The average commercial building in the UK wastes between 20% and 40% of the energy it consumes. The causes are consistent across building types: plant running on default settings, heating and cooling fighting each other, systems operating outside occupied hours, and control sequences never updated since original commissioning years ago.
The good news is that most of this waste is recoverable without capital investment in new plant. A well-configured building management system can recover the majority of it through software changes and reconfiguration. Here are the strategies that deliver the biggest returns.
The single most common source of wasted energy in commercial buildings is plant running outside occupied hours. HVAC systems should only run when people are in the building, with a pre-heat or pre-cool period of 30–60 minutes before occupation begins — not from midnight.
Check your BMS schedules against actual building use. If the building is occupied 08:00–18:00 Monday to Friday but the BMS schedule shows 06:00–22:00 seven days a week, you are paying for 16 extra hours of HVAC operation every weekday and a full weekend of unnecessary heating or cooling. On a medium office building, correcting schedules alone can save £5,000–£15,000 per year.
Ensure bank holidays and seasonal shutdowns are programmed. Most BMS systems have calendar override features that are rarely used.
Simultaneous heating and cooling — where the heating system and cooling system both run at the same time in the same zone — is extremely common in buildings with poorly sequenced plant and is often invisible to facilities managers unless the BMS is specifically configured to flag it.
On mild days, air conditioning and heating can run simultaneously for hours. In buildings with four-pipe fan coil systems, individual FCUs can be simultaneously heating and cooling adjacent zones. The fix is correctly configured dead bands in the control sequence — a temperature range within which neither heating nor cooling is active — and proper inter-lock logic between heating and cooling plant at the BMS level.
Optimum start is a BMS function that calculates the latest possible start time for HVAC plant to reach target conditions by the beginning of occupied hours, based on the current building temperature and the outside air temperature. It replaces fixed early-morning start times with a dynamic calculation.
On a mild spring morning, a building may reach setpoint by starting 20 minutes before occupancy. On a cold winter morning, it might need 90 minutes. Optimum start ensures the building is always ready on time while never running plant longer than necessary. Buildings without optimum start typically use a fixed start time sized for the worst case — which means they over-run for most of the year.
Most modern BMS controllers support optimum start as a built-in function. If it's not enabled on your system, ask your BMS contractor to activate it — it is one of the lowest-cost, highest-return changes available.
Rather than turning heating completely off overnight, night setback maintains a reduced temperature setpoint — typically 12–16°C — to avoid the building getting so cold that the morning pre-heat period extends into occupied hours. This is more energy efficient than turning heating completely off in cold weather, because the energy to reheat a very cold building over several hours exceeds the energy saved by running at a lower setback.
Frost protection is a separate function that prevents pipework freezing in unheated spaces. It should be enabled specifically for plant rooms, roof-level plant, and any areas where pipework is exposed to outside temperatures. Combined with trace heating systems for vulnerable external pipework, frost protection prevents the kind of burst pipe damage that can cost tens of thousands of pounds to repair.
Free cooling — also called economiser control — uses outside air for cooling when outside temperatures are below inside temperatures. Instead of running the mechanical refrigeration circuit, the AHU opens its outside air damper to bring in cool air directly. On a 14°C day in March, you can cool a building entirely for free while the chiller sits idle.
Most air handling units have the physical hardware to support free cooling — the dampers and mixing boxes are already there. The question is whether the BMS control sequence is written to take advantage of it. Many are not. Enabling free cooling typically requires changes to the AHU sequence in the BMS controller and is one of the highest-value software changes available on older systems.
Variable speed drives (VSDs) reduce fan and pump motor speed — and therefore energy consumption — when full capacity is not required. A fan running at 80% of full speed consumes only 51% of the energy of the same fan at full speed (following the cube law). But VSDs only save energy when they're actually varying speed — which requires correctly configured BMS control.
Common problems: VSDs set to run at a fixed speed rather than responding to duct pressure or flow demand; BMS setpoints left at design maximum rather than adjusted for actual building loads; VSD faults not flagged to the BMS and therefore unnoticed for months.
You cannot manage what you cannot measure. BMS-integrated energy metering breaks down energy consumption by system, floor, or tenant — identifying the largest consumers and tracking the impact of optimisation changes. Electricity sub-meters on each HVAC circuit will quickly show whether an AHU is using significantly more energy than expected, which typically indicates a mechanical fault, an incorrect VSD speed, or a control strategy problem.
Half-hourly interval data from BMS-integrated meters directly supports several compliance obligations that affect UK commercial landlords. Under MEES, properties must achieve EPC Band E or above to be legally let; from 2027, the target rises to Band C. Sub-metering data can support EPC reassessments by demonstrating actual energy performance and the effectiveness of controls improvements. ESOS Phase 3 (the compliance cycle running to December 2027) requires qualifying organisations to audit energy consumption across their estate — metered building data significantly reduces the cost and effort of that exercise. BREEAM In-Use credits for energy monitoring depend on having demonstrable interval data from installed meters, not estimates. Getting the metering infrastructure in place now, integrated with the BMS, is considerably cheaper than retrofitting it under compliance pressure.
For buildings with an existing BMS that has never been re-tuned since original commissioning, energy recommissioning is typically the highest-return intervention available. Alpha Controls carries out BMS energy audits that identify wasted energy, misconfigured sequences, and disabled optimisation functions — and then implements the changes required to recover that waste.
A recommissioning project typically costs £5,000–£20,000 depending on system size and delivers 10–20% energy savings, often paying back within 12 months.
If your building has been running the same BMS for more than three years without any controls review, a recommissioning audit will almost certainly identify significant savings. Contact Alpha Controls to arrange an energy audit across London, Kent, Essex, and across the South East.
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