# Integration of the Adaptive Approach in HVAC System Operation: A Case Study
## 2 Materials and Methods
### Acquisition, Processing and Preliminary Analysis of Data  
Throughout the study, objective measurements (indoor and outdoor climate) and subjective measurements (thermal preference) were collected simultaneously. The study was carried out over 12 months (July 2023 to June 2024) in order to characterize all the seasons. An array of wireless technology sensors recorded the behavior of the room. The newly acquired sensors were verified prior to the study. A total of 685,152 indoor environmental records (located in Figure 2) and 35,136 outdoor records (Table 2) were collected. Measurements inside the room (temperature, humidity, etc.) were obtained at 10 min intervals. All sensors were new, calibrated, compared with similar sensors under the same conditions, and showed no significant differences in their measurements. Sensors were placed approximately 1 m from the occupants' workstations in order to describe their immediate thermal environment under typical working conditions. Outdoor weather observations were collected from a weather station close to the building [39] and located about 100 m from it, of which outdoor temperature was of the greatest interest. The 2859 working hours during which the users were working in the office were selected, after eliminating weekends, holidays, and intensive working days in July (when \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sensor** & **Number of Sensors** & **Operative Range** & **Accuracy** & **Units** \\ \hline Concentration of particle matter & 1 & 0 to 500 & \(\pm\)10\% & \(\upmu\)g/m\({}^{3}\) \\ CO\({}_{2}\) Concentration & 1 & 0 to 10.000 & \(\pm\)45 + 3\% & ppm \\ Relative humidity & 5 & 0 to 100 & \(\pm\)2\% & \% \\ Air temperature & 5 & \(-\)25 to 70 & \(\pm\)0.3 & \({}^{\circ}\)C \\ Globe temperature & 6 & \(-\)25 to 70 & \(\pm\)0.3 & \({}^{\circ}\)C \\ Temperature in the weather station & 1 & \(-\)50 to 60 & \(\pm\)2\% & \({}^{\circ}\)C \\ Relative humidity in the weather station & 1 & 0 to 100 & \(\pm\)2\% & \% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Data acquisition systems and characteristics. Figure 2: Floor plan of the field study room and sensors’ locations. the room was not used in the afternoon). A total of 1320 valid surveys were collected and were grouped according to the time of day, resulting in the evaluation of 483 declared thermal preferences. At the end of the study, the BMS register was obtained with the HVAC system states. The base setpoint value of the HVAC system applied the adaptive comfort algorithm for the building, in which the running mean temperature was calculated with an alpha of 0.8. The range associated with the adaptive comfort law is represented in Figure 1 by two green dashed lines, which indicate the total width of the comfort zone for the sample period. The same figure shows the behavior of the indoor and outdoor temperatures for the building, together with the comfort zone based on the implemented adaptive law. The range is indicated in its most restrictive form, with a scale of \(+2/-3\)\({}^{\circ}\)C, building category I according to UNE-EN 16798-1 [4]. This more restrictive range was adopted to prioritize perceived thermal comfort in this analysis, considering that even small variations can generate significant responses. Although in the UNE-EN 16798-1 [4] indoor comfort range for the design and evaluation of the energy performance of buildings would be \(+3/-4\)\({}^{\circ}\)C, in [PERSON] et al. [40] a comparative analysis of different adaptive thermal comfort models can be found, in which the most restrictive acceptability percentage corresponds to 90%. These percentages are justified on the grounds that current models cannot accurately predict how an individual will feel on a specific day, so it is not reasonable to expect all users to experience thermal comfort in the same environment, even when it complies with current standards. Based on the BMS register, the HVAC system was required as a punctual measure in 379 h (13.25% of the total active hours of office use).