## 7 Discussion and Conclusions  
This manuscript has investigated the electromagnetic interference (EMI) shielding properties of various building materials by measuring their shielding effectiveness (\(SE\)), reflection (\(R\)), and absorption (\(A\)) across a frequency range of 1 GHz to 9 GHz. The findings reveal that the shielding effectiveness of materials is a composite outcome influenced by both reflective and absorptive properties. Materials like mineral wool (MW), hardened polystyrene (PT), extruded polystyrene (PE), and polyurethane board (PUR) showed minimal \(SE\) and \(R\), indicating limited shielding capability, which was further corroborated by their low absorption (\(A\)) values that remained around the measurement uncertainty level. In contrast, materials with a more substantial structure, such as brick wall (BW), brick wall filled with mineral wool (BW-MW), and concrete wall, demonstrated superior EMI shielding properties. These materials not only showed high \(SE\) values but also displayed significant electromagnetic wave absorption (\(A\)), particularly at higher frequencies. It is noteworthy that while these materials exhibited similar trends in \(SE\) and \(R\), their absorption capabilities varied, with concrete wall exhibiting the highest absorption followed by BW-MW and BW. During the measurements, there were instances where significant deviations occurred at certain specific frequencies, diverging from the range of other measured values. As a result, a test measurement was conducted on a brick material with a thickness of 30 cm, focusing on the vicinity of the problematic frequency with smaller steps. Figure 10 shows that even with reduced frequency steps, fluctuations only occurred at one measurement point (at one frequency). For this reason, these problematic spots were removed from the measurement results and replaced with values from the surrounding measurement points. This removal of problematic points was performed to prevent distortion of the shielding effectiveness and electromagnetic wave reflection curves, smoothing out the course of shielding effectiveness and reflection of the electromagnetic waves--Figure 11. This elimination was carried out only when a single value was problematic, not when fluctuations occurred over a wider frequency range. Approximately 1-2 data points for each dependency of SE or R of the electromagnetic waves were removed. The manuscript outcomes are significant for the selection of materials for EMI shielding applications. The trend of increasing SE and A with frequency suggests that materials' shielding properties may be optimized for specific frequency ranges. This is particularly relevant in an era where the frequency spectrum of devices is broadening, and the need for effective EMI shielding is critical in ensuring device performance and compliance with regulatory standards. Moreover, the observed plateau in R values for BW within the 6 GHz to 9 GHz range, which did not translate to a similar trend in absorption, highlights the complex interplay between different mechanisms of EMI shielding. This suggests that while reflection con  
Figure 11: Modified data. Figure 10: The dependency of shielding effectiveness (SE) on frequency—a detail from the measurement results. tributes to SE, absorption plays a critical role in the attenuation of electromagnetic waves, particularly at higher frequencies where wave penetration can be more pronounced. The close similarity in absorption trends for BW-MW and concrete wall materials, despite their different compositions, indicates that material density and structural properties may have a more pronounced effect on absorption than material type alone. This underscores the potential for composite materials to provide enhanced EMI shielding through a combination of reflection and absorption. In conclusion, this study advances the understanding of EMI shielding by dissecting the contributions of reflection and absorption to overall shielding effectiveness.