This article of Specifier Review on ‘The Science of Sustainability’ was practically developed by a team of South East England based structural and civil engineers. Apart from enlightening us on the Science of Sustainability, Perega elaborated here on how the built environment is to be developed and maintained as per the latest sustainability norms as established by international institutions.

Perega and Perega Clear Structures deliver engineering services for CABI’s new eco-friendly offices.

Perega, one of the UK’s most-respected structural and civil engineering practices, and its leading glass engineering arm, Perega Clear Structures, have recently completed work on one of the UK’s most anticipated building projects: The Centre for Agriculture and Bioscience International’s (CABI) new headquarters in Wallingford, Oxfordshire.

With construction completed last month, it’s been an exciting and rewarding contract for both firms, putting their team’s extensive skills to the test to address some unique challenges.

Involved from the very outset, Perega and Perega Clear Structures worked with forward-thinking architectural practice Scott Brownrigg, and contractor Barnwood Construction, to provide full civil, structural, and glass engineering consultancy.

Supporting Sustainable Structures

Specifically, Perega’s engineers provided structural consultancy for the composition of the new building’s first floor.

Photo Credit: Hundven Clements Photography

Consisting of a hybrid precast/in situ podium, the on-site team suggested the most effective solution would be the exploitation of a precast twin wall system for the concrete walls. By encouraging the use of precast concrete, Perega was able to obtain a high-quality finish on exposed surfaces and deliver the required thermal mass.

Further, expert advice was given for an extensive green roof, helping to design a robust steel roof structure to support the weight of the soil and turf intended for it. This, in turn, was positioned on steel columns directly bearing onto the podium columns below.

Attenuate the Positive

The Civils team was also kept busy, sharing its considerable knowledge and skill for the design of the site’s drainage and hard paving.

Photo Credit: Hundven Clements Photography

The drive for sustainability and achieving a minimal environmental footprint was central to the CABI development. To help deliver these requirements, the drainage strategy used a sedum green roof, which stores rainfall in the substrate and the drainage layer and allows it to be absorbed by plants. This delays the discharge of rainwater to the sewerage system, purifies it, and also allows for evapotranspiration to occur.

The below-ground drainage also used sustainable systems (SuDS) from the higher tiers of the drainage hierarchy. Soakaways were used to infiltrate surface water to groundwater. This ensured surface water was attenuated and discharged on-site, placing no burden on the public sewerage system. This proved a challenge as infiltration rates were variable, and there were elevated groundwater levels. This required careful ground investigation and soakaway placement to ensure they were in areas that would allow uninhibited surface water infiltration.

The overall drainage strategy was designed to accommodate, and discharge, a 1 in 100-year rainfall event, including an additional allowance of 40% for climate change. This ensured the drainage system was designed in accordance with the latest climate change guidance and had future peak rainfall estimates incorporated into its design.

Clearing the Path to Success

Perega Clear Structures proved pivotal in the delivery of CABI’s glasswork, issuing advice for glass balustrading across the building’s internal landings and bridges, as well as the full height frameless office partition screens.

Photo Credit: Hundven Clements Photography

One challenge faced was the choice of glazing system originally specified for the frameless glass partition screens for the project.

Here, the performance data as provided by the system manufacturer, gained from testing of the proprietary partition system, did not correlate with Perega Clear Structures’ design calculations for the required partition configurations.

However, following considerable and extensive investigation, a hybrid design was developed, allowing the original specification to be delivered with minimal adaptation or disruption.

Building Better, Building Greener

Commenting on the construction journey, Perega’s senior engineer, Corina Robea, says, “It’s great to be involved in a project for such a prestigious organisation doing such important work. Building to a sustainable brief always makes for interesting work and there were many specific, material choices that needed to be made to deliver structural integrity but also ensure carbon neutrality. Furthermore, we needed to be sensitive around the visual impact of the finished structure which led us to make some swaps, for example, switching from poured to precast concrete to deliver a more pleasing effect.

Photo Credit: Hundven Clements Photography

She continues, “I’m particularly proud of the design of a set of impressive, central scissor staircases. We played an integral role in ensuring the feasibility and stability of this striking feature and I’m so pleased with the results, they really add to the overall aesthetic whilst serving a useful function.”

Rob Parsell, Associate at Perega Clear Structures, concludes, “One of the most satisfying parts of the job is being able to provide a constructive answer to what initially looks like an insurmountable problem. Working in a collaborative fashion, with the glazing system manufacturer, and maintaining an open dialogue allowed us to pool our collective expertise. Ultimately, we were able to develop a workable solution without compromising on the original vision and design of the finished building, a win-win situation all-round.”

CABI’s new offices are sustainable to the core, reflecting the organisation’s ongoing work to encourage biodiversity and eco-friendly philosophy. Designed to be as energy-efficient as possible, materials, components, and systems were specifically chosen on their high-performance, low-impact credentials. The facility is now open for business and staff will be populating the space over the coming months.

To find out more about Perega’s work within the commercial property sector, visit

About Perega

Perega is an employee-owned UK structural and civil engineering practice. Headquartered in Guildford, Perega’s works dynamically with its clients across a wide range of sectors, notably healthcareeducation and retail.

The company prioritises a forward-thinking approach to engineering, adding value through effective communication to deliver high quality, innovative and cost-effective engineering solutions.

The Perega team’s experience spans from private houses and retirement villages to large retail parks, major hospital redevelopments and town centre regenerations.