Don’t drift into energy waste

One of the many advantages of a building management system is that it works largely in the background of day-to-day building operation, ensuring that internal comfort is maintained. Occupants are unlikely to notice the BMS, unless something goes wrong.

However, this benefit can also mean that the BMS is left to operate with little thought given to checking or verifying its functions. The danger for building owners and managers is that this situation leads to what is known as ‘energy drift’.

Drift is an underlying, often unobserved, problem that causes buildings to lose anywhere between 10% and 20% in energy efficiency every year. Energy drift is effectively a slow puncture in the building’s energy performance, leading to energy leakage – and higher than necessary energy bills.

From a building controls point of view, a number of factors can lead to energy drift. Some of the main causes of drift include temperature and time overrides being abused by occupants; temperature sensor failures; or incorrect control system programming. This last point may not necessarily mean that the system was improperly set-up at the start.

Buildings are constantly changing in their use, but when the purpose of a space changes the control system may not necessarily have been changed to reflect this. For example, an open plan office is changed to multi-office space; or more occupants are moved into a space than originally planned.

Building management systems are designed to be flexible, because buildings have to be flexible too. But every day use takes its toll: occupants override set points on cooling and heating systems, or they turn lights to ‘on’ without putting the settings back to their original, intended state.

Building control systems should be regularly recommissioned to ensure that they are functioning effectively, and to keep the building’s energy efficiency at the highest level. It is important to be proactive in this process, and not to simply react to problems as they arise because by then the energy efficiency levels may have fallen away significantly.

Of course, continuous commissioning of building services equipment is already being recommended by bodies such as CIBSE in order to maintain levels of energy efficiency. However, it is easy to overlook the building management system, even though it sits at the heart of a building’s overall energy performance. The building management system is increasingly expected to oversee the smooth operation of all the building services, so it is vital that the BMS itself is running correctly.

As we approach the start of the first year of the CRC Energy Efficiency Scheme, more organisations will come to understand the dangers of energy drift. Keep an eye on your building controls, and this is far less likely to happen in your building.

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