Why is your brand-new office building a Faraday cage?
Roel De Frene
Welcome to the paradox of modern new construction: the more energy-efficient the building, the worse the mobile connectivity.
The physics
Building standards have rightly become stricter in recent years. But what is good for the energy bill is dramatic for radio signals. A few figures every building owner should know:
Low-E glazing (low-emissivity glass with metal coating): 30+ dB signal loss, and that is a conservative value — at mid-band 5G (3.5 GHz) it runs higher.
Triple glazing with double low-E coating: easily 35 to 40 dB loss. For comparison: every 10 dB of loss means 90% of the signal disappears. At 40 dB, only 0.01% gets through.
Metal-foil vapour barriers and PIR insulation boards with aluminium film: reinforce the Faraday effect across the entire facade.
Solar panels on the roof: form an additional reflective layer.
Steel reinforcement in concrete + warehouse sandwich panels: block radio waves in all directions.
Green roofs and external insulation with metal meshes: extra attenuation.
Below is an overview of the typical losses caused by the building, per frequency.
Overview of dB losses per building type per frequency
80% of all mobile data transmission happens inside buildings (Ericsson Mobility Report, via Ookla). Networks have historically been designed "outside-in" — signals travel from outside to inside. That approach simply no longer works with today's building materials.
User experience when the outdoor signal is -75 dB
Overview of mobile reception quality per frequency band
The commercial effect: frustration becomes a contract killer
What happens when a company moves into a building without indoor coverage?
Phase 1 — Frustration (weeks 1–4). Employees complain. Meetings get moved. Someone has to step outside to make a call. IT tries to force wifi calling — works half the time.
Phase 2 — Workarounds (months 2–6). Private hotspots are installed, femtocells requested from providers (long waiting times, limited coverage), 4G cameras freeze up. The productivity cost gradually becomes visible.
Phase 3 — Escalation (months 6–12). The tenant raises the alarm with the landlord. Either the relationship sours, or an expensive retrofit follows (MO-DAS system, small cells) — and the discussion about who pays always turns explosive.
Phase 4 — Departure. The lease is not renewed. The business looks for a building where connectivity IS guaranteed — and is willing to pay 10–15% more rent for that certainty. In a market where commercial real estate is under pressure from hybrid working, this makes the difference between a vacant building and a satisfied tenant with a long contract.
I hear it more and more from the field: "connectivity" now ranks at the same level as parking, charging stations and HVAC in the tenant's requirements list.
Why this is now a real estate issue, not a telecom issue
Until recently, the reasoning of many building owners was: "Isn't that the telecom operator's business?" That is no longer true, for three reasons.
Operators build "outside-in", not "in-building". The macro networks outside are fine, but without active indoor infrastructure that coverage simply no longer passes through your facade.
Wifi calling is not a safety net. It requires per-device configuration, doesn't work for visitors, and is unreliable on many corporate VoIP platforms for critical communication (including 112 emergency calls, which in many European markets are preferably routed over VoLTE).
5G mid-band (3.5 GHz) is the bandwidth that delivers truly fast mobile data, but it has even more trouble penetrating buildings than 4G. As operators phase out 3G (2G is already gone in many markets), the "old reliable" low frequency that still provided some indoor coverage is disappearing.
For a modern business, poor mobile coverage is therefore no longer an inconvenience — it is an operational risk.
The future: IoT makes this exponentially worse
If you're thinking today "my tenant doesn't need heavy connectivity", think ten years ahead. We are moving from buildings with people making calls to buildings with thousands of connected devices per m². Some concrete applications already rolling out:
In offices and retail:
Smart building sensors (temperature, air quality, occupancy per room)
Access control and badge systems on 4G backup
Payment terminals, checkouts, digital signage, fully on 4G
IP cameras with AI analysis (perimeter security, people counting)
Asset tracking for IT equipment and furniture
In warehouses and logistics:
Autonomous AGVs and AMRs (self-driving forklifts, robots) — running on private 5G networks or public 5G with ultra-low latency
Drones for inventory management in high-bay warehouses
RFID and BLE gateways reporting to the cloud in real time
Digital twins combining hundreds of sensors per 1000 m²
Robot arms and cobots with OTA updates
In industrial buildings:
Predictive maintenance on machines (IIoT)
Energy management per machine or production line
Safety equipment (lone-worker detection, lone-worker alarms)
Connected PPE (helmets, safety vests with sensors)
Across all sectors:
EV charging points that bill and manage via mobile connectivity
Smart meters and submetering for ESG reporting
Fire prevention (ASTRID/TETRA, smoke detection with mobile backup)
The number of cellular IoT connections worldwide is estimated at several billions by 2030 (Ericsson, GSMA Intelligence), with the strongest growth in logistics, industry and smart buildings. A building that does not have decent indoor cellular infrastructure today is structurally out of the market tomorrow for the tenants willing to pay the most.
What does this mean for the building owner, developer or real estate investor?
In concrete terms: indoor connectivity is becoming a building utility that you include in the design just like electricity, data cabling, HVAC or sprinklers.
The good news: whoever includes it from day one in the design saves up to 30% on installation costs compared to a retrofit. An in-building cellular system (DAS or hybrid active/passive) typically consists of:
Donor antenna on the roof or fibre connection
Head-end base station or repeater in a technical room
(MO)DAS distributed antenna system via coaxial cable or fibre optics
RF antennas distributed across all floors and zones
Support for multiple operators and frequency bands (4G, 5G, ASTRID/TETRA, private LTE/5G)
For a new-build project this mainly means: providing conduits, power points and a small technical room during the design phase. Antennas are mounted on ceilings — easy with suspended ceilings, complicated with fixed ceilings. A 1/2" coax cable needs to be pulled through the building using stiff cable.
How does Mercuron approach this?
Step 1: Site survey of current indoor and outdoor reception + technical walkthrough
Step 2: RF design to plot every antenna
Step 3: Heatmap simulation of reception after amplification
Step 4: Installation / delivery of passive equipment
Step 5: Evaluation of reception after commissioning of active equipment
Step 6: Annual inspection and remote monitoring of the infrastructure
Request a no-obligation quote today to see how we can help you.