Editor’s note: FM Perspectives are industry op-eds. The views expressed are the authors’ and do not necessarily reflect those of Facilities Management Advisor.
For facilities managers, sustainability is no longer optional. Modern buildings are engineered to meet stringent energy-efficiency standards, using advanced materials and construction techniques to minimize heat loss and reduce carbon emissions. From low-emissivity (low-E) windows to reflective coatings and insulated walls, every component is designed to seal the building envelope tighter than ever before.
According to the U.S. Department of Energy, low-E glass can reduce energy loss by up to 50% compared to standard windows, but studies have also shown these coatings can block up to 70-90% of cellular signal frequencies (particularly in the 700 MHz–2.6 GHz range used by carriers).
Therefore, as energy performance improves, another challenge has quietly emerged inside many “green” buildings: poor wireless connectivity. Tenants and staff increasingly rely on mobile devices, Wi-Fi networks, and building management systems to operate efficiently. But those same energy-efficient materials that keep conditioned air inside are also remarkably good at keeping wireless signals out.
This paradox has become one of the defining issues of the modern-built environment, where comfort and sustainability sometimes come at the expense of connection.
When the Building Envelope Blocks the Signal
Wireless signals, whether for cellular, Wi-Fi, or emergency communication, travel as radio frequency (RF) waves. These waves can easily pass through open air, but every material they encounter either absorbs, reflects, or weakens the signal to some degree. Modern construction compounds these effects.
Low-E windows, for instance, use microscopic metallic coatings to reflect infrared energy and keep interiors cool. Those same coatings also reflect portions of the RF spectrum used for 4G, 5G, and public safety radios. Concrete and steel, both staples of durable, sustainable design, further attenuate the signal as it passes through floors and walls. Even radiant barriers, roofing membranes, and specialized insulation can contribute to dead zones where wireless service drops or fails entirely.
These signal losses add up. In many newly constructed or renovated facilities, it’s common for exterior cellular coverage to drop 20 to 40 decibels once inside, a difference large enough to make a strong outdoor signal unusable indoors. The result is a building that performs beautifully on energy metrics but struggles to deliver the seamless connectivity that occupants expect.
Operational and Safety Implications
The consequences of weak indoor connectivity extend beyond convenience. For facilities managers, unreliable signal coverage can disrupt nearly every aspect of building operations.
Employees experience dropped calls and slow data speeds, impacting productivity and customer service. Smart building systems, such as connected lighting, security, and environmental controls, may lose communication with cloud platforms or fail to report critical data. Tenants may experience inconsistent Wi-Fi in conference spaces or lobby areas, leading to frustration, complaints, and eventually, decreased satisfaction that could affect lease renewals.
Most importantly, public safety communications can be affected. Firefighters, police, and emergency medical personnel depend on radio systems to coordinate responses during incidents. Many jurisdictions now enforce coverage requirements for these systems under the International Fire Code (IFC) and National Fire Protection Association (NFPA) standards. The NFPA 1225 and IFC Section 510 updates in recent years have tightened enforcement, requiring testing of public safety radio coverage in most new or substantially renovated buildings. Several Authorities Having Jurisdiction (AHJs) now mandate annual recertification to maintain occupancy permits. If a facility’s construction materials block those frequencies, the building could fall out of compliance or require costly post-construction retrofits to restore signal reliability.
In short, the same energy-saving materials that make a building greener can have an unintended consequence—make it less resilient in emergencies and less functional in day-to-day operations.
Bridging the Gap Between Efficiency and Connectivity
Fortunately, facilities managers don’t have to choose between sustainability and signal strength. The two goals can coexist when connectivity is treated as a core building system rather than an afterthought. Below are some best practices:
- Engage early in the design process. Connectivity planning should begin alongside architectural and mechanical design, not after occupancy. Early RF modeling and site surveys can predict where coverage gaps may occur and help facilities managers and consultants identify the right mix of technologies to address them.
- Incorporate RF-friendly materials where feasible. Some glass manufacturers now offer RF-transparent low-E coatings that preserve both thermal efficiency and signal permeability. Strategic placement of windows with these coatings or ensuring certain sections of the façade allow signals to penetrate can make a measurable difference in performance.
- Implement distributed systems for consistent coverage. Distributed antenna systems (DAS) or small-cell networks can amplify and distribute carrier signals throughout large or shielded buildings. Similarly, enterprise Wi-Fi networks and public safety radio systems can be designed to operate reliably even in dense or reflective environments. These solutions are now considered best practice for facilities exceeding certain size or material thresholds.
- Test and maintain regularly. Even well-engineered systems degrade over time. Routine RF testing, particularly after renovations or tenant fit-outs, ensures that connectivity remains consistent across all occupied areas.
By integrating these strategies, facilities managers can create environments that are both energy-efficient and digitally connected—buildings that conserve resources without isolating the people and technologies inside them.
The Connected Future of Sustainable Design
As the built environment evolves, the intersection of green building and digital infrastructure will only grow more important. Future-ready facilities will be defined not just by how efficiently they use energy, but also by how effectively they support communication, safety, and occupant experience.
Balancing these priorities requires collaboration across disciplines. Industry leaders increasingly describe this as the next evolution of sustainable design. As one real estate CEO recently commented, “Sustainability is no longer just about reducing carbon, it’s about enabling the human and digital systems that make buildings work.” Architects, engineers, sustainability consultants, and wireless specialists must work together to ensure that design decisions enhance both performance and connectivity.
When that balance is achieved, energy-efficient buildings can truly live up to their promise: sustainable, resilient, and connected spaces that meet the needs of every occupant, from the first responder to the everyday smartphone user.
Craig Gillespie is the CEO of Airtower Networks, which designs, installs, and operates custom 5G cellular, Wi-Fi, private LTE, and emergency responder radio networks across various industries. Gillespie has been active in the real estate and facilities management markets for more than 20 years, specializing in technology and services. Before joining Airtower, he served as managing director of MRI Software’s Occupier division. Previously, he was the CEO of Manhattan Software.