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Getting Spray Foam Right

Spray polyurethane foam is an incredible material when applied correctly — but in the wrong hands it can be finicky

Horror stories about spray foam abound on the internet, but the truth is that spray foam failures are incredibly rare.
Image Credit: Dunktanktechnician / Creative Commons license / Flickr

Spray foam insulation scares homeowners more than it should — although this is hardly surprising given the horror stories that abound on the Internet. While some of these stories are legitimate, more are based on skewed perceptions or flawed science. The truth is that spray foam is an incredibly effective insulation material and that failures are incredibly rare.

Spray foam also scares contractors less than it should. When we first started using spray foam in 1995 we were captivated by its ability to stop convective as well as conductive heat loss, its versatility, and its ease of installation (among other things). It almost seemed magical, certainly compared to alternatives like fiberglass and cellulose.

While some of the magic has worn off over the past twenty years, many in our industry continue to take quality installation for granted. The truth is that spray foam is a highly sophisticated, occasionally finicky material that’s manufactured from the back of a truck on a construction site in conditions that are hard to control by people who are probably not paid nearly what they deserve. If you get it all right, you have a great insulation system in place. If you get something wrong, you can find yourself with a real mess on your hands. We’ve learned that the hard way, which is why we no longer take safe and effective installations for granted.

To maximize the chances of getting things right, we’ve started working with spray foam expert Henri Fennell. Over the course of a 40-year career, Henri has installed spray foam in projects as wide-ranging as the recent Guggenheim Museum renovation in New York City, the ARRO Research Station in McMurdo, Antarctica, and Boston’s own Big Dig. Recently Henri hung up his installer’s hat and started consulting with installers, contractors, architects, and building owners to ensure that their spray foam installations are safe and effective.

Twenty years of experience coupled with Henri’s expert guidance has taught us that there are six steps to getting spray foam right:

1. Select the right installer. We work with installers whose client service ethic, concern for safety, and commitment to quality match ours. This makes all the other steps much easier.

2. Select the right product(s). “Spray foam” is a single term used to describe a broad range of materials that vary in cost, insulating value, and moisture management ability, among other things. Manufacturers also continue to develop new formulations and product characteristics every year. We tend to shy away from new products (we’ll let others be the guinea pigs when we can), and, working with Henri, we base our product choices on the optimum balance of cost, effectiveness, and environmental impact.

3. Prepare the job site. This is our responsibility. We need to make it as easy as possible for the foam crew to access the work area and install the foam correctly and effectively. Often this requires us to remove some existing insulation. We also need to make sure that the site is safe for everyone, during installation as well as during the curing period (which typically lasts 24 hours). We set up ventilation for the duration of installation and curing; we require workers to wear personal protective equipment while in the spray zone; and we ask our clients to vacate their house until curing is complete.

4. Spray the foam on-ratio. Pretty much all spray foams are manufactured on site by mixing together and heating two liquid components (part A and part B) to cause a chemical reaction of which spray foam is the result. Most air quality problems homeowners have with spray foam installations are a result of an imbalanced mixture that impedes the chemical reaction. Training and field experience go a long way towards helping ensure that the mixture is on ratio.

But Henri has taken it a step further by developing a way to test the ratio. The first time we hired Henri to commission a job, he found that the mixture was off-ratio and spent several hours troubleshooting with the installer to correct the problem. While the installer knew the mixture was off, the ratio test proved invaluable in helping correct the problem in the mixing tank, before any foam had been applied. As a result the job was delayed by about half a day — a mild nuisance compared to tearing out uncured foam.

5. Spray the foam at the proper temperature. Each manufacturer specifies a temperature range for installation, both for the materials and for the surfaces they are applied to. When components or surfaces are too cold, serious performance degradation can result. As a commissioning agent, Henri makes sure the installer relies on the manufacturer’s instructions and uses measurement equipment — not instinct — to evaluate whether the conditions are right for the work.

6. Perform quality control testing on all installations. The best foam crew in the world will only get us 90% to 95% of the coverage that we’re looking for from a foam insulation job. This isn’t because spray foam crews are sloppy but because foam is hard to install evenly. Once the foam crew is done and the 24-hour waiting period is over, our own crew comes in with a blower door and infrared camera to test whether the installed product meets our expectations. More often than not, there are voids or gaps that we need to fill. We find them and fix them.

By following these six steps, we believe we can and do deliver safe and effective spray foam applications. Some of our clients nonetheless want to avoid spray foam at all costs. More often than not, we can find alternatives for these homeowners; these alternatives are usually more labor-intensive and expensive than spray foam (otherwise we would have suggested them to begin with), but we find ways to make them work.

Manufacturers and installers tend to view spray foam primarily as a product to be sold — and it certainly is that. But for it to be safe and effective, it also needs to be viewed holistically, as one integral part of a system that’s designed to provide efficiency, comfort, and safety for our clients. With Henri Fennell’s expert help, that’s the key value we try to add to our spray foam projects.

Paul Eldrenkamp is the owner of Byggmeister Design Build. Rachel White is the company’s performance manager. This post originally appeared at the Byggmeister website.


  1. AlanB4 | | #1

    You go above and beyond, no
    You go above and beyond, no spray foam installer i have ever met does the blower door and IR camera, so while your process is amazing the rest of us have average installers available to choose from.
    Also choosing from those installers how do we know which are better and which are not, even with your detailed process you still find voids or gaps you need to fill, suggesting its even more prevalent with average installers and is never found and remedied.

  2. Paul Eldrenkamp | | #2

    who does the blower door & IR

    Just to be clear, we do the blower door and IR quality control ourselves. I haven't found a foam installer who does that routinely on their own projects, either. I have met some who claim to own a blower door, but it seems always to be back at the shop. I can't blame the spray foam installers -- it takes extra time and money to do the blower door and IR quality control work, and if general contractors aren't asking for it, why bother?

    --Paul Eldrenkamp

  3. AlanB4 | | #3

    As a customer i want the best
    As a customer i want the best performance i am paying for, but finding out i probably won't get it makes me less likely to opt for spray foam, though in some circumstances it should be the best insulation option. I would like if the option was offered for IR/blower door, but no installer i know does, i would love to own my own blower door and IR camera tbh, but until they come down in cost to consumer territory they are professional grade tools.

  4. woodreader | | #4

    foam shrinkage
    There always has been a lot of talk about foam shrinkage. The fact that wood expands and contract, you can touch up a fresh spray attic and in 6-12 months do another blower door/IR tests and maybe find more leakage. Pro foam folks jump up and down about their 6", R 19, OC spray rafter encapsulation that hold a temperature difference of 10 degrees between the attic and the floor below. I feel this is bogus consider the radiating and leakage of the HVAC ducts. Has anyone try fixing HVAC leakage, foam the ducts, encapsulate rafters and reported on a larger than 10 degree swing between attic and floor below?

  5. Expert Member
    ARMANDO COBO | | #5

    Misleading and cheating the homeowner
    I agree with Richard. The typical standard foam encapsulation I see in CZ2, CZ3, CZ4 & CZ5 is 5.5" of open cell foam, because it is allowed in the performance code, and because it is a price competitive approach. However, not only R20 is 52% and 40% respectively what it is required by code for good insulation value against outdoor temperatures, but shows a lack of building science knowledge that open cell foam been air-impermeable, but it is not moisture impermeable, which can create moisture and condensation issues. It is a deliberate manipulation of the facts by the foam industry and many builders to make a sale, the verifying industry, and building inspectors that allow this practice to continue, while the homeowner is left with possible problems in the future. All encapsulations most have closed cell foam either above or bellow the roof decking.

  6. charlie_sullivan | | #6

    blowing agent global warming potential
    This article is incomplete without an acknowledgement of the high global warming potential of the blowing agent. Selling this to a customer who is interested in a green building without making that clear is irresponsible to that customer and to the planet.

    I am glad you are addressing the other problems, but sweeping that one under the rug seems disingenuous.

  7. JC72 | | #7

    New blowing agents don't have the GWP of the past. IIRC on this site a Honeywell product was reviewed as having a GWP that was only 7 times greater than CO2.

  8. charlie_sullivan | | #8

    phaseout of hfc blowing agents
    Chris, yes ccSPFs with low GWP blowing agents are beginning to be available. But they are not mainstream. All the more reason that attention to this issue is important in the kind of discussion provided here. EPA's phasedown rule for HFCs issued in 2015 sets a timetable for removing HFCs from most insulation ... But not spray foam!

  9. Expert Member
    Dana Dorsett | | #9

    Name one! (for Charlie, Chris, anyone?)
    OK, if they're "...beginning to be available..." , name just one foam brand & product sold in the US that is using a low GWP HFO1234_ _ type blowing agent (such as the Honeywell goods).

    They arguably should be available, but "should be" isn't the same as "is". I'd like to celebrate those that are actually stepping out there, if they really are available in the market now, in January 2016, not just some guinea-pig test installations.

    Almost all polyurethane foam under 1lb density is blown with water, not HFCs. If I had to guess I would hazard that most of the foam (by either R-value or lbs of polymer per square foot ) installed in the US is probably half-pound open cell foam blown with water, not 2lb foam blown with the nasty stuff.

    The polymer quantity also has an environmental footprint. Half-pound foam uses a bit less than half the polymer per R as 2lb foam, since it's 1/4 the polymer per inch of depth, and a bit more than half the R-value per inch. Even if they were to use carbon-consuming blowing agent for 2lb foam it still has some verditude issues, just fewer issues. Whenever/wherever you can use open cell instead of closed cell in the stackup it's arguable on environmental grounds that you should.

  10. charlie_sullivan | | #10

    I don't know how widely available this really is, but Lapolla's version is listed on their web site as being available, and a fine home building article from May 2015 described it as being "already offered"

    They also said in a 2014 press release that they'd stop using HFCs "by 2016".

    Demilec has announced that they will have an HFO spray foam available by "mid-2016" and will transition completely by the end of 2017. But as far as I know, Lapolla is the only one you can buy today.

  11. Paul Eldrenkamp | | #11

    GWP of foam
    We consider carefully the global warming potential of the foams we choose. As noted in the article, "we base our product choices on the optimum balance of cost, effectiveness, and environmental impact."

    We generally assume closed-cell will have a higher gwp than open-cell. This seems a safe assumption, at least for now, with the products currently available. That being said, in the Boston climate we believe that closed-cell has an important role to play. We spray 2" to 3" of closed-cell on old foundation walls when we do a basement retrofit. I haven't figured out another material/system that can provide all the benefits of closed-cell spray foam in that particular situation. When we do rafter insulation, we have the foam crew apply 2" to 3" of closed-cell against the underside of the sheathing, and then switch material and complete the job with open-cell. This offers more robust moisture management than all open-cell would, meets state code, and, in my view, strikes a favorable balance of gwp avoided versus gwp created.

  12. Foamer | | #12

    Take a deep breath
    Thank you for an enlightening post Paul. It is encouraging to read about your engagement with spray foam technology and your points are well made. Our industry is growing by leaps and bounds with new installation companies appearing on the scene every day. This poses a challenge for everybody given the steep learning curve and the potential for less than ideal outcomes but there are many companies out there who take their responsibility seriously. The Spray Polyurethane Foam Alliance is aggressively promoting it's training and certification program, which may help bring some clarity to the market place.

    Specifically to some of the comments made above:
    - we own a blower door and test every new construction project we are involved in, during installation and after completion
    - lower than code r-values is a bogus approach unfortunately used by some manufacturers and installers in attempt to be cost as well as quality competitive with other insulations
    - water blown foam is available in higher densities - we spray a closed cell, water blown foam
    - 1# density foam can achieve the necessary vapor permeability levels to work well in cz5 and above

    Not all spray foam installers are hacks who must be micromanaged to achieve quality.

  13. user-417066 | | #13

    It's available
    Charlie, and all,
    The foam-lok-2000-4g product is readily available. I have used it on a number of projects in the last six months. Our insulator claims its GWP =1. Also, I was just at the IBS and watched a presentation that included a Flir IR camera for $700. I realize it isn't peanuts - but it isn't $7000 either. For most builders I know, client appreciation of the contractor's concern for using an IR camera, would easily warrant the cost of $700 . Good article Paul!!

  14. Dana1 | | #14

    OK, we have one!
    Labpolla Foam-Lok-2000-4G, blown with an HFO124 blowing agent!

    Any others? A list of one is pretty short.

    I'm aware of Aloha Energy's water-blown 1.8lb foam lineup, as well as Icynene's water blown 2lb & 2.1lb MD-R-200 and MD-R-210, but I'm still looking for other water blown or HFO1234 type blowing agent products.

    Torsten Hansen: Can you point me to a data sheet on a 1lb foam including it's ASTM E96 test numbers?

  15. charlie_sullivan | | #15

    Thanks for the confirmation
    Steve, Great to hear that the Lapolla HFO product is really available in the field! Time to celebrate with some bubbly (which also uses a GWP = 1blowing agent).

    Paul, great to hear that you have been thoughtful about the tradeoffs ... but given the availability of the Lapolla product, you are no longer between a rock and a hard place (or between a fieldstone foundation and a high GWP foam). You can have you cake and eat it too! There's no longer any way to justify using HFC foam.

  16. bencarsan | | #16

    Getting toxicity right
    Unfortunately, here, as in many places, there is no consideration of the health implications of the chemical flame retardants added to foam insulation. It took decades, but those chemicals have been mostly phased out of furniture and appliances because they are known to be persistent, bio-accumulative, and toxic. They've been implicated in cancer, brain damage, endocrine disruption, diabetes, and fertility problems, with effects found even at low doses. The scientist Arlene Blum has been a very effective voice in pushing for bans on these widely toxins.

    These chemicals are present in all foam insulation--XPS, EPS, and PU SPF, 10-20% by weight in SPF, usually added to polyol or "b side".

    A Chicago Tribune series "Playing with Fire" documented how the chemical industry lied to the public and regulators about the risk of FRs and also about their effectiveness. It's sort of mind boggling--a product that's highly toxic and then doesn't actually work. In response California finally revised it's flammability standards. (

    Green Science Policy Institute has more on the science:

    Considering that there are plenty of less toxic alternatives, the enthusiasm for foam within green building circles is hard to understand.

  17. GBA Editor
    Martin Holladay | | #17

    Response to Bennett Sandler
    Here are links to two GBA articles on the topic:

    Making Healthier, Greener Foam Insulation

    California Law Addresses Fire Retardants in Homes

  18. Expert Member
    KOHTA UENO | | #18

    Value of Blower Door QC on Spray Foam
    Another energy geek who strongly votes for using a blower door (and infrared) as a quality control measure on spray foam. Spray foam is a great air barrier material, but it does nothing where it isn't--the classic wood-to-wood connections (rafter-to-joist attic connection, king/jack stud joints, etc.) The pics below are just one of multiple times I've done IR/BD testing and found significant point leaks in spray foam houses--the shots below are flash and batt.

  19. GBA Editor
    Martin Holladay | | #19

    Response to Kohta Ueno
    Thanks for sharing the photos. They remind us, once again, that an insulation material like spray foam is only as good as the conscientiousness of the installer.

  20. RACHEL WHITE | | #20

    Response to Bennett Sandler
    As a remodeling contractor, we frequently encounter situations where there are no practical alternatives to spray foam.

    After last winter we were called on to insulate a lot of attics, of which I'd estimate less than 10% were suitable candidates for cellulose along the attic floor. Most of the attics we work in are filled with stuff, ducts and an air handler. We recently priced a cellulose-in-the-rafter-bays approach in just such an attic for a client who was highly motivated to avoid spray foam. The cost for the cellulose approach was almost double the cost of spray foam. She decided to go with spray foam.

  21. leighadickens | | #21

    one tool in the toolbox
    you can get an IR camera attachment for iphone and android for ~$350. I haven't tried it, I'm sure it's not as good as the whole hog, but at least it's something.

    I don't agree that the R-value trade-off approach with foam is totally bogus**--(**in the context of a true performance alternative code compliance pathway whereby you are upping your performance numbers elsewhere in the envelope and that the efficacy of your trade-off design is verified with a HERS rating and blower door testing.) Just like anything else, the level of quality installation available for the spray foam vs what's available for any alternate type of insulation you'd otherwise be using, how much higher than code you go in other areas to make up for it, how much lower than code low you're going in the area that is under prescriptive R-value, the condensation risk, the interior moisture production risk levels, are all part of that calculus, and that calculus is climate and budget specific. If somewhat below prescriptive code R-values in the roof don't raise condensation flags and help get the ceiling airtight when another method wouldn't, (based on the sub contractors and installers I have available) while also helping the foam option be a bit more affordable (because spraying thick foam does get expensive), I'm fine with it, with the caveat that this is done thoughtfully, the foam is installed right, and that the house has many other above code performance measures, typically include above-code R-values in other places in the envelope. That's what the performance alternative option in codes is all about, allowing flexibility to use your available resources most appropriately.

    The other thing with foam is safe re-entry time for homeowners in retrofit situations. Many of the fears and horror stories around chemical sensitivity and safety seem to me to be coming from situations when people were not out of their houses when they should have been during foaming, or came back too soon after completion. A frustration for me has been an inability to get clear guidance on safe re-entry times from foam manufacturers. What's appropriate? 24 hours? 72? Two weeks? In new construction, you have plenty of time for foam to cure before homeowner moves in, (although subcontractor safety, there's another thing. I've had to have a talk with my site superintendent about not scheduling other subs during foam installation) but I have seen some shady stuff in retrofits. It makes foam an even harder sell: not only is it more expensive than other options, but you also have to leave your house for (some period of time I can't get a good answer on), so if an installer is not good on client expectation control then that can get shady real fast.

  22. user-1123621 | | #22

    Righting the Wrong
    My house was stripped down to the studs and Demilec APX open cell foam (fire rated with a retardant) was applied to create a conditioned attic. The Demilec “authorized installer” applied the SPF while a Demilec territory manager was on site. After installation the house had a strong awful odor for days, continuing for weeks. With the direction from Demilec we continued to ventilate for weeks with box fans, the commercial fan system from the installer, and a large commercial HVAC squirrel cage fan. Windows were open 24 hours a day. One weekend the wood stove was reinstalled and the house was super-heated hoping to cure the foam.
    Seven weeks later the installers removed the SPF foam from the attic and samples were collected for VOC testing. The chamber test of the foam samples resulted in extremely high levels of a fire retardant off gassing. At this extremely high rate what are the health implications? Per the Protective Action Criteria (PAC) at these extremely high off gassing rates a “one hour, once in a life time exposure” states, irreversible or other serious health effects. The PAC protocol is used by health professionals to assess the impact to emergency responders who were exposed to a “one hour, once in a life time exposure”. We need to remember this foam sample had 7 weeks of ventilation to cure and the chamber test is conducted at 73°F.
    After the foam was removed the house continued to smell. Two indoor air quality studies have been conducted. The first study was conducted 2 months after foam removal and then 13 months after removal. The two IAQ studies verify the same fire retardant continuing to be emitted, but at lower rates. The house remains vacant and devoid of other products that could be emitting this fire retardant.
    An analysis of the data by an Industrial Hygienist states as a minimum the truss and roof shall be removed and the rest of the materials in the house tested. Demilec states in their own application guide to “Ventilate during spray foam application and for a minimum of 24 hours following the application or until no unobjectionable odors remain”. “ If not adequately ventilated during and shortly after application, the odors can be absorbed in adjacent materials such as fibrous insulation, wood framing, and household or stored items. “ The EPA website states “EPA is not currently aware of standard accepted removal and/or remediation practices. This is an area for further investigation and research as future renovation and deconstruction of buildings where SPF has been applied are anticipated”.
    The house remains vacant and unoccupied for over three years. There have been many suggestions on how to remediate the problem, soda blasting, dry ice blasting, encapsulate with a sealant, cover with closed cell foam, however none of these come with a guarantee to fix the problem.
    We are often told that such a small percentage of the homes have a problem. We don’t know because there has not been a random study of homes. Levels of VOC emission may be below the “smell” test by the occupants, but they have exposure. A friend of mine had his roof sheathing sprayed in his attic with closed cell foam, every summer he gets an occasional whiff of the SPF smell. VOC test for VOC labelling is not done with a field produced product; it’s done with a factory produced product under optimal conditions.

    The SPF industry needs to be proactive:
    • Homeowner shall be informed of the risks, potential problems, and possible health problems with SPF. Sometime similar to a consent form. Example is the isocyanate exposure from SPF dust and the need to protect from inhalation. Should the homeowners or other contractors enter the house when the installation and cleanup of SPF is not complete?
    • During the off gassing phase or when odors are detectible home owners or other contractors/laborers should not reenter the home unless they are equipped with PPE that protects their respiratory system.
    • If odors remain, the owners should not be allowed to reoccupy the house until IAQ studies are conducted.
    • Develop protocols for VOC testing. The VOC chamber test of the APX removed from my house passed the Section 01350 chemical list, but found to be extremely high in fire retardant because I requested a broad spectrum VOC test.
    • Studies and trials need to be conducted to determine methods of effective remediation.
    • Guidelines on how to conform to environmental law when disposing of failed SPF installation. Will the house require tenting during deconstruction to protect the neighbors from the SPF foam dust? If the foam is producing toxic emissions what form of PPE shall the workers be equipped with? What type of landfill will accept this material?

  23. Expert Member
    MALCOLM TAYLOR | | #23

    That's a simply awful situation. It's hard to think of another building material where the results of incorrect installation are as far reaching and remediation so difficult (perhaps in a different context foam SIPs?).

    For a wide variety of reasons I hope the energy efficient building movement finds other alternatives strategies that don't rely on foam.

  24. LucyF | | #24

    Relatively inexpensive IR camera
    I am a layperson with an interest in residential energy efficiency. I've used the Flir One and it is very effective at telling you where your heat loss is. The first photo is a back bedroom ceiling. I had been in the attic insulating when I found an unbelievable colony of carpenter ants (hundreds and hundreds with a nest). I pulled back the insulation sprayed boric acid and diatomaceous earth. I haven't replaced the insulation as you can plainly see.

    The second photo is around my chimney.

    I posted this in reply to one of the comments above. So for about $250 you can get a IR camera that easily will let you see where heat escapes.

  25. Paul Eldrenkamp | | #25

    spray foam gone bad
    Brad: I feel your pain. I have direct experience with four spray foam installations going bad (one on one of our projects; three in which I was less directly involved). In all four cases the installers acknowledged problems and were eager to help out; in all four cases the manufacturers (via their reps) at worst lied and at best stonewalled, and were ultimately less than useless.

    One obvious remedy would have been removal, but as you have pointed out (and as Henri Fennell has also pointed out), there is no approved protocol for foam removal. And I don't think we should expect one anytime soon -- manufacturers appear to view having a foam removal protocol as a Pandora's box.

  26. mdhokie | | #26

    BASF Spraytite
    Reading the literature on BASF Spraytite and it says it uses ZONE3, a zero ozone depleting blowing agent. Does anyone know what exactly they use? Does it have a better GWP than other products?

  27. Paul Eldrenkamp | | #27

    Workshop by Henri at Building Energy 16
    For those who might be interested, Henri Fennell is giving a workshop at Building Energy 16 in Boston on March 8:

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