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Community and Q&A

Spray foam odors — time to pull the plug?

Jeremy_G | Posted in Energy Efficiency and Durability on
This post is going to read a lot like some others on GBA about spray-foam insulation. I’m looking for suggestions on how to proceed given an objectionable odor from the SPF.
CZ4a, D.C. area
1930s Dutch Colonial, brick-on-block, slate roof
Open-cell SPF sprayed over soffit-ridge baffles in 5.5″ rafter bays to encapsulate attic
2″ rigid foam on gable walls
Attic access via pull-down stairs
New A/C unit with existing sheet metal ducts in attic
The Saga
My original intent was to insulate, drywall, replace A/C and add an ERV, then seal and re-insulate the attic ductwork. The A/C and ASI were part of a Maryland home performance program that covered about 25% of those costs. (Side note: the ASI plus fireplace top damper cut the blower door number by 45%.)
The SWD Urethane open-cell SPF was installed in mid-May. It was rainy and 60ºF that day. They claim a re-entry time of one hour. I removed cut-outs in the rigid foam to allow the attic to vent via the gable vents (later sealed up), left the attic hatch open and opened several windows. My family stayed with my in-laws for a couple nights.
By mid-June the weather was getting significantly hotter and we were starting to get a strong odor on the 2nd floor. I was getting headaches, itchy eyes and throat irritation. I had recently sealed up the gable vents for the blower door test to finalize the rebate, but the ERV was back-ordered. I had originally assumed that I wouldn’t need mechanical ventilation based on 62.2 (used by MD rebate program), but the blower door number was much lower than expected. So, the blower door test would have to be repeated after the ERV was installed.
I contacted the contractor and SWD in mid-June. The contractor came out promptly, but on a cool morning, so the smell was minimal in the attic itself. He said it was a humidity problem, lack of sufficient R-value (not sure how that’s relevant) and the crew not having cleaned the old loose insulation out of the “soffits”. The house has a Gambrel roof with no soffits per se — I’m using that term to refer to the place where the rafters meet the joist bays. Maybe there’s a better description or term? There’s blocking between the “soffits” and the 2nd-floor wall top plates where the roof changes pitch.
The SWD rep was professional, but was hard to get ahold of to put together a plan to evaluate and potentially remediate. After about two weeks he suggested cutting out a 12″x12″ sample and sending it to the SWD lab. I did that in early July. Meanwhile, hot and sunny weather meant a lot of A/C operation and a heavy odor in the attic. I resorted to opening the gable vents and putting a fan in one. Plus, I left a window cracked in each bedroom and at least one in the living area. Not great for energy use or comfort…
Early August: SWD finally finished their analysis and said the foam is fine. I had a conference call with the contractor and SWD where I couldn’t really get traction on the idea that SPF should be odorless if it’s completely reacted and cured. The contractor repeated most of the same rationale from the first visit and the SWD rep wouldn’t put the contractor on the spot. I agreed to close up the gable vents (the ERV had since arrived) and install a dehumidifier. The contractor would come out again to select another sample to send to SWD.
I installed the ERV and set it to pressurize a bit to try to prevent SPF odor in the living space. In combination with the dehumidifier, the odor has been lessened both in the attic itself and substantially reduced in the living space. The day before the contractor returned was nearly full-sun and 90ºF+. I walked up to the attic briefly and the odor was almost overwhelming. The day the contractor was here was similar weather, yet the odor wasn’t that bad in the attic. I’m flummoxed, and have subsequently noticed a lot of odor variation on primarily sunny, hot days with similar dew points. I suspect small pressure differences are either driving the odor (via vapor) in or out of the roof deck depending on conditions I can’t detect. It’s rarely windy here in the dog days of summer.
The contractor was more cooperative this time and acknowledged that he can’t really smell it after years of working in the business. And I think he believed me that it had been much stinkier the previous day. I sniffed around for areas that seemed worse and he cut out a couple. He found some foam in the middle (i.e., covered by the second pass or “lift”) that looked different, and sniffing those pieces gave me an instant headache. He said that he would send out a crew to fix the “soffits”, fill in the spots that had been cut out, and was willing to replace sections that I marked after doing a smell test. Or I could have it removed.
In the intervening time between the 2nd sample and results, very hot and humid days mean we still get an odor for a few hours even with the ERV running a bit more than my 62.2 number. If I turn off the ERV while we’re away for a couple nights, the whole house reeks. I don’t mind boosting the ERV temporarily, though it does have an energy penalty, especially with latent load.

I did an RH test recently and found that the odor is significantly reduced at 40% vs 50-55%. But maintaining that RH would have a huge energy penalty, and it seems like SPF would have higher RH once behind drywall.

I spoke with the SWD rep today and he said the second sample was a little denser than the first, but still in the acceptable range. So, he suggested an air quality test if I wanted to try to keep it. Since the samples tested OK, SWD isn’t going to try to lean on the contractor for particular action.

With SPF that appears to be mostly correctly installed, I’m struggling to figure out a path forward. Complete removal is obviously a lousy option. Plus, then what? On the other hand, I’m wary about installing and finishing drywall and just hoping there won’t be any odor problems. The best time to get it fixed is now. I have two young kids who don’t know how to talk about any symptoms they may be experiencing, and it’s clearly affecting me. My wife seems to be less sensitive to it.

Does anyone have experience specifically with SPF odor after drywalling? Are there tests that can detect where part A and B aren’t fully reacted? What’s a good way to find someone to do an air quality test? Other thoughts about how to proceed are welcomed, also.


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  1. GBA Editor
    Martin Holladay | | #1

    I wish you the best of luck in your difficult situation.

    This isn't really a building science question. You may need to talk to a lawyer, and you probably want to sit down with your wife at the kitchen table for a heart-to-heart.

    You've got to make this decision on your own. If odors linger for several weeks, as you describe, I've never heard of a case where the odors go away. If the odors go away in cool weather, they can return in hot weather.

    1. swdengineering | | #7

      Some background:

      Samples were sent to us from the contractor in which we analyzed and determined the foam was within specification with no notable odor observed at both ambient and elevated temperatures.
      A second set of samples were then sent to us directly from the home owner, analyzed again with the same result.

      SWD foam that is in specification does not produce an objectionable odor. The presence of an odor is highly subjective and most often “odor” in this context is synonymous with VOC’s (Volatile Organic Compounds) and we have significant data and third party evaluations certifying that our products comply and perform better than the highest industry standards recognized for building product emissions.

      The statement, “I've never heard of an air quality test that is useful in this type of case. The only value of an air quality test is when a spray foam contractor or a spray foam manufacturer is trying to confuse a jury to limit their liability.” is inaccurate. Quantitative air sampling can be performed in which chemicals and their associated concentrations can be determined which most often can lead to identification and source of a foreign/objectionable odor.
      We made our recommendations based on efforts to help the homeowner who recently had our product installed in an honest attempt to pursue a remedy to this. We continuously strive to ensure our customers experience with SWD is positive. Rarely do we receive concerns that our foams may be producing an objectionable odor but in those instances what we almost always discover is that an odor(s) such as mold for example has always been present but diluted as a result of air leakage. The application of our spray foam reduces that air leakage and subsequently the dilution process creating a concentrated odor appearing foreign to the home owner. Logically, with the recent addition of our spray foam, the homeowner believes the foam is producing the odor. SWD takes these concerns very seriously and we work expediently to analyze the samples, compile the data and transparently determine if the foam is in specification. We go above and beyond what most manufacturers do with our available support functions to homeowners and we offer our experienced suggestions on possible paths forward to ultimately arrive at a workable solution even when we have determined our foam is not the source.

      Furthermore, SWD is a large manufacturer that produces significant quantities of product. When we make a specific product such as the one referenced here we are not making one set of material but rather a batch that will accommodate hundreds of sets of product that are sold and applied throughout the US and Canada. SWD’s stringent internal QC program accompanied by our third party auditing requirements ensures that we consistently provide the highest quality products to the market. With respect to this referenced batch, this is the only concern that we have received.

      The goal in forums like this should be to help people fix real problems, not exacerbate them. It is troublesome when questions/concerns are posted and responses clearly identify a lack of expertise in the subject matter but will still have an influential impact on the membership. Finding productive ways to add value to the conversation such as directing them to an expert in the field who can provide some meaningful insight and potential suggestions/recommendations towards a real and viable resolution would provide participants with more reliable feedback.

      Paul Warren
      Building Scientist/Codes and Engineering Manager
      SWD Urethane

      1. Jeremy_G | | #14

        Hi Paul,

        Thanks for your response. I guess I didn't have the e-mail notifications option checked and just saw this now.

        I think SWD did an adequate job with regard to testing and recommendations. I would have strongly preferred that the combination of manufacturer and contractor actions would have led to an acceptable result, though I'm not faulting SWD.

        As a more general followup, I got a couple quotes for AQ testing, specifically for an isocyanate panel. The cost would have been $1000+ for testing in the attic and 2nd floor (floor below the attic). Since the job was billed at ~$2500 I decided it wasn't worth it.

        We just got a beautiful 11" snow and I'm having some ice damming, which didn't happen with a vented attic. So, it appears that open-cell wasn't the right choice for my application for an additional reason. Also, I went up there yesterday and could smell the SPF with the temp in the mid-50s (much less objectionable than a hot day, but still noticeable). I didn't pay the bill, and after one last hurrah with the contractor's GM to try to determine a solution in late Oct, I haven't heard back.

        So, I'm probably going to rip it out myself and then figure out a new plan, likely to be one of:
        a) return to vented attic and remove ERV
        b) cut-n-cobble rigid foam + rockwool + drywall (I know there are major drawbacks)
        c) closed-cell SPF + rockwool + drywall (hard to consider SPF again, but I would really prefer to keep the AHU and ducts in conditioned space, plus the ERV)

  2. Jeremy_G | | #2


    You're right, the ultimate decision is mine. I could use some input on some building science-related items such as finding an air quality specialist or other independent person to evaluate the installation, and what an alternative to SPF on the roof deck might be if we get it removed.


  3. GBA Editor
    Martin Holladay | | #3

    I've never heard of an air quality test that is useful in this type of case. The only value of an air quality test is when a spray foam contractor or a spray foam manufacturer is trying to confuse a jury to limit their liability.

    The best test is your nose. If it stinks, it stinks.

    The main alternative to spray foam (for anyone interested in creating an unvented insulated roof assembly) is to install rigid foam above the roof sheathing. For more information on this approach, see "How to Install Rigid Foam On Top of Roof Sheathing."

  4. STEPHEN SHEEHY | | #4

    It seems as though this problem arises sort of randomly. If you can't predict whether use of a product will create a serious health or comfort issue, maybe the continued use of the product should be discouraged here.

  5. user-2310254 | | #5

    In my last home, I installed a ventilating dehumidifier. It overpressurized the house slightly and controlled the spray foam's residual odor. You could probably test this approach with a blower door. Just an idea...

  6. Jeremy_G | | #6

    Thanks for the ideas.

    Martin, thanks for the perspective on air testing. I've wondered how useful it could be. Removing the slate roof to insulate isn't something I want to consider at this point, so it looks like SPF is my route to an encapsulated attic. Part of my rationale was that the ERV could go up there — which on its own was a similar cost for me to DIY install as to have an electrician run the wires and install two bath fans on the second floor (plus additional complications with fitting the fans under the roofline and rerouting some A/C ducting). But maybe I need to revisit that decision.

    Steve, I'm currently overpressurizing with the ERV and that does control the odor except for late afternoon and evening hours on the hottest days.

  7. GBA Editor
    Martin Holladay | | #8

    Response to Paul Warren of SWD Engineering (Comment #7, several comments above this one on the page):

    Paul, I still think you have some more customer service work to do.

    Jeremy Good, the homeowner who started this Q&A thread, wrote, "If I turn off the ERV while we’re away for a couple nights, the whole house reeks. ... I spoke with the SWD rep today and he said the second sample was ... still in the acceptable range. ... Since the samples tested OK, SWD isn’t going to try to lean on the contractor for particular action."

    You wrote, "We [SWD, the foam manufacturer] continuously strive to ensure our customers experience with SWD is positive."

    If SWD is serious, there's more work to do. You're not there yet. It sounds like SWD is ready to walk away -- and that's not acceptable.

    1. Jeremy_G | | #15

      Thanks, Martin. I somehow missed the follow-ups back in Sep.

  8. walta100 | | #9

    Martin, would it be possible to restore the now apparently deleted post #7 for the enjoyment of thou of us that missed it fleeting appearance.

    I must be a tuff job to defend such a complex product applied that is applied under such variable conditions by contractors that may not always follow your instructions.


  9. GBA Editor
    Martin Holladay | | #10

    Comment #7 appears after Comment #1.

    This is due to a quirk of the new web site -- comments don't always appear in chronological order as they used to on the old web site. It can get confusing.

  10. Joel_K | | #11

    If attic is sealed and strongest odor comes from there, why not do an air quality test to determine what kind of substances are in the attic air and go from there? Like SWD company said, making room more air-tight can concentrate bad vapors and odors.

    After a flooring contractor refinished our hardwood floors and used solvent-based polyurethane by mistake, we stayed ouf the of already-plastic-sealed-off area for several more months, then did several air quailty tests around entire house to see what kinds of VOCs were lingering ... air quailty turned out fine, VOCs nearly non-existent... we also live in airy, old house and have no new furniture or carpets or underlayments that could also off-gas either.

  11. Expert Member
    MALCOLM TAYLOR | | #12

    The placement of comments depends on whether you use the "leave a reply box", or click on "reply" below a specific post.
    Many websites use this format, but it would work a lot better if the "leave a reply" box was instead titled "Post a new comment" to distinguish the two choices.

  12. Deleted | | #13


  13. newmedia | | #16

    Hello Jeremy,

    How are you doing? Did you fix your problem? I hope SWD rectified your problem.

    Recently i bought a new house and moved in. When I did home inspection, I thought it's just a new house smell. (new paint, etc. ). After the move, my wife was staring to complain about the smell from the third floor. It's a room existing in a attic. There is two crawl spaces and SPF is in there. The odor is very strong.

    I'm devastated because they installed SPF in 1st, 2nd, 3rd walls. I'm not sure how I can rectify this.

    Any comments from you will be helpful to my family.

  14. mikeolder | | #17

    The ratio was probably off .

  15. newmedia | | #18

    Yes. I think more Part B is used somehow. I saw that video too.
    This is a new house and i didn't put the foam in. The builder did.

  16. newmedia | | #19

    Jeremy. Are you still having this problem?

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