Guideline 3 - Insulation Systems / Cellulose
Cellulose
Insulation made of natural materials
Cellulose fibre is the basic raw material for both wood fibre and wood wool insulation. The cellulose fibre comes from paper (fresh or recycled) or wood.
During the production process, the raw materials are shredded to create fibres. Binding products and additives6 are used to form final product. In final product 82 - 85 % by weight is cellulose, the remaining being chemical fire retardant in form of dry powder.
Two final products can be obtained based on the thickness of the fibres – wood fibre or wood wool. For wood fibre the typical ratio between the length and thickness is 20:1, for wood wool even smaller. Typical wood wool products are distributed in as filling materials and mats. The wood wool can be used to fill in cavities and also used in the same manner as mineral wool when coming in mats. Wood fibre insulation is usually coming in boards.
Thermal properties of cellulose insulation are dependent on temperature, moisture content and mass density of the material itself. Typical values for thermal conductivity of cellulose insulation is 0.04 – 0.066 W/(mK). Thermal conductivity of cellulose insulation depends on temperature, moisture content and mass density and increases by 40 % (from 0.04 W/(m K) to 0.066 W/(m K)) in the case the moisture content in the insulation material increases from 0 vol% to 5 vol% (usually boric acid and borax and ammonium sulphate for mould, insect and rodent resistance).
For wood wool EN 13168:2012 gives values of 0.09 – 0.15 W/(mK) and for wood fibres EN 13171:2012 gives values of 0.037 – 0.042 W/(m K), in both cases for dry material at 10°C.