I Used To Hate XPS
I used to hate XPS, and I was right to. At least I was right based on my own moral compass which is guided by a desire for energy efficiency as a method of improving health, comfort, and most of all environmental impact. I’m open to having my mind changed as technology improves, and my mind has changed.
XPS is a fantastic product in terms of performance. High R-value per inch, cuts well, high compressive strength, and it can be used in wide applications both below and above grade. It also used to be produced using HFC’s (hydrofluorocarbons, and yes I’m impressed with myself for spelling that correctly first try).
We've all seen it on the job site, many of us have never thought about the product beyond its performance. Image via https://bewi.com/products/insulation-board-xps-rabbet-edge/
The global warming potential (GWP) of hydrofluorocarbons (HFCs) previously used in the production of extruded polystyrene (XPS) insulation is significantly higher than that of the newer hydrofluoroolefin (HFO) blowing agents. The most common HFCs used for XPS insulation include HFC-134a and HFC-152a. Here are the typical GWPs for these HFCs:
HFC-134a: This was one of the most commonly used blowing agents in XPS insulation. Its global warming potential (GWP) is approximately 1,430 over a 100-year time horizon. This means it is 1,430 times more effective at trapping heat in the atmosphere than carbon dioxide (CO2). This also means that XPS produced with this blowing agent will likely never be able to offset its own climate debt from production by reducing energy consumption. I watched miles and miles of highway be underlaid with this product in Edmonton when the ring road was being built and I just shudder to think of what we have done to the climate with this product.
HFC-152a: This blowing agent has a lower GWP than HFC-134a but is still quite high. Its GWP is approximately 124 over a 100-year time horizon. This is the blowing agent widely used in “next generation” XPS that’s being touted as environmentally friendly by many manufacturers at the moment.
Comparison with HFO Blowing Agents:
Now here’s where XPS wins me back, at present several manufacturers have moved to HFO blowing agent for XPS production.
HFO-1234ze, the newer blowing agent replacing HFCs, has a GWP of 1 over the same 100-year time horizon. This represents a dramatic reduction in the contribution to global warming compared to HFCs.
Soprema's SOPRA-XPS uses a large portion of recycled plastic for production, and HFO-1234ze as a blowing agent with CO2. I took this image from their website where they have a very in depth EPD that can be found here: https://www.soprema.ca/en/transparency-sopra-xps-epd#epd
Manufacturers like Soprema in North America are leading the market by producing XPS with high levels of recycled content and blowing agents which are dramatically less impactful to the climate. I’m not normally one to swoon over a corporation, but when one does something right it should be acknowledged.
The raw materials used in the SOPRA-XPS extruded polystyrene thermal insulation board include a variety of components, primarily focused on plastics like polystyrene. Here’s a summary of the raw material inputs, particularly focusing on plastics, their recyclability, and the environmental impacts based on the Environmental Product Declaration (EPD) and analysis from other sources:
Raw Material Inputs:
Polystyrene (Virgin and Recycled):
The SOPRA-XPS board is made of both virgin and recycled polystyrene, with 20% virgin polystyrene and up to 70% recycled or recovered polystyrene content depending on the specific product variation.
Recycled polystyrene is sourced from various post-consumer and pre-consumer materials. The recycled content is validated by external consultants based on data from supplier chains and the quantities of non-virgin materials used.
The use of virgin polystyrene is necessary to maintain the structural integrity and thermal properties of the board, while recycled polystyrene contributes to reducing the product’s overall environmental impact.
Blowing Agents (HFO-1234ze and CO2):
The blowing agent HFO-1234ze is used for its low global warming potential, replacing the older HFC-based agents.
Carbon dioxide (CO2) is also used as part of the blowing agent process, though it diffuses out of the board shortly after production.
Additives:
The board includes various additives such as flame retardants, talc, co-agents, and colorants, each sourced from different regions globally. These additives help to enhance the product's durability, fire resistance, and moisture control, though they add to the environmental impact through their production and transport.
Environmental Impacts of Raw Materials:
Polystyrene and Plastic Production:
Energy Consumption: Virgin polystyrene production is a highly energy-intensive process. According to various studies, producing polystyrene requires significant fossil fuel inputs and contributes to greenhouse gas emissions. This is reflected in the EPD, where raw material production accounts for 63% of the global warming potential of the product(EPD_Sopra_XPS_EN).
Emissions: The production of virgin polystyrene contributes to emissions in the form of greenhouse gases (GHGs) and other pollutants such as nitrogen oxides and sulfur oxides, contributing to acidification and eutrophication(EPD_Sopra_XPS_EN).
Recycled Polystyrene:
Recycling Challenges: While polystyrene is technically recyclable, the actual recycling rates remain low. This is because many recycling facilities do not accept polystyrene due to its lightweight and bulkiness, making it less economical to process. Although SOPREMA includes up to 70% recycled polystyrene in its boards, the infrastructure for widespread polystyrene recycling is still underdeveloped(EPD_Sopra_XPS_EN)(EPD_Sopra_XPS_EN).
Reliability of Recycled Content Data: The EPD suggests that SOPREMA uses third-party validation to ensure the accuracy of recycled content in their products. This provides a level of reliability regarding the claims of recycled material use. However, the recyclability of post-consumer polystyrene remains inconsistent across regions, limiting the overall impact reduction(EPD_Sopra_XPS_EN).
Recyclability and Circular Economy:
Recyclability Claims:
SOPREMA’s EPD claims a high recycled content, but it acknowledges that there is no current recovery system for the insulation boards at the end of their life cycle. This means that although the board is recyclable in theory, it is typically sent to landfills after the building's life cycle, and remaining HFO emissions are released over time(EPD_Sopra_XPS_EN).
While post-consumer recycling of polystyrene is increasing in some areas, the availability of these services is highly localized and limited in scope(EPD_Sopra_XPS_EN).
Reliability and Data on Recyclability:
External validation and ISO compliance help ensure that SOPREMA’s claims about recycled content are accurate. However, the actual life-cycle environmental benefits of recycling polystyrene are limited by the lack of a widespread, efficient recycling system for post-consumer waste(EPD_Sopra_XPS_EN)(EPD_Sopra_XPS_EN).
Conclusion:
The use of recycled polystyrene in SOPRA-XPS products is a positive step towards reducing the environmental impact of virgin plastic production. However, despite the high recycled content, the overall lifecycle environmental benefits are constrained by the limited infrastructure for post-consumer polystyrene recycling. This is really an US problem, as in you and I, recycling infrastructure is improving, but we need to keep pushing to keep products circular rather than disposable. The reliance on virgin polystyrene and other plastic components continues to drive significant environmental impacts, including energy use and emissions.
Recycling rates and the efficacy of the recycled content are validated and reliable based on third-party assessments, but there remains a gap between the potential recyclability of the product and its actual end-of-life treatment, which is often disposal rather than recovery. The full environmental benefit of recycled content in SOPRA-XPS boards will only be realized when end-of-life recycling systems are more widely adopted. As for the XPS that was produced with HFCs? Lord help us it’s still leaching that stuff into the atmosphere.
This article was largely written by me, with the aid and input of summary material from an LLM.