## 6 Conclusions  
As building materials and technologies evolve, modern building envelopes are being designed not just to provide shelter but to enhance comfort, health, privacy, and energy efficiency, while addressing cybersecurity concerns. Frequency-selective surfaces are at the forefront of this evolution, offering a cutting-edge solution for controlling electromagnetic signals within buildings. Over the past decade, FSSs have progressed from research prototypes to real-world applications, with exciting possibilities emerging for urban environments and advanced architectural designs. FSS technology enables buildings or specific rooms to achieve electromagnetic isolation by selectively blocking certain frequency bands while allowing others to pass through. This has significant implications for privacy, security, and comfort. For example, FSSs can block non-essential signals (such as radio amateur transmissions or trunk TV emissions) while allowing critical services like cellular, TV, and radio broadcasting to function uninterrupted. This selective blocking of signals not only helps prevent interference but also improves cybersecurity by shielding WiFi signals from neighboring areas, reducing the risk of external cyberattacks. Moreover, FSSs can be designed to control signal strength, allowing weaker signals to pass while attenuating stronger ones. This is particularly useful in urban environments where strong signals might pose health risks, as FSSs can mitigate potentially dangerous electromagnetic levels while maintaining access to essential services like mobile communication. One of the most promising applications of FSS technology is its potential to harvest electromagnetic energy from blocked signals. Instead of simply reflecting unwanted RF energy, FSS panels can be integrated with energy-harvesting circuits, converting the absorbed electromagnetic energy into usable electrical power. This harvested energy could be used to power low-consumption devices in common areas of buildings, such as lighting or IoT systems, without the need for additional wiring. By complementing traditional energy sources, this approach contributes to energy savings and a more sustainable electricity budget for smart buildings. To fully realize the potential of FSS technology in the construction industry, it is essential to integrate FSS properties into Building Information Modeling (BIM) systems [86]. BIM is a digital representation of the physical and functional characteristics of buildings, used by architects and engineers to design and manage building projects. By adding electromagnetic behavior data to BIM databases, building envelopes can be designed with RF transparency parameters in mind, ensuring optimal performance for wireless communication and energy efficiency. For instance, walls, windows, and other surfaces can be enhanced with metadata detailing their frequency response, transmission, reflection, and absorption properties at different electromagnetic wavelengths. BIM extensions or plugins could simulate how FSS panels interact with wireless signals, enabling designers to optimize signal propagation and mitigate challenges related to signal interference or attenuation. This integration would support the design of smart buildings with improved wireless communication capabilities, reduced electromagnetic interference, and enhanced overall functionality. FSS technology holds immense promise for the future of building design, contributing to electromagnetic isolation, energy harvesting, and improved cybersecurity in modern urban environments. By incorporating FSSs and other RF-transparent materials into BIM systems, architects and engineers can create more efficient, secure, and sustainable buildings that meet the demands of smart city infrastructure. Conceptualization, I.C. and D.A. ; methodology, I.C. and I.E. ; software, I.E. and R.F.S.C. ; validation, M.G.S., A.V., and I.C. ; formal analysis, I.E. ; investigation, I.E. ; resources, M.G.S. ; data curation, I.C. ; writing--original draft preparation, I.E.