June 4, 2026 · 6 min read · Case Studies
A 30-story building has three connectivity domains: the BMS backbone on BACnet, the floor-level sensors on LoRaWAN, and the basement meters on NB-IoT. None replaces the others. The IoT layer monitors; the BMS controls. The SIM goes where neither the BMS network nor LoRaWAN reaches —sub-basement utility meters, rooftop HVAC units, elevator machine rooms.
A smart building does not have one network. It has three: the BMS backbone (BACnet/IP over structured cabling —controls the chillers, air handlers, and fire panels), the floor-level IoT layer (LoRaWAN sensors for occupancy, CO2, temperature —battery-powered, no wiring), and the cellular penetration layer (NB-IoT for sub-basement water meters where neither the BMS network nor LoRaWAN reaches). The IoT procurement question is not "which one?" It is "which layer for which device, at what cost per data point?"
| Layer | Technology | What It Connects | Power | Cost/Device/Month |
|-------|-----------|-----------------|-------|------------------|
| BMS backbone | BACnet/IP, Modbus TCP | Chillers, AHUs, VAVs, fire panels, main meters | Mains | N/A (wired) |
| Floor IoT | LoRaWAN | Occupancy, CO2, temperature, light, desk sensors | Battery (5-10 yr) | ~EUR 0 (unlicensed) |
| Cellular penetration | NB-IoT / LTE-M | Sub-basement water/gas meters, rooftop HVAC, elevator rooms | Battery (5-15 yr) | EUR 0.10-0.50/SIM/month |
The BMS does not need IoT. It already works. The IoT layer adds data that the BMS was never designed to collect —occupancy patterns per desk zone, CO2 levels per meeting room, energy consumption per tenant floor. The cellular layer covers locations where wiring is impossible (concrete sub-basement, rooftop unit with no structured cabling, elevator shaft).
A water meter in a sub-basement is surrounded by 3 floors of reinforced concrete. A LoRaWAN gateway 15 floors up receives a signal attenuated by 40+ dB through concrete, steel, and electrical conduit. NB-IoT at 164 dB MCL penetrates where LoRaWAN at 155-160 dB link budget does not. For the three water meters, two gas meters, and one district heating meter in the basement: one NB-IoT SIM per meter. EUR 0.10-0.50/month per SIM. No gateway. No wiring. No spectrum license.
The alternative —running BACnet cable from the 30th floor to the sub-basement —costs EUR 500-2,000 in labor and materials per meter. The NB-IoT SIM pays for itself in month one.
Hybrid AI-IoT occupancy systems combining PIR motion, CO2 sensors, and desk-level presence detection achieve 20-40% HVAC energy reduction by dynamically zoning airflow to occupied zones only. A 30-story commercial building spending EUR 500,000/year on HVAC saves EUR 100,000-200,000/year. The sensor network costs approximately EUR 30,000-80,000 to deploy (300-800 sensors at EUR 50-150 each plus gateways). Payback: under 1 year.
The sensors run on LoRaWAN —battery-powered, 5-10 year life, no wiring. One LoRaWAN gateway per 5-10 floors serves 50-100 sensors. The gateway backhauls over the building's existing IP network or over LTE-M if the IT department will not allow IoT traffic on the corporate LAN. The SIM is in the gateway, not in every sensor.
Source: MDPI Energies, "A Systematic Review of Building Energy Management Systems (BEMSs): Sensors, IoT, and AI Integration", December 2025. Available at https://www.mdpi.com/1996-1073/18/24/6522
Three scenarios where the gateway should use LTE-M instead of the building LAN: the IT department refuses IoT traffic on the corporate network (security policy, VLAN complexity), the building has no existing IP infrastructure in the target zone (rooftop, parking garage, basement), or the deployment is a retrofit where running Ethernet to each gateway location costs more than the gateway and SIM combined.
For these cases: one LTE-M gateway with multi-IMSI SIM routes LoRaWAN sensor data to the cloud over cellular. EUR 0.10-0.50/month for the SIM. The building owner does not need IT's permission. The data path is encrypted (DTLS from sensor to gateway, TLS from gateway to cloud). The deployment is isolated from the corporate network by design.