How operational energy was reduced at Three Chamberlain Square, Birmingham

The operational energy at Three Chamberlain Square was reduced by first improving the efficiency of the fabric of the building, followed by reducing internal gains, selecting efficient HVAC systems, and then refined through operational fine tuning.
The client approached the Cundall team with an ambitious project brief: the 180,000 ft²  building would be a landmark building with exceptionally low carbon targets and pioneering standards of sustainability.

Three Chamberlain Square, Birmingham

To ensure that Three Chamberlain Square was able to significantly optimise its operational energy usage, the Cundall team undertook four key steps.

1.    Optimising the façade

A fabric first approach allowed the optimisation of the façade before anything else. A key decision was to choose between triple glazing or double glazing. Early in Stage 2, the team undertook a detailed comparison of the two options, assessing operational performance, embodied carbon, and cost. While triple glazing reduced heat loss in winter and limited heat gains in summer, it also carried significantly higher embodied carbon. When assessed over a 60-year building lifespan, the analysis showed no meaningful whole life carbon benefit compared with high-performance double glazing. Additionally, triple glazing carried a cost uplift of around 20%. On this basis, the team concluded that double glazing offered the optimal balance of performance in regard to carbon and cost. This allowed investment to be redirected towards other envelope and fabric improvements that delivered greater overall benefit, reinforcing the importance of whole-life carbon thinking rather than focusing on individual components in isolation.

2.    Reducing internal gains

Internal gains were a key early focus for the project as they strongly influence cooling demand and overall operational energy. When the project commenced in 2020, the default approach would have been to follow the 2019 edition of the British Council for Offices (BCO) Guide to Specification, which assumed relatively high internal gains from lighting and small power to allow maximum tenant flexibility. This approach would have been energy intensive and would be difficult to meet the project’s sustainability ambitions. Instead, the design team aligned more closely to emerging industry guidance for lighting and small power cooling allowances, significantly reducing assumed internal gains. This approach pre-empted the BCO 2023 update by approximately three years and directly enabled lower cooling loads, smaller plant sizes, and improved operational energy performance. Since completion, these internal load allowances have proved to be sufficient to suit the building’s tenants and has been a key contributor to achieving the building’s NABERS UK 5 Star rating.

3.    Selecting efficient Heating Ventilation and Air Conditioning (HVAC)

The HVAC system choice was also the subject of detailed optioneering at an early stage. The team assessed chilled beams alongside fan coil units, considering not only operational energy but also flexibility for future tenants, cost, system complexity, and contractor risk. While chilled beams offered better energy performance in principle, concerns relating to buildability and the contractor’s risk appetite led to the adoption of fan coil units. This decision was not taken lightly; energy modelling demonstrated that the fan coil solution would result in an approximate 7% increase in energy use compared with chilled beams. Rather than accepting this impact, the team quantified it and actively mitigated it through other efficiency measures, including optimised controls and the use of water-source heat pumps for selected domestic loads. This ensured that value engineering decisions did not undermine the project’s overall energy and carbon ambitions.

4.    Fine tuning user operation

A final step in optimising operational energy was ensuring the building operates in line with its design intent. The Building Management System was set up with efficient operating schedules, energy focussed temperature deadbands, and demand-led controls, with particular focus on minimising unnecessary out-of-hours operation while retaining tenant flexibility.

Beyond initial commissioning, an ongoing working group has been established comprising the facilities management team, tenants, landlord, and contractor. This group actively monitors energy use at individual meter level, reviews performance against the agreed operational model, and identifies opportunities for continual improvement. Regular dialogue and data-led reviews ensure that building operation, tenant behaviour, and management practices remain aligned with NABERS requirements. This collaborative, iterative approach has been central to maintaining performance and supporting the achievement of a NABERS UK 5 Star rating.

The operational energy performance achieved at Three Chamberlain Square demonstrates the value of early, evidence led decision making combined with a whole life carbon perspective. Crucially, no single decision delivered the outcome in isolation. It was the cumulative impact of many considered choices, informed by robust analysis and continual collaboration, that is enabling  the building to perform as intended.

This article is part of Cundall's Zero Carbon Deep Dive series, showcasing the practical steps we are taking to embed Zero Carbon Design 2030 across our projects.