## 2 Method
### Life Cycle Cost Calculation Method
#### 2.1.2 Model Inputs
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Baseline**} & \multicolumn{2}{c}{**OAT**} \\ \hline
**Category** & **Parameter** & **Unit** & **Value** & **Source** & **Range** & **Source** \\ \hline
**Operation** & * District heating & EUR/MWh & 69.29 & & 18–128 & \\ (Energy supply) & * Gas & EUR/m\({}^{3}\) & 0.796 & DEA [33] & 0.635–0.913 & Database \\  & * Electricity & EUR/MWh & 230.1 & & 210–330 & min/max \\  & * Electricity-HP & EUR/MWh & 93.54 & & - & \\ \hline
**Implementation** & * DH sub-station & EUR/system & 15,600 & & 12–20 K & \\  & * Gas boiler & EUR/unit & 24,600 & TDC [34] & 20–30 K & TDC [25] \\  & * Heat Pump & EUR/unit & 249,000 & & 235–265 K & \\  & Root-mounted PV & EUR/system & 80,300 & TDC [35] & 49.5-134.2 K & Assumed \(\pm\)20\% \\  & Ex. wall insulation & EUR/m\({}^{2}\) & 20.7 & & 17–25 & \\  & Ex. wall cladding & EUR/m\({}^{2}\) & 17 & & 13–20 & \\  & New windows & EUR/m\({}^{2}\) & 73 & & 69–88 & Assumed \\  & Attic insulation & EUR/m\({}^{2}\) & 130 & & 104–156 & \(\pm\)20\% \\  & Pipe network ins. & EUR/m & 11.8 & & 9–14 & \\  & Circulation pump & EUR/unit & 1098 & & 879–1318 & \\ \hline
**Maintenance** & * DH sub-station & EUR/year & 136 & & 108–189 & \\  & * Gas boiler & EUR/year & 651 & TDC [34] & 531–814 & TDC [25] \\  & * Heat Pump & EUR/year & 1650 & & 1070–2850 & \\  & Roof-mounted PV & EUR/year & 1144 & TDC [35] & 781–1342 & TDC [26] \\  & Ex. wall insulation & EUR/year & 551 & & 440–660 & \\  & Ex. wall cladding & EUR/year & 894 & & 715–1072 & \\  & Windows & EUR/year & 1147 & & 918–1376 & Assumed \\  & Attic insulation & EUR/year & 228 & & 1814–2722 & \(\pm\)20\% \\  & Pipe network ins. & EUR/year & 373 & & 298–447 & \\  & Circulation pump & EUR/year & 11 & & 9–13 & \\ \hline
**Lifespan** & * DH sub-station & year & 25 & & 20–30 & \\  & * Gas boiler & year & 25 & & 25–40 & TDC [25] \\  & * Heat Pump & year & 20 & & 15–25 & \\  & Roof-mounted PV & year & 30 & TDC [35] & 25–40 & TDC [26] \\  & Ex. wall insulation & year & 50 & & 40–60 & \\  & Ex. wall cladding & year & 120 & & 95–145 & \\  & Windows & year & 50 & & 40–60 & Assumed \\  & Attic insulation & year & 50 & & 35–65 & \(\pm\)20\% \\  & Pipe network ins. & year & 80 & & 65–95 & \\  & Circulation pump & year & 25 & & 20–30 & \\ \hline
**Amount** & * District heating & MWh & 483.37 & & 387–580 & \\  & * Gas & m\({}^{3}\) & CC & calculated & & Assumed \\  & * Electricity—DH and gas & MWh & 51,072 & BE18 & 41.6–62.4 K & Assumed \\  & * Electricity—HP & MWh & 216.8 & & & \\   Ex. wall insulation & m\({}^{2}\) & 2660 & & & 2128–3192 & \\  & Ex. wall cladding & m\({}^{2}\) & 2660 & & 2128–3192 & \\  & Windows & m\({}^{2}\) & 1570 & Measured & 1256–1885 & Assumed \\  & Attic insulation & m\({}^{2}\) & 1750 & & 1400–2100 & \\  & Pipe network ins. & m\({}^{2}\) & 3160 & & 2528–3792 & \\ \hline \hline \end{tabular}
\begin{tabular}{c c c c} \hline \hline  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of input parameters. at the building, collected during an energy audit described in [29]. The energy demand is calculated by the Danish compliance tool BE18 and already accounts for energy savings, which were achieved by the implementation of the renovation package and the energy produced by the roof-mounted PV [28]. The improved building element (m\({}^{2}\); m; piece) is determined through documentation and building audit, presented in [29]. The lower and upper bounds for the uncertainty range of the different parameters are shown in Table 1. Unit cost for represented energy sources is determined from available data in the price database published by the Danish Energy Agency (DEA) [33] in 2018. The granularity of the different energy supply sources differs for DH, gas, and electricity. The baseline model's district heating unit cost is determined by averaging the available data for 392 different locations across Denmark (2018 database). Electricity unit cost data are available as annual values, categorized with respect to usage type (household or industry) and consumption range.