Towards net-zero carbon buildings: tackling uncertainty when predicting the carbon footprint of construction products and whole buildings

To counter significant levels of climate change and biodiversity loss, the UK and numerous other countries have set targets for "net-zero" greenhouse gas emissions. Rapid reductions in the built environment are crucial, since it drives 42% of global energy-related carbon dioxide emissions.

To achieve net-zero carbon buildings, we must reduce both:
1. OPERATIONAL CARBON - the emissions caused by a building's operational use
2. EMBODIED CARBON - the emissions caused by 'everything else', such as the manufacturing of materials, transportation to site, onsite construction, refurbishment, and disposal.

Given the huge amount of construction required for new build and retrofit around the world, it is critical that embodied carbon is addressed, while we continue to tackle operational carbon.

Indeed, the UK Government's 'Industrial Strategy: Construction Sector Deal' aims to halve the greenhouse gas emissions from the built environment by 2025, and to shift focus from operational to whole-life performance. Since May 2019, over 1,000 architecture and engineering practices have committed to reducing both embodied and operational carbon (these are together referred to as whole-life carbon; WLC). The Royal Institute of British Architects has set WLC targets for 2030 and 2050 in its 'Climate Challenge', and the new London Plan will require all 'referable planning applications' to calculate and reduce WLC.

However, there are persistent challenges to predicting embodied (and therefore whole-life) carbon, and thus minimising it in practice.

In particular, uncertainty is typically ignored. At the levels of individual construction products and whole buildings, models are typically deterministic in nature, producing single-point estimates of WLC. In practice, it is then unclear how confident designers and engineers can be that one option will be lower-carbon than another. In other scientific disciplines, probabilistic approaches are more common, producing results with confidence intervals and using statistical significance tests when making comparisons. Such rigour is now essential for predicting the WLC of buildings, to ensure that low-carbon design intentions are achieved in reality.

This research therefore aims to significantly improve the treatment of uncertainty when predicting the WLC of construction products and whole buildings. We will work with project partners across the supply-chain of low-carbon buildings, including product manufacturing, low-carbon policy, and the design of structures and buildings. At product level, we will improve the treatment and communication of uncertainty in Environmental Product Declarations. At building level, we will develop and test a probabilistic approach for predicting whole life carbon through the design process. To achieve impact, we will engage international initiatives and standards that will define industry practice into the future.