Is Using Closed-Cell Foam Worth the Trade-Offs?
This insulation material is popular for its high R-value and good air-sealing and vapor-blocking properties, but cost, health, and environmental concerns cause some builders to have second thoughts.
Synopsis: Contributing editor Michael Maines takes a detailed look at closed-cell spray foam, which is growing in popularity as an insulation material. Maines identifies its advantages—a high R-value per inch, a capacity for air-sealing and for blocking water-vapor movement, and its enhancement of the framing-to-sheathing connection. He then discusses its disadvantages—including high cost, messiness and potential health risks, and the fact that it can’t be used in many transitional areas where air leakage is high. But Maines focuses primarily on closed-cell foam as a contributor to global warming because of the blowing agent that is used in most closed-cell foams, which is over a thousand times worse than carbon dioxide.
Closed-cell polyurethane spray foam is amazing stuff. It’s a great insulator, with a higher R-value per inch than almost any other commonly available material. (Polyisocyanurate foam can be equivalent, but it varies with product and temperature.) When installed at least an inch or two thick, it essentially blocks water vapor and air movement. It even has some structural benefits: It’s good at adhering sheathing to framing, and it also enhances racking resistance. Thanks to these qualities and more, including strong marketing from the industry, foam is only getting more popular. Unfortunately, it also has some serious issues that aren’t typically discussed outside of greenbuilding circles. Understanding these drawbacks may convince you to limit its use to those special situations in which it makes the most sense, or even to avoid it entirely.
Polyurethane foam starts as two containers of liquid chemicals, referred to as the “A” side (isocyanates, the primary component of the solid foam) and the “B” side (a blend of resins, catalysts, a blowing agent, a flame retardant, and other compounds). When combined at installation, the chemicals react to create a polymer filled with tiny bubbles. The bubbles, or cells, are filled with a blowing agent and provide the insulating value, while the polymer forms the cell walls.
The ingredient that makes closed-cell foam special is the blowing agent—typically HFC245fa—but that’s also its biggest drawback.
HFC245fa is a hydrofluorocarbon refrigerant and a persistent greenhouse gas; it goes up into the atmosphere and stays there, preventing heat from escaping the earth. Carbon dioxide is commonly used as a measure of the damage a greenhouse gas can do, and HFC245fa is considered 1030 times worse than CO2. The only common building product more potent is the blowing agent in conventional XPS rigid foam. According to the Environmental Protection Agency, “Although [HFCs] represent a small fraction of the current total volume of [greenhouse gas] emissions, their warming impact is very strong. HFC emissions are projected to increase substantially over the next several decades if left unregulated” (from EPA Rule 21 Fact Sheet).
Insulating valuePro
Con
Air-sealingPro
Con
Environmental impactPro
Con
Vapor blockingPro
Con
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SafetyPro
Con
Sticky and structuralPro
Con
ExpensePro
Con
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Update from the author:
A couple of representatives from the spray-foam industry offered two corrections to my article.
- Honeywell has been making its Solstice low-GWP (global-warming potential) blowing agent for about four years, but another company, Chemours, has a similar blowing agent, called Opteon, which some foam manufacturers are using instead of Solstice. Opteon has been available since late 2017.
- I noted that the federal government had mandated a move away from HFC blowing agents by January 2020. It’s true that they had, but Brett Kavanaugh struck the rule down when he was a judge for the U.S. Court of Appeals. My research had indicated that he had only ruled against the portion of the regulation regarding refrigerants, but it was actually the entire thing. The day after the UN released its devastating report, the U.S. Supreme Court decided not to hear an appeal to the rule being rescinded, as the EPA no longer supports that type of regulation.
Also, my wording for the section about the quantity of foam in an average house wasn’t clear. An average-size house of about 2400 sq. ft.—either a single-story home on a slab with an insulated cathedral ceiling, or a two-story home with an insulated attic and a spray-foamed full basement insulated to meet code in one of the colder climate zones—requires between 4000 and 5000 lb. of foam. That’s using the LTTR (aged R-value) for foam.
To view the entire article, please click the View PDF button below.
More about spray-foam insulation:
- Spray-Foam Problems
- Spray Foam for the Rest of Us
- What’s the Difference: Open-cell vs. closed-cell polyurethane-foam insulation
View Comments
Closed cell has been my only choice since using on a mid 90's project. I'm a serial remodeler -- often very old (1810/ 1870) or unusual buildings (fire house/church). Foam allows a coating in very tight or thin areas when space does not allow 6" of another material -- or even 4". Even 1" of close cell is amazing stuff for both insulation and air sealing. Foam transformed my drafty, inefficient and more importantly uncomfortable cape at the beach a few years ago. A few inches on my 1810 federal in the city 20+ years ago ... a full 4+ inches on my new project expanding a Pa stone building. Also, lived though a fire w/ foam -- the fire cut through the wood rafters and broke through the windows before burning through any foam. The foam eliminated any passage for the fire (and smoke) to find it's way through the structure. I can't comment on the environmental aspect -- except to say structures use smaller HVAC equipment and are energy efficient.
I am frustrated that the article doesn't address the foams that are out there that use a different blowing agent. I don't have any experience with them but I have heard about them (probably from FHB and the podcast) multiple times. Is nobody using them? Are they not really available?
... (pause, use Google)
After some quick research, including a story from Green Building Adviser almost 2 years old, there are closed cell foams with other blowing agents out there including a generally available product from honeywell with a Ozone score of 1, same as CO2. After 5 minutes of web research this posting sounds more like a ill informed opinion than the type of information FHB usually publishes.
There's this guy at the University of Alabama, Huntsville, who runs NASA's satellite remote temperature sensing program. I know he's not a contractor, but he swears there has been no increase in atmospheric temperatures. Another guy--not a contractor--was professor emeritus in atmospheric sciences at M.I.T. for 40 years. He says that we really shouldn't panic over a 2 degree projected temperature change in 100 years. Take that with a grain of salt, because, like I said, he's not a contractor.
I'm eagerly awaiting a paper written by Princeton physicist whatshisname on the proper way to flash chimneys when using metal tiles.
Albany_Chris, if you read my entire article, you'll see that I discuss low-GWP blowing agents.
Justacabinetguy, climate scientists aren't concerned with atmospheric temperatures; they measure an average of surface and ocean temperatures. It's true that there is not 100% agreement among the scientific community that we have a problem. Merely 97 out of 100 scientists worldwide are concerned.
Unfortunately you're quoting a bogus "fact" that a thoughtful person ought to question. It's a shame that the truth about atmospheric gases isn't better known, but I hope you'll avoid giving so much attention to alarmist concerns in future articles. Let's focus on known homebuilding challenges, not alarmist worries about the possibility of some slight warming (which would be a blessing for those of us up north).
ddwieland, which fact are you claiming as bogus? We are already seeing the early results of climate change, and if the current predictions are accurate (2° to 7° rise this century) the results will be significant, to say the least.
The predictions are never right but get ever more extreme, but the climates (yes, climate is regional) stubbornly refuse to play along. Slight warming is followed by slight cooling is followed by more warming then cooling and so on. Trends in the past were much steeper than in our remarkably stable times. Please don't confuse occasional extreme weather events with signs of climate change. Even NOAA and the (rarely read) science sections of IPCC reports don't make that claim, just Al Gore, enviro-radicals and headline hunting media. But we should try to build for extreme weather and avoid building in predictable trouble zones. That's where we can actually do some good. What we know is that there will be storms and floods. Let's build with that in mind.
I also didnt see any real discussion of low GWP products and I searched the article several times. The only thing I can find in the article is the statement that : "HFC emissions are projected to increase substantially over the next several decades if left unregulated". In fact, closed cell spray foam insulations (high pressure type) will have to use the new HFO blowing agents by Jan 2020, and that these new blowing agents are already available in products used today and have a GWP of just 1. This would completely eliminate this concern in the article. This information was not mentioned yet is readily available, and useful to readings looking into this discussing this topic.
This article states that "high embodied carbon, the measure of everything it took to make the product". Checking other sources, “embodied carbon” refers to carbon dioxide emitted during the manufacture, transport and construction of building materials, together with end of life emissions. Maybe” embodied energy” was the better metric to bring up here.
Sure its probably one of the single best uses of petroleum, but first of all, polyethylene bags and water bottles are mostly a byproduct of natural gas production and do not really effect the resource. A good next step in this conversation would be to talk about a life cycle analysis when mentioning resources and embodied energy (see the LCA completed on spray foam insulation which was also done to full ISO standards). Its interesting to look at the OTHER uses of petroleum other that what is combusted or used as lubrication. These other products end up using up a very small fraction of a barrel of oil. When you then look at the fraction used in a product like spray foam insulation it gets silly small. I have also been told that approximately 40% of spray foam insulation comes from other than petroleum sources.
The article states "whatever it touches is essentially ruined"? This is bit of an over exaggeration, and might indicate an unfounded bias. Sure its harder to remove than batts, but do you want to cripple your envelope for 50 to 100 years so its easier to remodel?
SDI1, did you click on "view PDF," as noted at the bottom of the preview? Almost the entire last page was omitted from the preview, including the discussion of HFO blowing agents. The quote about HFC emissions was pulled directly from the EPA fact sheet.
The EPA rule 21 that had been accepted by the Federal government, to require low-GWP blowing agents by 1/1/2020 was struck down by Brett Kavenaugh. My research had shown that he had just blocked the portion of the law that affected refrigerants, but this week I confirmed with Rick Duncan, technical director of the spray foam alliance, that the entire law was nullified. So the discussion is still valid, as it's now going to have to be a market-driven change, as apparently protecting our environment is the last thing the current administration wants to do.
Neither "embodied carbon" or "embodied energy" have universal, specific definitions. For the purposes of my article, they are equivalent. Bruce King and his contributors write more about this topic in his book, The New Carbon Architecture.
When you provide a market for a byproduct of resource extraction, as with polyethylene and gas production, you are still supporting the resource extraction. We could go deep into a discussion about various plastics and their production methods; I find chemistry and plastics to be an interesting topic. As it is we had to cut about half of what I had wanted to include, and I think most people would understand that my point was rhetorical. Of course there are other areas where a lot more petroleum is used, but this is an article about spray foam. I've tried to read the LCA but it's not easy to understand. With global warming a priority, lifecycle costs are much less important--what matters is the carbon (or, more properly, carbon dioxide equivalent) we emit over the next few years, so any insulation that is not plant-based is a poor choice except when nothing else will work. 40% of spray foam insulation comes from sources other than petroleum? I'm dubious without a reference.
Yes, whatever spray foam touches is essentially ruined. Starting with a lot of my own clothes... Have you ever tried to renovate a home with spray foam insulation? Have you ever advised homeowners on how to remove foam that did not cure properly? How about cleaning up foam sprayed during retrofits that either splattered over existing finishes, or that melted due to the temperatures being too cold for the mix? Have you tried to pull wires through foam? One foamed, they are in there permanently. I have done all of the above, and stand by my statement. Perhaps you have not done a lot of renovating, or live in an area of new homes. Most homes will eventually be renovated, and although not critical, it's a whole lot easier when the assemblies are made to be repaired, something that used to be common in every field but that in our throwaway society is under-appreciated.
Your claim that a home without spray foam will "cripple the envelope" is a serious exaggeration. My personal experience is that homes with spray foam have a much higher chance of problems developing than homes without foam. I don't have data on that and doubt any exists, but it would be interesting to study.
Why do you have to bring your political prejudices into an article about insulation? Brett Kavanaugh did not strike down Rule 21, the court did, BK simply wrote the decision. I'd also note the EPA agreed with the decision and changed the Rule and that the Supreme Court basically upheld the decision when they refused to hear the case.
I see no reason to have a house be 100% closed cell foam or 100% conventional insulation. For a bathroom where there is blocking to support grab bars or plumbing in an exterior wall then the closed cell foam is far more effective and far easier to apply than glass or other insulation material.
The attic is a different situation from the walls of a house with different constraints and concerns. Big variation in mitigation costs with a bad closed cell foam installation depending upon where it is applied.
No need to post ignorant comments about global warming which is agreed upon by 100% of those scientists not on the pay of the Koch brothers and the energy industry. One can always pay people to lie and all that is surprising is how so many people place so little value on their personal integrity.