Cellulose

Basic info is found in Chapter 10.

Cellulose products can be generated from a wide range of plants, but most commonly from timber. Cellulose is used in corrugated insulation boards and papers for air tightening vapour retarders and wind proofing membranes. Loose fill thermal insulation of cellulose was patented for the first time in England in 1893. It was made of shredded newspaper containing a fire retardant and a water repellent. Loose cellulose fill also has valuable properties as acoustic insulation. Most cellulose products regulate humidity well - suggesting that a room well filled with papers and books goes a long way towards providing a sufficient humidity buffer for a house (Derluyn et al., 2007).

14.26

Loose fill of cellulose fibre.

14.26

Loose fill of cellulose fibre.

Thermal insulation of recycled cellulose fibre is usually treated with fire retardants and fungicides and is used on site as loose fill (Figure 14.26). The proportion of these additives is often as high as 18-25%. The most commonly used compounds are boric acid and borax. The fibres also contain traces of silica, sulphur and calcium from fillers in the initial paper waste.

Recycled cellulose fibre can also be used in the production of matting by adding an adhesive (often being lignosulphonates, a by-product of the cellulose industry). Jute may be added as reinforcing, plus wood resin as water repellent. As fungicide, a mixture of ammonium phosphate and tannin can be used as an alternative to borates. These mats are fairly stiff. A more flexible type is produced from virgin cellulose, with up to 9% polyester (e.g. polyethylene terephthalate) or poly-olefine (e.g. polypropylene) fibre melted in (thermal bonding). Virgin cellulose is also formed into cellulose strips which can be used as joint fillers between window and door frames and the building fabric.

Resources for most products are unproblematic; energy use is initially low, though substantially higher for virgin cellulose products, especially when thermal bonding with synthetic fibres is used. Loose-fill cellulose fibre has been widely used as building insulation since the 1920s, and the material's durability is good as long as it has been placed in the walls or roof space in the correct way. This involves applying a high pressure when blowing in the fibre, to avoid settling later on. At densities above 70 kg/m3 no settling should occur (Hansen, 2000).

In the production process workers can be exposed to dust made up of paper and fine particles of borax and boric acid. Exposure to dust will also occur at the building site, but once installed correctly the fibres should cause no problems for those using the building. Cellulose fibre products have good moisture regulating properties and are less susceptible to mould than the mineral wool alternatives.

The products can be re-used. Energy recovery of products treated with fire retardants requires mixing with other more combustible wastes (Krogh et al. 2001). As waste, borates can seep into the earth and ground water and must be handled specially. Products with ammonium phosphate and tannin can be composted, but effluents contain eutrophicating substances.

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