# Retrofitting a Building's Envelope: Sustainability Performance of ETICS with ICB or EPS
## 6 Discussion and Conclusions  
The results of this study show that external wall alternatives of ETICS with ICB are environmentally advantageous when producing the construction materials used, in terms of the categories \"Global Warming Potential\" (GWP) and consumption of nonrenewable primary energy (PE-NRe) in comparison with the same solution with EPS. If ETICS with ICB and with EPS are compared considering the same thickness, the EPS solution requires lower energy consumption to fulfil the heating and cooling needs of the flat due to its lower U-Value. This solution always presents a lower \"Cradle to Cradle\" (C2C) cost because of its lower acquisition cost. If two solutions with similar U-values are compared (but with different thicknesses, since the ICB boards require a bigger thickness due to the higher thermal transmittance), the consumption of energy to satisfy the heating and cooling needs is almost the same, but their acquisition cost and the energy and resources necessary for the production of their materials are different. Due to the higher cost of ICB, the EPS solution always presents a lower net present value (NPV). The 3E-C2C analysis showed that reference alternatives only perform better in the economic dimension, and only for an energy consumption to fulfil less than 25% of the heating and cooling needs. Therefore, to provide more specific support for decision-making, Tables 6 and 7 present, respectively, single-leaf and cavity external wall solutions with the best performance (in each dimension and life-cycle stage), without considering the reference walls. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Approach** & **C2C Life-Cyde** & **Performance** & **Heating and** & **Best** & **Difference to the Best** \\
**(I.CA)** & **Stages Considered** & **Aspects** & **Coiling Needs** & **Performance/Design** & **Alternative Using the** \\ \cline{3-6}
**GWP** & A1–A3; A4; A5; B2–B4; C2–C4 & & & & & 22\% (WE2) \\
**PE-NRe** & and D, without energy use for heating and cooling & Environmental & - & W2 & 30\% (WE2) \\ \cline{3-6}
**GWP** & & & 10 & W27 & 2\% (WE2) \\ \cline{3-6}
**GWP** & & & 30 & & & \\
**A1–A3; A4; A5; B2–B4; B6; C2–C4 and D & Environmental & & 50 & & W27/WE2 \\ \cline{3-6}
**PE-NRe** & & & 10 & & & 4\% (WE2) \\ \cline{3-6}
**WLC** & A1–A3; A4; A5; B2–B4; B6; C2–C4 and D & Economic & & 25 & & 6\% (W7) \\ \cline{3-6}
**WLC** & C4 and D & & 35 & & & 5\% (W7) \\ \cline{3-6} \cline{3-6}  & & & 50 & & & 4\% (W7) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Single-leaf external wall solution with the best performance, without considering the reference wall (the colour of each row depends on the best performing solution for each indicator: Brown for ICB and blue for EPS). When comparing the single-leaf external wall solutions in the study, it was found that solution W9 presents the best environmental performance if energy use for heating and cooling is not considered (Table 6). At the same time, when taking into consideration the energy used for heating and cooling, W7 shows the best environmental performance. The most economical solution is WE7 for energy needs higher than 10%. When comparing the cavity wall solutions, it was found that solution W9 presents the best environmental performance if energy use for heating and cooling is not considered (Table 7). When taking into consideration the energy used for heating and cooling, the best environmental performance is shown by W14. For energy needs higher than 10%, the most economical solution is WE14. The research presented in this paper provides an advance to current state of art by including all the life-cycle stages and dimensions of the LCA in the analysis of solutions for energy renovation of building envelopes. The analysis presented here can be replicated in other solutions for thermal insulation of the building's envelope, or similar solutions applied in other buildings or weather conditions (namely other countries).