Why buildings aren’t like vegetables: tackling embodied carbon

19 Jun 2023

Cornerstone Climate

Apartment block with many balconies

By Estelle Dehon KC and Rowan Clapp

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We begin by recounting a conversation. In providing his views on planning in a large city, an officer reportedly said he thought of “buildings as a bit like vegetables, if you don’t like the ones you have planted, you can pluck them out of the ground and start again.”  

It is debatable whether this view was ever apt. Certainly, it is only within the last 100 years or so that architecture and development has assumed a ‘blank slate’ site, requiring the demolition of whatever buildings are in a space and ignoring the materials already in existence. In light of the growing importance of re-use in the planning system’s response to the global existential threat of climate change, we explain in this paper just how inapposite the ‘vegetable’ simile is. We highlight how calculating the environmental credentials of any development requires not only an appreciation of its operational emissions but also the ‘embodied’ carbon emissions within the project’s materials. We argue that embodied carbon emissions are a previously overlooked frontier for emissions reductions and emphasise that accurate calculation and reduction of this aspect of the development control process will likely be the subject of increased regulation in both legislative and policy terms in the UK. The effect, we explain, will be a prioritisation of retrofitting over demolition and replacement.

Developers therefore delay calculation of the embodied carbon within their proposals at their peril. Any attempt to display genuine environmental credentials or to engage with the future of the planning system requires close consideration first of embodied emissions of a proposal, and second of whether retrofitting an existing building would result in emissions reductions. In short, buildings are not like vegetables (apart from the Gherkin).

Climate emergency: a familiar story

Use of the term ‘climate emergency’ climbed by more than 10,796% between 2018 and 2019 and was accordingly crowned 2019 Oxford Word of the Year by Oxford Dictionaries. It is defined as “a situation in which urgent action is required to reduce or halt climate change and avoid potentially irreversible environmental damage resulting from it.”

Increased reference to ‘climate emergency’ was no etymological accident. Between 2018-19, 11,000 scientists signed an article in BioScience declaring “clearly and unequivocally that planet Earth is facing a climate emergency”. Bristol City Council first declared a climate emergency in November 2018 and since then, over 300 local authorities have followed suit.

The importance of the issue is (hopefully) beyond question. This year saw the UK confirm a new record-high temperature of 40.3oC and Europe suffered its worst drought for 500 years.

It is no surprise then, that UN Secretary-General António Guterres remarked in an address titled The State of the Planet that “[m]aking peace with nature is the defining task of the 21st century. It must be the top, top priority for everyone, everywhere.”

The Climate Change Act 2008 (“CCA”) is the statutory basis for the UK’s response to climate change. It identifies a need for the reduction in emissions of CO2 and other harmful greenhouse gasses, sets reduction targets for those, and seeks to establish a framework by which the targets may be delivered. Section 1(1) of the CCA (as amended by The Climate Change Act 2008 (2050 Target Amendment) Order 2019 commits the UK to reducing greenhouse gas emissions by 100% of 1990 levels by 2050 (“net zero target”). The net zero target is partly aligned with the UK’s commitment within the Paris Agreement to hold increase in global average temperature to “well below” 2oC and to “pursue efforts to limit the temperature increase to 1.5oC above pre-industrial levels.”

The CCA requires the government to set “carbon budgets” as ‘stepping stones’ to meet the total emissions reduction target within s.1 CCA by 2050. By s.4(1)(a) CCA, such budgets are to be set for a period of five years and the Secretary of State has an obligation to ensure that the UK carbon account for any period does not exceed that budget (see s.4(1)(b) CCA). Adopting the advice of the Climate Change Committee, the Sixth Carbon Budget requires the UK to achieve a 78% emissions reduction by 2035 to achieve the net zero target by 2050. (See Art. 2 of The Carbon Budget Order 2021 (S.I 2020/750).

Climate and the construction industry

The Global Status Report for Buildings and Construction 2021 revealed that the building and construction sector accounted for 36% of global final energy consumption and 37% of energy related CO2 emissions. Reductions in the construction sector would therefore have a meaningful impact on overall carbon emissions and make a real contribution to meeting the net zero target.

A crucial distinction is central to unlocking our ability to reduce constructions emissions. Considering the carbon emissions of a development has typically focussed on ‘operational’ emissions, namely those concerning the energy needed to heat, cool and/or power a project. But we can also measure the often overlooked ‘embodied’ emissions of a development: those arising from the production of the materials that will be used throughout its lifecycle, including CO2 produced in demolition and construction, the manufacture of materials and, depending on the circumstances, the eventual demolition of the building and the disposal of associated waste.

Thus far, reducing the carbon impact of developments has focussed on their operational efficiency. For example, in last year’s Heat and Building Strategy (“HBS”) the Government identified that decarbonisation would involve “improving our buildings’ fabric efficiency, changing the way we heat and cool our buildings, and improving the performance of energy-related products.” Producing the HBS involved the collection of data on the operational emissions of buildings, which has led to further tightened targets for those emissions. The government, however, resisted similarly extensive analysis in terms of embodied emissions within the HBS, and the closest the 2021 Net Zero Strategy comes to mandating such consideration is a proposal to “aim […] [to] improv[e] reporting on embodied carbon.” This is despite the UK Climate Change Committee (CCC) recommending, in 2020, that plans needed to be developed rapidly to “support the assessment and benchmarking of whole-life carbon in buildings.”

Overlooking the contribution that embodied carbon makes to the overall emissions picture is a mistake: embodied carbon makes up a staggering 11% of global carbon emissions. Indeed, as Alan Muse, Head of Construction Standards at the RICS put it recently, “if cement were a country, it would be the third largest emitter of carbon in the world.”

There is, therefore, plenty of room for future legislation and policy to aim significantly to reduce embodied emissions in the context of reducing overall emissions from the construction industry. The World Green Building Council agree: in a recent report titled Bringing Embodied Carbon Upfront, they demonstrate how we could reach 40% less embodied carbon emissions as soon as 2030 in all new buildings, infrastructure and renovations.

Indeed, there is an increasingly strong trend towards the regulation of embodied carbon across Europe. Five EU countries (Sweden, France, Denmark, Finland and the Netherlands) have passed regulations requiring mandatory consideration of the whole life carbon emissions from buildings, including embodied carbon emissions. There has also been EU-wide focus on embodied carbon, with the European Commission proposing a revision to its Energy Performance of Buildings Directive which proposes that as of 2027, new buildings over 2,000 m2 will be required to have a whole-life carbon assessment. The proposed Directive also calls for national building renovation plans which will require Member States to describe policies for reducing whole lifecycle embodied carbon emissions.

It follows that even if there is no present mandatory regulation of embodied carbon in the UK, the principle of such regulation appears to have been accepted by our neighbours and the adoption of future controls on embodied carbon is therefore increasingly likely, especially if the UK wishes to continue to claim it is a leader on climate issues.

This is not just an Oxford Street development proposal…

A recent development in a prominent London location reveals much about the direction of travel in assessing embodied carbon and considering the appropriateness of new development. The proposed development for the demolition and replacement of the present Marks & Spencer flagship store at 456-472 Oxford Street was recommended for approval by Westminster City Council on 23 November 2021.

The proposal was not without sustainability credentials. It was aiming to achieve BREEAM Outstanding, WELL Platinum and WIRED Platinum accreditation, included a carbon offset payment of £1,198,134, and was accompanied by a whole life-cycle carbon assessment which included embodied carbon impact calculations.

Nevertheless, opponents highlighted that the buildings proposed for demolition were only between 36 to 90 years old and challenged the embodied carbon costs of the development. The demolition and replacement of the buildings is expected to release just under 40,000 tonnes of embodied CO2 during the construction phase, with the total embodied cost over a 60-year lifecycle reaching 53,000 tonnes of CO2. A Westminster Councillor who voted against the proposal explained: “last week the council announced that we are going to spend £17m to retrofit all of our buildings to save 1,700 tonnes of carbon every year. And so, this is 23 years of what we have just saved as a council, going into one building.”

High levels of embodied carbon were also instrumental in Mr. Gove’s dismissal of The Tulip, a proposed 305m observation tower that was to be sited at 20 Bury Street at the heart of the City of London. The Secretary of State’s decision to dismiss the appeal against refusal for The Tulip (dated 11 November 2021) recorded his view that the proposal was a scheme with very high embodied energy and an unsustainable whole life-cycle” and that “the extensive measures that would be taken to minimise carbon emissions during construction would not outweigh the highly unsustainable concept of using vast quantities of reinforced concrete for the foundations.

In the case of the proposed M&S development, the embodied carbon cost of replacement caused many to question the value of demolition and building anew, highlighting the increased value of retrofitting and refurbishment in the climate crisis context. Government architecture adviser Nicholas Boys Smith noted “the environmental case […] is gossamer thin at best. We should be adapting the remaining building not smashing it up.”

Simon Sturgis, former Sustainability Advisor to the RIBA Stirling Prize, produced a report criticising the M&S proposal and emphasising the importance of reuse/retrofitting in the fight against climate change. In his report, Mr. Sturgis found that a “comprehensive retrofit on this site is an opportunity to explore a new form of architectural solution for sites such as this”. Mr. Sturgis went on to stress the importance of retrofitting in meeting net zero:

“If WCC allows proposals for existing buildings to be demolished and replaced without properly prioritising comprehensive retrofit solutions, then it will not meet its stated climate change commitments. Meeting UK, GLA and WCC Net Zero targets does not mean ‘business as usual plus a high BREEAM rating’. A very different approach must be adopted and as soon as possible. […]  you cannot separate the new build from the fact that there are valuable carbon assets already on the site eminently capable of reuse. To meet UK/GLA/WCC carbon targets you must look at the total carbon equation including a comprehensive retrofit.”

If there were any question that embodied carbon is likely to be a central issue in large redevelopment schemes, that has been answered by responses to two further schemes proposed by the City of London: (1) the proposed “London West Wall” development of part of the Barbican, which includes plans to demolish Bastion House and the Museum of London, has been strongly opposed on carbon impact, including embodied emissions, with publication of its whole carbon lifecycle assessment having invigorated, rather than quelled, the opposition;and (2) the “Justice Quarter” scheme, which involves replacing six historic buildings with three new ones, provoked the ‘RetroFirst’ campaign to commission an embodied carbon analysis which concluded the scheme was incompatible with net zero and caused the Chair of the CCC to call for a change in planning policy to disincentivise demolition.

The promotion of retrofitting has already been recognised as a key political planning issue in the context of climate change. The new Labour administration at Westminster City Council are currently consulting on a new “retro-fit” policy designed to prioritise the retrofitting and refurbishment over unnecessary demolition and redevelopment, and previously campaigned to reduce VAT on retrofitting to 5%.

Importantly, in March, the Mayor of London issued London Plan Guidance which states that “retaining existing built structures for reuse and retrofit, in part or as a whole, should be prioritised before considering substantial demolition, as this is typically the lowest-carbon option.” There is also a clear presumption against demolition which an applicant will be required to rebut: “if substantial demolition is proposed, applicants will need to demonstrate that the benefits of demolition would clearly outweigh the benefits of retaining the existing building or parts of the structure.” Local planning authorities across the country are considering issuing similar policies.

Revealingly, although two Greater London Authority reviews confirmed that the Mayor would not disturb the Council’s recommendation to approve the M&S development, Michael Gove chose first to pause consideration of the development and has now called-in the matter for a Public Inquiry beginning 25 October 2022. The Secretary of State’s intervention is a sure sign that the argument for retrofitting, refurbishment and redevelopment is gaining traction.


Tackling embodied carbon and the consideration of retrofitting over redevelopment are also key issues being raised by the construction industry itself. The 2021 Prizker Prize (the ‘Nobel prize for architecture’) was awarded to a French firm, Lacaton and Vassal, famous for retrofitting unused social housing. Their motto? “Never demolish.” An Architect’s Journal campaign called ‘Retrofirst’ which prioritises retrofitting over demolition and rebuild has attracted support from over 200 architecture practices, organisations and individuals.

Recognising that tenants are increasingly demanding buildings with better environmental credentials has driven significant re-fitting projects in practice: flexible office provider Workspace recently purchased a former bus factory in Islington for £45m and is refitting it into modern offices. Elsewhere, Grosvenor, the Duke of Westminster’s property company, has pledged £90m by 2030 for retrofitting its buildings, including the repurposing of a former ice factory built in the 1830s near Victoria for offices, shops and a rooftop restaurant. The business case is obvious, as Grosvenor’s chief executive James Raynor explains: “[a]t the top end of the office market, we are starting to see that people will walk away from buildings that don’t offer great environmental credentials.” Investors and funders are arguably the main reason for what appears to be a “step-change” in ESG (Environmental and Social Governance) requirements. The “E” in ESG – environmental and social governance – is ever more focused on carbon reduction, “which is arguably the most pressing concern for the industry“. BREEAM ratings are increasingly no longer considered sufficient, especially by international investors whose funds require demonstrable whole-life carbon reduction.

The future: embodied carbon and repurposing the past

Data is fundamental to calculating embodied carbon and therefore appreciating the carbon savings of a retrofit over replacement. There is a growing emphasis on the mandatory assessment of a proposal’s carbon impact over its whole life (as against just the operational phase) in the form of whole life carbon assessments. Again, industry is driving the change: in December 2021, seventeen industry leaders wrote a letter to the construction minister demanding the urgent introduction of whole life carbon assessments.

The UK Green Building Council’s Net Zero Whole Life Carbon Roadmap for the Built Environment recommends mandatory measurement and reporting of ‘whole-life’ carbon by 2023 and the imposition of minimum standards for embodied carbon by 2025. That recommendation chimes with that of the Climate Change Committee on the need for mandatory whole life carbon assessments to be required by 2025 (see its June 2022 Report: Progress in Reducing Emissions).

Again, there is support for regulation within industry. In July 2021, five construction industry professionals proposed Part Z, an amendment to the UK Building Regulations 2010 which would require whole life carbon assessments for projects greater than 1000m2 (or 10 dwellings) starting from 2023 for buildings other than dwellings and extending to dwellings by 2025. The proposed amendment also proposes a regulation for minimising carbon emissions for all buildings from 2027. The proposal has attracted significant support from those in the construction industry, including from the Royal Institute of British Architects, JLL, and British Land.

A recent Environmental Audit Committee Report, Building to net zero: costing carbon in construction criticised governmental “inaction” on embodied carbon and urged the introduction of a mandatory requirement for whole life carbon assessments as “the single most significant policy the Government could introduce” which would also “incentivise greater retrofitting.” The Committee recognised that a “broad cross-section of the construction industry” was willing to undertake whole life carbon assessments, referred to the proposed Part Z amendment, and recommended that regulations mandating whole-life carbon assessment be introduced in keeping with the same (although amending the timeline).

The EAC report recorded that a Bill seeking to enact Part Z had recently been introduced in the Commons. That is a reference to the Carbon Emissions (Buildings) Bill which had its first reading on 18 March 2022 and was scheduled for a second on 18 March 2022. The Bill was subsequently shelved when the proposer, Duncan Baker MP was promoted to a position within Michael Gove’s Department for Levelling Up, Housing and Communities. It was then reintroduced on 20 June 2022 by Jerome Mayhew MP, who commented that the Bill “is a development that has come from the industry and is supported by it.” The Bill is expected to have a second reading within a few months.

The government’s response to the Environmental Audit Committee Report foreshadows the likely introduction of both mandatory whole life carbon assessments and carbon emissions limits on development, both of which will promote retrofitting. The response confirms, for example, that whole life carbon assessments “are likely to have a significant role” in lowering emissions and that “a standardised method of calculation is required” such that the government would consider whether “endorsement of specific standards, methodologies or tools for assessing whole-life carbon is appropriate.”

Tellingly, the response confirms the government “intends to consult in 2023” on amendment to the Building Regulations 2010 and also that it “intend[s] to review the [NPPF] to make sure it contributes to mitigation and adaptation as fully as possible.” In that context, then, it appears highly likely that the proposals set out within Part Z will amend the Building Regulations 2010 and that there may be amendment to the NPPF to reflect the importance of considering embodied carbon and/or retrofitting in both plan making and in decision taking. Simply put, it looks as if embodied carbon won’t be the “concrete and steel elephant in the room” for very much longer.


The potential for emissions reductions within the construction industry is vast, and achieving them likely to make an invaluable contribution to meeting the net zero target to which the UK is committed. Doing so, as we’ve outlined, involves an appreciation of both the operational and embodied carbon impacts of a development. There is a growing adoption of mandatory whole life carbon assessments among our European neighbours, the UK construction industry is clearly calling for regulation requiring the same, and the recommendation of the Environmental Audit Committee is that such regulation should be imposed without delay. We consider that whole life carbon assessments, embodied carbon limits, and policies limiting demolition (perhaps through a rigid hierarchy for decision-making, akin to the cooling hierarchy) are likely to be key elements of the planning system in future. As we’ve explained, accessing data of this kind is likely to promote retrofitting as an alternative to redevelopment, and it is already the stated policy of some authorities to express a preference for re-use in planning.

Forward thinking developers will therefore consider the embodied emissions of their proposed developments now and consider whether alternative retrofitted schemes may be more appropriate in the circumstances in order to maximise their chances of obtaining funding, securing permission and evidencing their environmental credentials to clients.