Why Use Wood Fibre Insulation?

We’ve added Wood Fibre insulation to our product line-up, and we’re really excited about it because Wood Fibre is a completely renewable material with a very low environmental impact. The insulation can bring down the U-values of your external walls enormously, requiring just 120mm to reach a 0.3w/m2k U-value. We know that many customers who consider external wall insulation are very environmentally aware and are eager to choose materials that do not have a negative impact on the environment – we are keen to encourage environmental friendliness wherever possible, and we think that Wood Fibre insulation is the way to go to achieve this.

Because of its recent addition to our systems we thought we’d talk a bit about the benefits of Wood Fibre insulation, including where it comes from and why it’s so great.

Wood Fibre Insulation is Environmentally Friendly 

We source our Wood Fibre insulation boards from a company called Pavatex, who are dedicated to the notion that using secure and healthy forests for production helps to stabilise and manage the environment. Their Diffutherm Wood Fibre insulation boards serve as complete evidence for this, as they boast the achievement of being absolutely sustainable and environmentally friendly. This achievement has not gone unnoticed; Pavatex are certified by the renowned NaturePlus standard – the European quality standard for building materials set up by the WWF, FSC and Greenpeace.

Not only does the nature of their product contribute positively towards the environment, their manufacturing process is environmentally conscious as well. The Pavatex production locations in Cham and Golbey claim to be dedicated to being efficient and environmentally friendly, which has resulted in the Diffutherm Wood Fibre insulation having an overall positive CO2 balance of around 600kg per tonne of product.

When used as part of an external wall insulation system, Diffutherm Wood Fibre insulation helps to reduce the carbon footprint of property owners by lowering the U-values of the external walls of their property, resulting in reduced energy requirements. Wood Fibre boards are also safe to dispose of due to the fact that they are recyclable and compostable once they have reached the end of their lifespan.

The Diffutherm Wood Fibre boards are therefore eco friendly throughout their entire lifespan, and when used as part of our EWI system they will improve indoor air quality, reduce emissions and enhance the thermal performance of the building.

What Type of Property is Best for Wood Fibre Insulation?

Wood Fibre insulation is compatible for use on masonry, steel frame or timber frame structures and even historic or hard to treat buildings; Pavatex have worked with many organisations such as English Heritage, the National Trust, Scottish Heritage and Cambridge University (to name a few), and Wood Fibre also works really well with our new Heritage range of lime products. However, for the purposes of this article we are going to focus on the use of Wood Fibre insulation for timber frame structures.

Wood Fibre insulation is excellent for EWI on timber frame buildings because timber frames need to be able to breathe in order to resist damp and rotting of the timbers. Air circulation is essential, and because of this it can be incredibly difficult to insulate a timber frame property without increasing the risk of damp. This is where Wood Fibre insulation comes in to its own.

When used with a breathable render, water vapour is able to pass through the existing external walls and out through the many layers of the insulation system. We recommend our Silicone or Silicone Silicate renders for use with Wood Fibre insulation, as the breathability of both materials means that they will work well in conjunction with each other. Wood Fibre insulation boards must also be fixed to the substrate with mechanical fixings and our Premium Basecoat adhesive (our strongest and most breathable adhesive), so it will be able to completely support the weight of the Wood Fibre boards and maintain breathability.

Diffutherm Wood Fibre boards are waterproof so they won’t absorb rainwater or moisture, but they’re also vapour permeable at the same time. This essentially means that the Wood Fibre boards will allow water vapour from within the warm building to pass through walls without becoming trapped behind the insulation.  

Breathable ‘Nature Plus’ Systems with Wood Fibre

In breathable systems, the insulation materials are arranged in such a way that the layers become increasingly more vapour permeable from the inside to the outside so that moisture can safely escape from within the house. This creates a harmonious climate within the house where moisture and the risk of damp is reduced.

To achieve this, we recommend an environmentally friendly ‘Nature Plus system’. This consists of fitting OSB (which can be taped for air-tightness) behind plasterboard on the interior of the timber stud-work, then laying Nature Plus certified Thermafleece insulation in between the stud-work. You would then install our Nature Plus certified Diffutherm Wood Fibre onto the exterior before rendering as a final step.

How are Wood Fibre Insulation boards made?

Pavatex Wood Fibre insulation is made from local, sustainably managed fir and spruce trees from FSC (Forest Stewardship Council) and PEFC (Programme for the Endorsement of Forest Certification) forests. They are manufactured from untreated softwood in the form of sawmill slabs, chippings and splinters which are a byproduct from the manufacture of timber or sustainably built furniture.

The Pavatex Diffutherm Wood Fibre insulation boards are manufactured in Switzerland under tight environmental regulations against high emissions and pollutants. In order to make Wood Fibre insulation boards, the previously mentioned waste wood is ground together to form a pulp. Water is then added and mixed with the pulp, then heated to activate the lignin that the wood naturally contains and which glues the fibres together. The pulp is then pressed into boards, dried and cut to size. Sheets of varying densities are then laminated together to produce optimal strength and stability as well as moisture control and vapour permeability.

Do Wood Fibre Insulation Boards Pose a Fire Risk?

For many, this is the first question that springs to mind when thinking about externally insulating with Wood Fibre. Pavatex Wood Fibre insulation boards are certified as Class E combustible materials. This is the same as many other insulation materials, however there is a key difference with Wood Fibre boards in that because they are made of timber they characteristically char, which actually slows down the spread of fire. To explain this, Pavatex state that:

‘In a fire a layer of ash forms on the surface of Pavatex Wood Fibre insulation boards. This acts as a safety shield, preventing oxygen from reaching the flames and slowing down the spread of the fire. This means the construction can withstand a fire for 90 minutes. In addition Pavatex Wood Fibre insulation systems do not release dangerous gases in case of fire.’ Check out the video below, which demonstrates this further:

We are really excited to be stocking Wood Fibre insulation! If you have any further questions about installation and technical advice, then comment below or give us a call.

We upload a new blog post every Tuesday and Thursday, so stay tuned for more future content about Wood Fibre insulation and EWI!