Buildings and construction account for about 35% of all CO2 emissions globally, much of which is operational. Any measures to reduce the amount of materials in each new project, or to prolong the lives of the embodied materials by reusing, retrofitting, refurbishing, repurposing or deconstructing the infrastructure at the end of its first life could contribute significantly to GHG reductions over the medium term. The EU allows members to mandate the use of Building information Modelling (BIM) systems for state contracts and suggests that it could save between 13-21% in construction and 10-17% in operation of buildings.
BIM is generally understood as complex software which can link together all the elements in a building so that in the design stage, changing a single element (such as wall height) automatically modifies all other connected elements of the design. In essence, once the ‘bones’ of a design have been set down, the individual constructors (from ground works to heating and ventilation contractors) can work on their sections simultaneously while still able to electronically check back with the other constructors to ensure that the designs fit seamlessly together.
The main advantages cited are in early design visualisation, better coordination and early detection of design clashes which would otherwise cause waste and rework. However, more advanced specialist ‘tools’ can run off the platform, for example enabling iteration of the operational thermal efficiency against embodied carbon in materials chosen, offering tangible, measurable benefits to the client. Disadvantages include the investment in skills development and software, plus enforced changes to long-established ways of working – keeping a BIM model’s inputs accurate and complete across multiple businesses and inputters is essential to reap the benefits but requires considerable discipline. Notably, the key benefits are all intangible which makes calculation of a return-on-investment awkward and the decision to invest in BIM more difficult.
The CircEUlar project has an emphasis on GHG reductions: here in Oxford we are looking at how BIM can help. It is apparent that the benefits for small architects and constructors, working (for example) on single home projects with a single contractor, may be limited, and in addition they may not have the resources to devote to its implementation. We are arranging a series of interviews to understand this better. Larger developers building office blocks, industrial units and public infrastructure appear to have increasingly adopted BIM in certain countries. Again, we are arranging interviews to explore this further. There appears to be the potential for a ‘digital divide’ between an industry working on 3D CAD and an industry working on BIM, which could become increasingly unbridgeable as tools get more complex.
BIM can also contribute to the Circular Economy through the use of its data in many other areas. Buildings are currently overspecified in terms of materials: better data could give designers the confidence to reduce (for example) the thickness of pillars and walls, or allow substitution of existing materials for composites of lower embodied carbon and higher thermal resistance. Transfer of BIM data into operational management systems could be the basis for sensor-driven systems to reduce operational energy use – the phase of a buildings life with the highest energy demand – and at end of life enable refurbishment of the building’s skeleton, or reuse of dismantled parts such as steel girders and concrete beams.
We are continuing to research towards the goal of understanding how large the multiple impacts from BIM could be, and how these could feature in modelling future GHG emissions.
By Martin Burgess, Environmental Change Institute, Oxford.