Spray Foam and Global Warming Potential (GWP)
What “GWP-1” actually means, why closed-cell foam changed its blowing agent, and how to make sure the foam going into your house isn’t leftover old-formula stock.
The short answer
GWP-1 spray foam refers to closed-cell spray foam made with a next-generation HFO blowing agent that has a global warming potential of about 1 — roughly the same as water vapor. Older closed-cell foam used HFC blowing agents with a GWP of 700–1,400. A nationwide ban stopped US manufacturers from making new HFC closed-cell foam as of January 1, 2025, though foam made before that date could legally still be sold and sprayed through January 1, 2028. Open-cell foam is a different story: it’s water-blown and has always had a GWP near 1, so this whole issue is really a closed-cell question.
That’s the summary. Below is what GWP actually measures, why the industry switched, and the question to ask so you know which generation of foam is going into your walls.
GWP-1 Spray Foam: What GWP Actually Measures
Global warming potential is a scale that compares how much heat a gas traps in the atmosphere versus carbon dioxide over a set time period, usually 100 years. CO2 is the baseline, set at 1. A refrigerant-style gas with a GWP of 1,000 traps roughly a thousand times more heat, pound for pound, than the same amount of CO2 released into the air.
Spray foam is relevant here because of the blowing agent — the gas or liquid that expands during application to create the foam’s cellular structure. A small amount of that blowing agent stays trapped in the cells or off-gasses slowly over the life of the foam. If the blowing agent itself has a high GWP, that trapped gas is a small but real climate liability sitting inside the insulation. GWP-1 foam means that liability is effectively gone.
HFC vs. HFO: what actually changed
For years, closed-cell spray foam in the US was blown with HFC-245fa, a hydrofluorocarbon with a GWP in the 700–1,400 range depending on how it’s measured. Manufacturers spent the past decade reformulating around hydrofluoroolefin (HFO) blowing agents instead — chemically similar gases engineered to break down in the atmosphere much faster, landing around a GWP of 1.
| Blowing agent | Typical GWP | Status |
|---|---|---|
| HFC-245fa (older closed-cell) | 700–1,400 | Manufacture banned nationwide since Jan. 1, 2025 |
| HFO-based (Solstice, Zephyros, etc.) | ~1 | Current standard for new closed-cell foam |
| Water / CO2 (open-cell) | ~1 | Has always been the case for open-cell |
This wasn’t a marketing refresh — it was a regulatory phase-out under the federal AIM Act, following state-level bans that started rolling out several years earlier. Manufacturers can no longer produce new HFC-245fa closed-cell systems. Foam made before the cutoff could still legally be sold and sprayed through January 1, 2028, which is why some contractors may still be working through old inventory. Most reputable suppliers have already converted their product lines.
Open-cell vs. closed-cell: this is really a closed-cell issue
Open-cell foam has always been blown with water — the reaction with the isocyanate produces CO2 as the expansion gas, not a synthetic refrigerant. Its blowing-agent GWP has never been the high number closed-cell used to carry. If you’ve read a headline suggesting spray foam in general is a climate problem because of GWP, it’s almost always the closed-cell HFC story being told without that distinction.
Closed-cell still has real advantages worth choosing it for — higher R-value per inch, moisture resistance, structural rigidity. See our open-cell and closed-cell pages for the tradeoffs. The GWP conversation isn’t a reason to avoid closed-cell foam; it’s a reason to confirm which generation of it you’re getting.
Why the blowing agent matters beyond climate
Insulation performance
HFO-blown closed-cell foam isn’t a downgrade to hit a climate target — several manufacturers report R-values running higher than the older HFC formula at the same thickness, along with more consistent yield.
Regulatory compliance
Some states banned HFC-blown closed-cell foam outright before the federal deadline. New construction, commercial projects, and anything touching state green-building requirements may specifically require low-GWP foam on paper.
Resale and inventory age
A contractor still spraying pre-2025 HFC stock isn’t doing anything illegal through the 2028 sell-through window, but it does mean their material is old formula — worth knowing before you sign.
What to ask your contractor
One question settles it: “Is this a GWP-1 / HFO closed-cell system, or older HFC-245fa stock?” A straight answer with a product name is a good sign. A dodge isn’t.
Ask for the product name and manufacturer’s technical data sheet, not just a verbal “yes, it’s low-GWP.” Every current HFO-based closed-cell system has documentation listing the blowing agent and its GWP. If a contractor can’t produce it, that’s worth pausing on — same as any other spec you can’t verify.
Common GWP questions
Want to know exactly what’s going into your house? Ask us directly.
Ask us what’s in the tank
We spray current-generation GWP-1 closed-cell systems and can show you the technical data sheet before we start. Free on-site estimates across Arkansas.