Increasingly, carbon accounting and carbon cost management is being promoted as a service by construction cost planners as being complementary to the more traditional cost management on projects.

(image via Freepix)

Design stage and pre-contract QS services now include embodied carbon measurement, benchmarking, carbon budgets and risk allocation for carbon pricing.

Defining the amount of carbon emissions attributed to infrastructure and building projects has never been so important and so widely promoted by leading cost management firms as services marketed to clients. Whereas economists and policy makers mull over the impacts of international and domestic cross border carbon taxes, carbon credit and trading schemes, emissions targets and the like, it is the design, engineering and consulting teams that are now more frequently tasked with accounting and reporting carbon emissions on projects.

Major QS firms such as Rider Levett Bucknall now report they are being asked to provide whole life carbon assessments on schemes on as many as 1 in 3 of their projects. A 2023 survey by QS software company RIB reported that amongst 253 unique responses from respondents working in the architecture, engineering and construction industry across Asia Pacific, Europe, the Americas and the Middle & East & Africa some 26% of consultants now track embodied carbon content in some form on their projects.

Under its ‘Decarbonising Infrastructure Delivery Policy’ aimed at reducing upfront carbon in infrastructure, the NSW government last year produced technical guidance for embodied carbon measurement for infrastructure projects. And in the UK and adopted internationally by members of the Royal Institution of Chartered Surveyors (RICS), there is now a new RICS badged training programme entitled “Certificate in Whole Life Carbon Assessment”. This has been developed to provide participants with the skills and tools to carry out carbon assessments in line with the requirements of the whole life carbon assessment (WLCA) standard 2nd edition which was also released last year. This training programme developed for quantity surveyors is designed to be completed within a 9-month period, which includes the time allotted for final assessments.

Tracking the carbon through a project’s life cycle is a very tricky exercise and it is taking the industry quite some time to agree on methodologies and reporting standards such as preferred by the RICS WLCA. We are not talking here about capturing the carbon footprint of a business entity or government organisation where various ‘green’ carbon mitigation measures can be implemented for procurement and business operations.  For specific projects, modelling various design scenarios to assess their carbon content and cost can be challenging. For this reason, involving sustainability consultants early and using carbon calculators is essential to provide feedback to the architects, design team and contractors throughout a project. Clear information, such as adding an adjacent carbon column to cost plans, makes decision making faster and more effective.

Figure 1 below is an illustration of an iterative stage by stage approach to carbon cost assessments for buildings given by one leading QS firm in Australia/Oceania.

(Fig 1. Embodied carbon assessment through the project lifecycle (Source: Turner & Townsend, www.turnerandtownsend.com)

The basic principle of calculating embodied carbon is to multiply the estimated quantity of each material or product by a carbon factor (normally measured in kgCO² e per kg of material), ‘e’ meaning equivalent global warming impact which for carbon is a factor of 1. However, this new costing approach involves converting carbon emissions into a monetary value, typically using a carbon price or monetary rate. At its most simplistic, it aims to summate the carbon costs for all materials and activities to get the total carbon cost for the project. The Environmental Product Disclosure (EPD) of a building product is then a key indicator of carbon content and quantity surveyors are of course ‘numbers’ people at core.

A headache of sorts is that there are quite a number of competing EPD databases that QS’s can use. Of these, some can be used for-asset level data whilst others can be used for more specific product level emissions via specific manufacturers EPD data sets. The figures in databases are often contested values and some databases might not just show individual product disclosures but also results of project level carbon assessments primarily from (EPDs) containing A1-3 Global Warming potential (GWP values) and cradle to gate CO² values.

The primary EPD database for construction in the UK is considered to be “UKCoMDat” (United Kingdom Construction Products EPD/LCA Database). This compiles environmental performance data for construction products available in the UK market, allowing for building LCA calculations and green public procurement initiatives. Globally and here in Australia various other EPD repositories exist. These include the ECO portal, One Click LCA, EC3 and the Epic database developed by researchers at the University of Melbourne. These collect embodied and/or operational carbon as well as key non-carbon data for specific benchmarking. The literature points to some different approaches to using these databases internationally based on jurisdictional factors or differing carbon accounting standards.

At its core, construction cost planning involves setting budgets based on target elemental rates from historical cost data. Similarly, establishing carbon budgets can help decrease carbon footprints throughout design stages via allocation of carbon targets from the overall building target to individual building elements or layers based on available benchmark data. The goal of ‘designing to a cost’ rather than merely ‘costing a design’ becomes a more holistic goal of designing to a carbon cost. The environmental impacts of the material and Co2 emissions factors are drawn from the relevant database and applied to the quantities in the Cost Plan model for the building. Having interoperable data allows quantity surveyors to integrate this data into popular take-off and estimation tools used, like CostX, Candy, Procore and Buildsoft.

(Fig 2. Using OneClick LCA database for and RC Concrete CO2 calculation

The introduction of a carbon budget allows a breakdown of where the carbon emissions are found within the building that is being assessed. Benchmarking allows a carbon comparison of each iteration of the proposed design which can be linked back to considerations around the size, morphology, height and functional spaces of the building. Consultants can integrate carbon assessment with BIM models to enhance accuracy and streamline data flow or create an embodied carbon rate library using the pre-existing embodied carbon rates.

(Fig 3. Sample Model Building 3 Storey A Grade Modern office 2700m2 GFA)

In the illustration of a typical modern 3 storey A grade office building, I have used a reference building with CO2e emissions factors drawn from databases to illustrate a QS approach to an embodied carbon budget for key elements of the proposed design. The focus in this model is on the key materials being steel, cement and aluminium however other material including lower emission materials such as timber can be brought into the model.

So in my basic modelling, there are quite a few assumptions as to product sourcing, transport etc. that all have an impact on the carbon accounting and the model needs to be priced at a prevailing Carbon KgCO₂e price that is jurisdictionally relevant.

More broadly, my examination of the growth of QS services in this area shows Carbon measurement is becoming more established across the industry, nonetheless with some caution in using carbon factor database figures in calculations.

My conclusion is that peak professional bodies have prioritised developing a robust carbon assessment methodology and appropriate training for the QS industry as it increasingly develops new approaches to assessing cost and risk in terms of carbon assessment reporting.

Looking ahead, we will need more comprehensive modelling and fully understood methodologies that can dynamically model the Co2 emissions at various stages of the life cycle of buildings. These assessments will need to provide reliable and robust results to support decision-making with the overarching goal of carbon footprint reductions.

By Dr Timothy O’Leary, Lecturer in Construction Economics, Melbourne School of Design, Melbourne University