# Energy Demand and Supply Simultaneous Optimization to Design a Nearly Zero-Energy House
## 3 Results
### Financial Objective--Sequential Optimization and Energy Demand
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Parameter** & **Unit** & \begin{tabular}{c} **COST-** \\ **OPTIMAL** \\ \end{tabular} & **MIN\_EP** & **MAX\_EP** & \begin{tabular}{c} **MAX** \\ **Global Cost** \\ \end{tabular} \\ \hline \multirow{8}{*}{\begin{tabular}{c} Building \\ Parameters \\ \end{tabular} } & Thermal resistance of the & \multirow{2}{*}{\
\begin{tabular}{c} Thermal resistance of the \\ outwall insulation \\ \end{tabular} } & [m\({}^{2}\)K/W] & 2.7 & 12.6 & 0.9 & 16.2 \\  & Thickness of the outwall massive layers & [m] & 0.1 & 0.5 & 0.1 & 0.3 \\  & Thermal resistance of the roof insulation & [m\({}^{2}\)K/W] & 1.8 & 13.5 & 0.9 & 16.2 \\  & Thermal resistance of the slab insulation & [m\({}^{2}\)K/W] & 2.7 & 3 & 0.9 & 10.8 \\  & Vertical window type (south Grade) & [-] & & Double glazing with air & \\  & Vertical window type (east–west–north) & [-] & Triple glazing, low-e with air & Double glazing with air & \\  & Road window types & [-] & & Triple glazing, low-e with Argon & \\  & Ground floor window width & [m] & 2.2 & 2.2 & 4.6 & 7.8 \\  & (south, height = 2.15 m) & [m] & 0.2 & 0.2 & 6.2 & 5.6 \\  & (south, height = 0.8 m) & [m] & 0 & 0 & 1.2 & 4.8 \\  & Roof window height (width = 2.3 m) & [m] & 153.61 & 97.67 & 225.00 & 122.06 \\ \hline \multirow{4}{*}{
\begin{tabular}{c} Results \\ \end{tabular} } & Primary energy consumption & [kWh/m\({}^{2}\)] & 153.61 & 97.67 & 225.00 & 122.06 \\  & Net annual heating demand & [kWh/m\({}^{2}\)] & 89.12 & 47.14 & 138.66 & 50.02 \\  & Net annual cooling demand & [kWh/m\({}^{2}\)] & 6.88 & 7.56 & 11.74 & 29.12 \\  & Net DHW annual demand & [kWh/m\({}^{2}\)] & 14.37 & 14.37 & 14.37 & 14.37 \\  & Gas volume consumption & m\({}^{3}\) & 1762.52 & 1110.58 & 2531.83 & 1155.24 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Values of parameters of the resulting cost-optimal point and of other significant points. Concerning the transparent envelope, window type 1 (double glazing with air) was selected as optimal for south-oriented openings, of which the dimensions were reduced to their minimum. The highest performing window type (triple glazing, low-emissive with argon) was optimal for other openings. For this cost-optimal building configuration, the annual heating and cooling demands were equal to 89.12 kWh/m2 and 6.88 kWh/m2, respectively. This low cooling demand was coherent with the resulting optimal parameter values that were set so that the cooling demand was reduced. As mentioned, the amount of nonrenewable primary energy consumption was quite high (almost 154 kWh/m2, according to the primary energy conversion factors provided by the Italian legislation), but it was not surprising, as (in this phase) the modelling of the technical systems was not considered and reference values and efficiencies for systems were used without contributions from renewables. When comparing the set of resulting cost-optimal values to the other highlighted significant points, high values of insulation, together with high-performance glazing, led to the lowest primary energy consumption, which simultaneously increased the associated global cost, and vice versa. This also emerged from another type of result representation, reported in Figure 5. The grey profiles represented the entire set of evaluated design alternatives, while profiles representing significant points were highlighted in colors. One of the main advantages of the simulation-based optimization method here adopted was that it was not a deterministic method, providing a single solution as the final output of the whole optimization process, but it allowed exploring the space of the solutions in which it could be possible to find solutions that fit the problem better than the one selected by the optimization algorithm. This was particularly possible in the neighborhood of the resulting optimum, where it was possible to find different design alternatives leading to a very small increase in the objective function with respect to the minimum.