## 3 Simulation Results and Discussion
### Effect of Thermal Resistance
In those with a mild winter (La Paz), the slope was shallow, while it was steep in those with harsher winters (Yakutsk), where the minimum comfort conditions were not met at thermal resistance values greater than 0.10 m\({}^{2}\) K/W. The worst-performing dwellings (Series 2) exhibited behaviour similar to that observed for the mean except that the downward slope was steeper. In Moscow, once a given resistance value was exceeded (around 0.20 m\({}^{2}\) K/W), the number of comfort hours in this group of dwellings dropped to zero, and in Yakutsk the number was zero at all thermal resistance values. Finally, regarding the start-up lag time, in the case of the best-performing (Series 1) and mean (Series 3) dwellings, greater thermal resistance induced an increase in the number of hours needed to reach the set-point temperature, although the slope varied with winter severity, increases being more substantial in cities with a severe winter climate. In all the cities, the rise in the mean value was steeper for all dwellings than for those with the best thermal performance. Certain anomalies were detected in the mean values in Moscow and Yakutsk, where the number of hours decreased slightly before increasing again. The explanation lies in the fact that the mean value for a given thermal resistance was calculated only for dwellings where the set-point temperature was reached within the first 72 h (limit time period used in the start-up lag time simulations). Since with rising thermal resistance fewer dwellings met that condition, the relative weight of the best performing dwellings rose, causing the mean lag time to decrease slightly with rising thermal resistance. In the worst-performing dwellings (Series 2), rising thermal resistance had a significant impact on the number of hours required to achieve comfortable conditions. Above a certain resistance value, the set-point could not be reached within the 72-h time limit, particularly in the coldest cities. In Moscow and Yakutsk, the set-point was only attained within the specified time in dwellings with the two lowest resistance values, i.e., with the granite floor and with the wood floor with highest thermal conductivity and thinnest wood. The discontinuities observed in this series were explained in detail in Appendix C of the previous research [30]. In these cases, although the radiant floor is in operation, the drop in temperature during the night interrupts the increase in the indoor temperature, resulting in the set-point temperature not being reached until the second or third day, leading to the discontinuities observed. Overall, in the best-performing dwellings, the thermal resistance of wood played a very minor role in the energy demand and thermal comfort, irrespective of climate. In these dwellings thermal resistance was only found to induce a considerable rise in the number of hours needed to reach the set-point during system start-up in the coldest climates. The data for the mean of all the dwellings may be summarised in similar terms, although the thermal resistance of wood had a greater effect on the three parameters. In the worst-performing dwellings, the greater thermal resistance of wood prompted substantial variations in energy demand, thermal comfort, and start-up lag time, especially in the coldest climates. In view of the results, dwellings can always be found in which a wooden floor with any level of thermal resistance provides similar comfort conditions to granite floors, and with similar energy demands. This is even the case in the coldest climates. Referring to mean values, with the exception of Yakutsk, wood floors always provided the required minimum levels of comfort, with very similar performance to granite. These results suggest that there is no justification for rejecting a flooring on the basis of its thermal resistance value. In any event, if it were necessary to choose a thermal resistance limit, a plausible criterion would be to do so according to the mean behaviour of the dwellings in a specific climate.