## 2 Materials and Methods
### Assumptions Made in Building Energy Modelling  
As previously mentioned, energy simulations of the reference house with the HVAC system were performed in DesignBuilder software. Below are selected assumptions related to modelling the building and indoor environment:  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Total** & **North** & **East** & **South** & **West** \\ \hline Gross Window–Wall Ratio [\%] & 38.87 & 28.49 & 50.23 & 33.85 & 45.07 \\ \hline Ground Wall Area [m\({}^{2}\)] & 261.08 & 69.54 & 61.00 & 69.54 & 61.00 \\ \hline Window Opening Area [m\({}^{2}\)] & 101.48 & 19.81 & 30.64 & 23.54 & 27.49 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Wall area and window–wall ratio.  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Parameter** & **Year** & **Winter Period** & **Warm Period** \\ \hline \multicolumn{4}{c}{**Bialystok**} \\ \hline Outside dry-bulb temperature [\({}^{\circ}\)C] & 6.87 & 0.36 & 13.38 \\ \hline Wind velocity [m/s] & 2.53 & 2.94 & 2.12 \\ \hline Wind direction [\({}^{\circ}\)] & 175.00 & 188.51 & 161.49 \\ \hline Direct normal solar irradiance [W/m\({}^{2}\)] & 38.95 & 16.38 & 61.52 \\ \hline Diffuse horizontal solar irradiance [W/m\({}^{2}\)] & 51.63 & 23.61 & 79.66 \\ \hline \multicolumn{4}{c}{**Kiruna**} \\ \hline Outside dry-bulb temperature [\({}^{\circ}\)C] & \(-1.15\) & \(-8.44\) & 6.15 \\ \hline Wind velocity [m/s] & 3.79 & 3.88 & 3.69 \\ \hline Wind direction [\({}^{\circ}\)] & 187.19 & 187.10 & 187.28 \\ \hline Direct normal solar irradiance [W/m\({}^{2}\)] & 45.58 & 21.30 & 69.85 \\ \hline Diffuse horizontal solar irradiance [W/m\({}^{2}\)] & 41.56 & 9.16 & 73.96 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Monthly averages of meteorological data describing the climatic conditions.  
* The simulation period was one year, and the calculations used meteorological data for TMY--POL_BIALYSTOK_IMGW and SWE_KIRUNA_IWEC--Kiruna [28];
* It was assumed that 4 people lived in the reference building;
* Schedules for occupant behaviour were implemented as typical for residential spaces;
* Blinds with highly reflective slats placed inside provided shading for the windows;
* Activity in the form of light manual work, clothing thermal resistance in summer--0.5 clo, and in winter--1 clo were assumed in order to estimate the PMV index;
* Linear controlled lighting was used. It consisted of a linear change in artificial lighting intensity depending on the change in daylight intensity;
* Energy-saving lighting was used: \"surface-mount\" type with a visible fraction of 0.84 and a normalised power density of 2 Wm\({}^{2}\)-100 lux; In the case of HVAC system modelling, shown in Figure 4, the following assumptions were made:  
* Mechanical ventilation with heat recovery with an efficiency of 0.7 at design flow and 0.75 at 75% airflow;
* A ground-source heat pump was used to heat the building with an average COP of around 4;
* The rooms were cooled using a single-speed DX cooling coil with a gross rated COP coefficient of 3;
* The set air temperature during heating was 20 \({}^{\circ}\)C in the rooms and 24 \({}^{\circ}\)C in the bathroom, while the cooling process started when the air temperature exceeded 25 \({}^{\circ}\)C;
* Underfloor heating system made of pipes with an internal diameter of 13 mm and regulated by variable flow.  
Figure 4: Diagram of the HVAC system used in the reference building (_scrawshot from DesignBuilder software_).