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Matthew Mapp

Associate Head of Buildings Whole Life Carbon


A refurbishment renaissance is quietly taking place in towns and cities across the country – but more needs to be done and faster if we are to meet net zero targets and meaningfully improve the way we plan and build the developments of tomorrow in the process.

Here, our Associate Head of Buildings Whole Life Carbon, Matthew Mapp looks at the importance and implementation of low carbon retrofitting, along with the role it can play in moving society towards reuse, repurposing and recycling – from wasteful to resourceful – in a net zero focused circular economy.

Why is it so important that we deliver low carbon buildings right now?

There is a growing need to address the climate emergency against the backdrop of the ever-increasing focus on whole life cycle carbon emissions, and the understanding that significant steps need to be taken within the built environment to even get close to the UK’s Net Zero 2050 target.

Key to this change is the rise of embodied carbon as a significant contributor to lifecycle emissions, given the (mostly) narrow industry focus on operational emissions over the last few decades. The move away from fossil-fuel-led combustion technologies to 100% electric HVAC buildings with high-efficiency systems that can take benefit from a decarbonising UK grid over their lifecycle, and the advent of 100% renewable electricity supply opportunities, has swung the carbon dial decisively towards embodied carbon, with >70% of the life cycle emissions typically being embodied carbon.

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However, although in carbon terms this means embodied is the major focus, having low or zero operational carbon does not equate to a low energy development. For example, if you had a 100% electric building that has a 100% renewable electricity supply, the carbon emissions are effectively zero regardless of whether you have a development energy use intensity of 70 kWh/m2/yr or 200 kWh/m2/yr. Clearly one is significantly better in energy performance than the other, and one is fit for a low carbon, low energy future and the other is not. This has given rise to what we see as the two pillars of assessment: Embodied Carbon, and Operational Energy.

Is the world ready for low carbon retrofitting en masse?

The short answer is, ‘not quite’…but we need to change that quickly.

For embodied carbon, there are currently no Building Regulations that require assessment or set targets, although there is a currently an industry-proposed amendment known as ‘Part Z’ that may bring this into focus over the coming year. Requirement for assessment was largely driven by forward-thinking clients (like GPE, British Land, Argent) who have set their own requirements and benchmarking using industry publications such as those from LETI and RIBA.

This is still considered ‘voluntary’, undertaken by developers who appreciate the shift in carbon impact towards embodied and the move from operational emissions focus to operational energy focus. A key move has come recently from the Greater London Authority (GLA), the strategic regional authority for Greater London. In the London Plan 2021, Policy SI2 requires whole life carbon assessments (WLCA) to be submitted in detail for all referrable developments. This has been supplemented by the recent release of detailed guidance for assessments and submissions in March 2022.

This is a key move, because it takes it from ‘voluntary’ to ‘mandatory’ for referable developments. This has also been picked up by a number of Local Authorities (LAs) in London such as City of London, Westminster, Southwark etc., who now often include a requirement to follow this guidance and submit a whole life cycle carbon assessment even when the project is not referable to the GLA. This is of course still a bit of a London-nucleus, which we tend to see a lot – the advent of something like the previously mentioned Building Regs amendment Part Z would be needed to take this to the wider UK audience.

The key shift in my view though has been beyond the developer, and in those areas that have a critical influence on developer decision-making. The developer is now under pressure from shareholders, investors and tenants themselves to achieve specific carbon and energy targets. These parties have their own onerous ESG and CSR policies that demand strong approach to carbon and energy reduction, and this is in turn driving developer decision-making. In the last 6 months I’ve presented to more shareholders, investors and tenant parties/lease agents than I have in the entire previous 8 years of my career at Sweco.

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There is still an education piece here in understanding what targets mean and what value meeting them can add, but this is moving rapidly. Our sustainability and WLCA teams make sure that we are on hand to help our clients to answer questions from these key stakeholders and support them in delivering the best outcomes from their projects.

For embodied carbon, evolving industry understanding and our own portfolio of over 30 developments with WLCA to the full RICS Professional Statement shows us that in new-build developments, approximately 50% of emissions are associated with building structures (substructure and frames/slabs). A further 15% is associated with facades. Clearly a focus on major retention and refurbishment of buildings that prioritises retention of these elements can make a significant difference to embodied carbon, and make achieving the more onerous LETI and RIBA benchmarks more viable.

The new GLA 2022 WLCA publication also specifically notes that opportunities for major refurbishment should be prioritised and alternatives justified in applications, moving this from concept to a requirement. However, this is a balancing act; often significant intervention is required to improve operational energy, particularly in elements such as facades and building services that dictate operational performance, and the more intervention, the more embodied carbon is typically expended. This is a fundamentally important consideration for WLCA of refurbishments, and one that underpinned our approach on 1 Exchange Square for example.

What are the key considerations for successful low carbon retro-fitting?

1. Context is EXTREMELY important

What you have already on site dictates your ability to undertake a meaningful refurbishment and actually save carbon.

These decisions need to be made on a case-by-case basis, there is no one size fits all approach for strong WLCA performance of refurbishment. Gathering existing information on the building, conducting surveys and undertaking studies that engage the entire design team are important to make sure that viable options are presented that demonstrate which option is best to progress.

This is both qualitative and quantitative, on which carbon plays a supporting role in the overall decision-making. There are various industry barriers to this that I could go on about all day…

2. Embodied expenditure vs operational savings assessments (or vice versa)

key decisions should be supported by this type of assessment, and this can be at macro or micro scales. For example on 1 Exchange Square in London, we studied double glazed glass units vs. triple glazed glass units for new façade systems. The extra layer of laminated glass had a significant embodied carbon expenditure, but an even more significant reduction to operational energy.

The embodied emissions, although increased, were still within our project target, and the improved operational story was compelling for the client because this is still something the prospective tenants are more interested in for now (as its directly effects their operations and is still the priority for them, although embodied considerations are increasing).

Having both embodied and operational data on the table the client could make an informed decision on what their priority was, and this led to effectively and timely decisions that could then be appropriately costed and progressed.

3. Refurbishment alone is not enough to meaningfully tackle embodied carbon

My opinion is that a thorough and comprehensive WLCA should always be able to undercover further opportunities to reduce embodied carbon – just retaining a frame and saying “I’ve done my bit to reduce embodied carbon” is not enough, there are always viable and often cost-effective ways to reduce embodied emissions even further.

Every one of our refurbishment WLCA studies also includes a suite of quantified material reduction opportunities that can be discussed with the client and design team and interrogated to realise achievement of even better embodied carbon performance.

How does low carbon retrofitting, fit into the groundswell for circularity?

To me, it means not just thinking about reuse of materials, systems and products from an existing building, but also how we can facilitate better reuse of materials through encouraging and enhancing future adaptability and flexibility in our new and future buildings. The two are not mutually exclusive, but can sometimes conflict (refer to ‘context is extremely important’ above).

Circularity is achieved when the economy creates resource systems that are regenerative and cyclical and sustainable. It can be both a philosophy and a set of practical actions. At the philosophical end, it can be the notion that there is no such thing as waste – only resources – and the challenge is in how to design systems that recirculate it.

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We can also help to stimulate material reuse marketplaces (things like Globechain) and find better ways of standardizing systems and materials to more easily reuse them in different contexts. Information is also extremely important. It is often problematic to find information on buildings and materials that exist today, given poor historic storage and availability of information, which can make clear identification of material-specifics problematic to pin down, and at the larger scale impact the ability to meaningfully understand whether a refurbishment is a viable option to explore.

Engaging with better data and modelling tools as identified in our latest Urban Insight report can help us to quantify and understand existing materials, and other opportunities such as Materials Passporting can be used within digital building models to influence end of life treatment for new materials.

A combination of measures is required to enhance building circularity:

  1. Prioritise major refurbishment in the first instance – and undertake suitable studies that compare options against a new-build alternative, remembering that this is context-specific and that there is no one-size-fits-all approach to this. Consider the WLC emissions against the wider context of decision-making around viability of refurbishment.
  2. Consider how materials can be reused in a hierarchical way where refurbishment of existing assets is not viable – reuse ‘parts’ of the buildings in situ (i.e. can the basement box be reused?), reuse materials directly on site, remove from site then reconstitute into new products, recycle offsite. Better understanding on what materials exist in the first place is required, and we need better tools to quantify and split out materials for reuse – current pre-demolition audits and the use of basic WRAP waste tables in the UK does not provide enough granular detail for meaningful reuse and repurposing opportunities to be explored at very early stages.
  3. Challenge the longevity of certain elements within any new building – why, in a building built in 20205, should the new structure not last 100, 120, 150 years? Studies should be conducted to demonstrate that this is possible for new structures to enhance longevity of high-embodied-carbon systems and building elements. Choosing to benchmarking using EN 15978:2011 Modules A-C can help support and interrogate this.
  4. Focus on future flexibility, adaptability and deconstructability of our new buildings – the structure should facilitate this, but all of the building components should work together to ensure that there aspects are integral to building design so that the need for future waste is reduced.