Why the manufacturer choice made at initial installation can lock a building owner in for decades.
When a building automation system (BAS) is specified, one decision matters more to the building's next thirty years than almost any other line item in the controls submittal: does the equipment talk to each other using an open protocol — a published, standardized specification any manufacturer can implement — or a proprietary protocol— a closed, manufacturer-specific scheme that only that manufacturer's own equipment speaks. It rarely looks like a consequential choice on day one. Both options control the same dampers, valves, and chillers just fine at commissioning. The difference only shows up years later, when the building owner wants to add a vendor, switch controls contractors, or discovers the original manufacturer has moved on.