These days, when building owners, facility managers or consultants want to specify a new Building Management System (BMS), they invariably say they want an “open system”. This comes from a fear of becoming locked into a single service provider with the perceived risk that this may result in high service prices and poor service levels.

It’s not always clear what is meant by the term “open”, and some people use the description “open protocol” which describes the technical interoperability of the system when really they are looking for service flexibility.


Where the BMS head-end can communicate with field controllers using openly-available, industry-standard protocols, which allow users to select system components from a wide range of suppliers.


Where the system developer/manufacturer certifies selected vendors as System Integrators (SI’s) for their products, who are then able to supply, commission and service the system using specially licensed software tools giving building managers a choice of suppliers.


Where the system contains the software tools such that, with appropriate training, a licensed end user or their nominated service providers can service and maintain the system.

These concepts are largely independent. It is possible to have an open-protocol system which may or may not be multi-vendor, or it is possible to have a user-managed system which may or may not support open protocols. For building owners, operators and consultants, a clear understanding of the difference in these concepts and how this affects the success of the system and the facility, is crucial to choosing the right solution.

This document clarifies the realities associated with the ‘open’ concept and sets the context within which building operators and users should select the system that provides them with the most benefits, most cost-effectively, across its lifetime.