## 3 Predicted Mean Vote Index  
The definition and control of indoor thermal environment conditions for reaching the optimal level in buildings are difficult to be established. The heat transfer of the human body is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not exert enough heat, which leads to discomfort [33]. Thermal comfort can be stated as the condition of the mind that expresses satisfaction with the thermal environment in agreement with ANSI/ASHRAE Standard 55 [34]. Similar to ASHRAE Standard 55, there are other comfort standards like EN 15251 [35] and the ISO 7730 standard [36]. However, the PMV model stands among the most disseminated models for evaluating indoor thermal comfort. It was developed using principles of heat balance and experimental data collected in a controlled climate chamber under steady state conditions [37]. The PMV refers to a thermal scale that runs from Cold (\(-3\)) to Hot (\(+3\)) as shown in Figure 1. In addition, \(0\) is the ideal level, considering a comfortable environment recommended by the international standard [38], and the comfort zone is defined within a certain tolerance (\(-0.5\) to \(+0.5\)). Positive values of the PMV indicate warm environments while negative values denote cold environments. Furthermore, the PMV index is mainly influenced by the following six variables from indoor-air and human condition: metabolic rate, clothes' thermal insulation, air temperature, relative humidity, air velocity and mean radiant temperature. Most of these variables can be easily gained through sensors or by means of simple methodologies [39]. However, some variables like metabolic rate and clothes' thermal insulation are difficult to calculate since they are on the basis of the location of people and the season, tabulated values have been procured for them [40]. For example, \(1\) and \(0.5\) are the associated clothing insulation values for the winter and summer season, respectively. Moreover, for a relaxed seated person, the corresponding metabolic rate is fixed to \(1.0\) met. In some research, the mean radiant temperature was assumed to equal the air temperature due to the requirement of multiple sensors and the difficulty of measurement [41]. However, this is not the case of buildings with powerful ventilation or near heating or cooling facilities where deviations between the mean radiant temperature and the air temperature can be bigger with uncertain effects in terms of PMV values [42]. In addition, the mean radiant temperature has a strong variation with the room shape including room height and length [43]. In well-designed low energy buildings, the accuracy of PMV values are acceptable only if the difference between mean radiant temperature and air temperature is less than \(2\)\({}^{\circ}\)C [44]. The PMV index within an indoor environment can be obtained according to Equation (1). Where \(W\) (\(W/\text{m}^{2}\)) is the rate of mechanical work performed by human for the development of a certain task, \(M\) (\(W/\text{m}^{2}\)) is the metabolic rate which measures the human activity level, \(T_{a}\) (\()\) is the air temperature, \(I_{cl}\)\(\left(\text{m}^{2}\cdot\frac{\text{K}}{\text{W}}\right)\) is the clothes thermal insulation and the \(P_{a}\)\((\text{Pa})\) represents the vapor pressure in the indoor air,  
\[ \begin{array}{c}PMV=\left[0.303\cdot e^{-0.036\cdot M}+0.028\right]\cdot\left\{ \left(M-W\right)-3.05\cdot 10^{-3}.[5733-6.99.\right.\\ \left.\left(M-W\right)-P_{a}\right]-0.42\cdot\left(M-W-58.15\right)-1.710^{-5} \cdot M\cdot\left(5869-P_{a}\right)-\\ 0.0014\cdot M\cdot\left(34-T_{a}\right)+\frac{1}{I_{cl}}\cdot\left(T_{cl}-35.7+ 0.028\cdot\left(M-W\right)\right)\right\}.\end{array}