Bio-based buildings: “The route to market would be a cautious one”

There is no question that there is a newfound interest in building materials that are more local, minimally processed, regenerative, and health-promoting. In many respects, the built environment seems to be “catching up” with credentials promoted in other industries.

Despite the enthusiasm for – and greater use of – bio-based materials, many hurdles remain. Planning and regulation, supply chain readiness, developer reluctance, and practitioner scepticism tend to frustrate their widespread adoption.

The generally risk-averse construction industry has yet to embrace bio-based materials on a large scale. Whether it is questions about flammability and durability or simply familiarity with conventional products, the adoption of bio-based materials will take time. Given concerns about health and safety – not to mention regulatory compliance – it is understandable that the route to market would be a cautious one.

There are many more hurdles to mortgaging and financing bio-based projects than those constructed with conventional building materials. Chief among these are regulation and conventional business practices, especially concerning insurance (underwriting). Even as net zero carbon drives timber and other bio-based materials into buildings, regulations in the UK (particularly fire and building regulations) limit their widespread use. Historically, insurers have been unwilling to underwrite timber-framed buildings. The duo of regulatory restraints and market hesitancy is a difficult combination to overcome.

Currently, regulations do not allow timber cladding on buildings above 18m. While this ostensibly covers the facade, it has also dampened enthusiasm for timber-framed buildings in general. Although other countries build tall buildings using timber, in the UK, this has not happened on a large scale.

When it comes to plant-based materials, objections extend beyond fire. Water damage is as important as combustibility in discouraging plant-based materials. Timber is viewed as more susceptible to water damage to finishes, delamination and structural deterioration. Both fire and water concerns contribute to uncertainty about timber’s safety and integrity.

The generally risk-averse construction industry has yet to embrace bio-based materials on a large scale.

There appears to be momentum in both regulation and best practices (first internationally and now in the UK), favouring wider adoption of bio-based materials. In 2022, France mandated that all public buildings comprise 50% or more bio-based materials – which also applied to buildings constructed for the 2024 Paris Olympics complex.

It is no coincidence that France is also the first country to have regulations around embodied carbon. France’s RE2020 regulation requires developers to produce and report a life-cycle analysis detailing carbon from materials and construction – the wrong carbon profile at planning can doom a project. This is widely seen as a driver of demand for bio-based materials of all types since meeting the standards will require non-conventional materials.

Even in the UK, various Government agencies (DEFRA and DESNZ) are moving to actively promote timber in construction. Some insurers have begun to expand underwriting of engineered timber for commercial buildings. The appetite for insuring bio-based materials appears to be increasing, albeit slowly.

Ten European countries have introduced whole-life carbon emissions regulations, addressing embodied and operational emissions. Not surprisingly, a strategy of choice – often mandated – is the use of timber and bio-based materials for buildings.

The European Performance of Buildings Directive (EPBD), best known for introducing energy performance certificates (EPCs) into the UK, is undergoing revision. New regulation changes will likely incorporate the reporting of whole-life carbon emissions in the next few years. This could change the way embodied carbon is addressed at a European scale. If it does, bio-based materials will likely be the products of choice for meeting new measurement and reporting categories.

The lack of embodied carbon regulation in the UK on a national scale fails to focus attention on the impact of embodied carbon and the potential benefits of bio-based materials. Indeed, UK timber interest comes mainly from companies employing voluntary net zero carbon frameworks.

That is why the recent work by DEFRA and other Government agencies in promoting timber appears more hopeful, as does the possibility of changing building regulations to include embodied carbon (the so-called “Part Z”) in building regulations. Should more net zero carbon standards be required (including embodied carbon regulation), the experience of other countries suggests that bio-based materials will be the route to regulatory compliance.

The appetite for insuring bio-based materials appears to be increasing, albeit slowly.

There is initial evidence that the insurance industry is becoming a little more comfortable with using more bio-based materials like timber. There is also increasing pressure on insurers to change practices as bio-based materials become more attractive in a carbon-constrained industry.

The same hurdles that timber faces also apply to other bio-based materials. Typically classified as “non-standard” construction, it may be possible to get insurance and underwriting from some specialist companies. However, getting insurance for buildings where plant-based materials comprise the facade, the structure – or both – is more complex and expensive.

Likewise, there has been movement in the insurance industry. The tenor of the debate has changed as it becomes clear that traditional modes of building and underwriting may no longer be sufficient. It is not surprising that among conventional players, there is still a reluctance to take on risks. However, some larger firms are softening their approach to insuring timber buildings, which is bound to continue.