Reducing carbon emissions at Bristol's Temple Quarter Enterprise Campus

Project overview

The Temple Quarter Enterprise Campus for the University of Bristol is one of the UK’s largest city centre regeneration schemes. The development site is adjacent to Bristol Temple Meads station on a site previously occupied by a derelict and dilapidated Royal Mail sorting office. 

At the core of the development is the 38,500m2, 6-storey Academic Building (TQA1) being constructed by Sir Robert McAlpine. This will be the eventual home of the University’s Business School, digital engineering research groups, Centre for Entrepreneurship and Innovation, and the Quantum Technologies Innovation Centre, while providing dedicated facilities for enterprise and community partners. 

In line with our commitment to reducing carbon emissions in construction, this case study, carried out in partnership with Buro Happold, demonstrates the benefits of early collaboration in the design stage and engagement with supply chain partners that share the same sustainability ethos and carbon reduction aspirations.

Low Carbon Design
The project demonstrated significant embodied carbon savings after a value engineering exercise conducted by Buro Happold in collaboration with Sir Robert McAlpine. The original design consisted of a 15m x 7.5m structural steel frame grid, answering the brief for maximum flexibility defined early in the design process. The grid size was reduced to 7.5m x 7.5m and the frame changed from hollow core precast planks supported on steel beams to a reinforced concrete solution slab solution. At ground floor level, 30m long steel trusses provided additional support for the large open-plan areas along with important rooftop elements. This change allowed for a more focused provision of flexible space, as the design had settled sufficiently to understand where these flexible spaces needed to sit. 

The newly optimised design had reduced upfront embodied carbon by almost half, from an estimated 29,560 tCO2e to circa 15,569 tCO2e (A1-A5). Approximately 70% (10,884 tCOe) of these remaining emissions were associated with the embodied carbon of the ready-mix concrete.  Reducing the carbon intensity of the concrete material therefore became a priority during procurement.  

Lower carbon concrete procurement and concrete zero 
The design stage embodied carbon calculations assumed a minimum of 35% GGBS would be utilised in each concrete mix design as a supplementary cementitious material (SCM), and this was reflected in the designer’s specification. Where feasible, the team were keen to further reduce the associated embodied carbon, partly driven by both Buro Happold’s and Sir Robert McAlpine’s corporate commitments under ConcreteZero, and the University’s 2030 net-zero commitment.

Sir Robert McAlpine’s commitments under ConcreteZero:

• 2025 (interim): Minimum of 30% by volume meeting definition of ‘low embodied carbon concrete’ – less than or equal to the LCCG benchmark rating of ‘B’
• 2030 (interim): Minimum of 50% by volume meeting definition of ‘low embodied carbon concrete’ – less than or equal to the LCCG benchmark rating of ‘B’
• 2045: 100% of total concrete consumption meeting the definition of ‘Net Zero’ 

To further reduce emissions, Sir Robert McAlpine and Buro Happold collaboratively engaged with key supply chain partners, such as framework partner Heidelberg Materials and their nearby batching facilities. We also held collaborative workshops with Buro Happold and all relevant concrete using sub-contractors such as Bachy Soletanche, Toureen Group and Churngold. These sessions looked to reduce the embodied carbon intensity of the works whilst also managing the associated cost, programme and quality implications. The sessions typically focused on material efficiency, optimising the total cementitious content of each mix design and substituting Portland cement for GGBS, where feasible. 

All proposed concrete mixes were assessed against the Lower Carbon Concrete Group’s (LCCG) benchmark rating scheme. This scheme scores the emission intensity of a mix design against industry data, rating mixes from A (low carbon) to F (high carbon). The central banding of a ‘C’ rating is considered UK average emission intensity. The project team were aiming to score as many ‘B’ rated (or better) concrete as possible, in accordance with the ConcreteZero’s definition of ‘low embodied carbon concrete’.

Key outcomes from the exercise included:

• 93.7% of the concrete poured (by volume) achieved the definition of ‘low embodied carbon concrete’ (B rated or better)
• 55.9% of the concrete poured (by volume) was ‘A’ rated 
• A comparative 2,254 tCO2e (A1-A3) was saved through low carbon procurement – relative to industry average emissions (C rated concrete) – a 25.7% tCO2e saving.
• Emissions reductions were predominately achieved through maximising GGBS proportions as a supplementary cementitious material – the GGBS was sourced relatively locally from Port Talbot.
• Individual mix designs included up to 85% GGBS – such as the mix used for the foundations of the site cabins (temporary works).
• Excess and waste concrete was utilised to create temporary site platforms – reducing the total amount of concrete ordered. 
• Over 35,000 m3 of concrete was poured onsite which accounted for 6,509t CO2e, all of which was assessed by Sir Robert McAlpine and monitored via our ‘Tracker+ KPI’ system. An ‘as-built’ embodied carbon assessment is also being prepared using the ‘One Click LCA’ industry software. 
• The project was used as a ‘sample project’ for our ConcreteZero submission requirements in both 2023 and 2024, in the process informing the next revision of the LCCG benchmarks.  

In conclusion, the results have highlighted the clear benefits of early collaboration with engaged supply chain partners who share our carbon reduction aspirations. This collaborative approach proved instrumental in achieving our goals. It showed that emission savings of approximately 25% are achievable at the procurement stage for ready-mix concrete. However, while these procurement stage savings were considerable, the greatest savings were realised through design stage optimisation. This underscores the importance of embedding low-carbon engineering principles in the design phase to maximise emission reductions.