*2.3. Field Measurements*

The measurement campaign was developed in the selected classrooms according a data collection protocol [16,17,60] in which physical parameters relating to hygrothermal comfort, CO2 concentration, and illuminance were obtained in a spatial matrix [61] previously and throughout the survey distribution period (30 min, twice per day), taking the average of the values obtained, both outdoor and indoor, as can be seen in Figure 3 and Table 2:

**Figure 3.** The 3-D array of measurement points superimposed in a multipurpose classroom. Red dots show values at 0.6 m, dark red dots at 1.7 m, orange dots represent measures in the room's envelope, and blue dot is the window.


**Table 2.** Acquisition points per physical parameters measured.

During the measurements both the initial state and the operation of doors, windows, solar devices, heating systems, and electric lighting, as well as changes in the occupants' distribution, were collected. Performance and uncertainty of measurement instrumental are described in Table 3:



<sup>1</sup> The instruments for hygrothermal measurements listed comply with the requirements of ISO 7726 standard [62] for class C (comfort).

Mean radiant temperature (*tr*, in ◦C) was calculated using Equation (6) [63]:

$$\overline{t\_r} = \left[ \left( t\_\% + 273 \right)^4 + \frac{1.10 \cdot 10^8 \cdot \upsilon\_a^{0.6}}{\varepsilon \cdot D \lg^{0.4}} \cdot \left( t\_\% - T\_a \right) \right]^{\frac{1}{4}} - 273,\tag{6}$$

where *va* is air velocity (in m/s), Ta is dry bulb air temperature (◦C), *tg* is black globe temperature (◦C), ε is emissivity (dimensionless, 0.95 for black globe), and Dg is globe diameter (m).

The operative temperature (to, in ◦C) was obtained through Equations (7) and (8) [64]:

$$\mathbf{T\_o = A \times T\_a + (1 - A) \times \overline{t\_r}}\tag{7}$$

$$\mathbf{A} = \begin{cases} 0.5 & \text{if } \mathbf{V\_a} < 0.2 \text{ m/s} \\ 0.6 & \text{if } 0.2 \text{ m/s} \le \mathbf{v\_a} < 0.6 \text{ m/s} \\ 0.7 & \text{if } 0.6 \text{ m/s} \le \mathbf{v\_a} < 1.0 \text{ m/s} \end{cases} \tag{8}$$

where va is air velocity (in m/s), Ta is dry bulb air temperature (◦C), and tg is black globe temperature (◦C).
