XPS & HFCs
Does extruded polystyrene (XPS) use HFCs in its manufacture?
Extruded polystyrene (XPS) insulation boards made and sold in the UK don’t use hydrofluorocarbon (HFC) blowing agents as part of their manufacture. They may have done in the past, but it is no longer the case. A series of international agreements, drawn up as a result of better understanding the environmental impact of different blowing agents, have helped to phase out their use.
That is not true globally, as not all countries have signed up to the same agreements at the same pace. In North America, for example, the phasing out of HFCs has been slower than in Europe. Because of the popularity of XPS in North America, and the volume of product produced by well-known manufacturers, negative environmental impacts continue to be associated with UK-manufactured material, creating an inaccurate perception.
What are blowing agents?
A blowing agent is a substance used to create a gaseous, cellular structure within liquid materials. Blowing agents have a wide range of applications, including creating foam products from liquid resins.
For the purpose of this blog post, we are interested in blowing agents as part of the manufacturing process for thermal insulation materials. A number of rigid foam insulants, including XPS, start their life as a mix of liquid raw materials. Injection of a blowing agent helps to create the cellular structure that characterises the end product.
Crucially for the performance of the product, the cells formed in the process contain a gas that slows heat transfer better than normal air. The choice and use of blowing agent therefore plays a significant role in the declared thermal performance of the insulation material.
Why do HFCs have a negative environmental impact?
Previously, the use of HFCs as a blowing agent was actually seen as a positive for the environment. They replaced hydrochlorofluorocarbons (HCFCs), which themselves replaced chlorofluorocarbons (CFCs).
The phaseout of CFCs started in the late 1980s, thanks to an agreement called the Montreal Protocol. CFCs contributed to the depletion of the ozone layer, and had a considerably higher global warming potential (GWP) than carbon dioxide.
HCFCs improved on CFCs, but still had high ozone depletion potential (ODP) and high GWP. The introduction of HFCs reduced the ODP of blowing agents, but still resulted in high GWP.
What blowing agent does Polyfoam XPS use?
Although HFCs have been replaced by new blowing agents that have zero ODP and low GWP, there remains an association between XPS insulation and HFCs that is hard to shift.
For example, in the recent A Guide to Building Materials and the Environment Third Edition, by Chris Halligan and Joanne Denison, a section about XPS insulation says: “XPS traditionally uses HFCs as a blowing agent.”
Although true, it’s a statement that doesn’t reflect current XPS manufacturing. Many blowing agents, including the one used by Polyfoam XPS, are now proprietary. Their precise composition is not detailed publicly but they are not HFCs.
Now that the Green Guide to Specification has been phased out by the BRE, the contribution of blowing agents to an XPS product’s environmental impact is assessed through environmental product declarations (EPDs).
Polyfoam XPS has EPDs available for its floor and roof insulation ranges, and they are available to download from the technical support section of our website. You can also find copies of our BBA certificates and BES 6001 responsible sourcing certification, among other things.
We hope this blog post has served as a useful introduction to blowing agents and the environmental impact of XPS. If you have any questions that we haven’t answered in this post, contact us.