Low Energy House

Low Energy House - What is Cellulose Insulation?

Cellulose insulation is produced from old newspapers and other waste paper. Because of its sustainability and low embodied energy, cellulose fibre is becoming an increasingly popular material for house insulation

Production of Cellulose Insulation

Cellulose Fibre Loft Insulation - Image Provided by WarmcelRecycled paper is shredded then treated with borax for flammability and smoulder resistance. The borax also makes the insulation unattractive to vermin and resistant to insects, fungus and dry rot. 

Uses of Cellulose Insulation

Cellulose insulation may be used directly from bags for insulating internal floors and loft floors. For other cavities, including sloping roof voids, the material can be blown to completely fill voids to prevent air circulation.

Recycling Cellulose Insulation

Manufactured cellulose insulation consists of approximately 80 per cent recycled waste paper with the remaining 20 per cent made up of fire retardants, to ensure the product is fire resistant.

Recycled cellulose insulation has a low embodied energy compared to rock wool and glass wool insulation and, when removed from a building, it may be used again or disposed of safely without creating toxic waste.

Advantages of Cellulose Insulation

  • Less conductive heat loss and better protection against air infiltration than other fibres (performance 38 per cent higher than glass wool)
  • Low embodied energy as it takes up to 20 times less energy to manufacture than other fibres
  • Low cost raw material as 75 to 80 per cent recycled content (fire resistant provided by chemicals and dense structure)

Spray Applying Cellulose Fibre to a Stud Wall - Image Provided by WarmcelFormats of Cellulose Insulation

Four major types of cellulose products have been developed to deal with different applications of the material in different locations in the building. These are generally characterised as dry cellulose, spray applied cellulose, stabilised cellulose and low dust cellulose.

Dry Cellulose (Loose Fill)

Dry Cellulose is generally blown into new or existing wall construction. During installation by this method, the material will settle by as much as 20 per cent and must therefore be permanently supported.

Spray Applied Cellulose (Wet Spray)

Spray applied cellulose is used for insulating new studded timber frame wall construction. The only difference between this application and the dry cellulose method is the addition of water, and sometimes with an adhesive, to the cellulose while spraying. Wet spraying helps seal cavities against air infiltration and eliminates settling problems.

Stabilised Cellulose Insulation

Stabilised cellulose is most often used in rafter and loft floor insulation. It is applied with a very small amount of water and adhesive which reduce the impact of settling and consequently the amount of cellulose needed.

Low-Dust Cellulose Insulation

Low dust cellulose has a small percentage of oil or similar dust dampener added in order to reduce dust. This material was developed for use in homes where occupants are sensitive to newsprint or paper dust.

Qualities of Cellulose Insulation

  • Cellulose Fibre in Timber Stud Walls - Image Provided by WarmcelCellulose insulation treated with borax provides superior control against mould, insects and pests such as rodents
  • Unlike mineral fibre and glass fibre insulation, cellulose does not cause skin irritation during installation
  • Borax treatment provides cellulose insulation with a rating of Class 1 surface spread of flame

Cellulose Insulation - Thermal Performance

The thermal performance of loose filled cellulose insulation compares favourably to other types of insulation. These results are similar to those for glass wool or rock wool.

The thermal conductivity of cellulose insulation is 0.035 W/m K at 10 degrees C in horizontal applications and from 0.040 to 0.038 W/m K at 10 degrees C in walls

In the UK, when comparing the thermal values of insulation materials, it is important to remember that the best performing material is the one with the lowest thermal conductivity value

About Cellulose Insulation - Loft Insulation - Wall Insulation