The clocks went back on 25 October and the heating season is well under way. Christmas is under eight weeks away. For an FM team, this is a good moment to look hard at the BMS.
None of the checks below needs new plant or a capital budget. Most can be done from the BMS front end in an afternoon, with an engineer brought in only for what you find. Hotels can apply the shutdown advice to closed floors and function rooms.
1. Load the holiday calendar
A weekly time schedule knows nothing about Christmas unless someone tells it. This year the bank holidays in England and Wales fall on Friday 25 December, Monday 28 December (the substitute day for Boxing Day) and Friday 1 January.
Take a typical office with a 12-hour weekday schedule that closes from Christmas Eve until Monday 4 January. If the holiday calendar is not loaded, the plant treats six of those days as normal working days. That is 72 hours of heating and ventilation for an empty building.
While you are in the schedules, check that the clock change went through. A controller that missed it starts plant an hour out, and nobody notices until somebody complains. Then ask whether the schedules still match how the building is used.
2. Find what is running out of hours
Schedules only work if the plant is obeying them. Fans, pumps and chillers left in hand after a fault or a complaint will run all night until somebody puts them back in auto. SSE Energy Solutions makes the same point: BMS savings erode when setpoints and timers are changed or plant is left on manual.
The quickest test is to look at what the building does when it is empty. Pull your half-hourly electricity and gas data for a recent weekend and compare it with a weekday. Then trend the main plant status points over the same period. Anything running without a good reason goes on the list.
Well-run portfolios are not immune. When The Crown Estate reviewed BMS settings across its London commercial portfolio, it reported that many had become misaligned, and adjusting plant run times to remove out-of-hours use was among the fixes commissioned across 21 properties.
3. Put setpoints back where they belong
Setpoint creep rarely happens all at once. Someone is cold in January, an engineer adds a degree, and it never comes back down.
The Carbon Trust's long-standing rule of thumb is that heating costs rise by about 8% for each 1°C of overheating. NHS Property Services uses the same figure of around 8% in its guidance. It is a guide rather than a promise, but a single degree is worth chasing.
Export the current setpoints and compare them with the control strategy. Where there is a mismatch, find out why before changing it. If a floor is genuinely cold, a raised setpoint may be hiding a stuck valve or a poorly placed sensor. Fix the cause, then reset the number. Any temporary override should have an end date.
4. Stop heating and cooling fighting
This waste is easy to miss because the space feels fine. NHS Property Services' cooling good practice guide says it can exceed 20% in affected zones, while noting that its figures are general estimates that vary by site.
Cold mornings are a good time to look. On each air handling unit and a sample of fan coils, compare the heating and chilled water valve positions. Both open at once needs an explanation. Some AHUs reheat on purpose to control humidity, so check the strategy first. The usual culprits are:
- A passing valve or a failed actuator
- Too narrow a dead band between heating and cooling setpoints
- Neighbouring zones with different setpoints working against each other
- A chiller enabled in winter with no real cooling load to serve
5. Check the sensors you rely on
A BMS only knows what its sensors tell it. Optimum start and weather compensation both lean on the outside air sensor, so if that one reads wrong, the whole heating strategy is working from bad information. Check it first, and make sure it is out of direct sun and away from exhaust air.
Next, trend a sample of space and duct sensors. A line that sits perfectly flat, or a reading that makes no sense for the time of day, points to a failed or disconnected sensor. Compare a few against a calibrated handheld thermometer. Then walk the floors, because a good sensor in the wrong place, such as above a kettle or beside a heater, is still a problem.
Your checklist before the break
- Load the Christmas and New Year dates into every holiday calendar on the system
- Confirm that every controller changed its clock on 25 October
- Compare a weekend's half-hourly energy data with a normal weekday
- List everything in hand or overridden, and return it to auto or record why not
- Export setpoints and compare them with the control strategy
- Check AHU and fan coil valves for heating and cooling running together
- Check the outside air sensor and spot-check a sample of space sensors
Where we come in
Our engineers have worked on Trend, Tridium, Distech, Delta and Schneider systems since 2008. If your team has the checks but not the hours, we can carry out a BMS health check, fix what has drifted and leave you with a clear list of what we changed and why.
Sources: GOV.UK bank holidays; GOV.UK clock changes; The Crown Estate BMS optimisation case study; SSE Energy Solutions; Carbon Trust guidance (2011) as reported by IEMA; NHS Property Services heating guidance and cooling good practice guide; HSE hot and cold water systems. Correct as of 2 November 2026.