## 3 Economic Profitability Analysis of GERO Perforated Bricks with Mortar Doped with Olive Stones  
The economic, social and environmental assessment is based on the previous research of [PERSON] et al. [24]. This research studies the replacement of two sheets of GERO brick with conventional mortar (11.5 cm thick) for another mortar brick containing ground olive stone as substitute for fine aggregate in percentages of 5% to 15% replacement [24]. The facade is modelled for a newly constructed building, based on a building typology of RESIDENTIAL IN BLOCK recognized in model 6.2 of the document \"Energy rating of existing buildings of the IDAE--Institute for diversification and energy saving of Spain\" [45]. This building with an exterior facade of 988.50 m\({}^{2}\) complies with the current construction requirements of the Technical Building Code in Spain in terms of limiting energy demand for air conditioning. Table 5 shows the energy savings per m\({}^{2}\) of facade as a function of the percentage of substitution of ground olive stones as fine aggregate. The results are extracted from the research of [PERSON] et al., from the multiple energy simulations in the different climatic zones existing in Spain [24]. Considering the average seasonal performance of the air-conditioning machines (300% in aerothermal, 100% in condensing gas boilers, 75% in biomass boilers) which provide the final useful energy required in the building, the heating and cooling demand is calculated as the final energy saved by the consumer per m\({}^{2}\) of facade. The results of the energy savings are shown in Table 6. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Final Energy kWh Reduced per m\({}^{2}\) of Facade**} \\ \hline
**Power Source** & \
\begin{tabular}{c} **Air-Conditioning** \\ **System** \\ \end{tabular} &
\begin{tabular}{c} **Seasonal Average** \\ **Yield** \\ \end{tabular} & **Doped Mortar 5\%** & **Doped Mortar 10\%** & **Doped Mortar 15\%** \\ \hline Electricity & Aerothermal & 300\% & 0.143 & 0.185 & 0.219 \\ Natural Gas & Condensing boiler & 100\% & 0.430 & 0.554 & 0.658 \\ Ground Olive Stone & Biomass boiler & 75\% & 0.573 & 0.739 & 0.877 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Energy savings per m\({}^{2}\) of facade depending on the air-conditioning system and its stationary coefficient. Figure 5: Example of perforated GERO brick. The main advantage of these final energy savings is that they occur throughout the life of the building. Thus, each year there will be an economic saving equivalent to the energy saved multiplied by the average price of the energy source paid by the final consumer. On the other hand, taking into account that the data are linked to a 23 cm thick facade, the cost increase per m\({}^{2}\) of facade with two sheets of perforated GERO brick (11.5 cm each) is calculated in Table 7. As such, the value of the cost increase that exists when doping 1 m\({}^{3}\) of mortar with ground olive stone is used (see Table 4). From this price, we obtain what would be the price increase of 1 m\({}^{3}\) for a facade using GERO perforated bricks. And finally, this value is converted to the economic increase for 1 m\({}^{2}\) of facade using GERO perforated bricks. These values are those that must be recovered in order to achieve amortization of the initial investment. For this purpose, an economic profitability analysis is carried out based on the financial indicators NPV (Net Present Value) and IRR (Internal Rate of Return), which allow the analysis and quantification of the possible return on investment. The NPV is determined by discounting the project's future income and expense streams, minus the initial investment. The project is viable if the result of this operation is positive. On the other hand, the IRR is defined as the value of the discount rate that equals the NPV to zero for a given investment project.