Wood fibre insulation lowers the carbon footprint of construction and enhances building physics, yet regulation and limited assessment practices constrain its use. Recent research shows that current metrics fail to capture the true performance of wood fibre-insulated structures, leaving part of the climate benefits of timber construction unrealised.
Emission reductions in the construction sector increasingly rely on material choices. The structures of the building envelope play a decisive role in both energy consumption and the total life cycle carbon footprint of a building. Nevertheless, regulation and testing still guide design toward classifying individual materials rather than assessing the actual performance of building assemblies.
In his recent study, Potential for wider adoption of wood fibre insulation in building construction, architect and doctoral researcher Jami Järvinen examines the barriers a technically functional and climatically promising material faces in progressing toward widespread use. In his research, Järvinen integrates building physics, fire safety, and life-cycle thinking and analyses how current testing and regulatory systems affect the actual climate benefits of timber construction.
In our interview, Järvinen explains the key findings of his research and discusses the types of changes needed for low-carbon materials to compete on equal terms with existing solutions.
1. What was the most surprising finding in the study when comparing wood fibre insulation with conventional insulation materials?
Perhaps the biggest surprise was how poorly current assessment methods identify the real performance of wood fibre insulation. The differences are not so much related to the intrinsic properties of the materials, but to what is measured and how. The fire behaviour, hygrothermal performance, and thermal buffering effect of wood fibre insulation remain largely invisible because they do not fit prevailing test frameworks based on the reaction of individual materials. At the same time, current methods can present an acceptable picture of materials whose actual performance within a building assembly is, in many respects, weaker, yet they meet the simplified criteria currently in use.
2. At which stage of the building life cycle do the climate benefits of wood fibre insulation become tangible?
Regardless of the insulation material, the greatest climate benefit is achieved during the building’s use phase, when the energy required for heating and cooling is reduced, particularly in northern climates. The specific advantage of wood fibre insulation, however, is already evident during the construction phase, as the emissions from its production are generally lower than those of most conventional insulation materials. In addition, wood fibre insulation stores carbon throughout the building’s service life. Over the long term, the climate benefit becomes even more pronounced as use-phase emissions decrease and biogenic carbon remains stored in the material for as long as possible. Furthermore, recyclability or reuse at the end of the building’s service life enables the continuation of climate benefits beyond the building’s service life.
3. Does the climate benefit of timber construction remain incomplete with current insulation solutions?
Yes. If fossil-based or highly energy-intensive insulation materials are systematically used in timber structures, part of the climate benefit of timber construction is lost. The research indicates that material choices in the building envelope are decisive and that current regulations may steer choices away from holistically low-carbon solutions. At the same time, it is important to examine solutions at the level of the entire structural system: a low-carbon insulation material does not automatically yield a low-carbon overall solution if its use necessitates, for example, significantly heavier or more emissions-intensive fire protection measures. Climate benefits only emerge when both the insulation and the surrounding structure can be optimised as a whole.
4. How do fire regulations relate to the use of wood fibre insulation?
In Finland, fire regulations are interpreted particularly cautiously, and in multi-storey construction strong emphasis is placed on non-combustible A-class materials. This highlights material-level classifications at the expense of the overall behaviour of building assemblies. In principle, the use of wood fibre insulation would also be possible in P0 fire-class solutions, where fire safety is demonstrated on a case-by-case basis through structural and functional design. In practice, however, P0 solutions are rarely pursued because they require extensive additional assessments, specialised expertise, and approval processes that increase uncertainty, costs, and project risks. Based on the research, the problem is not the safety objectives themselves, but rather the lack of sufficiently well-established calculation methods to characterise the overall performance of assemblies, as well as the inability to replicate previously tested and approved structural solutions without new, project-specific testing.
It is also important to note that the Finnish building stock consists largely of detached housing, in which the use of wood fibre insulation would be permitted from a fire regulation perspective and where the amount of insulation relative to the built volume is often greater than in multi-storey buildings. Despite this, usage remains limited, indicating that fire regulations are only one clear bottleneck, or even an obstacle within a broader context that also includes costs, established practices, and a lack of expertise.
5. How does the assessment outcome change when the material is examined as part of a structure rather than in isolation?
The difference is significant. A material-level assessment may present an image of a high-risk, combustible product, whereas at the level of a structural solution, the same material may function safely and predictably. For example, the charring behaviour and slow heat transfer of wood fibre insulation improve the fire resistance of an assembly, but this is not captured in tests of individual materials and only becomes evident in assembly-level testing.
6. How will fire-retardant wood fibre insulation change the situation in the coming years?
Fire-retardant wood fibre insulation may act as a bridge between current regulations and low-carbon solutions, even though it does not, at least for the time being, achieve the highest A-class Euroclass rating. It improves the likelihood of achieving required fire classes without compromising the material’s ecological benefits. At the same time, it raises new questions, such as the long-term durability of additives, environmental impacts, and potential health effects. Depending on the fire-retardant agent used, treatments may compromise the ecological properties of wood fibre insulation and impose requirements for indoor air quality and exposure assessment, underscoring the need for further research.
7. What kind of regulation would enable equal treatment of low-carbon materials?
It would be essential to move toward more performance-based assessment, in which the overall behaviour of building assemblies is examined rather than individual materials, for example, with respect to fire safety, energy efficiency, and hygrothermal performance. This requires established calculation and assessment methods, as well as the possibility to utilise and replicate already tested and approved structural solutions without project-specific additional studies.
The current system still poorly recognises environmental benefits, even though they are documented in LCA and EPD data, and it does not steer design toward holistically low-carbon solutions. In addition, shortcomings in calculation methods for biogenic carbon storage disadvantage bio-based and wood-based materials relative to many conventional solutions.
8. In which European countries is development progressing most rapidly, and why?
Based on the research, several European countries have developed individual practices that could serve as examples. In France, construction guidance is more closely linked to climate policy, and biogenic carbon storage is better accounted for in calculations under the RE2020 regulation. In addition, the state has supported low-carbon construction through both regulation and financial incentives.
In Germany, the market for wood fibre insulation is well developed, with a wide and technically diverse product range, which has increased practical experience and the number of approved solutions. In Sweden, functional fire engineering has long been in use, and its application is more established across many project types, although the basic requirement level is largely comparable to that in other Nordic countries.
9. How high are costs compared to regulations and established practices?
Costs play a significant role, especially in the early stages of projects, where material choices are often made within tight budget constraints. Wood fibre insulation is typically more expensive than conventional insulation materials, which influences decisions before other properties or life-cycle impacts are considered. However, the research shows that cost impacts are closely intertwined with regulations and established practices: regulatory frameworks, approval procedures, and a lack of expertise can increase uncertainty and indirect costs, further weakening competitiveness. As regulation and expertise develop and solutions become more repeatable, cost differences may narrow, and life-cycle economic considerations gain greater prominence.
10. What should a developer or designer understand about wood fibre insulation right now?
Wood fibre insulation should not be considered as an individual material, but as part of an entire structural system. Its use requires an understanding of how thermal, moisture, and fire performance are integrated, and where the properties of wood fibre insulation provide real added value. In practice, the use of wood fibre insulation is not particularly complex or expensive, provided that it is considered sufficiently early in the design process and integrated into the overall solution from the outset.
