February 12, 2017

Foam Fails Reason #6: Inflexible and Prone to Cracking


Poor installation quality control results in cracked, crumbling foam that has little insulation value. This foam was estimated to be less than 10 years-old at the time of retrofit.

It’s important that a building’s air barrier and insulation be dimensionally stable – or resilient to movement. Foam is neither.

The curing process after spray foam is applied inherently entails shrinkage and hardening.  Not only can such shrinkage result in pulling back from stud bays and other connections – which often leads to gaps in the insulation layer – it can lead to cracking within the foam structure itself. Because foam’s performance is hypersensitive to slight manufacturing variations, it is best controlled by factory application. But too often spray foam is applied on the job site under poorly controlled conditions – something we’ll talk more about in a later post.

Gregg Labbe, of BlueGreen Consulting Group, writing in GreenBuildingAdvisor says,

“The first rule with spray foam is ‘hire the installer spraying the foam, not the foam manufacturer or the foam brand.’ By this I mean, the installer’s brain is the most valuable asset in selecting who will do the job. All else is secondary.”

Spray foam lifts shouldn’t be thicker than 2” each time and should be allowed to cool before another lift is applied – but sometimes, to achieve 6” thickness, operators apply two 3” lifts and in quick succession. This generates massive amounts of heat and increases the likelihood of cracks.  Gregg has a great video investigating such a problem here:

Spray foam is rigid and inflexible once it cures, and foam boards are rigid from the outset. So when these materials expand and contract because of temperature changes – and that’s when, not if  – they can crack. In the case of boards, we’ve heard of those who have peeled back the exterior sheathing of their building to reveal that the tongue has completely separated from the groove in a foam board system, making the fiberglass insulation below visible.

These cracks are incredibly hard to repair. Interior walls must be entirely deconstructed to fill them in – probably with more foam, which is likely to crack yet again before long. It is nearly impossible to repair cracked, compromised foam insulation. Once it’s cracked or pulled away, its effectiveness as an insulation layer isn’t just diminished – it’s devastated. It ends up a long-term, toxic, wall-filler without insulative value, which is super difficult to remove.


Spray foam in the ceiling of a new construction project in Connecticut.

Even when foam is applied perfectly, it’s better to choose insulating materials that are resilient to these shifts in temperature and humidity, and which are capable of stretching without compromising the integrity of the insulation layer and air barrier. Dense-packed cellulose, wood fiber, or fiberglass insulations don’t entail the negative environmental and health impacts of foam – each are great alternatives. These insulations can be blown in behind a vapor-intelligent interior air barrier like the INTELLO Plus membrane which can be sealed with flexible tapes, ensuring an assembly that is resilient to movement, and capable of withstanding environmental fluctuations without the risk of compromised building performance.

Foam cracks. Continuous insulation is important to a high-performing building – so why take the risk of having a crack-laden insulation layer whose performance degrades over time? For being brittle, rigid, and crumbling, we see yet again that foam fails.

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11 Responses to Foam Fails Reason #6: Inflexible and Prone to Cracking

  1. Edward 'Ed' Latson February 15, 2017 at 3:28 pm #

    “Urea-Formaldehyde foam was used in homes during the 1970’s and early 1980’s. However, after many health-related court cases due to improper installations, UF foam is no longer available for residential use and has been discredited for its formaldehyde emissions and shrinkage.”
    https://energy.gov/energysaver/insulation-materials 2017

    We all hated working with, around or near that crap [UF Foam] back in the 70’s. While cutting into it you found difficulty breathing, your throat would quickly become irritated, it burned your eyes and skin and it smelled absolutely rotten.

    During the last decade of the 1800’s there were, by several accounts, around 100 toxic building ‘materials’ (lead, arsenic, etc, etc) that could be found in an average new home—just 100+/-. Enter the WW II era and man made chemicals began skyrocketing in numbers. Depending on which source you use, there are an estimated 60,000 new chemicals just since WW II. And of this ever expanding number of new ones, just maybe, yes-maybe, our EPA has a ‘sort of’ handle on ‘around’ 10% of the total.

    So, why mess around with foam to begin with?! I fail to comprehend our amnesia surrounding failures and failed/hazardous building products from our past, and this renewed Big Corporate zeal propagated to incorporate similar failed/failing/hazardous materials in our lives today. I guess it takes a perspective from being 65 and looking back over my shoulder…but, I don’t know the answer.

    Still not convinced? Read any of Alison Johnson’s books on chemical sensitivity, such as-” Amputated Lives: Coping with Chemical Sensitivity.” 2008 Cumberland Press

    • John February 15, 2017 at 3:52 pm #

      Thank you for the comment and the references, Ed. Powerful statement.

  2. Dave February 16, 2017 at 9:46 am #

    I very much like your products and general approach. But your foam fails series seriously damages your credibility. You can find case studies of failures with ALL insulation materials – including your beloved mineral wool when installed incorrectly. The question isn’t whether a material fails but how frequently it fails. None of your articles address failure frequency.

    • John February 16, 2017 at 11:53 am #

      Hi Dave,

      Thank you for the feedback – we’re always happy to dialogue. I think it would be absolutely be valuable information to gather failure rates – that sort of information would be difficult for us to gather reliably, but is certainly worth looking for reliable sources that have done that work.
      That said, our ultimate argument goes beyond rates of failure, and looks more critically at the risks associated with those failures. The worst risks associated with improper installation of fiberglass are discomfort and perhaps in extreme cases, uneven temperatures that lead to condensation – something that can lead to mold and rot if a measures are not taken allow drying of the assembly. The worst risks associated with foam failures are complete degradation of insulation value, exposure to unhealthy levels of toxicity, and potentially even fire and loss of life. When it comes down to it, mineral wool will never cause an explosion – it’s not even in the realm of possibility. Collectively throughout the Foam Fails series, we reason that the risks are greater than we should be willing to accept for the potential benefits of a job done correctly and properly.
      We all have personal experience with projects that use foam insulation, we have just come to believe that when you weigh the potential risks and benefits of foam – less is always best. Keeping foam use to a minimum mitigates risk. And we ultimately will do best to wean high performance building off its dangerous reliance.

  3. Edward 'Ed' Latson February 16, 2017 at 1:35 pm #

    OK…I’m an old fart in this realm. I’ve made more mistakes than probably half of your younger subscribers/clients combined. So what? OK again–the one constant I’ve come to learn, is about building-in the need for durability, the resiliency and the longer term success of a building’s performance. And performance how? Health of the occupants; does the building actually deliver a consistent level of performance via bills, like heating and cooling costs; is the building living up to its promises of: overall health, safety, durability, and even curb appeal? Will that fabulous blower door test upon completion still give you your 0.006 ACH (or whatever magic number you’re shooting for) that you initially nailed with high fives all around?? I had my BPI Building Analyst cert for its first 3 year term–I chose to not renew it.I was finding this consummate glee in nailing those lower and lower scores….without concern for long term durability, health and performance. It’s simply been my experience (since 1973) that foam is NOT that long term component required for a durable and consistently successful building product.

    And if it was…… we would not be having this conversation, or the ones explored by 475 over the past several years or the horror stories from the 70’s and 80’s that continue to resonate in current statistics on performance.

    I mean, hey! I got shocked when I accidentally grabbed the hot side of an electrical box the first time. Have I done it again and again? Of course not. Foam is the same animal but wearing different clothes. If foam was able to do what it promised—-sign me up. It fails…again….and again…and again. Ask those homeowners and contractors who’ve suffered irreparably from health problems and financial problems. If your foam contractor will stand behind and remediate a problem…more power to them! Ours can be a difficult and often very trying profession. What’s one secret? Stick with what works, and what is healthier and and safer for all–us builders, our clients and the creators and suppliers of our building products. And don’t complicate the common sense approaches.

  4. Daniel Karpen February 18, 2017 at 4:17 pm #

    Depends on the type of foam.
    I have seen failure in old foam installed in the early l980’s, believe it was Urea Formaldehyde.
    I have never seen a failure with closed cell polyurethane foam yet.
    Daniel Karpen, Professional Engineer

  5. WIlliam Calfee February 21, 2017 at 10:06 pm #

    I was an Energy Auditor for 5 years in Southern VT and NY. I was called to be an expert witness several times and to diagnose problems after foam jobs. I agree with your assesment of foam. I have seen even the best foam aplicators in the area have major failures. These were almost impossible to resolve without completely removing the interior walls or the exterior…

    I think the only possible application would be to use a couple inches of foam in conjuntion with Celulose or other flexible insulations when the cavity is especially thin.

    Thanks for the good article

  6. Henry Finch March 12, 2017 at 7:40 pm #

    This article never mentions open cell foam nor closed cell foam. I am not a big fan of either but this article appears to be written with an agenda to discredit by any means possible.

    • Ken March 13, 2017 at 10:14 am #

      Thank you for your comment, Henry. Our observations in the post apply to both open and closed cell spray foams – so we didn’t see a basis or need for the distinction. Of course we do have strong opinions on the subject, which we don’t hide. Our motto regarding spray foam is that Less is Best: https://foursevenfive.com/is-foam-evil-a-new-paradigm-of-foam-less-is-more/
      Hope this helps.
      All Best,

  7. Tim March 24, 2017 at 2:22 am #

    It would be fair to state at the beginning of your articles that y’all are not qualified in fire science, not professional firefighters, and that y’all are extremely biased against closed cell and open cell (polyurethane) spray foams.
    Following up with a statement that y’all trying to sell your own products would be beneficial. One of the articles that was written in the “Foam Fails” series ended talking about the products that475 sells and was very clear about proper installation. I am quite sure it would be very easy to find improper installation of pro clima products or similar. The results would be the same. A failure of the system.
    Please stop cherry picking firefighting stores and foam. I was a professional firefighter for over 15 years. Maybe y’all should look up what the number one cause of structure fires is. How about the top ten? The example of the reckless workers on a roof cutting metal and the sparks ignited foam on the roof is ridiculous. I would not blame the fire on the foam. It was the workers being careless. When you are cutting metal, sparks fly. Anything that might be flammable should be protected. Anybody working around those tools should have proper protection. When firefighters are cutting vehicles while performing extrication of a patient, usually the patient is covered to protect them from hot sparks, metal, glass and plastic. So again, those workers were probably at fault. Not the foam.
    If you want to discuss causes of fires, why not bring up smoking cigarettes. How about space heaters, Christmas trees, candles, curtains? There is also the rest of the synthetic products in a house and lots of nasty chemicals. I am sure that when working around wood, it is a good idea not to breathe in wood dust. Fiberglass insulation is nasty stuff. It is way worse than y’all described. I would not want that in my lungs. Any fiber in your lungs is bad.
    I am going by the stories written on this website. Right now I am just going by memory, but like your other articles on foam and fires is plain stupid. Playing on people’s ignorance and fears while making a buck off of it is pathetic. The other examples that were lame had to do with the workers in China. I am sure the Chinese government really cares about having laws to protect it’s workers. I think another example was a skyscraper being built in Dubai I believe. I may be wrong on the exact location, but I am curious if this building had a sprinkler system. Have you any of y’all been to the Middle East? Have y’all seen the work conditions of the average worker? It is very typical in the richer Middle Eastern countries that the workers are not from that country. They live in horrible conditions. They are treated horribly. Basically slave labor. You will lose this argument if you even try to argue what I am saying. I am not surprised at the outcome of the building catching on fire.
    If you want to make the world less toxic, please stop spewing what would be basically called lies by some people and or propaganda by others.
    If y’all have great products, than please just focus on those great products and how to properly use them. The more y’all try to bash other products to the point of being dishonest is pathetic. It is very simple to do research on the internet and also there are a lot of professionals in this industry that can provide useful information.
    To end this long rant of mine, please keep the articles to good building practices and ideas with the products that 475 carries. Most importantly, I would personally appreciate it y’all just cease the type of examples that y’all are using as far as fires and/or anything related to firefighting since it is way outside of 475’s expertise.
    Hope y’all have a great day and an awesome weekend.

    Please ignore the types and/or grammar mistakes if any. It is after 2 AM and I am a little tired.

    • John March 24, 2017 at 9:49 am #

      Hi Tim,
      Thanks for sharing your thoughts, we encourage debate on the matter. We’re going to continue focusing on articles about good building practices, and speaking our minds on what we consider to be risky building practices goes hand in hand with that. Given that, hope you keep reading – and hope you can get some sleep! Be well.

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