In prior articles in this series, we have looked at issues (net zero carbon, healthy buildings) and innovations (new materials, technological developments) that have propelled the idea of plant-based spaces. This is the positive side of the discussion. What also needs consideration, however, are some of the limitations and hurdles facing further adoption of plant-based materials.

Chief among these are regulation and conventional business practices, especially as they relate to insurance (underwriting). Even as net zero carbon drives timber and other plant-based materials into buildings, regulation in the UK (particularly fire and building regulations) limits 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.

Other countries, most notably France, are positively promoting plant-based buildings through new regulation. Even in the UK, there is a movement afoot among various Government agencies (DEFRA and DESNZ) to actively promote timber in construction. Added to this, 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.

Three key messages

There are three key messages from this article:

  1. Before plant-based materials can be adopted at a greater scale, there will need to be changes in regulation, underwriting and – perhaps most importantly – long-held attitudes. Currently, regulations do not allow timber cladding on buildings above 18 m. While this ostensibly covers the façade, in practice 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.
  2. When it comes to plant-based materials, objections extend beyond fire. According to a report by RIBA, 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.
  3. As important as these concerns are, there appears to be momentum in both regulation and best practices (first internationally and now in the UK) that favours wider adoption of plant-based materials. France has recently enacted regulation that requires 50% plant-based materials in new public buildings. Other European countries, particularly those in Scandinavia, are similarly using regulation to encourage plant-based materials in construction. Globally, the use of timber in tall buildings has grown considerably. Across Europe and North America, the capabilities of engineered timber are recognised, and an increasing number of taller timber skyscrapers are being built.

Regulation and the concurrent growth of plant-based buildings

What’s happening in France?

Beginning in 2022, France required all public buildings to be composed of 50% or more bio-based materials. The mandate can be fulfilled by bio-based materials made from matter derived from living organisms such as hemp and straw and will apply to buildings constructed for the 2024 Paris Olympics complex. What is interesting about the French case is both the attitude toward plant-based materials (of all kinds) and the interest in promoting such materials throughout the building – not just the façade and frame. Indeed, one of the objectives of such high targets is to foster bio-based materials in all kinds of building items – floors, ceilings, walls, insulation, finishes, etc. For more information on the growth of materials and their applications, see here.

It is impossible to understand France’s bio-based materials law without seeing it as part of a much larger trend towards decarbonised construction. It is no coincidence that France is also the first country to have regulation around embodied carbon. France’s RE2020 regulation requires that developers produce and report a life-cycle analysis that details 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 plant-based materials of all types (and not just timber), since meeting the standards will require non-conventional materials.

The role of whole life carbon assessments

Nine other countries in Europe have introduced regulation on whole-life carbon emissions, addressing both embodied carbon and operational emissions. Not surprisingly, a strategy of choice – often mandated – is the use of timber and bio-based materials for buildings. What’s more, these countries recognise that carbon requirements might change what gets built and how, including the possibility that more commercial development will be low-rise rather than tall buildings. Indeed, changing the size and structure of conventional buildings appears to be part and parcel of the regulation.

The European Performance of Buildings Directive (EPBD), best known for introducing energy performance certificates (EPCs) into the UK, is undergoing revision. New changes in regulation are likely to 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, plant-based materials are very likely to be products of choice for meeting new measurement and reporting categories.

What would happen if the UK adopted similar whole life/embodied carbon regulation?

UK regulation presents a challenge for the adoption of plant-based materials, through fire safety guidance and limits placed on where bio-based materials can be used. But perhaps more importantly, 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 plant-based materials. Indeed, interest in timber in the UK comes mostly from companies employing voluntary net zero carbon frameworks. Without the equivalent regulatory “push” found in other countries, the low carbon benefits of plant-base materials remain in the background.

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. It is best practice (through adoption of voluntary net zero carbon building standards) that is driving the use of bio-based materials in new construction. 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.

Underwriting and insurance

Material safety perceptions have also affected the availability and cost of insurance for timber framed buildings. In the UK, many insurance companies can be reluctant to take on buildings with wooden construction or will do so only with increased premiums.

A primary reason that plant-based buildings face difficulties is the tendency for insurers to view timber as being a 100% Estimated Maximum Loss (EML). EML is the most used number for the analysis of insurability. The lower the number the better and timber is generally assigned the highest risk for the total loss of a building. Insurers also claim that they do not have enough testing data to know how timber buildings will react in fire events.

Fire is certainly a concern, but insurers note that water damage events are both costly and frequent. Long-term exposure to moisture and water may or may not be covered under a construction or property insurance policy but may be a matter for a warranty or professional indemnity.

The cost of insurance plays a decisive role in material and building design choices. There is now a reluctance among funders to use timber for construction, even in buildings not directly affected by the ban on combustible materials. Material safety perceptions have also affected the availability and cost of insurance, making it difficult for developers to use timber in high rise or medium rise buildings.

Luckily, this is beginning to change as organisations come together to tackle these objections. One such example is the Mass Timber Insurance Playbook. It was written by insurance and building resilience specialists, to facilitate understanding between the insurance and construction industries. The goal of the publication is to remove barriers that can hold back mass timber construction. This effort, and the work of G&T’s Mass Timber Forum, are direct efforts to provide step-by-step guidance to make timber buildings more acceptable to the insurance industry.

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

Changing Industry Perceptions and Practices

Best practices for whole life carbon assessments (WLCA) developed by RICS (supported by G&T through the working group) are ahead of regulation in this regard. It is fundamentally the need to address the new issue of embodied carbon that is likely to fuel changes in regulation and insurance practices.

An example of this is Waugh Thistleton’s “New Model Building” an exemplar methodology for building residential developments. The model is a set of design principles illustrating how engineered timber can reduce the embodied carbon footprint of a building by over 50%, while remaining safe. G&T helped to develop the methodology in partnership with other pioneering companies. It is work of this kind that will pave the way for assurance around lower developments (residential, schools, etc) and possibly open the way for acceptance of timber structures in taller buildings.

Not Just Timber

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

For advocates of plant-based materials, this is an obstacle, but not the whole story. Internally, there are a range of plant-based options available to significantly replace traditional materials with lower embodied carbon options. Internal walls, flooring and ceilings are all possible areas where plant-based products could make an impact.

Green shoots

It is a well-known cycle that pioneering products and expectations generally run ahead of regulation, and that eventually Government weighs in. That is exactly what is happening in the UK. Expectations around low carbon buildings are encouraging products and practices that are rapidly forcing a rethink among Government officials. Already, some governmental bodies are showing a newfound willingness to expand the role of timber in construction, even if only in certain types of buildings.

The experience of countries outside the UK is also relevant and influential. When France became the first company to regulate embodied carbon, this gave an enormous boost to proponents of “Part Z” here in the UK. Likewise, France’s move to promote plant-based materials on a large scale demonstrates the kind of forward movement that tends to cross borders. If nothing else, the experience of other countries represents a “proof of concept” that hastens the adoption of practices elsewhere once they are allowed.

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 not be sufficient to address issues of whole life carbon in buildings. It is not surprising that there is still a reluctance among conventional players to take on risks. But some larger firms are softening their approach to insuring timber buildings – this is bound to continue.

What is perhaps the biggest driver of all for more plant-based materials is the issue of net zero carbon and how it is driving new products and ways of building. In a very short period, net zero carbon has become a mainstream concept and an industry-leading standard. At present, and for the foreseeable future, plant-based products will be the least costly and readily available solution to net zero carbon frameworks. This, above all, is likely to shape the industry and move regulation and business practices in the UK as we have seen elsewhere.