Embodied carbon: Farringdon Station

Material gains

1 March 2013

The construction industry is under increasing pressure to understand its carbon footprint. Piotr Berebecki and Sean Lockie show how this can be done through the assessment of London’s Farringdon Station redevelopment

Network Rail owns and operates the UK’s rail infrastructure including the tracks, signals, tunnels, bridges, viaducts, level crossings and more than 2,500 stations. It also manages 18 of the busiest railway stations in the UK, catering for more than 3.5 million journeys per day, and is the country’s largest floor space provider to small- and medium-sized business enterprises, with more than 7,000 properties and 18m sq ft of space.

Farringdon Station is being transformed into one of London’s most important transport hubs and by 2018 it will:

  • be the only station from which passengers can access Thameslink, Crossrail and London underground services, offering links to four major airports and international rail links
  • cater for 200,000 passengers per day and up to 20,000 per hour
  • have a new ticket hall for Thameslink and Crossrail services and a new concourse and entrance to the side of the existing station building
  • be able to handle 240m (12-car) trains
  • offer access to all platforms for those with luggage or disabilities.

Network Rail is committed to reducing its environmental impact throughout its portfolio. For stations and major investment programmes, this means looking for opportunities to reduce waste, increase renewable energy supply, use more sustainable materials, minimise water consumption and find greener ways to transport construction materials to and from site.

As part of this, Atkins/Faithful+Gould provided design and sustainability advice on the Farringdon project to ensure that Network Rail's sustainability strategy is delivered and was commissioned to assess the embodied carbon impact. The carbon assessment was divided into three areas (see Figure 1).

Embodied carbon

The cradle-to-site embodied carbon assessment was largely based on the factors from the University of Bath's Inventory of Carbon and Energy (ICE) database. Defra's greenhouse gas conversion guidelines have been followed to establish carbon emissions during transportation.

Embodied carbon Operational carbon  

Lifecycle                      replacement carbon

Emissions included in the study

Materials production: cradle-to-gate (factory)

Energy demand for lighting, heating, cooling, auxiliary equipment Maintenance activities
Transport of materials: gate-to-site (construction site) Embodied carbon assets being replaced and demolished
Construction activities on site
Emissions not included in the study
Transport of labourers to construction site Energy demand for office equipment Cleaning activities
Urban infrastructure (e.g. roads, drains, water)  Energy demand for signage boards Administration activities
Energy used by the project team  Energy demand for external lighting Transport of labourers

 Figure 1: Carbon assessment boundaries

The final fit-out and furnishing of the station was excluded (other than tiles and paint) due to limited opportunities to reduce carbon and difficulties in estimating material quantities. The study focused on key materials found in the building envelope and services. The primary elements were foundations, steel, block/brickwork, floors, insulation, windows and roofing.

The quantities of materials were established based on the design drawings and bill of quantities prepared by the cost consultant. The ICE database was then used to calculate embodied carbon associated with the key materials. Retaining parts of the existing building saved around 2,800 tonnes carbon dioxide equivalent (tCO2e) and illustrates the importance of retention when saving embodied carbon. However, it was decided not to include this saving in the baseline calculations because the retained building was listed and it had to be preserved anyway due to local planning requirements.

The baseline totalled 6,479 tCO2e. It was possible to reduce this by 11%, bringing the emissions down to 5,758 tCO2e. One of the key ways of reducing embodied carbon of a project was to specify higher recycled content. The materials specification was mapped against the Waste Resources Action Programme recycled content toolkit and
potential quick wins identified to improve from 'standard' to 'good' or 'best practice'. This included terrazzo tiling, concrete blockwork and paving, and cement replacement materials such as ground granulated blastfurnace slag and pulverised fuel ash.

Some low embodied carbon alternatives were also identified and recommended to the design team. These included precast concrete beams, micro-perforated aluminium panels and tiling, exposed concrete ceilings, castellated steel beams and flexible plumbing.

A simple to use embodied carbon estimator tool was also developed that allows the contractor to monitor the construction stage embodied carbon performance against the design team's specifications.

Operational carbon

Operational carbon emissions were modelled using the IES and iSBEM compliance tool for Part L. It has been estimated that the buildings will emit around 85kgCO2e/m2 per year, which totals 235 tCO2e for the whole project per year or 11,750 tCO2e (assuming a 50-year life cycle).

Life cycle carbon assessment

Over the life of the building certain elements (containing embodied carbon) will be replaced and, although life cycle carbon assessment was not part of the original commission, it was conducted as a theoretical study after the main carbon assessment had been finalised. The exercise involved comparing the embodied carbon figures with operational and life cycle replacement carbon emissions. Life cycle replacement emissions were based on applying the estimated service lives to the assets already covered in the embodied carbon study. The energy used to install a given element was also included.

Outcome

Although the life cycle carbon assessment was commissioned relatively late in the design process, the project team's drive to improve the sustainability performance of the station has led to some significant carbon savings by focusing on material selection. We evaluated the performance of materials against value, cost effectiveness, aesthetic characteristics and climate change. While embodied carbon was not considered from the first stages of the project, a considerable reduction (11%) was achieved through appropriate material selection, but more could have been achieved if this had been considered earlier. Another important factor was having the contractor involved in the design development early so it was able to have an input into the materials choice considerations, and the final 'carbon budget'.

The life cycle carbon assessment applied on the project has shown that it is possible to analyse embodied, operational and replacement impacts of design solutions at the same time. This ensures that optimal climate change mitigation measures can be considered and implemented. However, we found that the accuracy of quantifying carbon reduction/mitigation measures rises in the later stages of the assessment. A cross-check of results of any similar analysis is therefore recommended using different methodologies, tools and databases.

Piotr Berebecki and Sean Lockie of Atkins/Faithful+Gould were Lead Authors of the Methodology to calculate embodied carbon of materials information paper

Further information

Related competencies include: M009, T065