Low-GWP Spray Foam: HFO vs HFC Blowing Agents and the EPA Dates

Low GWP spray foam is foam made with a blowing agent whose global warming potential is far below the older HFC agents. HFO spray foam is the best-known kind: hydrofluoroolefin blowing agents with GWP figures in single digits, in place of HFCs with GWP figures in the thousands. The change came from EPA rules, not from a new insulation idea, and this page sets out what the rules say, what the published numbers are, and what we can and cannot claim about the foam we spray.

Low GWP spray foam: what a blowing agent does

Closed-cell foam is a mass of tiny sealed cells. A blowing agent is the ingredient that creates the gas in those cells while the foam rises, and some of it stays in the cells afterward. Water also acts as a blowing agent, which is why one maker's guide bars spraying over wet surfaces; that side is on spray foam and moisture. The agent matters for two reasons: its climate effect if it escapes, and its part in how the foam insulates, which the product page on our product's published properties shows through the data sheet.

The climate measure is global warming potential, GWP. EPA defines it as a measure of how much energy the emission of one ton of a gas will absorb over a given period, relative to one ton of carbon dioxide, with CO2 at 1 and the usual period 100 years (EPA, Understanding Global Warming Potentials, updated December 29, 2025). A GWP of 1,030 means a ton of that gas traps about as much heat as 1,030 tons of CO2 over that period.

The EPA dates

Two separate federal programs touched spray foam blowing agents. They are easy to confuse.

1. The Technology Transitions rule, 40 CFR 84.54. The text was read on the Cornell Legal Information Institute copy (section dated October 24, 2023, with amendments shown through May 26, 2026), retrieved October 25, 2026 (40 CFR 84.54, Cornell LII). As read:

• The foam category covers "Rigid polyurethane spray foam (i.e., high-pressure two-component, low-pressure two-component, and one-component foam sealants)."
• The restricted blowing agents are those with a global warming potential of 150 or greater.
• Effective January 1, 2025, foam products in the listed subsectors may not use such a substance. EPA's sector table, page updated August 28, 2026, gives that date as the manufacture and import compliance date for the polyurethane foam row, with a GWP limit of 150 (EPA, Technology Transitions HFC restrictions by sector).
• Sale, distribution and offering for sale of those products is prohibited three years after the date for each subsector, which for spray foam makes it January 1, 2028. EPA's table footnote says the same.

What neither page says, in the lines read for this draft, is whether a contractor may install foam that was made before the date and is still on the shelf. The rule text read restricts manufacture, import, sale and distribution; no sentence was found either allowing or banning installation of existing stock. Do not read this page as saying that HFC foam already in a building is illegal, or that foam already on a truck is illegal to spray. For any particular drum, the maker or EPA answers that.

2. The older SNAP listings. Under a different EPA program, the agency lists HFC-245fa and HFC-134a as "unacceptable" for high-pressure two-component spray foam as of January 1, 2020, and for low-pressure two-component spray foam as of January 1, 2021, except in military and space-related uses (EPA SNAP, Substitutes in Rigid Polyurethane: Spray Foam, updated March 19, 2026). The same page carries a note that closed-cell foam products manufactured on or before January 1, 2020 may be used after that date. So by the 2025 date, the two best-known HFC spray-foam agents had already been off the acceptable list for years.

Both pages are federal and apply in Kansas and Missouri alike.

HFO vs HFC

The numbers below are from EPA's SNAP page for rigid polyurethane spray foam (updated March 19, 2026). They are GWP values EPA lists; a maker's own sheet may quote a different one.

Does it insulate differently? A foam's R-value is a property of the whole product, not of its blowing agent label. Scott Gibson's 2015 Green Building Advisor article quoted a maker claiming an HFO closed-cell foam with an aged 6.8 per inch at 4 inches (GreenBuildingAdvisor, June 2, 2015); one maker's current sheet for an HFO product lists an aged 7.4 per inch depending on thickness, with a maximum 6.5 inch lift and a blowing-agent GWP of 1 (Huntsman Heatlok HFO High Lift, technical data sheet version 6, December 2024, product page: huntsmanbuildingsolutions.com). Those are two makers' claims, one old, and they do not make a rule. Per-inch values, and how aged values are tested, are on closed-cell R-value per inch.

Two cautions on handling and footprint:

• Shelf life was a worry. The same 2015 article reported makers' unresolved stability problems with HFO agents in the polyol blend, cutting shelf life to two to eight weeks against the year or more that is needed. That was a decade ago and says nothing about products sold now; it is why we ask each maker for its current storage limit.
• The agent is not the whole footprint. In a Green Building Advisor thread on low-GWP foam kits, an expert noted that a denser HFO foam with GWP 6 uses roughly half again as much polymer as a 2 pound foam, leaving a total CO2-equivalent comparable to the HFC alternative (GreenBuildingAdvisor Q&A, 2020 to 2021). That is one expert's view of one product, not a finding.

The blowing agent on our product's data sheet

The line to look for on any technical data sheet or safety data sheet is the one naming the blowing agent, with its GWP and the date of the sheet. Hold the sheet against the table above: an agent that is not on EPA's acceptable list for two-component spray foam is a reason to stop and ask.

Green claims: what we say and don't

The Federal Trade Commission's Green Guides warn that an unqualified claim such as "eco-friendly" is likely to convey specific, far-reaching environmental benefits and is hard to substantiate (16 CFR 260.4, Cornell LII). So this page claims one fact only, once the product is named: the blowing agent on its data sheet and the GWP that sheet prints. We make no claim that foam is green, sustainable or "non-toxic". Safety and re-entry are separate questions with their own page: cured foam and health questions.

FAQ

What is low GWP spray foam?

It is spray foam made with a blowing agent whose global warming potential is below the EPA's 150 threshold in 40 CFR 84.54. Under that rule, manufacture and import of covered spray foam using a higher-GWP agent stopped on January 1, 2025, and sale and distribution follows on January 1, 2028 (text read on Cornell LII on October 25, 2026). The rule text read does not address installing existing stock, so this page does not say that already-made HFC foam is illegal to install. The blowing agent of the foam we spray comes from its data sheet.

Is HFO spray foam better for the environment?

HFO blowing agents have a much lower global warming potential than the HFCs they replaced: single digits against four-figure values in EPA's SNAP table above. That is a comparison of the blowing agents, not of whole products. A denser foam can use more polymer, as the Green Building Advisor thread points out, so use the data sheet and not the label.

Is there eco friendly spray foam insulation?

Some foams use lower-GWP blowing agents, and we name ours from its data sheet. We make no broader green claim, for the reason in the Green Guides section above.

Does low GWP foam work as well in a metal building?

The foam's job on steel does not depend on the blowing agent's name: it has to bond, be continuous and be thick enough. Those checks are on foam on the underside of a metal roof and on the product's own data sheet.

Book a free on-site measurement

At the visit we measure the building and look at the surfaces to be sprayed. If you want the data sheet for the product, ask for it by name and date. You get a written estimate after the visit. The visit is free. More on how it works: book a free on-site measurement.

Book a free on-site measurement

Pick "Spray foam insulation" on the booking form. We work within about 35 miles of Spring Hill, KS.

Spray foam insulation is a new PolyJacks service line run by its own crew and rig.

Who wrote this: PolyJacks spray foam team. How it was made: drafted with AI assistance from the sources below, then checked against each source.

Sources

• U.S. EPA, "Understanding Global Warming Potentials," updated December 29, 2025: epa.gov
• 40 CFR 84.54, Cornell Legal Information Institute copy (section dated October 24, 2023; amendments through May 26, 2026), retrieved October 25, 2026: law.cornell.edu
• U.S. EPA, Technology Transitions HFC restrictions by sector, updated August 28, 2026: epa.gov
• U.S. EPA SNAP, Substitutes in Rigid Polyurethane: Spray Foam, updated March 19, 2026: epa.gov
• Scott Gibson, "Friendlier Foam Insulation on the Way, Eventually," GreenBuildingAdvisor, June 2, 2015: greenbuildingadvisor.com
• GreenBuildingAdvisor, "Low-GWP spray foam kits" (Q&A, January 2020 to January 2021): greenbuildingadvisor.com
• Huntsman Building Solutions, Heatlok HFO High Lift product page (technical data sheet v6, December 2024): huntsmanbuildingsolutions.com
• Federal Trade Commission Green Guides, 16 CFR 260.4, Cornell LII: law.cornell.edu