*2.4. Design and Distribution of Surveys*

The survey was designed to collect information and votes from occupants in order to comprehensively assess the environment in conjunction with the measurement of the physical parameters. The survey design was based on the experience of previous research [16,17,60,61,65] with the aim to collect data with an objective approach. The completion of the survey took around 20 minutes per classroom, being distributed during the measurement campaigns, and were performed twice per day both in a winter and a midseason day.

The survey distributed included questions about the following issues (the specific layout of the questionnaire is presented in Appendix A):

	- Sensation: Thermal sensation vote (TSV) using the 7-points ASHRAE scale.
	- Preference: Thermal preference vote (TPV) using the 7-points ASHRAE scale.
	- Acceptance: Thermal environment rejection percentage (PDacc) from 0 (rejection) to 1 (acceptance).
	- Level of comfort: Thermal comfort vote (TCV) from 4 (extremely uncomfortable) to 0 (comfortable).
	- -Difficulty concentrating (DC).
	- -Dry throat (DT).
	- -Dizziness (D).
	- -Itchiness (I).
	- -Dry skin (DS).
	- -Nausea (N).
	- -Nasal congestion (NC).
	- -Eye irritation (EI).
	- -Headache (H).
	- -Chest oppression (CO).
	- -Tiredness (T).

The perception of the hygrothermal environment was formulated to the occupants according the protocol established in the Spanish version of Standard ISO 10551 [66].

The clothing insulation values worn by the occupants were obtained from the surveys and subsequently quantified according to EN ISO 9920 [67] and EN ISO 7730 [23], considering the corrections proposed by Havenith et al. [68] for seated occupants, with a thermal insulation of clothing (Icl) lower than 1.84 clo and air velocities under 0.15 m/s.

In addition, the protocol for the analysis of the surveys included a screening for the exclusion of the sample when the participant had previous and subsequent symptoms, related health problems, were developing some sickness, were taking medication for a long time, or when a strange answer was found for the multiple choices of a given question. In this way, during the measurements, a total number of 977 valid surveys was obtained (Table 4).


**Table 4.** Students participating in the survey campaign according to season and sex.
