More BS* + Beer
This episode of the BS* + Beer Show includes guest co-host Dan Kolbert and featured guest Henri Fennell talking broadly about “How to Get Spray Foam Right.” Henri has returned to answer audience questions generated during his last appearance on the show. He collected them from the chat box and created a presentation of responses—so the information is wide-ranging.
Henri talks about how often he sees spray foam failures and at what point they show up—he says all failures are due to improper installation, no matter when they manifest. He explains the causes and effects of “thermal shock,” describes taped seams between rigid foam boards as “temporary air-sealing,” and gives a brief history of spray foam blowing agents.
He also explains why open-cell spray foam is rarely a problem solver (hint: vapor retarder), and notes the one situation where it does make good sense. The hybrid roof method gets dissected, we hear of two techniques for insulating rafter cavities, and there are some tips for quick-and-dirty field testing of spray foam installations—plus much more. Enjoy the show…
Bio
Henri Fennell is a building enclosure specialist and architect with over 40 years of experience in energy conservation design, products, and services. His work with polyurethane foam materials began with energy-efficient demonstration projects during the energy crisis of the 1970s. His background includes positions as a practicing architect, a building enclosure contractor, and a building envelope remediation and commissioning consultant. Since the early 1980s he has been involved in the design and construction of what are now called micro-load buildings, including a net-zero energy research structure in Antarctica.
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Kiley Jacques is senior editor at Green Building Advisor.
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16 Comments
OK, all failures are due to installation mistakes. Will any installers provide a serious guarantee, backed by insurance, that will fix the problem if it occurs, up to and including a gut rehab if that's what's needed to get rid of the smell? While paying for another place for the residents to stay?
Charlie, your question is probably rhetorical, but not that I know of.
I found it interesting that although we decided to focus not on, "is spray foam good or bad," but "how to do spray foam right," many viewers came to the same conclusion--it's so difficult to install perfectly every time that it's not worth the risk except in cases where nothing else will reasonably work.
Spray foam problems in Britain: https://www.theguardian.com/money/article/2024/aug/12/they-encouraged-us-to-insulate-our-home-now-its-unmortgageable
Please stop with spray foam. No bueno.
I use as little of it as possible, but I design a lot of renovations and work on old homes where it can do things that other types of insulation can't. Our idea for this 2-show series was that if you have to do it, you might as well do it right.
It was interesting in the first episode, where Henri, who is pro-foam, was explaining the necessary steps to get it right and the potential downsides if not done right, many people in the chat box decided for themselves that it was too complicated to use.
It's an amazing material, AND we should use as little of it as possible.
I would advise everyone against it due to my nightmare with spray foam. It maybe a great product but the 1 to 5% failure rate is killing families like our mentally, spiritually and physically! Use something that's not as permanent so IF you need to remove it it does cost you 2x what it cost to install plus all the resulting damages of hundreds of thousands of dollars. This is just my experience
I'm sorry you experienced a nightmare with spray foam and I avoid specifying it as much as I can because of how bad a bad installation can go. But your 1-5% failure rate is not accurate. I had estimated that between 0.1 to 1% of spray foam installations go badly, but spray foam expert Henri Fennell--who was an early adopter of spray foam and often deals with failures as part of his consultancy--says it's more like 0.01%, or 1 in 10,000 installations that have significant problems, when he was our guest on the BS+Beer Show: https://www.greenbuildingadvisor.com/article/residential-spray-foam-applications. Nobody knows the exact percentage but 5% is 1:20 and there's just no way that number of installations is going wrong or its popularity would be waning, not growing. I'll still avoid it when possible, and counter pro-foam propaganda when I see it.
There are no published studies on failure rates. Residential spray foam insulation has an estimated failure rate of 5–10% for off-ratio mixing and 1–5% for thermal-related issues like overheating. These estimates come from industry experts, contractor reports, and building science sources such as the Spray Polyurethane Foam Alliance and Building Science Corporation, though no official national data is published. Most of the failures in residential settle and sign non disclosures so you will not see these in any published study on all if most failures. My failure rate is 100%. The foam installer covered my problem up with another layer of foam hoping that i would not find it. I am not saying spray foam is bad but bad spray foam is a pain in the ass to deal with.
I know there are not published studies, which is why I asked an industry expert who is well-known to be trustworthy. In the show we did with him, we decided to make it not, "why is spray foam terrible" but "how to do it right." In explaining what goes into getting it right, many of our viewers were convinced that it's not worth the risk. He is an expert witness for cases where spray foam goes badly so he is much closer to reasonably accurate data than almost anyone else.
I have corresponded with Rick Duncan, long-time executive director of the SPFA on several occasions. I have also found him to be trustworthy, acknowledging unflattering evidence to be correct in a couple of articles I've written about spray foam, when some of his colleagues were adamantly opposed to the facts I presented.
If you have research that backs up your opinion, I would be very interested in reviewing it--I am always looking for evidence that would reduce our use of spray foam. Unfortunately, your sample size of one is not representative, though it is extremely unfortunate. I coached a friend of mine through fully gutting and remediating their brand-new multi-million dollar home because of foam issues, and I have worked with chemically sensitive clients, so I know how bad it can be.
I saved for over 20 years to build my dream home a custom, multimillion-dollar build paid for mostly in cash. Today, that home is being torn apart.
Your friend isn’t alone. I’ve personally spoken with several homeowners facing similar foam insulation failures, and the company removing mine says they’ve remediated 13 homes in just the past two years. It took me months to even find someone willing to take on the job.
I’ve spoken with building scientists, foam experts, and contractors across the country. One Portland-based company that helped me early on has worked on both commercial and residential foam failures. Several installers admitted they experienced a spike in problems during COVID due to material shortages, supplier changes, and inconsistent batches.
My installer is a larger company out of South Carolina not a small outfit. They admitted in writing that my foam was “off-ratio,” with crunchy sections, oversized cells, poor adhesion, and thick, uneven passes. This wasn’t a mystery it was a bad job from the start.
I'd love to see a real study that proves that. No one has ever shown me credible, independent research supporting that number. What I have seen is dozens of homeowners, reputable remediation contractors, and expert reports documenting serious issues. Failures may be underreported, misdiagnosed, or blamed on ventilation instead of the spray job. Just because it isn’t published doesn’t mean it isn’t happening.
This isn’t just a construction defect it’s a failed chemical process happening inside your home. Temperature, humidity, pressure, mix ratios, pass thickness it all matters. And when it goes wrong, fixing it is life-altering. It has cost me my life savings, my dream house and my marriage of 22 years. But this is just my story, one story. Most homeowners don't have the money to fight back or cant even climb in in their attic to investigate. It has taken everything from me and I wouldn't never want it to happen to anyone else.
After a year of testing, documenting, and fighting, I’m now paying for the remediation myself. It’s cost me more than money. And yet, no one is taking responsibility.
BreathinginSmoke,
Whatever the percentage of failures, it’s clear bad installations occur often enough, and the effects are devastating enough that anyone contemplating using spray foam should be made aware that these failures do occur, and that the effects may be irremediable. Any spray foam contract should include clauses identifying the contractor as being responsible when things go bad, and identify an independent third party responsible to adjudicating any complaints.
The problem in life is no one really cares until it happens to them or someone they are close to. This was avoidable if I used any other type of insulation. My GC sold it to me in our first meeting. I knew nothing about spray foam and I didn't ask for it.
Thanks everyone for the useful information and discussion.
We had spray foam put in our attic about two years ago and there are faint smells still on hot days. I'd like to measure it to have something more quantitative to say about how much this is a problem. I know there are different kinds of VOCs and consumer-grade monitors might not always do a great job with them. Does anyone have any experience with measuring off-gassing beyond "how bad does it smell?"
Thanks in advance for any advice.
TO 15 and an outdoor control TO15, bulk sample of foam, isocyanates in foam and air just to get started. Find a vapor intrusion expert and environmentalist who has foam experience. The price to properly test can exceed remediation cost quickly. If it doesn't bother you then leave it alone and install more mechanical ventilation or ERV for the attic space.
Thanks for the advice. And I'm sorry to hear about your own experience.
For us, the smell is not too strong, and it occurs only on hot days. But I don't know if I should worry about health harms if the smell isn't too bad.
Persistent spray foam smell = not normal. If it didn’t go away after the first few weeks, and it gets worse with heat, it’s off-gassing. That’s a defect. And pretending it’s fine is how foam companies protect themselves, not you.
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