CABI, Wallingford

Project overview  

Completed in October 2020, the new headquarters for the Centre for Agriculture and Bioscience International (CABI) in Wallingford, Oxford stands as a testament to innovative sustainable design and engineering excellence. The £28 million project, led by Scott Brownrigg, replaced CABI’s previous facilities – a repurposed school building that had served as their base since 1987.

Our team provided comprehensive civil, structural, and glass engineering services for this striking contemporary building. We worked collaboratively with the external team to realise the client’s vision of creating a low-carbon, energy-efficient workspace that would support biodiversity and provide flexibility for future expansion.

Client vision and sustainability goals

From the outset, CABI’s leadership team prioritised sustainability in their brief, focusing on three core elements:

1. Minimising carbon emissions during both construction and operational phases
2. Creating a highly efficient building envelope to reduce energy consumption
3. Enhancing biodiversity through thoughtful landscape integration

While the project predated the industry’s current strong focus on embodied carbon, the client demonstrated remarkable foresight in prioritising energy efficiency and sustainable design principles. This approach has delivered significant long-term environmental benefits and operational cost savings.

Engineering challenges and innovative solutions

The project presented several significant engineering challenges that required innovative solutions:

Site conditions and drainage

The Wallingford site comprised a high-water table and challenging infiltration rates, requiring our civil engineering team to develop an adequate drainage strategy. This included sustainable drainage systems (SuDS) designed to manage surface water runoff effectively, while supporting the site’s biodiversity goals.

Structural stability and design flexibility

The building’s distinctive shape posed challenges in providing an efficient stability system across the two levels, particularly given the client’s requirement for flexible spaces that could accommodate future expansion. Our structural engineers addressed these challenges through a hybrid structural design, combining the robust benefits of concrete with the flexibility of steelwork.

Material selection for sustainability

Material choices were carefully considered to balance structural requirements with long-term sustainability goals. The building’s relatively high embodied carbon meant significant reductions in operational carbon and much better support to biodiversity and air quality around the building.

• First floor precast concrete system – We recommended a hybrid concrete slab for the first-floor structure, comprising a thin precast lattice plate acting compositely with an in-situ structural topping. The slab was supported by a precast concrete twin-wall system and precast circular columns. The system enabled more efficient construction with reduced waste compared to traditional in-situ construction methods, resulting in lower overall embodied carbon. This approach also delivered multiple benefits in other areas, including high-quality architectural finishes without additional treatments and excellent thermal mass properties to regulate internal temperatures naturally.
• Steel roof structure –The complex curved roof was constructed using steel beams with lightweight metal decking. The roof plane was supported on steel columns that provided framing to the upper structure. These columns were bearing directly onto the precast columns below for a direct load transfer. This design efficiently supported the substantial weight of the extensive green roof while maintaining the building’s architectural aspects, both visual and technical.
• Internal glazing solutions –Our glass and façade specialists provided consultancy for the building’s extensive internal glazing elements, including glass balustrading and full-height frameless office partition screens. The team’s glazing strategy balanced structural and natural light requirements.

Taking a ‘fabric first’ approach

Central to the project’s sustainability credentials was the adoption of a ‘fabric first’ approach. This strategy prioritises the performance of the building envelope to minimise energy consumption before considering mechanical systems.

The building’s orientation was designed to maximise on solar gains while minimising heat loss, and exceptionally low U-values were achieved throughout the envelope. Concrete was used for its thermal mass properties, which naturally regulated internal temperatures, and a green roof improved the building’s overall thermal performance. These measures significantly reduced the reliance on carbon-intensive mechanical HVAC systems, creating a more passive and energy-efficient building.

As a result, the need for large plant rooms and heavy equipment was also significantly reduced. This approach has proven particularly effective in reducing operational energy consumption and associated carbon emissions, delivering significant cost savings for CABI while creating a comfortable working environment.

Green roof implementation

One of the project’s most visually striking and environmentally beneficial features is its extensive green roof. While this element required additional structural considerations and complex solutions, and therefore more materials were required, its long-term environmental benefits are substantial. The green roof significantly enhances biodiversity by supporting local flora and fauna, while improving stormwater management through reduced runoff and flood risk. It provides additional thermal insulation that further lowers energy consumption and extends the roof’s lifespan compared to conventional roofing systems. Moreover, the living roof contributes to external air quality, creating a more comfortable microclimate around the building, that subsequently influences internal air quality.

Our structural team designed an outstanding steel roof structure capable of supporting the significant weight of soil and vegetation, ensuring the green roof would remain viable throughout the building’s lifespan.

Passive ventilation and energy efficiency

To further reduce operational energy consumption, the building incorporates a state-of-the-art passive ventilation system.

The use of passive ventilation, thermal mass, and a high-performance envelope has created an office building that outperforms conventional energy efficiency standards, reducing the need for mechanical heating and cooling systems and lowering both carbon emissions and operating costs.

Image credit: Hundven-Clements Photography

Collaborative approach to sustainable design

The success of the CABI headquarters project stemmed from early engagement and close collaboration between all stakeholders. CABI’s leadership team maintained a clear sustainability vision throughout the process, while Scott Brownrigg developed the striking contemporary design that embodied these principles. Our multidisciplinary engineering teams provided integrated civil, structural, and glass engineering solutions that brought the vision to life.

This collaborative approach ensured sustainability considerations were integrated throughout the design and construction process, rather than being treated as add-on features.

Outcomes and benefits

The completed CABI headquarters delivers multiple benefits across several key areas. Its environmental performance is exemplary, with significantly reduced operational carbon emissions compared to conventional office buildings. The well considered structural design provides a robust building with decreased embodied carbon. The project also achieves remarkable cost efficiency through lower energy consumption and reduced maintenance requirements. End-user wellbeing is enhanced through abundant natural light, effective passive ventilation, and a strong connection to nature. The design incorporates future flexibility with adaptable spaces that can evolve with CABI’s changing requirements. Finally, the project makes a positive contribution to local biodiversity through its extensive green roof and thoughtful landscaping that support local ecosystems.

Although the CABI headquarters project predates the climate emergency era, it clearly demonstrates how a collaborative approach between client and designer, combined with thoughtful engineering and a commitment to sustainability, can deliver buildings that are both environmentally responsible and economically viable.

As the construction industry continues to advance its net zero carbon journey, projects like the CABI headquarters provide valuable insights into effective strategies for reducing both embodied and operational carbon while creating buildings that are functional, striking, and sustainable.

To find out more about our net zero work, please visit: https://perega.co.uk/netzero/.