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BIM and carbon performance

How far can BIM help improve carbon performance, and what are the requirements for achieving this? AECOM’s Robert Spencer and James Daniel assess.

We are all aware of the huge benefits that Building Information Modelling (BIM) can bring to projects in our industry. But one of the less-talked-about advantages is the potential for BIM to improve the carbon performance of an infrastructure project. The big questions now are how far can BIM help improve carbon performance, and what are the requirements for achieving this?

It’s certainly a good time to be asking such questions. The government has embarked on a four-year programme for sector modernisation, as outlined on its UK BIM taskforce website. One of the key objectives is to reduce capital cost and the carbon burden from the construction and operation of the built environment by 20 per cent.

"Carbon in relation to BIM is most useful when the attributes of materials and components in a design have an industry-accepted carbon emission factor associated with them." 

The carbon performance of a project is already seen as a key performance indicator by the Civil Engineering, Environment Quality and Assessment Scheme, commonly known as CEEQUAL, although the link with BIM has not yet been made explicit. However, it is expected that this will be addressed in future CEEQUAL revisions.

With that in mind, AECOM clients that are looking to embed BIM as a tool to assist in the feasibility, construction and maintenance of their infrastructure, are now also expecting carbon performance as a key outcome.

The Institution of Civil Engineers identified the concept of considering carbon emissions from the construction and operation of infrastructure in the same way capital expenditure (capex) and operational expenditure (opex) have always been incorporated. In this instance, operational carbon (opcarb) is the term used to describe carbon emissions during the operation, use and maintenance of an asset, as well as the emissions associated with the users of the infrastructure. Capcarb, meanwhile, describes those emissions embodied in a construction product – mainly the materials and emissions arising from energy used in the construction process.

Carbon in relation to BIM is most useful when the attributes of materials and components in a design have an industry-accepted carbon emission factor associated with them. Therefore, any adjustment in material requirements and component specifications has both a financial cost and carbon cost variation.

When aggregated using a BIM process, any shift in the overall design model will automatically indicate the costs or savings in carbon associated with the change. This empowers stakeholders with the decision-making process where carbon emissions are concerned. BIM is, therefore, not about directly reducing carbon, but rather goes some way in revealing how changes in the design process can reduce it.

To aid this process, AECOM has developed WLCO2T, which stand for “Whole life costs of carbon tool”, that measures the whole-life cost and whole-life carbon footprint of alternative maintenance strategies for pavement analysis over a 60-year period. Using this tool, AECOM has helped clients develop a whole-life cost model, finding ways to reduce quantities of construction materials used, thereby generating a smaller carbon footprint.

"Clients that are looking to embed BIM as a tool to assist in the feasibility, construction and maintenance of their infrastructure, are now also expecting carbon performance as a key outcome."

In order to achieve the full benefits of BIM, the process must be used with appropriate embodied carbon data included in the material and process specification. In summary, the requirements include having good capcarb and opcarb emissions indices linked to BIM attributes, as well as having a whole-life approach to procurement. Companies should also set out clear improvement objectives and benchmark data and have the latest BIM software to achieve the best results.

Another requirement is to deliver advanced modelling by industry standards, or client-defined, bespoke requirements together with lots of processing power and intelligent analytics in order to generate the biggest savings. This is something consultancies can help clients with.

As industry gets to grips with requirements of Level 2 BIM for publicly procured works from 2016, there is now a wider realisation of Level 3 BIM, part of the government’s recently announced Digital Built Britain. It’s clear to see that the focus on enabling total cost and carbon outputs is here to stay.

BIM is set to help more companies identify priorities for carbon reduction through modelling alternative options at an earlier stage of an infrastructure project. This, in turn, allows for an investigation of different construction materials to determine which is most effective to reduce in-use energy consumption and embodied carbon. The future looks bright for BIM and carbon performance. 

Robert Spencer is director for sustainability and James Daniel is technical director for technology and data solutions for AECOM

 

If you would like to contact Jackie Whitelaw about this, or any other story, please email jackie.whitelaw@infrastructure-intelligence.com.