Unlike modern controllers that remain readily available through multiple suppliers, proprietary BMS hardware eventually disappears from the market. Manufacturers discontinue products, production ceases, spare parts become scarce, and the few remaining components often find their way onto specialist refurbishment or second-hand markets.

It isn’t uncommon for building owners to pay three, four or even ten times the original purchase price for a replacement controller or communication module simply because no new stock exists anywhere else. When an entire building depends on a single obsolete component, the value of that component changes dramatically.

For many owners, purchasing an expensive second-hand controller is still considerably cheaper than undertaking an emergency Building Management System replacement. However, hardware is only part of the problem. The second—and often more significant—risk is the gradual loss of engineering knowledge.

Very few commercial buildings remain exactly as they were when originally commissioned. Over decades, they evolve. Equipment is replaced. Tenancies change. Air conditioning systems are upgraded. Energy-saving strategies are introduced. Fire interfaces are modified. Temporary overrides become permanent. Control sequences are altered to solve operational issues, often without the drawings or software ever being updated.

Eventually, the building no longer operates exactly as the original documentation suggests. This means that replacing the hardware alone doesn’t necessarily solve the problem. Unless someone understands how the building has actually evolved over the last thirty or forty years, important operational knowledge can disappear during the upgrade.

The most successful BMS modernisation projects don’t simply replace controllers—they capture and preserve decades of operational experience before it is lost forever.