Facility managers paying attention to the influx of Building Internet of Things (IoT) devices and systems know that we live in an increasingly wireless world. But for any specific building project involving facility automation and information technology, to wire or not to wire sensors and controls for smart building systems is a difficult question. The way to make the decision is to find the option — wired or wireless — that best matches the individual building’s needs and business plan.
Generally speaking, wired systems offer wider coverage ranges, can handle large data volumes, and are extremely reliable — plus individual devices may be slightly less expensive. However, wired devices are more costly to install, less flexible and frequently cannot make information available anywhere in the space.
While wireless options are a little more expensive than their hard-wired counterparts, their reliability has greatly improved over the past few years. Installation of wireless devices is less complicated and far more flexible as needs change. They also offer transmission of limited data packets and simplified control commands from anywhere in the room or space, not just along the wires.
Complexity sets costs
First costs of wireless “are about equal with wired in new construction,” says Thomas Grimard, associate partner at Syska Hennessy. “The competitive edge is not really there yet.” In fact, wired options are currently a bit less expensive for new buildings. But as more manufacturers enter the market and electrical installation costs continue rising, Grimard doesn’t see that slight cost advantage for wired solutions in new construction continuing.
“Where wireless options really save is in retrofitting existing buildings,” Grimard notes. “Redoing floor space is more cost effective with wireless technology. And the move toward flexible collaborative workspace in commercial space is helping that along.” If the business model for the building requires changing out the space every couple years, Grimard says, a wired system doesn’t make sense.
“Wireless devices are reliable, secure, and the cheapest way to bring IoT technology to existing buildings,” agrees Rick Szcodronski, senior associate, technology consulting for Environmental Systems Design, Inc.
When it comes to the Building Internet of Things (IoT) and essential building automation, savvy facility managers realize that both wired and wireless solutions have their place. Facility managers know that optimizing their buildings generally requires a blend of both large and small data transmission methods. Small data transmission is the bailiwick of many wireless options, while large data streams often need the higher capacity found in wired systems. The exception to this rule is Wi-Fi, which has the bandwidth for larger data streams.
Choosing the best solution requires looking at the facility’s business plan and the organization’s mission statement.
“The building manager needs to know what his end goals are for IoT,” points out Josh Thompson, principal consultant for Point Source.
Thompson suggests looking closely at lifecycle costs. First costs of wireless options are very appealing. “But they can come with a complex suite of problems,” Thompson warns. “Maintaining competent, diligent IT professionals to manage the network can be expensive.”
Once a wireless business plan is in place, the marketplace offers many wireless IoT options. Popular Building IoT wireless solutions are built on Z-Wave, ZigBee, Wi-Fi, Bluetooth, and EnOcean technologies.
1. Z-Wave. Z-Wave is a proprietary wireless technology for small commercial building applications, including tenant spaces, that operates in the 908.42-MHz channel. It uses a wireless radio frequency, operates on low power and is typically used for such devices as lights, thermostats, and locks. Devices are certified and scalable from one device up to 232 devices. Z-wave’s transmission rate is 100 kilobits per second.
Z-Wave’s limited size (232 devices) may reduce its use to small facility applications, but its slower data speed is not an issue for most building management functions.
“If you want to turn the lights on, does it matter if they go on in 100th of a second or 1,000th of a second? Could an occupant even tell the difference?” asks Thompson. “A typical control command is one bit out and one bit in.”
The Z-Wave hub is wired and provides two-way communication. The hub can receive and send communications from smartphones, tablets or computers. While the hub is wired, many Z-Wave devices operate on batteries. Other Z-Wave devices plug into the wall. Z-Wave controllable AC outlets can be used to control and monitor energy usage.
Each Z-Wave network has a unique ID that it assigns to every device in its particular network. This prevents a neighboring tenant’s Z-wave hub from controlling devices outside its own network. For high-security devices, Z-Wave has an additional security level that uses AES128 encryption, the level banks use to protect financial data. Many Z-Wave hubs and all Z-Wave Plus hubs use this encryption level.
2. ZigBee. ZigBee is a wireless language with similar applications to Z-Wave. However, it is more versatile as it can be configured for any short-range wireless task, thanks to a more robust protocol. It has data rates of 250 kilobits per second across its mesh network, which is plenty fast to handle many building system functions.
“ZigBee has vast market acceptance in the commercial building control systems community,” says Thompson. “That keeps development costs lower and offers a lower cost of deployment.”
ZigBee is commonly applied in buildings as either a device-to-controller or device-to-device system, according to Szcodronski.
Because ZigBee devices use very little power, their batteries can last for years. Early batteries had about a two-year life. But new batteries now last five or six years. Eventually, Grimard predicts, batteries might be phased out and only be used for certain specialized applications or replaced with self-powering energy storage devices.
With ZigBee’s Green Power feature, devices operate without batteries, relying on harvesting power from their environment.
ZigBee also uses the mesh network’s power to connect each ZigBee product to all others. Mesh network is self-healing: If one device fails, the others will continue uninterrupted communications. Thus, if one sensor along the path malfunctions, the network simply reroutes the information another way, explains Grimard.
Products carrying the ZigBee logo will work together even if they’re from different companies, because ZigBee standardizes everything from basic communication to how a product operates.
ZigBee Building Automation is a robust, BACnet-approved wireless mesh network standard for commercial buildings. As a result it can provide wireless connectivity between building automation system equipment controllers, lighting controllers, sensors, and other devices within commercial buildings.
ZigBee operates in the 2.4 GHz frequency band, according to IEEE 802.15.4. The same bandwidth is used for Bluetooth and Wi-Fi, but with 16 channels typically permitted in 2.4 GHz, ZigBee normally can operate in an open frequency with minimum interference. For further protection, many ZigBee devices have co-existence features to control interference.
ZigBee is secured by AES128 encryption, keys, and device authentication to prevent access to critical building management information.
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