## 3 Simulation Results and Discussion
### Comparison of Five Representative Cities
The explanation for that unexpected finding lies in that, given its higher thermal conductivity, granite induced a greater heat flow from the water circuit to the indoor space than wood. As a result, as the thermal comfort graph  
Figure 8: Energy demand and UA-value of outer enclosures for the dwellings of Moscow; in the part of the curve with a sharp increase in demand, around 35 kWh/m\({}^{2}\), a sudden rise of the outer enclosure UA-value occurs due to the increase in the glazing percentage from 15% or 30% to 80%. This change would induce the steep rise observed. for Yakutsk shows, granite delivered more hours of comfortable conditions than wooden floors, a difference that was more noticeable in dwellings with few comfort hours. The general observation from these demand curves is that the properties of wooden flooring are of little significance in cases where the monthly heating demand of a dwelling is under approximately 40 kWh/m\({}^{2}\), apparently irrespective of the city involved. In general, the differences observed in the four values (mean, maximum, and minimum for wooden floors and that for granite floor) in the comfort graph are somewhat greater than the demand graph. In dwellings with the greatest number of comfort hours, largely those where demand was lowest, the values for the wooden floors differed only slightly from those found for the granite floor, and in some cases performed slightly better. As the number of hours at comfortable temperatures declined, the dwelling demand increased, and that difference widened, particularly in the coldest cities. Granite floors exhibited more comfort hours than wood in those dwellings. In short, in dwellings with a greater number of comfort hours, the properties of the flooring in radiant heating systems are of relatively little importance. The choice of wood would have a marginal impact on comfort conditions, and some wooden floorings may be better than granite in this respect. At fewer comfort hours, the flooring properties had a greater impact, with granite performing better than wood, although as a rule wood floors could be found that would deliver comfort levels close to those of granite. More specifically, in mild and moderate climates, the number of comfort hours did not fall sharply as we move to buildings with a greater demand, the difference found being less than 2 or 3 h per day until reaching a point when there was a sharp decrease, typically for corner and badly insulated dwellings with the highest energy demand. In these climate zones, both wooden and granite floors comply with the minimum requirement established here of 14 h per day in practically all the dwellings, with the exception of those with the highest demand, where wooden floors were found to present under 14 comfort hours. Thus, the choice of a wooden floor may be important. In zones with the coldest and most severe climate, there was a steeper decrease in the number of comfort hours in the buildings with a greater demand, although the granite floor complied with the minimum requirement of 14 comfort hours in nearly all the buildings, except in the most severe climate, where it was not able to maintain comfort levels in the dwellings with the highest energy demand. In contrast, only the correct choice of wood flooring would provide a similar number of comfort hours to the granite floor in these climates. When the start-up lag time was close to 10 h in the dwellings with the lowest demand, the differences between the wooden and granite floors were small. As the lag time lengthened, the gap between the maximum and minimum values for the wooden floors and between those and the granite floor values widened. Nonetheless, some wood floors exhibited lag time values close although not equal to granite. An overview of the data in Figure 7 shows that:  
The properties of the flooring scarcely affect the energy demand in the following cases:  
* Dwellings located in climates with moderate or mild winters. * The vast majority of dwellings in cold climates.