A comprehensive assessment of indoor environmental conditions is performed on a
representative sample of classrooms in schools across southern Spain (Mediterranean climate) to
evaluate the thermal comfort level, thermal perception and preference, and the relationship with
HVAC systems, with a comparison of seasons and personal clothing. Almost fifty classrooms were
studied and around one thousand pool-surveys distributed among their occupants, aged 12 to 17.
These measurements were performed during spring, autumn, and winter, considered the most
representative periods of use for schools. A new proposed protocol has been developed for the
collection and subsequent analysis of data, applying thermal comfort indicators and using the most
frequent predictive models, rational (RTC) and adaptive (ATC), for comparison. Cooling is not
provided in any of the rooms and natural ventilation is found in most of the spaces during midseasons.
Despite the existence of a general heating service in almost all classrooms in the cold period, the use
of mechanical ventilation is limited. Heating did not usually provide standard set-point temperatures.
However, this did not lead to widespread complaints, as occupants perceive the thermal environment
as neutral—varying greatly between users—and show a preference for slightly colder environments.
Comparison of these thermal comfort votes and the thermal comfort indicators used showed a better
fit of thermal preference over thermal sensation and more reliable results when using regional ATC
indicators than the ASHRAE adaptive model. This highlights the significance of inhabitants’ actual
thermal perception. These findings provide useful insight for a more accurate design of this type of
building, as well as a suitable tool for the improvement of existing spaces, improving the conditions
for both comfort and wellbeing in these spaces, as well as providing a better fit of energy use for
actual comfort conditions
