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Sweco UK


The 2 Aldermanbury Square Design for Performance pilot project has successfully achieved NABERS UK 5 Stars Design Reviewed status, following completion of the NABERS IDR process, and is now in RIBA Stage 5, with the main contractor Lendlease having started to take the project forward into construction.

NABERS UK is a simple, reliable system for rating the energy efficiency of office buildings across the UK, which provides a rating from one to six stars based on annual energy consumption. NABERS UK is currently run by BRE, who has been confirmed as the administrator of the scheme within the UK. The strategic operations of NABERS UK are overseen by a steering committee comprising BRE, the Better Buildings Partnership and NABERS, as scheme owner on behalf of Australia’s New South Wales Government administrator. 

To ensure buildings are sustainable for their owners, operators and occupants, our Building Sustainability team focuses on designing buildings for better performance using an integrated approach and leveraging digital tools such as digital twins to enhance processes, meet (and exceed) rating systems and streamline frameworks. This forward-thinking approach enables our clients to create efficient buildings that are affordable to build and operate, comfortable and enjoyable to inhabit, and suited to their wider context.

The digital twinning undertaken by Sweco and GPE at Aldermanbury Square is a move away from traditional building services design process, which tends to focus on complying with regulations rather than on actual asset’s performance. Unlike conventional design-based ratings, NABERS Energy ratings measure and verify the actual energy use of offices, helping building owners to accurately track and report on their buildings’ energy performance.

Leveraging physics-based advanced energy and parametric modelling tools, Sweco’s Building Performance team is able to ‘build before the build’, creating an accurate replica of the building’s architecture and MEP systems. The building digital twin is then used to accurately size the central plant avoiding unnecessary capital expenditure, inform and implement innovative strategies to drive down operational energy consumption, predict the building energy use and NABERS rating. The development robustness to operational and environmental changes as well as eventual systems failure is also tested under several different operating and off-axis scenarios.

The Proposed Development at Aldermanbury Square. Image: Allies and Morrison Architects

Design for Performance

Like the efficiency star ratings on your fridge or washing machine, NABERS provides a rating from one to six stars for offices. This helps building owners to understand their building’s performance versus other similar buildings, providing a benchmark for progress. NABERS UK offers two products: NABERS Energy ratings and Design for Performance. Unlike design-based ratings, NABERS Energy ratings measure and verify the actual energy use of offices, helping building owners to accurately track and report on their buildings’ energy performance.

The UK has a design-for-compliance culture which has led to the well-known ‘performance gap’ that exists between original design intent and how a building truly performs in-use. Design for Performance (DfP) is a process that overcomes this, where a developer or owner commits to design, build and commission a building to achieve a targeted NABERS Energy rating.

Design for Performance is a framework for developers to help ensure projects deliver against their design expectations. A Design for Performance Agreement helps design teams to embed energy performance targets within delivery supply chains and provides the checks and assurance measures to help a building in design achieve set targets rating in operation. It helps ensure the design meets the needs of the building’s future occupants and minimises lifetime energy use and emissions.

As pioneering partners for implementing NABERS UK Design for Performance, GPE and Sweco paved the way for 2 Aldermanbury Square to be put forward as the pilot project. The project is currently entering RIBA Stage 5 and main contractors Lendlease have been appointed to carry forward the project to construction. Sweco are working on ten other significant office buildings for detailed Design for Performance (DfP). Canada Water Plot F, One Exchange Square, 105 Victoria Street and 21 Bloomsbury are four of the other Grade A office buildings under the DfP Process in London.

More about our work at Aldermanbury Square

Sweco is appointed by GPE as building service and sustainability consultants for one of their largest developments to date, known as 2 Aldermanbury Square. This new London building development will be located in the heart of the City, adjacent to London Wall, in close proximity to four transport hubs, and only five minute’s walk from the future Queen Elizabeth line Moorgate station. It’s adjacent to the Culture Mile, including the Museum of London, and Barbican Centre.

As shown in the diagram below, the development is to provide a 12-storey building comprising 29,658m2 (NIA) of office area, with 144m2 (NIA) of retail space, and 737m2 (NIA) of reception area located on the ground floor. Office use is planned for the Lower Ground level and 1st floor to 12th floor.


Building section showing area usage (Allies & Morrison Architects)

Base case modelling – Digital Twinning using advanced analysis and simulation digital tools

Base case modelling in accordance with the NABERS UK process, is a move away from the traditional building service design process. The focus of the design process turns to producing energy efficiency in design to ensure high-performance asset operation.

The following are key advantages of taking a Digital Twin approach to physics-based simulation modelling:

  • Comparing different building service solutions
  • Comparing alternative plant options for energy performance
  • Inform key Design Decisions to target high energy savings and Optimized Performance
  • Accurate sizing of the central plant system
  • Accurate sizing of the tenant floor plant systems
  • Digital twinning allows control solutions to be tested and verified prior to setting out specification
  • The RIBA Stage 4 digital twin allows accurate prediction of buildings’ actual energy consumption
  • Can be adapted to continue informing building operators and tenants on CAT A / B fit-out works

Sweco UK’s Building Sustainability team used IESVE software to carry out the base case modelling to create a digital twin of the building, see below. IES Virtual Environment (VE) is a suite of integrated digital analysis tools for the design and optimisation of buildings. The IESVE platform leverages the world-leading APACHE simulation engine to allow cross-team collaboration between architects, engineers and contractors, from schematic design to post-occupancy, and asset lifecycle management.

Digital Twin – Replica of the building, its HVAC systems and BMS controls

The resultant model accurately replicates the architecture of the building and the HVAC systems and BMS controls as per design specification. This physics-based modelling allows the prediction of building service loads and a detailed breakdown by end uses of building operational energy based on a set of building operation conditions. The performance and resilience of building design, to changes in operational conditions and parameters, is the tested part of NABERS UK off-axis analysis.


Digital Twin – modelling of HVAC systems and controls

Detailed estimate of building energy consumption breakdown by end-use

At Sweco, we’re committed to expanding both capability and capacity through the use of new and innovative digital and cloud-based tools. Whether we’re providing end-to-end advisory and remote asset management services or value-add animations, Digital Twins and other types of big data visualisation, we know that our focus on digital game-changing in partnership with both clients and tool providers will be fundamental to designing and optimising sustainable solutions. To discuss digital-first design in your projects, contact our Chief Digital Officer Willem Kok below.


We’re extremely proud to share that #SwecoUK Building Sustainability Lead Kartik Amrania has been named as a finalist in the CIBSE Performance Awards (BPA) 2024  Engineer of the Year category. Below are some of the reasons why our friends at GPE believe Kartik is a worthy contender having endorsed his nomination for work such as that carried out at 2 Aldermanbury Square…

Kartik has truly established himself as one of our trusted consultants of choice when it comes to energy related building sustainability at GPE. He has guided us through the NABERS Design for Performance process at one of our major developments and the NABERS Energy for Offices rating. We have benefitted from his vast technical knowledge, for example through his building energy optimisation projects at GPE, where applying learnings from these projects has enabled GPE to achieve significant energy savings in our operational portfolio in the last year. Kartik’s knowledge spans from energy related topics in buildings from design stage through to operation.
Kartik’s enthusiasm has demonstrated his commitment to driving progressive sustainability concepts and knowledge in the industry. He has acted as an advisory on the latest updates and guidance and introduced us to stakeholders in the industry to support GPE’s priorities and has keenly provided internal training on multiple occasions, to both the executive board, senior management, as well as middle management.
Kartik focuses on delivering projects to the highest standard and can do so due to his technical understanding. He has established himself as a true leader in the sustainability consulting space.

Frank Blande Sustainability Lead (Development) at GPE