While the terminology may have changed, the requirement to design economical and sustainable structures has been recognised at CSP for some time. The recently coined phrase of Climate Emergency has served to focus minds more pointedly within the Construction Industry. The increased awareness has also fostered the development of industry-wide tools, like the Institution of Structural Engineers Structural Carbon Tool spreadsheet which allows comparison of the effect of a building on the environment on a like for like basis. CSP welcomes this addition to the toolbox together with the Institution of Structural Engineers publication “How to calculate embodied carbon.”

CSP are working to incorporate these tools into new projects thereby providing a consistent measure of the effect of our buildings on the environment.

The need for action is well documented and CSP recognise that to meet the net zero emissions target of 2050 decisive action is needed immediately by Clients, Designers, Contractors and Product Manufacturers.

CSP also recognises that other parties have a key role to play in achieving the reduction in emissions, including Architects, Mechanical and Electrical Engineers and we are working alongside these partners to seek the necessary changes.

CSP appreciates that many of the decisions affecting the Embodied Carbon values are made early in a project’s life and seeks early involvement to educate and influence the decisions.

CSP adopts the hierarchy for carbon emission reduction of:

  • Build nothing and/or
  • Build less and/or
  • Build clever and/or
  • Build efficiently

Examples of early decisions include

  • Whether to build or renovate an existing structure
  • The extent of the new facility
  • The location of the new facility particularly with regard to ground conditions and suitable foundation options

Once a decision to proceed with a development is made there are several major decisions which have a significant impact on the total Embodied Carbon score, including:

  • Structural frame and column layout and spacing. With regular grids and short spans significant savings of carbon are possible.
  • Depth of structural zone. Unduly tight structural zone depths result in carbon heavy structures and are discouraged.
  • Flexibility of design. Designing for loads in excess of the Eurocodes to provide flexibility for future uses that may never materialise is discouraged and alternative strategies to provide for reasonably foreseeable changes should be explored.
  • Serviceability criteria. Establishing tight limits for acceptable deflection, vibration and, in concrete structures, crack widths can result in significant extra material being required to meet these criteria. CSP encourages a realistic assessment of these criteria early in a project.
  • Economical design. CSP aim to provide buildings with adequate factors of safety and limited over provision. This can be achieved by well-engineered structures and adequate peer review of the design but is more readily achieved with regular structural layouts, column grids or wall spacing. With irregular grids the desire for rationalisation and repetition can sacrifice the carbon target.

CSP is aware of the increased carbon utilised in developing higher strength concretes and works to match the minimum concrete strength with strength and durability criteria.

CSP aim to monitor the effect of decisions on carbon targets and alert our design partners to the consequences in a timely manner.

CSP are also aware that a decision minimising the carbon value of the structure may adversely affect the carbon value of the project, and vice versa, and works to get the maximum benefit overall.

CSP monitors the structural press for improved products which may result in lower overall carbon values for projects. However, CSP is also very aware that we cannot wait for, or rely on, improved products to meet the ever-tightening carbon targets that are required to meet the overall net zero target in 2050 and dramatic reductions are required now on all projects to limit the damage to the environment.

CSP also considers the future consequences of the building’s decommissioning and deconstruction but does not rely on this to meet carbon targets.

The road ahead

CSP welcomes the SCORS (Structural Carbon Rating System) rating scheme and the repeatability of results it provides and that allows realistic comparisons and is working to adopt it across all but the smallest projects. CSP concentrates on modules A1 to A3, the embodied carbon cradle to gate, as these are the modules most influenced by structural engineers and are the emissions, together with the construction phase (modules A4 to A5), which will be released early in a project’s life and thus most influence the outcome on the climate by 2050.

CSP aim to minimise the material quantities used in a project as this reduces the carbons values. Appropriate specification also has an effect on carbon values and is a focus of CSP.

CSP has modified its Building Information Modelling procedure (BIM) to better capture the data needed to populate the Structural Carbon Tool spreadsheet and will continue to review the procedure to capture improvements.

CSP review the carbon value as a project develops to monitor whether the early good intentions are maintained through to tender.

CSP plan to report publicly the results of the Structural Carbon Tool to the Built Environment Carbon Database to assist in benchmarking the results.

CSP need to target in our design:

  • Regular grid
  • Short spans
  • No transfer structures, where possible
  • No basement, where possible
  • Minimise loading
  • Relax serviceability criteria
  • Timber roof structure
  • Minimise balconies
  • Minimise concrete volume
  • Optimise concrete strengths
  • Minimise foundations – avoid piles
  • High utilisation
  • Use of 56-day strengths for concrete