GBA Logo horizontal- Facebook- LinkedIn- Email- Pinterest- Twitter- Instagram- YouTube Icon- Navigation Search Icon- Main Search Icon- Video Play Icon- Audio Play Icon- Headphones Icon- Plus Icon- Minus Icon- Check Icon- Print Icon- Picture icon- Single Arrow Icon- Double Arrow Icon- Hamburger Icon- TV Icon- Close Icon- Sorted- Hamburger/Search Icon-

Community and Q&A

Spray foam insulation post-install chemical smell (not rotten fish)

Scott Roberson | Posted in Green Products and Materials on

I’ve read many articles on this subject, but I wanted to ask a more specific question as my case doesn’t seem to match the other’s horror stories with poorly-installed Spray Foam Insulation.

Our contractor came highly rated by a friend who is an architect in our area. He’s worked with this contractor on numerous occasions. I’d gotten quotes from ~5 different spray foam insulation vendors and this guy’s estimate was a good 50% higher than the others, but I felt he actually knew what he was doing. In conversations he seemed to say all of what I considered “the right” things. He does 100% spray foam insulation for high-end homes in our state of Connecticut.

They did a great job as far as the job site was concerned. They were extremely clean and really cared about keeping things orderly.

We had a very large job as our house is a two-story 5200 sq ft house.

They removed the blown-in insulation on the floor of the attic and sprayed BioBased 501w open cell foam on the underside of the roof deck (~10 inches on roof deck, and ~6″ on vertical walls).

Prior to spraying, they shut off the upstairs air handler that was housed in the attic and disconnected the ducts. They laid down plywood sheets on the floor and laid plastic on top of that, stapled to floor. All surfaces were covered. (A subsequent HVAC guy remarked that he’d never seen such a neat job of spray foam insulation installation.)

The foam was also covered with a fire-retardant paint ()

The contractor used an air handler in the attic that was attached to a removed window to vent the attic air to the outside.

The reason for this posting, however, is that we’re still smelling a chemical smell in the house when the vent is turned off. And this is now 2 months after the installation. Installation was done 2nd week of July and it’s now mid-September.

The smell is worse on hot days. It is not the dead fish smell that others have experienced, but it is evident.

It’s possible that I’m getting used to the smell, but my sense is that it IS getting better. Yesterday we had another 90-degree day and we could smell it and were worried, but I went into the attic and noticed that the 12-inch flexible tube out of the air-handler had detached and was not sucking air out at all.

That was actually encouraging because while there was a distinct chemical smell, it was less than it used to be. After re-attaching the air handler, the smell went away.

I know people have said the smell will never go away unless we take out the part that smells (assuming there’s an area that didn’t cure properly.)

However, I do feel that it is better. The contractor has assured me the smell will, eventually, go away.

I’ve read that if there is not adequate ventilation when the installation happens, initially, when the foam expands and forms it’s air bubbles it will pull in the accelerant gas that is present in the air. That slowly leaching gas can lead to a smell.

If this is what happened, it seems reasonable to me that the lingering (and decreasing) smell may just take awhile to go away, since this was a very large job. Plus the surface of the foam was covered in that thick, fire-retarding paint. If there is a gas in there that needs to come out to be replaced by fresh air, that paint has to be slowing the process, right?

Does this idea make any sense to any professionals on this list?

I have a call in to an air-quality tester to see if we can determine what the chemical smell is, and to set a baseline to test again later to verify whether it is, indeed, going away.

Looking for any guidance on this issue.

— Scott

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. User avatar GBA Editor
    Martin Holladay | | #1

    I don't have any encouraging information to share. Others in your situation report that the smell returns every summer, with the arrival of hot weather. Running a ventilation fan continuously undermines the purpose of the spray foam, which is to save energy.

    I don't recommend testing the air. Tests will tell you nothing. If you can smell the foam, you've identified the problem.

    A few people report that the smell eventually fades. Others report that it comes back with warm weather, every year.

    I would document the facts of your case in a letter to the contractor and a letter to the foam manufacturer. Others in your position have ended up insisting that all of the foam be removed. Good luck.

  2. Brad Dorken | | #2

    I have been dealing with the odor problems in my house from the application (May-2013) of Demilec APX against the roof deck. I had to halt construction on the house, so I have not been able to live in the house. I had a sample of the foam removed from the attic chamber tested per Section 01350. This is the current standard to test products in California for VOC labeling. Eurofins and Berkeley Analytical do this test. My test resulted in a variety of VOC's. DEP (Diethly ethanephosphonate/CAS 78-38-6) had an extremely high emission rate. The rate is so high it is placed in the PAC 2 category. PAC stands for protective action criteria used by health professionals and first responders to evaluate the health impacts for a once in a lifetime exposure. For DEP that exposure is for only one hour. PAC 2 levels for DEP predict "Irreversible or other serious health effects that could impair the ability to take protective action". Those health impacts are for a one hour-once in a lifetime exposure. Occupational (work environment) or non-occupational (home environment) VOC levels have not been established for this chemical. These VOC levels were from a foam sample removed from house 7 weeks after installation. The chamber test is conducted at 73F where conditions in your attic get much hotter so you could expect higher emission rates in your attic. We are all told if installed properly the product is inert (not chemically reactive) after 24-72 hours. There are no know studies or trials to remediate the problem of continued off gassing of SPF. The only know solution is to remove the product, however this may not result in a complete elimination of the odor. My product was removed, but two follow-up IAQ studies of the attic show that DEP is still being emitted at much lower levels. One can only conclude the chemical has penetrated the wood truss system. My house requires the complete removal of the roof and truss.

    The problem with testing, is the B Side of the SPF mix is proprietary, so you don't know the chemicals to test for. Therefore, have the company do an extensive test for VOC's beyond those conducted in the section 01350 test. Have a sample of the SPF removed from your attic chamber tested and you will probably also need to independently test the fire coating.

    Work with an Industrial Hygienist or an expert in indoor air quality. SPF is a chemical mixture, you are in a situation where you don't know if the SPF off gassing is toxic or harmful when exposed for the long term. In my case I have an extremely offensive odor and emitting of an organophosphate fire retardant. The odor could be one of the other chemical VOC's

    More information; I used Eurofins in Sacramento CA. For the foam sample I did the 24 hour VOC chamber test. The test was $400 without shipping. The foam sample is shipped in a mason jar & kept cool (gel ice packs in small lunch box sized cooler). They are a certified lab per CA 01350 criteria (there is a lot of good info/history about this test on the internet). This test has been adopted by other countries as it tests for 35 specific compounds (mostly known carcinogens). The 24 hour test also includes other VOC's such as aldehydes. If you know the specific VOC's of concern, discuss that with them beforehand and they may adjust the test or put more importance on them.

  3. User avatar GBA Editor
    Martin Holladay | | #3

    Did Demilec step up to the plate and take financial responsibility for your disaster?

  4. Andrew C | | #4

    Good grief. I've been leery of using spray foam, but until now I'd thought that it was reasonable for basement rim joists only. After all, it's just a small area, and kinda tricky to airseal and insulate otherwise, so it should be okay, right? Nope, that's not going to happen in my house. If you know something is problematic, and that the fix is very difficult and expensive, and you still decide to go ahead with it...

    I feel badly for all the people that have been burned by bad spray foam installations. What a physical, emotional, financial mess.

  5. Kay Smith | | #5

    Brad, we are having a similar problem - which I just posted on this forum. We also have a smell on hot sunny days - and it is not a fishy odor or an ammonia odor - it just has a distinct chemical smell. Can you keep us updated on your situation and if you find a solution? Is your attic humid as well?

  6. Scott Roberson | | #6

    Kay, what brand of spray foam did you have installed? My situation is unresolved. I've been venting per the installer's recommendation and today was my first test of turning it off and closing the windows to see how bad the chemical smell is on the top floor.

  7. Kay Smith | | #7

    Covestro - Bayer Bayseal Open Cell.
    Here is what I posted:
    It smells much stronger on hot sunny days - less so on cloudy days. We are seeing high humidity as well, which seems to make the smell worse.

  8. Rin4 | | #8

    Hi Scott,

    Did you ever find a solution to your problem? We just had spray foam applied a month ago with the promise of it being "odor free", etc, and it still smells so strongly of paint that I'm afraid to let my daughter sleep in her room upstairs. This is particularly strong during a sunny day as you mention. This is our dream home and it's been ruined by this horrible stuff. We had Bayseal Open Cell and I just want to know if this is something that eventually corrected itself over time or if you found relief any other way. Like I said earlier, this is our dream home and I live in fear of the top floor being full of toxic off-gassing from the fumes. We are getting pretty close to having the roof and trusses ripped off and replaced. Did you ever try the MemBrain or an air exchange or anything?

  9. user-7266153 | | #9

    Scott and Rin4,
    Has your smell gone away? I have had a sweet chemical smell for two years in a residential gym I built on my property. My son developed respiratory problems. So I had to ban him from the gym (and I built it for him). I tore out the walls and dug out the open cell foam as best I could and replaced it with rock wool. But the foam is still in the attic. I also added more fresh air ventilation. The smell got much better when I tore out the foam in the wells, but it is not gone. You smell it when you walk in, but it soon becomes unnoticeable. But still scared to let my son in there. I am hoping the last of the smell will finish offgasing and just go away. Did you smell go away?

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |