Commercial Office Energy Audit Case Study
Commercial Office Energy Audit Case Study: The Blade, Reading
Finding further operational savings and developing a practical route to decarbonisation in an already efficient 13,250 m² commercial office building.
Commercial office energy audit case study
Finding further savings in an already efficient office building
Energy audit of The Blade, Reading
The Blade is a distinctive 86-metre office building in central Reading. Built in 2009, the 13-storey glass and aluminium building provides approximately 13,250 m² of conditioned floor space and was constructed to a BREEAM “Very Good” standard.
Unlike many buildings examined during an energy audit, The Blade was already modern, well maintained and comparatively energy efficient.
The purpose of the audit was therefore not to uncover obvious neglect or recommend wholesale equipment replacement. It was to examine the building in detail, identify remaining operational savings and establish a practical route towards eventual decarbonisation.
The audit was undertaken by Dr Russell Layberry while working through Pilio and included annual and half-hourly energy analysis, a full site inspection, discussions with the building and facilities managers, review of the building management system and consideration of previous energy reports.
The building
A highly serviced modern office
The Blade is a highly serviced, air-conditioned office building with:
- three 550 kW gas boilers;
- two large chillers;
- approximately 250 four-pipe fan coil units;
- central air-handling systems;
- several split air-conditioning systems;
- reversible VRV heat pumps serving part of the third and fourth floors;
- electric point-of-use hot-water heaters;
- extensive building-management controls;
- floor-level electricity submetering.
At full occupancy, the building could accommodate approximately 1,000 people. At the time of the audit, changing working patterns following the pandemic meant that overall occupancy was closer to 250.
The plant was generally in excellent condition. Heat exchangers were clean, insulation was comprehensive, the facilities team understood the building well and the principal heating and cooling schedules were already sensibly controlled.
Existing performance
A building that already performed well
Total annual energy use was approximately 2.43 million kWh. When adjusted for floor area, both electricity and gas consumption were below the relevant CIBSE benchmarks for a standard air-conditioned office.
The conclusion was important: The Blade was already a comparatively low-energy building.
A conventional audit focused on replacing old boilers, improving poor insulation or correcting gross control failures would therefore have added relatively little value. The remaining opportunities were in detailed operation, monitoring and longer-term system strategy.
The hidden opportunity
Electricity used outside working hours
The most significant finding came from the half-hourly electricity data.
Although daytime demand followed the expected office pattern, the difference between occupied and unoccupied consumption was much smaller than expected.
Approximately 41% of annual electricity was consumed outside the nominal office hours of 8am to 6pm.
Overnight demand was commonly around 80 kW and was highly variable, occasionally reaching approximately 160 kW. Weekend profiles were also inconsistent, with some Saturdays and Sundays showing demand much closer to occupied weekdays than an empty office.
Because the same unusual patterns appeared across both principal electricity supplies, the data suggested a building-wide issue rather than the activities of one individual tenant.
Engineering judgement
Necessary consumption or avoidable waste?
The audit did not simply assume that all overnight use was waste. Some equipment, particularly servers and heat pumps, may need to operate outside office hours.
The recommendation was to use the available floor-level submetering and BMS data to distinguish necessary consumption from avoidable consumption.
This distinction is central to a useful energy audit. The aim is not to switch off essential systems indiscriminately, but to understand what remains on, why it is operating and whether the level of consumption is justified.
Recommendations
Improving energy management through better use of data
The building already had good controls and knowledgeable facilities management. The next stage was to make better use of the information available.
Review half-hourly profiles
Routinely examine electricity patterns and investigate unusually high overnight and weekend consumption.
Analyse by floor
Use floor-level submetering to locate out-of-hours demand and distinguish tenant loads from central plant.
Improve meter mapping
Document precisely which equipment is connected to each main meter and submeter.
Strengthen gas data
Improve the quality and regularity of gas-meter information and equipment-level consumption estimates.
Verify interventions
Use future changes in consumption to confirm whether operational and technical changes have worked.
Target the real cause
Focus action on identified floors, tenants or plant rather than launching an untargeted awareness campaign.
Controls optimisation
Refining the BMS settings
The building-management system was already configured reasonably well, but the audit identified opportunities for further optimisation.
Typical room temperature setpoints were around 21–23°C, with control deadbands commonly around 2°C and occasionally as narrow as 1°C.
Narrow deadbands increase the risk of heating and cooling systems operating close together or repeatedly switching between modes.
The recommendations included:
- widening heating and cooling deadbands where comfort permitted;
- reviewing local setpoints;
- increasing the outside-air-temperature threshold below which chillers were prevented from operating;
- checking fan coil units and other plant outside occupied hours;
- introducing changes gradually and monitoring comfort and energy use.
These were predominantly low-cost adjustments, but in a large building even modest control improvements could deliver meaningful savings.
Lighting
Completing the lighting upgrade
Lighting in the common areas was almost entirely LED and generally controlled by occupancy sensors. However, fluorescent tubes and compact fluorescent lamps remained in some tenanted spaces.
The audit recommended completing the conversion to LED lighting and improving the granularity of occupancy control.
More localised sensors would allow lights to switch off in unused sections of otherwise occupied floors rather than illuminating an entire area unnecessarily.
Solar gain
Reducing solar cooling demand
The highly glazed façade gives The Blade its distinctive appearance, but also creates considerable solar gain.
A trial of solar-control film was proposed for the most exposed areas on the south side of the third and fourth floors.
A limited pilot, monitored through the local VRV systems, was recommended before any wider rollout.
Long-term strategy
A practical route to decarbonisation
Hot water was already electric, so natural gas was used principally for space heating.
Parts of the third and fourth floors had already been converted to reversible VRV heat pumps. These installations provided a useful real-world demonstration of how the rest of the building could eventually be electrified.
Rather than immediately removing the central boiler system, the audit proposed using the existing heat-pump areas as a monitored trial.
Their energy use, operating cost and ability to maintain comfort could be compared with gas-heated areas and used to inform the eventual design.
The outcome
A focused programme rather than unnecessary replacement
The audit concluded that The Blade was already an efficient and professionally operated building.
It did not recommend unnecessary replacement of serviceable equipment or claim that dramatic savings could be achieved through simplistic measures.
Instead, it established a focused programme based on detailed data, careful control optimisation, targeted trials and a credible long-term decarbonisation route.
“In a good building, the task is to use data and engineering judgement to find the remaining opportunities without recommending costly changes simply for the sake of producing a long list.”
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A detailed audit can still identify hidden out-of-hours demand, refine controls, test targeted improvements and create a practical route towards decarbonisation.
Oxford Energy Services combines energy-data analysis, site investigation and engineering judgement to help organisations find the remaining opportunities without recommending unnecessary replacement.
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