot be achieved naturally. The statistical analysis according to different parameters of a study sample of 200 centers resulted in the selection of 39 archetypal centers, 6 of which were distributed to represent each climate zone in Andalusia and selected as the subjects of field studies on indoor air quality and thermal comfort. The results show predictably good indoor air quality as a result of the Covid continuous natural cross-ventilation protocol, but also good thermal comfort due to the unusually high winter temperatures.