Modern buildings are typically equipped with a range of devices that will control HVAC, energy management, lighting, security and other systems. So, in theory, a building with a building management system (BMS) should be able to dim the lights when the sun is shining through the windows, and be able to set back mechanical systems automatically, such as chillers, boilers and air handlers. But can it?

Facility managers face a distinct choice when specifying controls for a BMS: Should they choose a single supplier (in other words, a proprietary manufacturer) for all the BMS components or opt for a range of best-in-class products from different manufacturers, all able to communicate with each other through “open” systems? The answer is contained within the question. Open systems make solid business sense because the ability of the devices to communicate with different manufacturers’ products increases choice and flexibility.

The definition of an open control system is one that can communicate with disparate manufacturers’ products over a common platform. This platform will utilize a common language, or a protocol, that allows communication between various vendors’ products. There are several protocols available that meet different standards. These standards are often governed by a trade body represented by multiple manufacturers and an independent governing body.

Within the construction industry, technology progresses at incredible speeds, and over the past two decades there have been many changes to open system design. Now it can go even further than just the choice of vendor; users can source products, have access to programming tools and training and enable future third-party integration with application programming interface(APIs) and various Internet of Things (IoT) devices.

An example of an open system is when there are three vendors, and they all supply components for a building management system based on a specific protocol. Those components should be able to “talk” to each other even though they are made by different manufacturers. The communication protocol used is simply a set of rules that establishes how systems communicate. Protocols are analogous with spoken languages. Protocols operate along similar lines, determining the structure, organization and functions of communication systems. An open protocol means the communication rules are publicly available. Therefore, it is not owned by an individual company and is not limited to a specific company’s products.

There are several pivotal communications protocols. Collectively, these protocols are termed operational technologies (OT), and they have shaped the industry:

  • M-Bus, or Meter-Bus, is a European standard (EN 13757-2 physical and link layer, EN 13757-3 application layer) for the remote reading of water, gas or electricity meters as well as other types of consumption meters, such as heating systems or water meters.

  • Modbus is an early open communications protocol originally published in 1979 for use with its programmable logic controllers (PLCs). Modbus has become a de facto standard communication protocol and is now a commonly available means of connecting devices used in building services.

  • BACnet (building automation and control networks) was formed by ASHRAE in 1995 and is commonly used in BMS applications. BACnet was designed to allow communication of building automation and control systems for applications such as HVAC, lighting control, access control and fire detection systems and their associated equipment.

  • LonWorks is an open standard for networking platforms for control applications. It uses a protocol called LonTalk to connect devices over various media, such as twisted pair, powerlines, fiber optics and RF.

What makes a BMS open?

There are four pillars upon which open solutions rest:

  • First, a truly open system must be listed with the protocol it is using.

  • Secondly, the controllers need to be unlocked and tested to ensure users can interact with this equipment using their own programming tools. An open solution also requires that the system is fully documented.

  • Thirdly, the building owner should be able to select the authorized system integrator with whom they wish to deal, and not be forced to deal with the regional branch of the manufacturer.

  • The fourth pillar is emerging in the marketplace. As buildings get smarter – it is fair to consider a smart building as a systems of systems – they rely on IT/IoT protocols, or native cloud APIs increase the overall performance and user-friendliness of the building by enabling interactions between all these services – BMS, access control, EV charger, ADR (Automated demand Response for utilities), visitor management, space optimization and room booking to name a few.

Comparing the systems    

There are several benefits to open systems. These benefits include the ability to select “best of class,’” for example the best zone controller with the best human machine interface.

There are also benefits of interoperability. Open systems employ standards-driven protocols, so security is fundamental to their operation. The designer must think about what has happened inside and outside the building because it must interact with its environment. Open protocols allow users to do both. Open systems also offer greater security. Both OT and IT networks must be safeguarded, and this is where cybersecurity comes in. These types of systems also offer customers a greater degree of flexibility, because they can choose from a variety of different suppliers, allowing them to install components which are completely suited to their specific circumstances. They also offer more transparency, so it is clear which devices are being used. Users are also not locked into a specific vendor and have the freedom to work with multiple vendors and with best-in-class companies, solutions and values.

There are also disadvantages to using an open system. One of the first elements FMs will consider is cost. Although the initial cost may be more than a proprietary system, open systems will cost less over time because users have a future-proof solution: New services can be added without needing a complete retrofit of the BMS. The initial cost of the equipment can also be balanced with the reduced cost of installation. There is also the issue of complexity. From a BMS and HVAC perspective, an open system is no more complex than a proprietary system. While it provides the same (or a better) set of productivity tools for designing and deploying projects, it offers an additional level of integration with third-party systems using open IT/IoT standards. Because those integrations require specific skills, they must be performed by IT/IoT professionals.

Looking ahead

With energy costs rising, the impact of climate change taking hold and the new flexible working habits, buildings — especially offices — need to change. This is prompting investors to offer more resilient and flexible buildings that can cope with any potential risks that become reality with minimal impact.

Today, a smart building is a collection of complex systems that must communicate with each other to provide the best experience for the various people who live, play, learn and work in the building. This requires knowledge of many domains, which is almost impossible to master within a single product brand. These new demands, which are generally outside the traditional field of building management systems, require collaborative solutions between the different actors of the world of OT, IT and, more recently, artificial intelligence. As the industry has seen with OT protocols, there are some new IT applications making waves in the way smart services can be delivered:

  • RESTful API: An API is a way for two or more computer programs to communicate with each other.

  • oBIX: Open building information exchange is a standard for RESTful Web Services-based interfaces to building control systems.

  • Docker Containers: Docker is an open platform for developing, shipping and running applications. Docker enables users to separate applications from the infrastructure to deliver software quickly.

  • MQTT: Message queue telemetry transport is a lightweight, publish-subscribe machine-to-machine network protocol.

  • JSON: Javascript object notation is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute-value pairs and arrays.

Open systems can provide important data  

There are platforms coming to market that offer system integrators, FMs and buildings owners far more data about their buildings. Buildings implementing intelligent solutions ensure the highest level of occupant satisfaction and minimal operational costs to maintain the highest level of asset value.

The building services sector is constantly developing. The industry is moving from simply creating efficient rooms to developing efficient buildings and portfolio management. Each building is unique, and each organization occupying all or part of a built space has specific needs. The beauty of open systems is that they allow FMs not only to be able to understand a building but also to gain insight into a portfolio of buildings.

By utilizing an open system, integrators, FMs and building owners can all benefit. Whether it is from ease of installation, simple and intuitive operation or more meaningful data, an open system can deliver that control while ensuring improved energy efficiency and occupant comfort.