# Improving the Energy Efficiency of an Existing Building by Dynamic Numerical Simulation
## 4 Simulations and Scenarios  
Designbuilder is a powerful tool for building simulation, using EnergyPlus software for energetic simulations, natural lighting, comfort, and CO\({}_{2}\) emissions. The architecture is built in 3D with a high matching level with the real building with its envelope (walls, windows, basement), as well as its interior zones. Introducing the building thermal zones, it is a very important step because we can introduce different temperatures for every created zone.  
After the construction of the architecture, presented in Figure 2, the next step is to choose the HVAC scheme's components from Designbuilder library [18] and to correlate then in order to create the real existing scheme, from the initial studied case. Figure 6 shows the heating and hot water supply systems scheme used in Designbuilder for the initial case.  
Figure 4: Thermal image from the living room, from the inside of the house.  
Figure 5: Thermal image from outside, ground floor area.  
For the retrofit case of the house, the following scenarios were simulated using the Designbuilder tool:  
Scenario 1: The retrofit of the building's envelope opaque components. The 'before' and 'after' of the envelope's retrofit thermal performances are listed in Table 1. The exterior walls are partially insulated, so a mean thermal resistance is listed in the table; but in the simulation measured, the mean for each element was considered.  
Scenario 2: As in Scenario 1, adding the exchange of well-insulated windows presented in Figure 7. For the heating system, there were not changes made. The wood fueled boiler was used to cover the hot water demand.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Envelope’s Component**} & \multicolumn{2}{c}{**Thermal Resistance [m\({}^{2}\)K/W]**} \\ \cline{2-3}  & **Initial Case** & **Retrofit Case** \\ \hline Insulated wall & 2.81 & 5.63 \\ \hline Not insulated wall & 0.91 & 5.63 \\ \hline Last floor ceiling & 0.92 & 5.11 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Thermal resistance for exterior walls.  
Figure 6: (a) Heating of the initial case with wood boiler and radiators in Designbuilder; (b) Domestic hot water initial scheme in Designbuilder.  
Scenario 3: Same as above--adding two flat solar panels, of 2 m\({}^{2}\) surface each, were used for hot water supply.  
Scenario 4: Adding thermal solar panels and photovoltaic panels (monocrystalline of 1.5 kW\({}_{\rm P}\) installed power, on grid type), to cover total on-site electric sources, for the retrofit envelope's case. Additionally, the envelope of the house is thermally insulated, the purpose being to obtain low energy consumption for the studied house.  
These scenarios were taken into consideration, to be able to apply for the funding of the National Environmental Program (AFM), to improve energy efficiency of buildings. These funds are obtained only by reducing energy consumption and CO\({}_{2}\) emissions, according to fixed levels imposed. Therefore, exploratory simulations using dynamic software are needed; later on, economic analysis for the investment is easier to obtain.