Home » Carbon calculators for the built environment – does yours add up?

Carbon calculators for the built environment – does yours add up?

Published: 06/06/2024

Reducing carbon emissions is one of the biggest challenges facing our industry. 40% of GHG (greenhouse gas) emissions come from the built environment and, if we do not act immediately, this figure could double by 2050. With the wide variety of carbon calculators on the market, it would appear progress has been made in finding a solution to the first part of the problem – calculating carbon.

It seems simple enough. With these figures the industry can begin to make better, informed decisions about the types of materials and components used in any construction project.

But how are these carbon calculators arriving at their assessments? Compare the results of one carbon calculator with another and you’ll find the figures vary considerably. What’s the reason for this?

Despite the good intentions behind many of the carbon calculators out there, here’s why they don’t always add up…

We need four things to make consistent carbon assessments of our projects and have a better chance of driving down emissions:

  • Methodology: a consistent, industry-agreed methodology that clearly outlines what will be included in the calculation
  • Data: a consistent data source used in the calculation
  • People: suitably qualified people to do the calculation
  • Regulation: regulation or certification to make sure that the methodology and data are being used correctly

And here’s our assessment of where we stack up as an industry against each one.



The industry has widely adopted the RICS (Royal Institution of Chartered Surveyors) Standard on whole life carbon assessments, but the application of the standard varies in the tools and calculators seen in the industry.

The various tools and calculators available today measure and include different things – some focus on the emissions of the initial construction, others include the in-use stage, some even include the end-of-life stage, but often these are calculated differently.

The methodology also needs to change depending on the stage that the project is at. At the early stage of design, you won’t necessarily know the materials you’ll be specifying, so the calculations you need to employ will have to change.



Unfortunately, we don’t have as rich a history of carbon data to draw upon as we do cost data. Although EPDs (Environmental Product Declarations) are becoming more common, they’re not available for every construction product. In some cases, the EPDs that are available for a product don’t have the information needed – mandatory fields might not be completed and critical pieces of information such as the unit of measure aren’t identified, or consistent, with other products of a similar nature.

Other assumptions – life expectancy, the installation process and what happens at the end of the life of the product – also have a dramatic impact on the figures used. Something, again, in which there lies inconsistencies.

Because of the lack of historical project data, we also find ourselves with the challenge of not being able to understand if our assessments are good, bad or indifferent. We simply need to know these benchmarks to ensure we’re confident that we’re making the right decisions on our projects.

We also need to make sure we have a data feedback loop. Assessing a project’s emissions before construction is one thing – making sure we understand the emissions during and after construction, and throughout its life is something else. We need to make sure we capture the ‘as built’ information and that this is fed back to help improve and refine assessments in the future.



Currently anyone can complete a whole life carbon assessment, qualified or not. This is likely to present issues as understanding on applying the methodology will vary dramatically. As an industry we like to confuse ourselves by using terminologies and acronyms.

These need to be understood by anyone undertaking an assessment, let alone a collective understanding of how and what to measure and report.

The likely outcome is that people without a common level of training and qualification will interpret things differently during assessments – even if we adopted a single methodology, calculation, and dataset.



There is currently no industry-wide regulation to ensure carbon calculators use consistent methodologies, are operated by appropriately skilled professionals, or use consistent data. Until this is resolved by the industry there will continue to be inconsistencies in the calculations.

We’ll also be limited in our ability to accurately benchmark, learn from each other, and drive down emissions in the built environment.


What is the answer?

We’re undoubtedly all trying to drive this critical issue forward. And we’re making good progress on several things – we now have a common methodology through the updated RICS Whole life carbon assessment (WLCA) for the built environment standard. We also have a growing bank of verified data in the product database section of the Built Environment Carbon Database (BECD). Currently we hold more than 34,200 product Life Cycle Assessments (LCAs) and Environmental Product Declaration (EPDs) dating back to 2012. And we’re beginning to see more EPDs being produced, despite their high cost, as more manufacturers see the benefits of demonstrating their green credentials.  

This data forms the basis of our new service, the Life Cycle Evaluator, which, combined with our trusted cost data, measures and reports on whole life costs and whole life carbon emissions at the same time.

However, if we’re to reach our goal of lower emissions, we need to work together, share our insights, and continue learning.

Life Cycle Evaluator

Life Cycle Evaluator (LCE) is a compliant whole life cost and carbon solution available for the UK Built Environment. Life Cycle Evaluator is designed to generate fully compliant capital cost, life cycle cost and whole life carbon assessments for your project at the same time.

Find out more