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Embed circular economy thinking into building retrofit

There are a number of strategies that have been set out to accelerate retrofit across the UK for example, the UK Green Building Council’s Retrofit Playbook4. It would therefore be logical to integrate CE thinking into the pre-existing approaches suggested to accelerate retrofit. These plans typically encompass the following five areas: (1) finance and incentives, (2) technology, (3) skills and supply chain capacity, (4) policy, and (5) engagement with consumers. Implications of a CE approach on each of these areas are discussed in the sections below.

Finance and incentives

How retrofits are financed is a critical question with which successive governments and retrofit stimulus packages have struggled. Putting a CE lens on the question introduces more financial options. For example, products as a service is a CE concept, in which rather than buying a product outright, you regularly pay for the service the product provides. In retrofit terms, this could mean paying a yearly fee for a warm home, or heat. Theoretically a supplier would install fabric efficiency and energy supply measures to deliver a warm home. The occupier would pay an agreed yearly fee for this warm home. The supplier is then incentivised to ensure on-going fabric efficiency and operational efficiency of the installations continues, as otherwise they would be responsible for increasing energy use costs. This means the supplier is more likely to replace elements as required to maintain the performance. They are then in a position to remanufacture these elements for reuse, or recycle materials back into their supply chain to reduce costs. This is a simplification of an incredibly complex scenario, the economics and business case of these requires research, particularly given the 20–30 year lifespans of retrofit products, and increasing fuel prices. Furthermore, implementation of performance-based models would be challenging as they hold manufacturers and installers to a performance level—which is currently rarely the case. Post-retrofit performance is seldom tested. The EnerPHiT standard does require an airtightness test post-retrofit5, but only a small sample of retrofits seek this certification. Nevertheless, this illustrates how CE thinking could also offer new financial opportunities to stimulate retrofit.


Retrofit products and systems need to be easily upgraded, remanufactured and reused, or at least the components recycled. Fig. 1 shows three typical wall insulation methods in the UK. There are different challenges for implementing CE solutions across each of these methods. When retrofitting cavity wall insulation (Fig. 1a), holes are typically drilled into the brick to access the cavity, insulation is then blown into this existing cavity. Upgrades would typically involve blowing more insulation into the cavity. This nature of construction makes it challenging to retrofit a CE solution—e.g. where the existing insulation material can be removed and recycled.

Fig. 1: Examples of wall insulation details.
figure 1

a An example of wall insulation details, with insulation fitted between two layers of masonry construction, brick and brick, or brick and concrete block. b An example of external wall insulation: insulations typically glued and mechanically fixed to a concrete wall. c An example of internal wall insulation. Insulation can be directly glued and/or mechanically fixed to the wall, or fixed between, or onto timber battens which are attached to the wall.

External wall insulation (Fig. 1b) presents different CE challenges. A CE solution requires reversible, mechanical connections so insulation can be easily removed and replaced. The mesh and render finish will be very difficult to remove from the insulation, contaminating it and likely prohibiting recycling at end of life. A CE solution is more likely to be a mechanically attached, layered panel, that can be removed and reused, or components mechanically separated and the insulation recycled and replaced so remaining panel elements can be reused.

A CE approach to internal wall insulation (Fig. 1c) again must move away from adhesive connections and finishes to mechanical ones. The typical plaster skim finish to plasterboard makes it challenging to remove or replace any layers without damage. A CE solution could have a panelised finish, or tape and joining of plasterboard to avoid the plaster skim. Screwing timber battens into the wall and close fitting of insulation between these would provide a reversible solution, and the vapour membrane will likely need to be taped and pinned, rather than stapled.

Developing CE retrofit approaches is an urgent interdisciplinary challenge, one that requires collaboration from academia and industry to develop solutions, pilots and demonstrator studies to test and showcase new technologies. This approach is being taken in the Dutch REHAB research project that is developing ‘Circular Skin’ systems6. Once solutions are shown to be viable, they must be deployed at scale to market.

Supply chain skills and capacity

A lack of specialist retrofit skills, and capacity within the construction sector are also barriers to implementation4. If there is to be a skills development programme for retrofit, then this should include an understanding of CE principles, and their application in this context. The resulting workforce would then be equipped to conduct circular, energy-efficient retrofits, and understand the importance of recovering materials for reuse/remanufacturing/recycling. From a design perspective many universities are increasing CE teaching within their architecture and engineering programmes, which should increase the awareness of those moving into these professions. In addition, the Circular Economy Club lists a number of MSc/MBA programmes7 which place the circular economy at their heart. Furthermore, developing the product supply chain for circular retrofits, alongside the technology development, will be essential for at scale deployment. Scale is critical. There are nearly 25 million homes in England alone, the majority of which will require some level of retrofit to deliver a net zero UK. There needs to be sufficient product supply to enable circular retrofits. The material demand implications of these also need to be understood, alongside quantification of the total embodied emissions, as already conducted by Li et al. for ‘typical’ retrofits.

End of life of both ‘typical’ and ‘circular’ retrofits must also be considered. There is a question of who takes responsibility for end of life remanufacturing, reuse, recycling or disposal. Should the responsibility lie with the manufacturer? End of life regulations, and producer responsibility exists for vehicles8, so should they for buildings and retrofits? A shift to producer responsibility for retrofit products implies a new role in the construction supply chain: an end of life specialist who can upgrade, or deconstruct and recover components from retrofits. It might be that installers also can evolve to conduct this role, but it would still require skills development. Producers would need to establish take-back schemes to facilitate remanufacturing and reuse, or recycling of different products. A further challenge is how the varying lifespans and technical specification of different retrofit products can be taken into account in take-back schemes.


UK policy to encourage and support retrofit is severely lacking given net zero ambitions by 2050. This means that there is an opportunity to embed CE thinking into any upcoming retrofit policies; this could be at local or national levels. Policies might include financial incentives, such as discounts for CE retrofits, stamp duty discounts/rebates if CE retrofit measures are implemented before selling a home, or within a set number of years of buying a new home, and VAT discounts for CE retrofit products.

Consistency and potentially mandating minimum product lifetime guarantee periods would also be beneficial. For example, all fabric efficiency retrofit products should maintain their thermal efficiency for a minimum of 30 years, as already offered by ‘whole house retrofit’ firms like Energiesprong9. Debate can of course be had over the particular lifetime chosen. But a minimum threshold would assist consumers in installing products that will last. How the measure can be replaced or upgraded after the specified lifespan likely also needs legislation. This could be in the form of producer responsibility, as discussed in the ‘Supply Chain Skills and Capacity’ section.

Engagement with consumers

Engaging with consumers on a CE approach will be similar to engaging with consumers on retrofit more generally. The UKGBC Retrofit Playbook outlines typical means of doing this for local authorities. The key difference with a circular retrofit is most likely that it can be easily upgraded, which will be more appealing to some owners than others given upgrades will likely be 30 years into the future. Given that this benefit will arise in the future, incentivising a CE retrofit for many consumers could be a challenge. This is often found to be the case with CE more generally. This is where policy or financial incentives, as discussed in the sections above, could play a role.

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