## 3 Simulation Description
### Radiant Floor Layout and Material Properties  
The flooring design applied in the simulations, depicted in Figure 6, was patterned on a typical radiant heating system that could be likened to layouts A and C in European standard 1264-1 [34], as noted earlier. The thermal properties of all except the covering (outer-most layer), which is described below, are listed in Table 2. The pipe wall thermal resistance was excluded from the simulations as negligible compared to the resistance of the surrounding mortar and insulation. The values for the thermal properties listed in Table 3 were drawn from an analysis of a number of commercial wood types used in flooring, specifically the types recommended for radiant floors by manufacturers such as Finsa, Pergo, Haro, Meister, and Junckers. Some of those manufacturers recommend a thermal resistance maximum of 0.15 m\({}^{2}\)K/W for coverings, whereas Spanish standard UNE 56810 on specifications for wood floors [66] sets the limit at 0.17 m\({}^{2}\)K/W. The thermal resistance was consistently under 0.15 m\({}^{2}\)W/K in all the commercial floors analysed, while the thermal conductivity ranged from 0.10 W/m\(\cdot\)K to 0.15 W/m\(\cdot\)K for the thicknesses listed (Table 3). Inasmuch as wood is a natural product, its characteristics vary, depending on its species and origin, the individual tree, or even the position of the wood in the trunk of a given tree. Thermal conductivity depends on several parameters, including microstructure, moisture and temperature, along with wood density [67; 68], which is also related to most other physical and mechanical properties [69; 70], including thermal conductivity. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Thermal Conductivity** & **Density** & **Specific Heat** \\  & **W/(m\(\cdot\)K)** & **kg/m\({}^{3}\)** & **J/(kgK)** \\ \hline Felt & 0.033 & 90 & 1000 \\ \hline Mortar & 1.8 & 2100 & 2000 \\ \hline Insulation & 0.033 & 30 & 1200 \\ \hline Waffle slab & 1.22 & 1090 & 1000 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Thermal properties of materials comprising the radiant floor. Figure 6: Radiant flooring layout. The behaviour of possible wood coverings was analysed after compiling information from previous studies on density and thermal conductivity in temperate hardwood (oak, beech, ash, maple, walnut, cherry), softwood (pine, spruce, larch), and tropical wood (iroko, teak, jatoba, Merbau, awong). Denser natural species were not investigated. On the grounds of the aforementioned inter-relationship between thermal conductivity and density, five mean densities were adopted based on the values found in previous studies (400 kg/m\({}^{3}\), 500 kg/m\({}^{3}\), 600 kg/m\({}^{3}\), 700 kg/m\({}^{3}\) and 850 kg/m\({}^{3}\)) with a view to covering a wide spectrum of wood properties. Three possible thermal conductivity values (consistent with earlier findings [14]) were assigned to each density, calculated from the mean conductivity values and standard deviations reported in previous studies [32; 71; 72; 73; 74; 75; 76; 77; 78; 79; 80], as well as from the commercial high thermal conductivity materials listed above. The findings are plotted in Figure 7, where the red dots denote the values adopted in this study. The fifteen thermal properties of the wood plotted in Figure 7 were each simulated for four thicknesses (10 mm, 15 mm, 19 mm, and 22 mm), yielding a total of 60 wood coverings. A further simulation was run for a high-conductivity reference, a granite floor characterised by a thermal conductivity of 3.50 \(W\)/(m\(\cdot\)K), a density of 2850 kg/m\({}^{3}\), and a specific heat of 1.0 kJ/(kg\(\cdot\)K), for comparison. This inclusion brought the total number of radiant floors simulated to 61.