## 4 Results and Discussion
### Life Cycle Assessment (LCA) Results  
The graphs present the results of LCA comparing two scenarios: the current state (SDF) and a refurbishment scenario (RIQ) achieved through the installation of photovoltaic panels. The evaluation has been conducted over a 30-year analysis period per square meter of gross floor area (GFA) to assess the cost-effectiveness of energy efficiency measures in the short to medium term. The results indicate that introducing photovoltaic technology leads to substantial reductions in all environmental impact parameters evaluated.  
The first diagram (Figure 16) compares the environmental impacts of each indicator in percentage terms relative to the first baseline scenario. From this overall assessment, it is possible to demonstrate a substantial reduction in environmental impact in the retrofitted scenario (RIQ) compared to the baseline (SDF). The photovoltaic system significantly decreases the global warming potential (GWP) by 33.44%. Furthermore, reductions are observed across other impact categories: ozone depletion potential (ODP) (11.60%), acidification potential (AP) (28.57%), eutrophication potential (EP) (22.84%), formation of ozone in lower atmosphere (FO) (17.78%), and primary energy demand (PE) (26.11%).  
The second graph (Figure 17) depicts the environmental impacts in each life cycle assessment (LCA) stage, with each color representing a specific analysis phase. In this way, it is possible to obtain a detailed comparison of the contributions from each phase under the current state (SDF) and the refurbishment scenario (RIQ) enabled by photovoltaic panel installation. In the SDF, the operational stage (indicated in blue) contributes a significant  
Figure 16: Environmental impacts in terms of GWP, ODP, AP, EP, FO, and PE for each of the two evaluated scenarios—\(\copyright\) authors.  
portion of the overall impact. With the introduction of photovoltaic panels in the RIQ, there is a significant reduction in the environmental burden associated with energy consumption in each parameter evaluated: GWP by 33.43%, ODP by 11.60%, AP by 28.57%, EP by 22.84%, FO by 17.78%, and PE by 36.11%. Part of the reduction in environmental impacts avoided through the use of electricity generated by photovoltaic panels is offset by the higher emissions resulting from the extraction and production processes required for panel manufacturing (A1-A3): GWP by 0.80%, ODP by 13.06%, AP by 0.82%, EP by 1.82%, FO by 2.73%, and PE by 0.65%. In addition, the environmental impacts associated with maintenance are also higher in the RIQ, as the service life of the photovoltaic panels has been considered to be 20 years, which is shorter than the evaluation period (30 years). As a result, maintenance accounts for 2.69% of GWP, 15.44% of ODP, 1.97% of AP, 2.74% of EP, 5.96% of FO, and 2.73% of PE. These data underscore the importance of durability in assessing environmental impacts at the building scale, particularly when incorporating components with a lifespan shorter than the building in which they are installed [64]. However, the increase in environmental impacts from the product stage (A1-A3) and use stage (B4-B5) remains lower than the reduction occurring in the operational stage (B6), underscoring the environmental benefits of retrofitting existing high-energy-consuming structures with photovoltaic panels.  
In addition to the significant reduction in environmental impact demonstrated through the LCA, it is worth emphasizing that the energy retrofitting of structures such as poultry tunnels can strengthen the economic competitiveness of agricultural enterprises and contribute to the vitality of rural areas [65], in line with the considerations introduced in Section 1.1.  
This phenomenon has also been observed by other authors and is well established within the scientific debate, within which this study positions itself [66; 67].