## 1 Introduction  
One of the goals of buildings is serving as a refuge for people from external climate conditions by using Heating, Ventilation and Air-Conditioning (HVAC) systems. However, using them excessively could decrease the capacity of people to adapt to the variations of the ambient temperature in a physiological and psychological way [1]. On the other hand, the effects from climate change are becoming more and more significant each year. Climate change originated by the decisions taken by human beings without considering their environmental impact [2]. Taking as a reference the surface temperature from the pre-industrialperiod, the temperature could increase between values close to 2.5 \({}^{\circ}\)C in 2050, 4.5 \({}^{\circ}\)C in 2100, 7.5 \({}^{\circ}\)C in 2200, and 8 \({}^{\circ}\)C in 2300 [3]. With the need to regulate the emission of pollutant gases and the resource depletion, it is established that the building sector reduces the greenhouse gas emissions by 90% by 2050 [4]. Based on the poor energy performance of buildings [5] and users' behaviour [6], data show that the total energy consumption between 30% and 40% [7], and the 40% of greenhouse gas emissions correspond to the building sector [8; 9]. Currently, the European standard EN 19798-1:2019 is the basic legal framework that regulates the indoor environmental parameters for thermal environment, indoor air quality, lighting and acoustics in buildings; as for the first topic, the standard recommends lower and upper set-point temperatures for both heating and cooling, depending on three categories of buildings. Heating setpoints range from 16 to 21 degrees for heating and from 25.5 to 28 degrees for cooling in the main residential and living spaces; an additional fourth category may exceptionally find application in spaces that do not meet the former criteria. The main energy conservation measures are usually the improvement of envelopes and the improvement of HVAC systems. Nevertheless, to avoid significant economic investments, as occurs with these energy conservation measures, the rational and appropriate use of HVAC systems has been extensively studied by varying setpoint temperatures: (i) [PERSON] et al. [10] used cooling and heating setpoint temperatures of 27.87 \({}^{\circ}\)C and 18.3 \({}^{\circ}\)C, respectively, in an office building located in different cities of United States, obtaining an energy saving between 32 and 73%; (ii) [PERSON] et al. [11] analyzed that an increase of the cooling setpoint temperature between 2 and 4 \({}^{\circ}\)C in an office building in Zurich would generate an annual energy saving of 66%; (iii) [PERSON] et al. [12] observed that cooling setpoint temperatures greater than 25.5 \({}^{\circ}\)C obtained savings in the cooling demand, both in current and future scenarios; (iv) [PERSON] et al. [13] observed that increasing the cooling setpoint temperature by 2 \({}^{\circ}\)C in a field study carried out in an administrative building did not affect the thermal comfort; (v) [PERSON] and [PERSON] [14] used setpoint temperatures of 20 \({}^{\circ}\)C for heating and 26 \({}^{\circ}\)C for cooling, thus generating energy savings of up to 45%; (vi) [PERSON] et al. [15] observed that by applying a series of energy conservation measures, including the decrease of heating and the increase of cooling setpoint temperatures by 1.1 \({}^{\circ}\)C, the energy savings obtained ranged between 12 and 20%. As previously mentioned, these research studies allowed the energy consumption to be reduced by varying the setpoint temperatures, although such setpoints were static (i.e., Predicted Mean Vote Index (PMV)-based). On the other hand, there is an increasing tendency in the number of studies which apply adaptive setpoint temperatures by assigning the value of lower and upper adaptive comfort limits to heating and cooling setpoint temperatures, respectively. This technique is widely used as most of the climate of the planet have possibilities of application in more than 50% of the days of the year [16].