Building insulation materials 4: Oil - based polymers

Expanded Polystyrene (EPS) insulation
Extruded Polystyrene (XPS) insulation
Rigid polyurethane (PUR/PIR) insulation
Phenolic foam insulation

Expanded Polystyrene (EPS) insulation


Expanded Polystyrene insulation is made from small beads of polystyrene mixed with a pentane as the blowing agent. Heating expands the beads. EPS boards are produced by putting the beads into moulds and heated further to fuse the beads together. Typical applications of EPS boarding are in walls, roofs and floors. Polystyrene beads are frequently used as cavity fill in masonry walls.

expanded polystyrene

Pro

Recyclable through grinding down

Pro

Reusable if in suitable condition

Pro

Fairly high compressive strength

Pro

Water impermeable

Pro

Inherently resistant to rot and vermin

Con

Derived from petrochemicals – causing resource depletion and pollution risks from oil and plastics production

Con

Styrene and other hydrocarbons are emitted as part of the production process. UK emissions are within legally defined limits

Con

HBCD, used as a fire retardant, is regarded as hazardous (15)

Con

High embodied energy

Con

The finished product can have some unstable residues of monomers of styrene which may outgas. (16)

Con

Badly disposed of EPS has become an acute environmental concern

Embodied energy cradle to gate

Various figures: example of 108 MJ/kg (for EPS Average of 2 Swiss factories) 2

More: Thermal properties of insulation.....

 

Extruded Polystyrene (XPS) insulation


Extruded Polystyrene (XPS) is made by mixing polystyrene with a blowing agent under pressure and the resulting fluid forced through a die. As it emerges from the die it expands into a foam, is shaped, cooled and trimmed to dimension. XPS is slightly stronger than EPS, and although it is used in many of the same applications as EPS, it is particularly suitable for use below ground or where extra loading and/or impacts might be anticipated.

extruded polystyrene

Pro

Recyclable through crushing

Pro

Reusable if in suitable condition

Pro

High compressive strength

Pro

Water impermeable

Pro

Inherently resistant to rot and vermin

Pro

In Europe, most blowing agents are zero ozone depletion (ODP) blowing agents

Con

Derived from petrochemicals – causing resource depletion and pollution risks from oil and plastics production

Con

Styrene and other hydrocarbons are emitted as part of the production process. UK emissions are within legally defined limits

Con

HBCD, used as a fire retardant, is regarded as hazardous (15)

Con

Can also release small amounts of chlorofluorocarbons (16)

Con

The finished product can have some unstable residues of monomers of styrene which may outgas. (16)

Con

Relatively high embodied energy

Embodied energy cradle to gate

Various figures: example of 95 MJ/kg (for XPS, calculated by Ecoinvent using data from leading factories in Germany and USA) 3

More: Thermal properties of insulation.....

 

Rigid polyurethane (PUR/PIR) insulation


Polyurethane (PUR), a closed-cell plastic, is formed by reacting two monomers in the presence of a blowing agent catalyst (polymerisation). Polyisocyanurate foam (PIR) is essentially an improvement on polyurethane where there is a slight difference in the constituents and where the reaction is conducted at higher temperatures. PIR is more fire-resistant and has a slightly higher R value. Applications include wall, floor and roof insulation. Polyurethane is also popular in laminate form in SIPS and as an insulation backing to rigid boarding such as plasterboard.

Rigid polyurethane (PUR/PIR) insulation

Pro

Recyclable through grinding down

Pro

Reusable if in suitable condition

Pro

High compressive strength

Pro

Water impermeable

Pro

Inherently resistant to rot and vermin

Pro

In Europe, most blowing agents are zero ozone depletion (ODP) blowing agents

Con

Derived from petrochemicals – causing resource depletion and pollution risks from oil and plastics production

Con

The production process produces a number of emissions to air and water and hazardous wastes as defined by EU Directive 91/689/EEC 17. UK emissions are within legally defined limits

Con

Relatively high embodied energy

Con

Shrinking of panels leading to gaps in the insulation layer, can reduce insulation effectiveness. Jointing of panels (eg tongue & groove) and multiple layers can reduce the problem

Con

Insulation performance can be reduced over the first 3 years due to gas exchange from the cells. This reduction of performance is usually included in the manufacturers declared value of thermal conductivity

Embodied energy cradle to gate

More: Thermal properties of insulation.....

101 MJ/kg 17

Phenolic foam insulation


Phenolic foam insulation is made by combining phenol-formaldehyde resin with a foaming agent. When hardener is added to the mix and rapidly stirred, the exothermic reaction of the resin, together with the action of the foaming agent, causes foaming of the resin. This is followed by rapid setting of the foamed material. Though more usually employed in building services applications, phenolic foam panels are suitable as insulation for roofs, walls and floors. Phenolic foam is also popular in laminate form as an insulation backing to rigid boarding such as plasterboard.

Phenolic foam insulation

Pro

Reusable if in suitable condition

Pro

Inherently flame resistant

Pro

High compressive strength

Pro

High thermal performance

Pro

Moisture resistant

Pro

In Europe, most blowing agents are zero ozone depletion (ODP) blowing agents

Con

Not readily recyclable

Con

Produced from phenol formaldehyde - a toxic petrochemical derivative (19)

Con

Shrinking of panels leading to gaps in the insulation layer can reduce insulation effectiveness. Jointing of panels (eg tongue & groove) and multiple layers can reduce the problem

 

Other types of insulation

Plant / animal derived insulation

Mineral insulation

 

References


2 Ecoinvent, 2007 supplied by Dr Andrew Norton, Renuables
3 Dr Andrew Norton, Renuables
5 'Insulation for Sustainability - A Guide', XCO2 Conisbee, 2003 (an industry-sponsored report)
15 DEFRA & CSF www.defra.gov.uk/environment/chemicals/csf/advice/hbcd.htm
16 SEDA: www.seda2.org/dfcrb/append.htm
17 'Polyurethane Rigid Foam', I Boustead, PlasticsEurope (an industry-sponsored report)
19 'Formaldehyde Found in Building Materials', Healthy Building Network, 2008

 

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