Insulation solutions for less waste as part of a circular economy

1 insulation solutions supporting principles of the waste hierarchy.
2 What is the circular economy?
3 1: Maximise reuse
4 2: Design for optimisation
5 3: Minimise impact and waste
6 Can XPS insulation be recycled?
7 Summary
8 Related articles on Designing Buildings

[edit] insulation solutions supporting principles of the waste hierarchy.

The most sustainable building is the one that does not need to be built. This idea is based on making use of assets that already exist and preventing the creation of more waste. This article looks at insulation solutions that can support the adoption of principles outlined in the waste hierarchy.

The waste hierarchy outlines methods of dealing with waste in order of desirability. A briefing paper by the Construction Products Association (CPA) shows the preferred option is to prevent waste altogether. This is followed by preparing for reuse, recycling and ‘other recovery’.

The worst option, according to the hierarchy, is disposing of waste – which is the most common outcome in the linear economy.

Designing buildings with a 60-100 year lifespan, demolishing them and creating waste, then building again from scratch is the linear economy in action. It is incompatible with a sustainable, net zero future that prioritises efficient use of the limited resources available to us and minimises negative biodiversity impacts.

[edit] What is the circular economy?

In the linear economy, a product is used once and then disposed of, requiring new resources to be extracted and new products to be manufactured.

As the global population grows and the demand for raw materials and construction products continues to increase, maintaining the linear economy approach will only put further pressure on already-limited resources. Instead, we must look to the circular economy.

The UK Green Building Council (UKGBC) describes the circular economy as follows: “At its simplest, the circular economy prioritises the reuse of materials, preventing the over-extraction of natural resources and the number of usable materials that end up in landfill.”

To support greater adoption of the circular economy, the UKGBC provides guidance on five circular economy principles for construction, in order of priority. Below, we discuss three of the five, and how extruded polystyrene (XPS) insulation products can contribute to them.

[edit] 1: Maximise reuse

In the first instance, this means reusing buildings themselves.

For example, you might still specify a traditional concrete slab ground floor, but featuring XPS insulation instead of an alternative rigid board. With its higher compressive strength, XPS would be capable of bearing a greater range of loads from unknown future uses.

Leaving the entire ground floor build-up in place during future conversion/adaptation works would leave the insulation undisturbed, ensuring it continues to deliver its performance.

Second, it means recovering materials from a site to be used on the same site or a different site.

Here, a good option might be a loose laid inverted roof build-up. As the insulation is neither mechanically fixed nor adhered, should the building be disassembled in future, the roof layers, including the XPS insulation layer, could be taken up. Assuming good installation at the outset, the insulation boards should be in virtually the same condition as when first used.

[edit] 2: Design for optimisation

There are four aspects to designing for optimisation:

Longevity
Flexibility
Adaptability
Assembly, disassembly and recoverability

XPS’s proven durability can contribute to the longevity of building design lives. And we have covered how it might support adaptability and assembly/ disassembly/recoverability.

The example of an inverted roof also plays into designing with flexibility in mind. A roof constructed today to achieve a certain level of thermal performance might require an increased insulation thickness in future. The loose laid nature of an inverted roof could play into this, allowing the roof finish and ballast layers to be lifted temporarily and an extra insulation layer added, prior to reinstating the layers above.

Issues like thresholds and their heights would need to be considered during the initial design. Overall, however, such flexibility is a realistic possibility.

[edit] 3: Minimise impact and waste

Three of the four aspects named by the UKGBC in this area are: use low impact new materials; use recycled content; and reduce construction impacts.

As a plastic-based material, it is hard to argue that XPS is a genuinely low impact material.

However, given the importance of thermal insulation in buildings generally, plus XPS’s characteristics and potential for adaptability/flexibility/reuse, there are justifiable trade-offs against that impact.

It is incumbent upon product manufacturers to be open and transparent about their processes, and the way they are striving to improve them – such as through better waste management or the use of recycled content in manufacturing.

Another way product manufacturers can demonstrate a responsible attitude to the impact of their activities is by making improvements to the sourcing of materials. The BES 6001 responsible sourcing standard is a form of third-party certification for construction products.

[edit] Can XPS insulation be recycled?

If embedding circular economy principles around reuse is not currently possible, then the next best option is to specify products that can be recycled at the end of a building’s life.

A leading recycling company has told us that extruded polystyrene can be recovered from existing buildings and recycled, even if it is contaminated (such as with adhesive or concrete).

We have recently put two sites in contact with the recycling company, who have been able to recycle insulation removed from existing roofs. One of those projects had some 40,000m2 of existing insulation stripped from the roof, which would otherwise have gone to landfill.

Neither site had our material installed, so we didn’t know anything about the age of the insulation, or how it had been installed. That did not prevent the recycling company being able to receive and process the material.

A few years ago, we first engaged with the recycling industry to better understand what was possible with XPS material. Unlike other rigid foam insulation boards, XPS has no integral foil facing. We were therefore confident that XPS products in buildings had inherent recycling potential, but we needed expert confirmation.

Now, we are encouraged that we will see a time when XPS products are routinely recovered from buildings and recycled when not being reused.

[edit] Summary

Extruded polystyrene insulation can play a role in the construction industry’s transition from the linear economy to the circular economy. XPS’s combination of performance characteristics mean it has the potential to be retained or reused across multiple building life cycles.

A significant barrier to reuse and recycling is that design and installation rarely takes into account the end of a building’s life. This is hardly surprising. As buildings can stand for 50, 60 or 100 years, or more, how can you ensure that someone follows through on intent so many years later?

Specifiers, installers and demolition contractors first need to know that reuse and recycling are possible, and then they need the incentive to make it happen.

Sustainability goals have to be agreed at the beginning of a project, ensuring design and specification decisions align with those goals. Contractual performance for contractors and installers should prioritise the goals being met and be measured accordingly.

A golden thread of information can also record such decisions being made and help carry that information through the life of the building so it is available to whoever makes end-of-life stage decisions in the future.

This article appears in the AT Journal issue 156 Winter 2025 as "Insulation solutions for less waste as part of a circular economy" and was written by Rob Firman, Technical and Specification Manager, Polyfoam XPS.

--CIAT