Loose fill insulation in the form of defibrated wood fibre resembles the better known cellulose insulation, and has been on the market in Europe for some 20 years. It is primarily thermal insulation but at higher densities also useful as sound insulation.Defibrated wood fibre also forms the basis for all fibre based matting and board products.
Defibrated wood fibre is usually produced from conifers; wood wastes can also be used. Fire retardants are added, normally about 5% ammonium phosphate; for higher fire standards up to 10% borates can be used, which also have an anti-fungal effect. Aluminium phosphate can also be used as fungicide.
The loose fill is blown into the construction using one of two methods. It can be blown into the finished wall through holes, or else blown before the interior cladding is fixed. The latter probably ensures better filling. Minimum density should be 65 kg/m3 to avoid settling with resultant uninsulated gaps at the top.
Energy use in production is low and additives used are relatively unproblematic, with the exception of the borates. Re-use should be quite easy, and these materials can also be combusted for energy recovery or composted.
Insulating with wood fibre matting. Source: Homatherm.
Wood fibre insulation mats are relatively new but are already widely used in central Europe (Figure 14.18). They are elastic, can be delivered in thicknesses from 40 to 200 mm, and in dimensions adapted to normal wall and floor beam framing. The weight is from 40 to 55 kg/ m3, but lighter versions of only 10 kg/m3 are being developed.
The production takes place in a dry process (see page 280). The mats are most often fixated by melting in about 6-10% polyolefine fibres (thermal bonding), fibres based on maize starch are also used. Ammonium sulphate is almost always the fire retardant used. Fungicides are not added.
Resource and energy use is moderate; the alternative bonded with starch fibres would seem most eco-efficient, since polyolefines are produced from fossil oils. Indoor exposure is unproblematic. Re-use is possible if the mats have retained their elasticity, but there is as yet insufficient knowledge of how the glues will perform over time. These products can also be used for energy recovery or, with the maize variety, composted.
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