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

Pro

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

Pro

Manufactured from renewable resources.

Pro

Reusable if kept dry

Pro

Recyclable

Pro

Sequesters CO2 during tree growth.

Pro

Very low embodied energy

Pro

Hygroscopic – provides a degree of humidity control

Con

Newsprint production can produce hazardous waste 1

Con

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

Con

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

Con

Possible risk associated with the inhalation of paper dust during installation

Con

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

Con

Thermal conductivity can be increased by compaction or settlement. 5

Con

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.

Pro

Manufactured from renewable resources (subject to management)

Pro

Reusable if not adhesive or render-coated

Pro

Recyclable as loose fill

Pro

Can be used in energy recovery

Pro

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

Pro

Cork production helps to sustain communities in poorer agricultural areas

Pro

Sequesters CO2 during tree growth

Pro

Waterproof

Pro

Naturally resistant to insect and rodent attack (except wasps)

Pro

Resistant to compression

Pro

Dimensionally stable

Con

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

Pro

Typically contains high percentage of pre-consumer waste material

Pro

Manufactured mainly from renewable resources

Pro

Reusable if in a suitable condition

Pro

Recyclable

Pro

Compostable or can be used in energy recovery

Pro

Sequesters CO2 during tree growth

Pro

Hygroscopic – provides a degree of humidity control

Con

Contains non-renewable material (polyester binder).

Con

Contains an ammonium phosphate based fire retardant

Con

Thermal conductivity can be increased by compaction and moisture. 5

Con

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

Pro

Hemp is a renewable material

Pro

Some products contain recycled material

Pro

Compostable or can be used in energy recovery

Pro

Reusable if in a suitable condition.

Pro

Recyclable

Pro

Sequesters CO2 during plant growth

Pro

Hygroscopic – provides a degree of humidity control

Pro

Pesticide use is very rare

Con

Contains non-renewable material (polyester binder)

Con

Production of fertilisers contributes to global warming

Con

Contains an ammonium phosphate based fire retardant

Con

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

Con

Thermal conductivity can be increased by compaction and moisture 5

Con

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

Con

Relatively untested

Embodied energy cradle to gate

Various: between 10.5 and 33 MJ/kg LHV dependant on binder type used and scale of production 3

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.

Pro

Hemp is a renewable material

Pro

Vapour permeable

Pro

Hemp sequesters CO2 during plant growth.

Pro

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

Pro

Thermal mass

Con

Use of cement contributes to global warming

Con

Production of fertilisers contributes to global warming

Con

Use of pesticides in crop production

Con

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

Pro

Flax is a renewable material

Pro

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

Pro

Reusable if in a suitable condition

Pro

Recyclable

Pro

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

Pro

Sequesters CO2 during plant growth

Pro

Space efficiency

Pro

Hygroscopic – provides a degree of humidity control

Con

Currently only occasionally available from overseas sources.

Con

Contains non-renewable material (polyester binder)

Con

Production of fertilisers contributes to global warming

Con

Use of pesticides in crop production

Con

Contains boron-based flame retardant and biocide

Con

Imported from the continent which adds to embodied energy

Con

Thermal conductivity can be increased by compaction and moisture 5

Con

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

Con

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.

Pro

Sheep’s wool is a waste product from renewable sources

Pro

Wool sequesters CO2 during animal growth

Pro

Hygroscopic – provides a degree of humidity control

Pro

Can absorb moisture without loss of thermal efficiency

Pro

Reusable if in a suitable condition

Con

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

Con

Contains boron-based flame retardant and biocide

Con

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

Con

Imported wool adds to embodied energy

Con

The possible use of pesticides in imported wool

Con

Thermal conductivity can be increased by compaction 5

Con

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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