Insulation materials compared

Key issues

• Reducing the amount of energy used from fossil fuels is the most important factor in promoting sustainability.

• Insulation has the greatest potential for reducing CO₂ emissions.

• Energy conserved through insulation use far outweighs the energy used in its manufacture. Only when a building achieves a ‘LowHeat’ standard does insulation’s embodied energy become significant.

• Insulation performance is the key selection criteria.

• The durability of insulation affects its performance eg settlement, physical degradation, vapour permeability and air movement.

• Careful detailing is needed to avoid the risk of moisture ingress into the insulation.

• Most of the materials below differ in their capacity to reduce heat flow. This means that different materials require different thicknesses to achieve the same effect. These differences need to be considered when planning wall cavity widths.

• Good insulation performance requires careful site supervision.

• Insulation only provides reduction of heat loss through the building fabric. Equally important is the energy lost through ventilation and glazing.

Types of insulation

There is a potentially bewildering array of insulating materials for the specifier to select from. They range from the familiar polystyrene and mineral wool through to alternatives now entering the market such as sheeps wool and hemp. In an attempt to give some semblance of order to the array, we have grouped insulation materials according to provenance:

1 Insulation derived from organic sources
2 Insulation derived from naturally occurring minerals
3 'Multi-foil' insulation
4 Insulation derived from fossilized vegetation

When selecting an insulation material, primacy should be given to performance in the construction context. Very few insulation materials are capable of performing all the functions called for eg sheeps wool is perfectly suitable for ventilated wall construction but not in unventilated cavities. The choice of insulation will be governed by choice of construction and vice-versa.

Though selection by performance continues to be the most important consideration, the current evolution of the market in 'green' products will complicate the choice for specifiers. Life cycle data is available for some products but other, often newer products have not had their claims verified by third party research. While this state of affairs continues, manufacturers' claims in a competitive market will be open to contention. This fact should be borne in mind when considering the nature of the information we have provided below. Not until all products have undergone LCAs will accurate comparisons be possible.

2 Insulation derived from naturally occurring minerals

Glass mineral wool batts and rolls  (BSI kitemarked available)

	Some brands utilise recycled glass (needs to be > 50% to be of significance)
	Fibres made from glass, a product of silica, an abundant mineral
	Can be re-used though there are no facilities for recycling
	High embodied energy (but more materially efficient than rockwool)
	Most mineral wools include a formaldehyde-based binder - though exceptions are beginning to appear on the market
	We have been obliged to remove this comment
	Manufacturing can result in the emissions of chlorides, fluorides, particulates, VOCs and solvents.
	We have been obliged to remove this comment
	Asphalt treated papers may emit odors
	Installation may cause irritation to skin, nose, eyes
	Durability: Long-lasting with an inherent resistance to rot. However, moisture ingress will reduce performance. Compression where occurring will reduce performance.
	0.033 W/m°C - 0.040 W/m°C
G	Green Guide rating: A+
E	Embodied energy: Embodied energy: 28 MJ/kg (source: Hammond & Jones, Univ of Bath) at 30kg m3 or 840 MJ m3 at 30 kg m3

Mineral (Rock & Slag) wool batts and rolls (BSI kitemarked available)

	Recyclable
	Mineral (Slag) Wool is made comprised of steel slag ( over 75%) with some basalt rock ( 25% or less). In some plants the recycled steel slag makes up almost 100% of the content
	Rockwool, made from rocks, has a high natural content
	Fireproof
	Most mineral wools include a formaldehyde-based binder - though exceptions are beginning to appear on the market
	We have been obliged to remove this comment
	We have been obliged to remove this comment
	Installation may cause irritation to skin, nose, eyes
	Durability: Long-lasting with an inherent resistance to rot. However, moisture ingress will reduce performance. Compression where occurring will reduce performance.
	0.033 W/m°C - 0.040 W/m°C
G	Green Guide rating: Ranges from A+ through to C according to density
E	Embodied energy: 16.8 MJ/kg (Rockwool) (source: Hammond & Jones, Univ of Bath) or 1,008 MJ m3 at 60 kg m3

Foamed glass slab (Foamglas)

	Reclaimable
	2/3 of content is from recycled glass
	Fireproof
	Hydrophobic
	High thermal mass
	Resistant to insect infestation
	Photochemical oxidants as well as SO2 and NO2 released as part of manufacturing process
	High embodied energy
	Mining of raw materials causes landscape degradation
	Uses bitumen or synthetic adhesives to install
	Durability: Long-lasting with an inherent resistance to moisture, air movement and rot. Dimensionally stable and resistant to compression.
	0.042 W/m°C
G	Green Guide rating: C or D according to density
E	Embodied energy: 27 MJ/kg (source: Hammond & Jones, Univ of Bath) or 3,240 MJ m3 at 120 kg m3

Perlite beads (volcanic glass expanded through heating)

	Reclaimable
	High natural content
	Safe to install
	Non-flammable, moisture resistant
	Increases fire resistance of cavity walls
	Can be used as an insulating aggregate in concrete
	Non renewable resource
	Mining causes landscape degradation
	Relatively high embodied energy through heat processing and transportation to the UK
	Must be installed in sealed spaces
	0.045 - 0.05 W/m°C
G	Green Guide rating: unrated
E	Embodied energy: unknown

Exfoliated vermiculite

	Reclaimable
	High natural content
	Safe to install
	Non-flammable
	Can be used as an insulating aggregate in concrete
	Relatively high embodied energy through heat processing and transportation to the UK
	Mining causes landscape degradation
	Avoid vermiculite produced in the US prior to 1990- it contains asbestos
	0.063 W/m°C
G	Green Guide rating: unrated
E	Embodied energy: unknown

Expanded clay aggregate

	Reclaimable
	High natural content
	Safe to install
	Balances relative humidity
	High embodied energy through the firing process and transportation to the UK
	Mining causes landscape degradation
	0.09-0.1 W/m°C
G	Green Guide rating: unrated
E	Embodied energy: unknown

3 Multi-foil insulation

Multi-foil insualtion (aka Radiant barriers)

	Opinion is sharply divided over the effectiveness of multi-foil insulation. Ultimately at issue is testing methodology. The latest guidance (LABC Technical Guildance Note, April 2008) to Building Control officers describes the problem: ‘Tests carried out by the National Physical Laboratory (who have UKAS accreditation) using test methods in accordance with BS EN ISO 8990 have indicated an “R” value for multi-foil products in a range of 1.69 to 1.71 m2K/W. Those manufacturers who use comparative testing are however, claiming “R” values for their products which range from 5 to 6 m2K/W. In other words, multi-foil manufacturers who have used the comparative testing route are claiming the insulating properties of their product to be approximately three times better than can be verified using existing National, European or International test standards.’ In conclusion to its Guidance Note the LABC remains of the opinion that ‘…the thermal performance of all insulation materials should be determined by testing to National, European or International standards by organisations which have been accredited to do so. On this basis we are not aware of any multi-foil product currently on the market that can meet the normal roof "U" value requirement of 0.2 when used as a single layer without the need for additional insulation’ • LABC Technical Guidance note 'Use of Multi-foil insulation products Compliance with Regulation 7 and Requirement L1' LABC, April 2008
	Can have recycled content (but check!).
	Its thinness makes it ideal for applications (eg refurbishment) where there is little room available within the construction to allow for more common insulation materials
	Derived from non-renewable petrochemicals and aluminium
	High embodied energy
	Non-biodegradable in landfill
	Poor airtightness
	Standard test method ('Hot Box') to BS EN ISO 8990: R values range between 1.69 - 1.71m2K/W Manufacturers' 'comparative testing' method: R values range between 5 - 6m2K/W
G	Green Guide rating: unrated
E	Embodied energy: unknown

4 Insulation derived from fossilized vegetation

Expanded Polystyrene board and beads (EPS)

	Recyclable through grinding down and adding to new sheeting
	Reclaimable
	Petrochemical derived (and therefore embodies both resource depletion and pollution risks from oil and plastics production)
	Expanded using pentane (Zero-ODP), no damage to ozone but produces smog
	Non-biodegradable in landfill
	Emits toxic fumes when burnt
	Deteriorates releasing gases under ultra-violet light.
	Durability: Long-lasting with an inherent resistance to moisture, air movement, rot and compression. Specifiers should make sure that the manufacturer's quoted conductivity is in accordance with the European Standard BS EN 13163 giving the 'aged' or long-term value.
	0.032 W/m°C - 0.040 W/m°C (Beads are towards the high end of the scale)
G	Green Guide rating: A+
E	Embodied energy: 88.6 MJ/kg (source: Hammond & Jones, Univ of Bath) or 1,772 MJ m3 at 20 kg m3

Extruded Polystyrene board (XPS)

	Some products use recycled polystyrene
	Reclaimable
	Petrochemical derived (and therefore embodies both resource depletion and pollution risks from oil and plastics production)
	Expanded using pentane (Zero-ODP), no damage to ozone but produces smog
	Some boards may still be expanded using HCFCs (use should have phased out in 2004)
	Non-biodegradable in landfill
	Emits toxic fumes when burnt
	Deteriorates under prolonged exposure from ultra-violet light.
	Durability: Long-lasting with an inherent resistance to moisture, air movement, rot and compression. However performance can suffer through gas exchange within the insulation over time. Specifiers should make sure that the manufacturer's quoted conductivity is in accordance with the European Standard BS EN 13164 giving the 'aged' or long-term value.
	0.028 W/m°C - 0.036 W/m°C
G	Green Guide rating: (HFC blown) E
E	Embodied energy: unknown

Polyurethane/Polyisocyanurate board and foam

	Board is reclaimable
	Very low conductivity
	Hydrophobic
	Petrochemical derived (and therefore embodies both resource depletion and pollution risks from oil and plastics production)
	Though technically re-cyclable through glycolysis and regrinding, most PU waste goes to landfill where it is non-biodegradable
	Emits toxic fumes when burnt
-	UK PU is not expanded using HCFCs, but check if sourced from overseas
	Durability: Long-lasting with an inherent resistance to moisture, air movement, rot and compression. However performance can suffer through gas exchange within the insulation over time. Specifiers should make sure that the manufacturer's quoted conductivity is in accordance with the European Standard BS EN 13165 giving the 'aged' or long-term value. The use of gas-tight foils such as aluminium can reduce the degradation.
	0.022 - 0.028 W/m°C (pentane as propellant)
G	Green Guide rating: A
E	Embodied energy: 72.1 MJ/kg (source: Hammond & Jones, Univ of Bath) or 2,307 MJ m3 at 32 kg m3

Phenolic foam board

	Reclaimable
	Very low conductivity
	Hydrophobic
	Petrochemical derived (and therefore embodies both resource depletion and pollution risks from oil and plastics production)
	Non-biodegradable in landfill
	Some boards are still expanded using HCFCs
	Emits toxic fumes when burnt
	Durability: Long-lasting with an inherent resistance to moisture, air movement, rot and compression. However performance can suffer through gas exchange within the insulation over time. Specifiers should make sure that the manufacturer's quoted conductivity is in accordance with the European Standard BS EN 13166 giving the 'aged' or long-term value.
	0.020 W/m°C
G	Green Guide rating: unrated
E	Embodied energy: unknown

We would specify:

First choice: Insulation derived from organic sources
Second choice: Insulation derived from naturally occurring minerals
Third choice: Insulation derived from fossil fuels. Always specify foams that use Zero-ODP (ZODP) blowing agents.