What about the fire safety of biobased insulation materials?

You are interested in biobased insulation but are now hesitant to use it because you've read or heard that it is flammable.

There is much attention surrounding biobased insulation such as cellulose, wood fiber, hemp, flax, and straw as environmentally friendly alternatives to conventional insulation products.

However, there is one problem: it is flammable.

We often receive questions about whether biobased insulation can be safely used in terms of fire safety.

The short answer is: absolutely.

The long answer is that it is indeed flammable, but it can be applied perfectly safely with the right finishing.

Until a few weeks ago, I was at the same point you are now. Not exactly knowing what you need to comply with for your overall construction. But now, thankfully, I do. And specifically for renovation projects, because I carry these out with my biobased insulation company, Isoleerbewust.

In this article, we discuss how biobased insulation can be applied safely in terms of fire spread with the right finishing, focusing on renovation projects. By the end, you will know what to check with your contractor and also be able to provide accurate information to others, such as an insurer.

…but first

Before we explain how biobased insulation materials can be applied perfectly fire-safely, let's first consider: why is fire safety a hot topic with biobased insulation and less so with synthetic insulation materials that sometimes have the same low European Fire Class E?

Why is fire safety a hot topic with biobased insulation materials?

Biobased insulation materials are gaining momentum. More and more biobased insulation materials are being used, partly because they are better for your health and the environment and store CO2 as they grow as plants.

However, there is a prevailing sentiment of flammability because we all learned in school that in the Middle Ages, entire city districts burned down because houses were built of wood and thatch. This is a common starting point for people's thoughts on the fire safety or flammability of biobased insulation materials.

Biobased insulation material has a low European Fire Class

However, this suspicion is not disproved by the low European fire class classification for biobased insulation materials.

Most biobased insulation materials fall into fire class E (normally flammable) or D (moderately flammable). Some, such as compressed wood fiber boards, even achieve fire class B (difficult to ignite). For comparison: the commonly used synthetic materials PIR and PUR foam are also in class E, and rock wool in class A1 (non-combustible).

Materials in class E burn relatively slowly. In fact, using biobased materials can increase the fire safety of buildings, provided they are applied correctly. For example, glass wool melts quickly in a fire, while materials like hemp and wood fiber retain their structure longer. Nevertheless, natural insulation also has risks. The fire load (amount of flammable material) is higher than with stone or concrete. Also, heat production can last longer because the material continues to burn in a controlled manner. Therefore, it is essential to consider the specific application.

Application in roofs, floors, walls, and ceilings

Research by Nieman Raadgevende Ingenieurs, commissioned by RVO, shows that biobased insulation can already be safely applied in many situations in roofs, floors, walls, and ceilings. Some conclusions:

• For fire resistance up to 20 minutes, all biobased materials are applicable, provided they are finished with a wooden board material (≥18 mm), gypsum plasterboard (≥12.5 mm) or a combination thereof.
• For fire resistance of 30-60 minutes, fire resistance can be achieved with cellulose or wood wool, provided it is tightly installed with a density >50kg/m3 in a tested construction with a (stud) width up to 40 mm (thus also with the commonly used 38 mm width in the Netherlands) in 40 mm thickness without additional measures. For thicker insulation layers or other materials, an additional protective board is needed.
• For ventilated facades with biobased insulation, stricter requirements apply, such as non-combustible infill or compartmentalization to prevent fire spread.
• For unventilated facades, more is possible. Often, a fire-resistant board on the outside or sufficient thickness of plaster material (lime, clay) on the substrate is sufficient.

The report provides concrete guidelines for various applications and can serve as a basis for substantiating an equivalent solution in the permit process.

Points of attention and areas for improvement

While much can already be done with biobased insulation, there are also areas for improvement. For example, fire expert Larson van Dijk advocates for more 'end-use' fire tests by manufacturers. Current laboratory tests do not provide a complete picture of real-world situations. There is also a need for more knowledge about the fire behavior of materials such as grass, cotton, and straw. For cellulose and wood fiber, much information is already available, but additional tests are needed to expand the application range of other materials. Furthermore, it is important that builders and architects are well aware of the possibilities and limitations. For instance, wooden constructions must be sufficiently dimensioned and equipped with appropriate board materials for optimal fire safety.

Learning from abroad

The Netherlands can learn a lot from other European countries regarding fire safety. In Germany and Scandinavia, there is a greater focus on the protective effect of board materials. This 'fire protection ability' ensures that underlying wooden or biobased insulation is protected for a certain period (30-60 min) against the effects of heat and fire. By clever design and using the right board materials, no additional fire load is released from the insulation during this time. This contributes to a more manageable fire situation. It is important that we apply this knowledge in the Netherlands as well.

Conclusion

Biobased insulation materials can be safely applied in many situations, provided you pay attention to the correct finishing and construction. With the information in this article, you now know what to look for and can confidently apply biobased insulation to your project.

Although biobased insulation materials are flammable, they pose no greater risk than conventional insulation if applied correctly. It is important to consider the specific application in roofs, floors, walls, and ceilings and ensure the correct finishing with board material.

As an expert in biobased insulation, I see the benefits of these sustainable materials daily. I am happy to help people make the switch to a healthier and more environmentally friendly way of insulating, without compromising on fire safety.

The next step is to discuss the application of biobased insulation in your project with your contractor or installer. Discuss the desired fire resistance, choose the right materials, and ensure correct execution. This way, you can confidently enjoy a sustainably insulated home.