## 4 Conclusions  
This work evaluated the potential energy savings derived from applying extended set point ranges for temperature and RH during unoccupied periods in a surgical suite of a Spanish hospital. Accordingly, simulations of different ventilation scenarios were performed with a dynamic energy model of the whole suite, calibrated and validated with experimental data from two different periods in 2019. The core findings of this investigation are as follows.  
The calibrated model is able to predict the thermal response of the suite with satisfactory accuracy, both during periods with surgical activity where the outdoor airflow intake is completely conditioned to maintain the current working conditions, and during off-use hours, where the range for the indoor air temperature was widened to 15-30 \({}^{\circ}\)C and the RH was not controlled.  
Simulation results reveal that the actual annual energy demand of the surgical suite may be reduced by up to 50% by applying the aforementioned extended set point ranges and maintaining the current ventilation conditions. This is a recommendation that is not included in the Spanish standard, but in the French standard. Further, if the indoor recirculation rates were increased according to the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) standard, that is 80% instead of the 0% currently applied, the energy savings could be increased up to 70%.  
The safety of the indoor environment is not compromised under any of the studied scenarios as they are based on the recommendations given by internationally recognized standards on the design of HVAC systems for surgical areas. In addition, the simulation outcomes show that no condensation issues occur during a typical year under the studied ventilation and hygothermal conditions.  
The starting time for the HVAC system to provide the required hygothermal conditions at the beginning of the occupied periods is found to be less than one hour when the outdoor temperature is above 5 \({}^{\circ}\)C. This is due to the high number of ACH considered in all scenarios.  
Conceptualization, J.L.L.-G., A.G.-G.; data curation, A.C.-R., J.L.L.-G., A.G.-G.; formal analysis, A.C.-R., L.F.-G.; funding acquisition, P.E.-O., E.G.-A.; investigation, A.G.-G., L.F.-G.; methodology, A.C.-R., J.L.L.-G., A.G.-G.; project administration, P.E.-O., [PERSON]-A.; resources, J.L.L.-G., E.G.-A.; software, A.C.-R., L.F.-G.; supervision, J.L.L.-G., P.E.-O., [PERSON]-A.; writing original draft, A.C.-R., A.G.-G., L.F.-G.; writing review and editing, A.C.-R., A.G.-G., L.F.-G., P.E.-O. All authors have read and agreed to the published version of the manuscript.  
This research was funded by his research was funded by the project SMARTHERM (RTI2018-096296-B-C21) by the Spanish Government (Science, Innovation and Universities Ministry) and the project INDENA (IN852A 2018/59) funded by the program CONECTA PEME (FEDER-GALCIA 2014/2020).  
Figure 19: Potential energy savings by applying the ventilation requirements of different scenarios.  
**Acknowledgments:** The authors acknowledge the General Manager of the Regional Public Health Care System of Galicia (SERGAS) for authorizing this research and the publication of its results.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.