Building insulation materials 2: 'Natural' / Organic

	Cellulose insulation
	Cork insulation
	Wood wool insulation
	Wet-formed wood fibre board insulation
	Hemp insulation
	Hempcrete
	Flax insulation
	Sheeps wool insulation

Cellulose insulation

Cellulose insulation is made from recycled newspaper. The material is usually treated with a mixture of borax and boric acid to provide fire resistance as well as to repel insects and fungi. The insulation is suitable for use between rafters and joists and timber 'breathing' wall construction. Cellulose insulation is available in a loose format for pouring and dry or damp spraying as well as in slab format for fitting within metal or timber frames.

cellulose fibre insulation

The cellulose component typically (around 80% of the total) contains over 90% post-consumer recycled material.

Manufactured from renewable resources.

Reusable if kept dry

Recyclable

Sequesters CO2 during tree growth.

Very low embodied energy

Hygroscopic – provides a degree of humidity control

Newsprint production can produce hazardous waste 1

Contains boron-based flame retardant and biocide (approx. 20% of total content)

Possible odour and formaldehyde off-gassing from printing inks – though containable through use of vapour control membranes

Possible risk associated with the inhalation of paper dust during installation

Mould has been known to be an issue in exceptional circumstancess.

Thermal conductivity can be increased by compaction or settlement. 5

Borates will leach if they are exposed to permanent or intermittent wetting such that the insulation remains damp to the touch for protracted periods. 6

More: Thermal properties of insulation.....

Embodied energy cradle to gate

Varied eg:

- 16.64 MJ/kg (cradle to grave) ⁷
- 7.6 MJ/kg (LHV for a major Swiss producer) ²
- 4.9 MJ/kg (for UK product) ⁸

Cork insulation

Cork insulation is made from cork bark that is harvested from the tree every 25 years. Cork granules are expanded and then formed into blocks, using the natural resin, through high temperature and pressure. The most common applications for cork insulation are in flat roofs and insulated render systems, both of which take advantage of cork’s dimensional stability and resistance to compression.

Manufactured from renewable resources (subject to management)

Reusable if not adhesive or render-coated

Recyclable as loose fill

Can be used in energy recovery

Cork forests support indigenous wildlife (but detailed research of impacts on biodiversity is still lacking)

Cork production helps to sustain communities in poorer agricultural areas

Sequesters CO2 during tree growth

Waterproof

Naturally resistant to insect and rodent attack (except wasps)

Resistant to compression

Dimensionally stable

Cork dust may be a health issue – avoid inhalation

More: Thermal properties of insulation.....

Embodied energy cradle to gate

Varied eg: 1.38 MJ/kg (LHV one major producer in Portugal using continuous and batch processes)²²

Wood fibre insulation

Wood fibre insulation is made from forestry thinnings and saw mill residue. Binding is provided by polyolefin fibres and the fire retardant is usually ammonium phospate. Wood fibre insulation is used in breathing wall construction, ventilated pitched roofs and in ceilings and floors.

wood wool insulation

Typically contains high percentage of pre-consumer waste material

Manufactured mainly from renewable resources

Reusable if in a suitable condition

Recyclable

Compostable or can be used in energy recovery

Sequesters CO2 during tree growth

Hygroscopic – provides a degree of humidity control

Contains non-renewable material (polyester binder).

Contains an ammonium phosphate based fire retardant

Thermal conductivity can be increased by compaction and moisture. 5

Imported into UK, adding to embodied carbon

Embodied energy cradle to gate

10.8 MJ/kg ²¹

More: Thermal properties of insulation.....

More: Designing with wood fibre insulation.....

Hemp insulation

Hemp insulation slabs are made from hemp or hemp mixed with either recycled cotton fibres or wood fibres, bound with a polyester binder and treated for fire resistance. Hemp insulation is used in breathing wall construction, ventilated pitched roofs and in ceilings and floors.

Hemp insulation

Hemp is a renewable material

Some products contain recycled material

Compostable or can be used in energy recovery

Reusable if in a suitable condition.

Recyclable

Sequesters CO2 during plant growth

Hygroscopic – provides a degree of humidity control

Pesticide use is very rare

Contains non-renewable material (polyester binder)

Production of fertilisers contributes to global warming

Contains an ammonium phosphate based fire retardant

Usually imported from the continent (though some material can be grown in the UK) which adds to embodied energy

Thermal conductivity can be increased by compaction and moisture 5

Borates will leach if they are exposed to permanent or intermittent wetting such that the insulation remains damp to the touch for protracted periods 6

Relatively untested

Embodied energy cradle to gate

Various: between 10.5 and 33 MJ/kg LHV dependant on binder type used and scale of production³

More: Thermal properties of insulation.....

Hempcrete

Hempcrete, first developed in France and now manufactured by Lime Technology Ltd as Tradical products in the UK, is a precast, insitu cast or sprayed mixture of lime, cement and hemp insulation.

Hemp is a renewable material

Vapour permeable

Hemp sequesters CO2 during plant growth.

Hygroscopic – provides a degree of humidity control through ‘moisture mass’

Thermal mass

Use of cement contributes to global warming

Production of fertilisers contributes to global warming

Use of pesticides in crop production

Drying time

Embodied energy cradle to gate

Trade figures unavailable but estimates in the region of 2 – 5 MJ/kg LHV are expected dependant on ratios of materials used and scale of production ³

More: Thermal properties of insulation.....

Flax insulation

Flax insulation slabs are made from flax with a polyester binder and treated for fire resistance. Flax insulation is used in breathing wall construction, ventilated pitched roofs and in ceilings and floors.

flax insulation

Flax is a renewable material

The flax used in insulation is a by-product of the linen industry – though not strictly waste, insulation flax fibres are of a much lower economic value than linen flax fibres

Reusable if in a suitable condition

Recyclable

Compostable (though presence of boron salts might be of concern) or can be used in energy recovery.

Sequesters CO2 during plant growth

Space efficiency

Hygroscopic – provides a degree of humidity control

Currently only occasionally available from overseas sources.

Contains non-renewable material (polyester binder)

Production of fertilisers contributes to global warming

Use of pesticides in crop production

Contains boron-based flame retardant and biocide

Imported from the continent which adds to embodied energy

Thermal conductivity can be increased by compaction and moisture 5

Borates will leach if they are exposed to permanent or intermittent wetting such that the insulation remains damp to the touch for protracted periods 6

Relatively untested

Embodied energy cradle to gate

Various figures:
- between 11 and 30 MJ/kg LHV dependant on binder type used and scale of production ³
- 39.5 MJ/kg ¹

More: Thermal properties of insulation.....

Sheeps wool insulation

Sheep’s wool slabs and rolls are made from wool with a polyester binder and treated for fire and insect resistance. Wool is suitable for use as insulation between rafters, joists and timber studs in timber ‘breathing’ wall construction. Sheep’s wool has excellent hygroscopic properties that help to moderate temperatures throughout the seasons.

Sheep’s wool is a waste product from renewable sources

Wool sequesters CO2 during animal growth

Hygroscopic – provides a degree of humidity control

Can absorb moisture without loss of thermal efficiency

Reusable if in a suitable condition

Contains non-renewable material (polyester binder). Other binders can be used which can be a source of concern. Check.

Contains boron-based flame retardant and biocide

Very cheap Chinese wool insulation is becoming available on the world market. Conditions in which the sheep are reared are unknown.

Imported wool adds to embodied energy

The possible use of pesticides in imported wool

Thermal conductivity can be increased by compaction 5

Sheep emit significant quantities of methane. 37% (1993 figure) of methane produced in the UK comes from sheep and cattle.

Embodied energy cradle to gate

Various figures:
- 20.9 MJ/kg ⁶;
- 12 – 36.8 MJ/kg dependent on the use of waste wool and scale of production. ³

More: Thermal properties of insulation.....

Other types of insulation

	Mineral insulation
	Oil-derived insulation

Insulation products on GreenSpec

References

1 'A Comparative Life Cycle Assessment of Building Insulation Products made of Stone Wool, Paper Wool and Flax'; Anders Schmidt et al, 2004 (an industry-sponsored report)
2 Ecoinvent, 2007 supplied by Dr Andrew Norton, Renuables
3 Dr Andrew Norton, Renuables
4 'Life Cycle Assessments of Natural Fibre Insulation Materials'; Murphy & Norton, 2008
5 'Insulation for Sustainability - A Guide', XCO2 Conisbee, 2003 (an industry-sponsored report)
6 Mark Lynn, Second Nature
7 'Cellulose Fibre Insulation', Eurima, 2004 (an industry-sponsored report)
8 BRE Environmental Profile
9 Lime Technology Ltd. Tradical
20 Steico
21 'Inventory of Carbon & Energy (ICE)' - 1.6a, Hammond & Jones, 2008
22 Cork industry

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