Six months before its scheduled phase-out, a chemical used to manufacture extruded polystyrene (XPS) insulation is getting the green light for continued use from the U.S. Environmental Protection Agency (EPA).
The EPA has proposed a new rule that would allow the insulation industry to continue using a hydrofluorocarbon blowing agent called HFC-134a in combination with other compounds to make XPS. That practice was to have ended on January 1, 2021 under terms of an EPA rule dating to 2015 as the government looked for ways to reduce the global warming potental (GWP) of the insulation. HFC-134a has a GWP of 1,430 (compared to the GWP of carbon dioxide, which is 1).
In a proposed rule posted by the EPA on June 12, manufacturers would be allowed to continue using the chemical for making insulation, but only as part of specific blends with other compounds. The blends were suggested by DuPont, one of three U.S. manufacturers of XPS.
The proposed blends would cut the global warming potential substantially, but still leave it hundreds of times higher than a complete conversion to a hydrofluoroolefin (HFO) blowing agent or C02. Manufacturers say a total switch to an HFO, with GWPs in the 1-to-6 range, isn’t practical.
Some green builders avoid XPS because of the high GWP of the blowing agent, the compound that creates tiny air or gas bubbles that slow the transfer of heat through the foam. Instead, they prefer expanded polystyrene (EPS) because its blowing agent, pentane, has a GWP of 7. XPS, however, has a higher R-value than EPS, R-5 per inch vs. R-3.6 to R-4.2 per inch (depending on its density, with some graphite-infused versions going to 4.7).
DuPont markets XPS under the Styrofoam trade name. Other manufacturers include Kingspan, a multinational based in Ireland, and Owens-Corning.
The proposed rule (Proposed Rule 23) was made under a program called Significant New Alternatives Policy, or SNAP, part of the Clean Air Act that gives the EPA authority to review substitutes for existing products and compare their relative risks. HFC-134a and HFC blends became widely used in XPS after 2010, according to the EPA’s docket. But in 2015, the EPA changed the status of certain HFCs used in XPS, including HFC 134a, from “acceptable” to “unacceptable.” That change was scheduled to take effect on January 1, 2021.
Now, EPA plans to list as “acceptable” three blends that contain 134a, thereby accepting DuPont’s claim that over a period of five years and hundreds of trials it had not been able to hit R-value targets with alternatives that included HFO-1234ze, HFC-152a, and C02.”Further,” the EPA wrote, “the submitter indicated that if in some cases it could meet R-value requirements with those neat blowing agents, these alternatives were not able to meet other requirements such as compressive strength, density and thickness, or fire test results.”
The XPS blends, containing up to 52% of HFC-134a, would have GWPs of 580 to 750.
Comments on the new rule will be taken until July 27.
Technical hurdles remain
One industry insider complained privately that European producers of XPS have been able to switch from HFC-134a to something else while producers in the U.S. say it can’t be done. (European versions are blown with C02 but have an R-value of about 4 per inch). And even though the blends cut the global warming potential by as much as 59% when compared to 134a alone, the person said, new blends do not eliminate it.
“They’re watering the whisky down, but there’s still whisky in the water,” they said.
DuPont said through a spokeswoman that it has been unable to find a “technically viable, cost-effective alternative” despite seven years of R&D.
“The blend alternatives that we proposed, and that were ultimately published in the Proposed Rule 23, offer the whole XPS market the opportunity to continue our HFC Phase-Down program, which is more aggressive than the Kigali Amendment Schedule and supports DuPont’s commitment to the Paris Agreement,” the company’s statement reads.
DuPont says there is still no drop-in HFO replacement for 134a that would work for its entire product line. The company pointed to an EPA statement in which the agency said that only one of the substitutes it was counting on would in fact be available by 2021, and that it could be used for only part of the XPS foam market.
“As acknowledged by the EPA, it is not the intent of SNAP regulations to limit the market by picking winners and losers,” DuPont’s statement said. “DuPont has innovated and found success with a portion of the XPS category using a novel HFC-134a replacement and is working to implement those conversions as quickly as possible.”
The company said one technical issue was that HFO-1234ze, a possible replacement for 134a, can be flammable under conditions typical for extruding XPS, especially at higher humidity. In addition, the company had trouble meeting “density and physical property code requirements” for some end uses. “Additionally,” DuPont said, “under infrequent circumstances, there remains an increased risk of toxicity concerns with replacement technologies that must be addressed.”
Owens-Corning says it can meet deadline
While DuPont apparently couldn’t hit the January deadline to rid XPS of 134a, Owens-Corning says it could.
Frank O’Brien-Bernini, vice president and chief sustainability officer, said in a telephone call that Owens-Corning has been working on the problem on the assumption that the order would be imposed on its original timeline. “We are well prepared to respond,” he said.
Owens-Corning’s Foamular XPS has a GWP of roughly 750 now, but the company is prepared to get that number down to 150 or so, the practical effect of removing 134a from the mix and using another HFC blend.
O’Brien-Bernini said he was not prepared to discuss the specifics of any rollout schedule for new blowing agents. “We don’t disclose compositions and all that,” he said. “We do use HFCs. It’s well known in the industry that there is 134a, there is 152, there are different blends and everybody’s got their cocktails. We don’t specifically disclose what we use.”
However, he said, consumers can check the Environmental Product Declarations of a product to check the GWP of a product.
Although it’s possible to use C02 as a blowing agent, as is the case in Europe, it must be combined with another component—pentane or butane, for example—and that raises concerns over volatile organic compounds. But the lower R-value, which O’Brien-Bernini said is about 4.2 per inch in those forms of XPS, is a more critical factor, and Owens-Corning isn’t convinced that consumers would be willing to give up a higher R-value just to get the GWP down.
“We have not been interested, we do not believe the market is interested, in reducing the R-value of the product in order to use C02,” he said. “We have been working ever since the Montreal Protocol in 2010 but most especially the last five years or so to match the current performance expectations of XPS in the North American market while reducing the GWP, so doing both.”
He said the company didn’t object to the original SNAP rule and viewed the changes more in the context of its own sustainability goals than it did as an added regulatory burden. The company, he said, is committed to reducing greenhouse gases by 50% by 2030 from its 2018 baseline, and a “material part” of that strategy involves using foam blowing agents with a low GWP.
Kingspan had no immediate comments on the EPA rule.
Scott Gibson is a contributing writer at Green Building Advisor and Fine Homebuilding magazine.