## 3 Results
### Putting It All Together: Thermal Comfort Control Systems  
All the studies included in this survey feature both a thermal comfort model and a control strategy; thus, it is possible to give a general overview of the analyzed systems and find correlations between the two aspects. Focusing on the two most advanced levels of readiness, which are 90% of the analyzed works, it can be observed that many simulation  
Figure 12: HVAC systems in the analyzed papers. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Reference** & **HVAC** & **H/C** & **Control Variables** & **Building** & **Control** \\ \hline [PERSON] et al. (2021) [154] & Chilled beams & C & \begin{tabular}{c} Chilled water flow rate, room \\ temperature set-point \\ \end{tabular} & Any & MM + O \\ \hline [PERSON] et al. (2020) [155] & Radiant system & H & Room temperature set-point & Any & MPC \\ \hline [PERSON] et al. (2018) [59] & Radiators & H & Indoor air set-point temperature & Any & MM \\ \hline [PERSON] et al. (2018) [136] & Radiant system & H & \
\begin{tabular}{c} Optimized heating curve for heat pump \\ flow temperature \\ \end{tabular} & Residential & MPC \\ \hline [PERSON] et al. (2018) [60] & Radiant system & Any & PMV & Residential & MM \\ \hline [PERSON] and [PERSON] (2017) [131] & Radiators & H & Radiator valve position & Any & MM \\ \hline [PERSON] et al. (2021) [98] & Radiant system & H & Heating/cooling device status & Any & MM \\ \hline [PERSON] et al. (2018) [156] & Radiators & H & Thermostat set-point & Any & MM + O \\ \hline [PERSON] et al. (2021) [132] & Chilled beams & C & Pump speed; valve opening & Office & MPC + RB \\ \hline [PERSON] et al. (2020) [157] & Radiators & Any & Indoor temperature & Any & MPC + ML \\ \hline [PERSON] et al. (2019) [158] & Baseboard radiators & H &
\begin{tabular}{c} Hourly room set-point temperatures in \\ typical days \\ \end{tabular} & Residential & MPC \\ \hline [PERSON] et al. (2019) [71] & Radiators & H & Room temperature set-point & Office & O \\ \hline [PERSON] et al. (2019) [72] & Radiant system & C & State of radiant coil valves & Office & MPC \\ \hline [PERSON] and [PERSON] (2018) [123] & Radiant system & Any & Supply water set-point & Office & ML + O \\ \hline [PERSON] (2018) [104] & Radiators & H & Thermostat set-point & Residential & RB \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Hydronic heating (H) and/or cooling (C) systems in the analyzed literature. studies used PMV thermal comfort models and MPC (Figure 13). The choice of a standard thermal comfort model and a complex control system indicates that the focus was on the latter aspect in these studies. Switching to papers presenting prototypes, purely rule-based systems prevail in conjunction with non-PMV comfort models, which can be explained with the trend to use real data to define the thermal comfort preferences of the occupants. Contrary to simulations, here, a generally simple control strategy was chosen, with a considerable effort invested in thermal comfort evaluation. Figure 14 qualitatively illustrates the composition of model complexities. Here, PMV and adaptive methods are defined as \"simple\" thermal comfort approaches. \"Simple\" control-related methods include RB, MM, and the combination of the two. Many works can be observed with simple thermal comfort model and complex control systems (quadrant \"S-C\"), and they are mainly at a simulation level. On the other hand, most of the works with complex thermal comfort approaches and simple control methods (quadrant \"C-S\") are prototypical. It is worth noting that \"simple\" in this context does not mean \"simplistic\", but it, rather, indicates a basic approach (for example, standardized, or not requiring high-level algorithmical skills).