## 4 Research Methodology
### Materials and Boundary Conditions  
The building envelope's materials used in this study, with their thickness and basic hydrothermal characteristics (thermal conductivities \(\lambda\) and water vapour diffusion resistance factor \(\mu\)), are shown in Table 2.  
Figure 7: Floor plan with position of technical systems. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Building Element** & **Layer (Internal to External)** & **Thickness [cm]** & \(\lambda\) [W/m-K] & \(\mu\) [-] \\ \hline Gypsum plasterboard & 1.25 & 0.25 & 8 \\ \hline Gypsum plasterboard & 1.25 & 0.25 & 8 \\ \hline Glass wool & 5 & 0.037 & 1.10 \\ \hline Vapour barrier & 0.015 & 0.50 & 230,000 \\ \hline Oriented strand board (OSB) & 2.20 & 0.13 & 50 \\ \hline Glass wool & 15 & 0.035 & 1.10 \\ \hline OSB board & 2.20 & 0.13 & 50 \\ \hline Stone wool & 8 & 0.034 & 1.10 \\ \hline Weather barrier (watertight, vapour open) & 0.20 & 0.50 & 5 \\ \hline Intensively vented air layer & 4 & contribution neglected & contribution neglected \\ \hline HPL cladding & 0.80 & contribution neglected & contribution neglected \\ \hline Gypsum plasterboard & 1.25 & 0.25 & 8 \\ \hline Stone wool & 5 & 0.035 & 1.10 \\ \hline Stone wool & 8 & 0.035 & 1.10 \\ \hline Vapour barrier & 0.015 & 0.50 & 230,000 \\ \hline OSB board & 2.20 & 0.13 & 50 \\ \hline Glass wool & 15 & 0.032 & 1.10 \\ \hline DHF board & 1.50 & 0.10 & 11 \\ \hline Weakly vented air layer & 2 & 0.30 & 1 \\ \cline{2-5}  & & 0.12 & 1 \\ \cline{2-5}  & Sheet metal & 0.05 & 50 & 1,000,000 \\ \hline Laminate & 1 & 0.13 & 50 \\ \hline OSB board & 2.20 & 0.13 & 50 \\ \hline Stone wool & 2 & 0.036 & 1.10 \\ \hline Vapour barrier & 0.015 & 0.50 & 230,000 \\ \hline OSB board & 2.20 & 0.13 & 50 \\ \hline Glass wool & 15 & 0.035 & 1.10 \\ \cline{2-5}  & OSB board & 2.20 & 0.13 & 50 \\ \cline{2-5}  & Bitumen waterproofing & 0.50 & 0.23 & 50,000 \\ \cline{2-5}  & Extruded Polystyrene (XPS) & 8 & 0.034 & 140 \\ \hline
**Additional** & **Description** & \(\lambda\) [W/m-K] & \(\mu\) [-] \\ \hline Steel & For LSF and perimeter columns and beams & 50 & 1,000,000 \\ \hline Polyvinyl Chloride (PVC) & Window subframe & 0.57 & 50,000 \\ \hline air\_gap\_1 & Chamber in the windowsill & 0.14 & 1 \\ \hline air\_gap\_2 & Chamber in the windowsill & 0.28 & 1 \\ \hline air\_gap\_3 & Chamber in the windowsill & 0.17 & 1 \\ \hline air\_gap\_4 & Chamber in the windowsill & 0.43 & 1 \\ \hline Window & Window & 0.165 & 50,000 \\ \hline Window insulation & Thermal insulation around window subframe & 0.038 & 1.10 \\ \hline Air in steel column & Air in reinforced vertical support and drainage pipe & 0.6812 & 1 \\ \cline{2-5}  & (corner of two walls) & & \\ \hline Air in steel beam & Beam support around the perimeter of the floor & 0.5456 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Building envelope assemblies—material thickness and basic hygothermal properties. The contribution of an intensively vented air layer in the external wall to the thermal resistance of the entire wall was disregarded. Modelling of other air layers inside the thermal envelope (roof, window subframe, drainage pipe, etc.) was performed using EN ISO 6946 [34], considering the equivalent thermal conductivity of a solid (Table 2). Additionally, the vapour barrier, weather barrier, and waterproofing layer were ignored as per recommendation from [35] for layers with a thickness less than 1 mm. Regarding the surface heat transfer coefficients needed for numerical calculations, they were taken according to [34]. The values of these coefficients, depending on the type of surface (external or internal) and the heat flow direction, are shown in Table 3. The same boundary conditions were used across the whole paper. Boundary conditions set for the external and internal environment are shown in Table 4, and they are in line with EN ISO 10211 [35]. The temperature of the external environment (\(-10^{\circ}\)C) also corresponds to the air temperature of the coldest day in the continental climate of Croatia.