Why our Part Z proposals must be a milestone on the road to net zero

The Carbon Emissions (Buildings) Bill was introduced to parliament in February 2022, mirroring the contents of the industry-proposed Part Z amendment to the building regulations.

This call for embodied carbon regulation is overwhelmingly supported by industry, and the environmental audit select committee said in its report in May that such a policy was the “single most significant” action that the government could take in the built environment to reduce emissions.

However, at the bill’s second reading on 25 November, the government declined to support it, intending instead to consult on embodied carbon in 2023 and 2024. As such, the bill will not pass, and the industry must now reflect on the next steps.

The government’s lack of support for the bill has been criticised by many as an inadequate response to the need to reduce the 50 million tonnes of embodied carbon emitted by the construction industry in the UK each year (according to statistics from the UKGBC). What is positive though is that embodied carbon is now squarely on the government’s agenda.

What is positive is that embodied carbon is now squarely on the government’s agenda

The formal response to the bill by Dehenna Davidson (parliamentary under-secretary of state for levelling up) included the admission that reducing embodied carbon in construction is critical to meeting the UK’s net zero target, and that the industry’s “choice of materials and how we design and construct buildings will also need to change dramatically”.

Even more encouraging is that the bill has overwhelming support across Westminster. The shadow business minister was clear during the debate that Labour supports it – as does the Conservative Environment Network, which counts 41% of Conservative MPs among its caucus. Similarly, in the Lords, the bill would be supported by the 150-strong Peers for the Planet group.

The government has indicated that it is considering using planning laws to control embodied carbon, rather than building regulations. There are three reasons why this is not a good idea.

The first is that planning is too early in the process to fully assess the carbon impact of a design. Many technical decisions are made after planning, which could for example lead to changes to the structural layout, the window design or the renewables strategy. Whole-life carbon needs to be reported in the final run-up to construction, after these decisions have been finalised.

Secondly, carbon calculations, just like floor slab strength (Part A), glazing g-value (Part O) and energy use (Part L) calculations, are technical matters signed off by building control officers, not planners. Planners do not have jurisdiction over technical design components such as structural integrity and energy efficiency, nor should they over carbon emissions.

Lastly, even the planners are calling for regulation. The Greater London Authority, whose carbon reporting requirements act as a planning-based stopgap in the absence of regulation, said during the environmental audit select committee hearings last year that embodied carbon “should be part of building regulations, and [it] is something we would like to see brought forward as a proposal as part of the consultation on future homes and future building standards”.

And ­– from the Part Z website – the Royal Town Planning Institute “joins this call for more measurement of embodied carbon and its use in regulation and policy”.

The government understandably wants to avoid the Part Z requirements becoming a significant burden to small businesses. Both Part Z and the bill stay clear of small schemes: the rules apply only to buildings over 1000m², or schemes with more than 10 homes. And many firms working above these thresholds are already undertaking these calculations – the bill simply serves to clarify the rules and streamline the process.

There is plenty of precedent for this: the Netherlands, France, Sweden, Denmark and Norway have already mandated reporting and have limits in force or planned. The rest of the EU will catch up in 2027, by when legislation for reporting of carbon is proposed – for all buildings and in all countries – many of which are currently less prepared than the UK.

This approach of setting out a firm roadmap is the policy signal that tells industry that the government backs innovation to reduce emissions – the same signal given to the car industry outlawing the sale of internal combustion engines from 2030. This common sequence of “report first, limit later” gives governments time to work out details and limits while industry gets on with the task of reporting and thus generating the data needed for eventual limit setting.

We cannot and must not wait around for years undertaking high-level consultations

The bill will thus in fact directly address the government’s concern of a perceived “lack of data” by accelerating its gathering and availability.

The government agrees with the need to reduce embodied carbon in the UK, and parliament is debating the details of how. But we cannot and must not wait around for years undertaking high-level consultations, only to lead to a need to introduce such regulation on an accelerated timescale.

Our built environment industry needs the clear policy signal from the government which the Carbon Emissions (Buildings) Bill represents – and it needs it now.

Detail on the proposed Part Z can be found at www.part-z.uk. Tim den Dekker is an associate at Feilden Clegg Bradley Studios and Will Arnold is head of climate action at the Institution of Structural Engineers