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Community and Q&A

Allergies from Blown-In Insulation

Tacocat99 | Posted in General Questions on


I had blown glass added to my attic and kneewall floors back in september to my cape cod house. I started to experience allergy symptoms soon after, which resulted in me removing the carpet, which didnt help. This issue only occurs upstairs and the symtpoms are mostly chest and lung irritation.

I was wondering if maybe blocking the baffles may have caused a build up in the kneewalls that is leaking into the rooms. The air in there is kinda bad. Insulator I originally had said since I didnt have soffits baffles werent necessary. However I had some other people over and they said old cape cods are leaky and still breath in air, and the baffles vent it out the roof.

I was thinking maybe the house was too tight but the issue only occurs upstairs where the insulation was added. Research seems to indicate blown fiberglass doesnt leach into rooms but Im not sure.

Was told blown glass was formaldehyde free.


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  1. Expert Member
    Zephyr7 | | #1

    Loose fill fiberglass can't really leak -- you need a pretty good-size hole for it to get through. There can be residual dust after installation though, and there can be some smell from binders. I suppose it's possible that you have a sensitivity to something used in the manufacture of the insualation product use, but that's unusual.

    Have you tried airing the place out for a day or two? All you need to do to do that is to open some windows and possibly run a fan or two on the opposite end of the level of the house where you're finding the air irritating. The idea is to create crossflow ventilation that flows through the entire trouble area. If that helps, but the allergic reaction returns a few days after you close the windows, then you probably are reacting to something inside the home.


  2. Tacocat99 | | #2

    I removed the carpet and have hepa vacced both of the bedrooms and there isnt any dust visible. Rooms have been vented for the last 2 months with window fans.

    Noticed it was particularly bad one day and found the kneewall door ajar from not closing it properly. Was wondering if the new insulation was offgassing something strange that didnt agree with me or if the house fumes/chemicals were collecting upstairs and in the kneewalls.

    Currently getting pricing for mechanical ventillation and wanted to see if adding baffles would be worth it or to spend money elsewere. Was qouted about $800 to seal/cover my ceiling fans and to add baffles. Ceiling fans arent sealed and wasnt sure if they were rated for insulation before I had it blown in.

  3. DCContrarian | | #3

    What is your theory about what's causing the reaction? Mold from excessive moisture or the insulation itself?

    I'm very sensitive to any kind of fiberglass, breathing the dust leaves me hacking to the point of vomiting. Your ceiling should be sealed to the point of air-tightness to keep the fiberglass out of the living space. That also helps with air infiltration and moisture control.

    1. Tacocat99 | | #8

      The insulation itself or possibly the carpet removal. The current situation is that there is a noticeable chalky dust flavor in the air that dries out my mouth and causes chest pain. I can taste/feel the issue as soon as I enter the room, and after like 10 minutes I start to develop lasting chest pain. I've had several insulators and estimators come by and they don't notice it, so not sure if I'm allergic or if the constant exposure to the substance is just building up in me.

      In the beginning of September I had insulation installed into the roof and the floor of the kneewalls in both the upstairs bedrooms. Afterwards I started to develop some mild allergic reactions (eye irritation, skin irritation), mostly after waking up. The problem was bad enough that I decided to remove my carpet from both of the bedrooms. Soon after the strange dry chalky smell started to fill the upstairs rooms. I thought it was just the tiles at first so I ignored it. I was able to sleep in the room but would wake up in the morning with mild chest pain. The dry chalky air became worse after a few weeks and I've been downstairs for about 2 months. When I sealed off both of the upstairs rooms, I learned that the smell was mostly concentrated in the guest bedroom and spreading to the master bedroom. The guest bedroom is where I had them install the attic hatch.

      Not sure if the chalk odor/taste was related to the carpet or if the issue with the insulation just happened to get worse around that time. I figured if it was the carpet it would have gone away by now since its been over 2 months, but instead it is getting worse. The only vent in that room is a supply vent, which was uncovered when the carpet was removed. I got pricing for duct cleaning but its expensive and in most cases people say it doesn't help that much, so I'm trying to make sure I cover other possible angles before I commit money to it.

      I had the master bedroom tested for mold and it came back negative (didn't know source was guest bedroom at time). I can get the guest bedroom retested for $300 but I don't think its mold. I figure if it was mold the issue would have happened earlier since I already had insulation in the attic and all I did was add more on top.

      1. Expert Member
        Zephyr7 | | #9

        I'd be suspicious of the carpet. All kinds of stuff can be hiding out under/on old carpet, and a lot of that dust goes into the air when the carpet is removed.

        You might consider renting a HEPA filter unit and running it for a few days to a weak to filter whatever might be hanging around in the air out. Normally dust will eventually settle out onto surfaces, but the filter will be faster, and will let you actually remove the contaminents instead of just waiting until they settle onto the floor.


        1. Tacocat99 | | #10

          I'll try vacuuming the room up again with my hepavac and seal off the vent with a hepa filter. Been running a hepa purifier on and off for 2 months but whatever it is seems to be filling back up into the room.

          I had a blower test done back in april when I was originally thinking about insulation and there weren't many large leaks beyond the kneewalls, which I currently have sealed up with window seal putty.

          1. DCContrarian | | #11

            Did you get an ACH50 number from the blower door test? I'm just curious.

          2. Tacocat99 | | #12

            Attached the blower report. The home energy report from this company is very vague on the details. The guy who did the blower test just cracked open the door and felt how much air was pouring out. I had to make him turn the blower back on so I could identify the leakage points.

            Can't reply anymore. Think we reached the max chain length.

          3. DCContrarian | | #13

            OK, I read the report saying you're currently at 1800 CFM50 and they're proposing taking you to 1600 CFM50 at "an industry standard for healthy ventilation rates."

            You can convert CFM to ACH by multiplying by 60 and dividing by the volume of the house (square footage times ceiling height). Current code is anything under 3 ACH needs mechanical ventilation. For a house with 8' ceilings 1600 CFM would equate to 3ACH with 4,000 SF of floor area.

            You can confirm actual dimensions of your house but I don't think you need additional ventilation. I think your problem is pollutants, not lack of ventilation. They're best dealt with at the source by keeping them out.

          4. Tacocat99 | | #14

            I would be around 7 ach based on your estimates.

            Im going to filter out the supply vent and then start investigating the insulation in the roof and kneewalls to see if I can pinpoint this.

            Appreciate the help, its been very informative.

          5. Expert Member
            Zephyr7 | | #15

            I would check your returns too, not just the supply vents. Ductwork is notoriously leaky, and leaky returns can suck in problem air from all kinds of places (attics, crawlspaces, etc.).


          6. Tacocat99 | | #16

            The only room thats causing any obvious issues is the upstairs guest bedroom all the other rooms have been fine, except the upstairs master bedroom which seemed to clear up after sealing it off.

            Im going to seal up the supply vent with a hepa filter and run some purifiers and fans. If that doesn't have any effect Ill start crawling around the insulation looking for mold or maybe some dead animals.

            I have snaked the vents with a camera and they are extremely dusty, even the supply vents. There are wads of dust/debris sitting in them. If covering the vents seems to help I'll get the professional duct cleaning done (rotating smacky brush thing).

  4. Tacocat99 | | #4

    I think im overly sensitive to either the blown fiberglass, some chemical drom the fiberglass, or possibly my house is too tight and the air upstairs is going bad. Issues showed up a few weeks after the fiberglass was blown in.

    The fiberglass blown into my ceiling and into the floor of my kneewalls. Doesnt seem to bother other people but I get sick from prolonged exposure.

  5. DCContrarian | | #5

    What do you mean by air "going bad?"

    If find it hard to believe that an old Cape is going to be excessively tight, unless you've done heroic measures to tighten it.

    1. Tacocat99 | | #6

      There was roughly 6 inches insulation in the roof and the floor of the kneewall was sporadic (large gaps in some places). I had over 10 inches of blown insulation pumped into the roof and the floor of the kneewalls was filled out. Also had the area underneath the upper floors where it meets the kneewall floor sealed off to prevent hot air from running underneath the upper bedroom floors.

      Didnt have any air sealing done prior to this and the slope of the kneewalls is clogged with insulation. It used to be open. Insulator who installed the blown insulation said blocking it didnt matter since I didnt have soffits, different person I got quote from said air still leaks into the kneewalls through the gaps in the roof, so you still need to vent the slopes.

  6. DCContrarian | | #7

    I think you're barking up the wrong tree thinking that the insulation has made the house too tight. Fiberglass is not particularly air-tight. From your description it sounds like something in the fiberglass is leaking into the house.

    Ventilation of the attic is not an air quality issue, it's a longevity of the roof issue.

  7. DCContrarian | | #17

    Does your ductwork run in the attic? If it's leaking into that space it can create a pressure imbalance which would blow whatever's in the attic into your conditioned space.

    Also, have you tried any kind of air quality monitor? It would be nice to be some sort of testing other than seeing if you start hacking when you enter the room.

    1. Tacocat99 | | #19

      The duct runs into a kneewall of the guest bedroom, and a indicidual duct runs into the masterbedroom as well. Kneewall is separated into 3 sections. Two half sections where the stairwell splits, and one longer section that runs between the two upstairs bedrooms.

      Air quality monitor didnt seem to pick up much than elevated hc20 levels, averaging about 0.065 ppm, with a high of 0.1 ppm.

      Vent barrier didnt seem to help so waiting for my dad to come by and see if he can isolate the area where the smell is coming from. Bought max level 10 filter and taped it to wall with ac tape.

      Yesterday I taped up the attic hatch with garbage bag/ac tape to see if maybe its the paint they used on the new attic hatch of the guest bedroom.

  8. Deleted | | #18


  9. Tacocat99 | | #20

    My dad came by. We covered the floor with plastic and then ran a large air purifier for about 8 hours. The smell mostly vanished after this.

    I pulled up floor samples (tar paper, vat tile, dirt between tiles). The dust had no smell and the tar paper smelled like gasoline after scraping it off the floor (no smell prior to scrapping). The strange chalk/chemical odor is coming from the back of the vat tiles where it was peeled away from the adhesive.

    Going to peel off a few more of the loose tile to verify, but it does seem to be the old vat tiles. I may spend the next few days removing all the tiles upstairs and then cover the floor with carpetting.

    1. Tom Wheeler | | #21

      And you are sure those aren't asbestos?

      1. DCContrarian | | #23

        VAT=vinyl asbestos tile.

  10. Walter Ahlgrim | | #22

    How you are sure those tiles aren't asbestos?


    1. Tacocat99 | | #24

      They are abestos tiles, had them tested. I'm not sure why they are producing this odor. I haven't seen any similar posts around this issue. I wonder if the carpet cleaning solution got under the loose tiles and caused some reaction.

      Top of tile is perfectly fine. Bottom is producing the smell. Never noticed this smell until I removed the carpeting back in september. The smell showed up shortly after and got stronger over several months.

      1. DCContrarian | | #25

        Asbestos tiles were usually put down with a mastic that was like black tar and pretty nasty. Paint thinner takes it up usually.

        1. Tacocat99 | | #27

          If the tarpaper doesnt smell would it be an issue to just lay the carpet/padding on top?

          There is a lot of exposed tar paper from missing tiles but it only smelled after I scrapped it up off the floor/sprayed with water.

          1. DCContrarian | | #32

            I have never regretted cleaning up completely. It sounds like a pretty small area, it's probably not that much work to clean the whole room down to the subfloor.

            Is the tarpaper over or under the tile?

          2. Tacocat99 | | #35

            Its under the tile and attached to a plywood subfloor. It ripped up in strips so a paint scrapper may work fine, then chemicals for any residue leftovers.

            It looked like sticky construction paper scraps when it was pulled up. The edges had that fuzzy paper look.

  11. Walter Ahlgrim | | #26

    I say spend the money now and have the asbestos removed as soon as possible.

    Unless you lie on the disclosure form the house is all but unsalable as it stands. The price of asbestos removal will never be lower than it is today and maybe the smell will go with it.

    1. Tacocat99 | | #28

      I will try to remove the tiles myself, the tar paper doesn't have abestos. My state has a how to guide for homeowners for removing these things.

      I'm not planning on selling the house any time soon and almost all the houses in my area were built in the 1960's and have obvious vat tiles in the basements and abestos siding. Don't think it will affect pricing too much in my particular situation.

  12. DCContrarian | | #29

    I have done asbestos tile removal as a homeowner and it's not that bad. The one thing I would advise is to have the disposal of the tile lined up before removing it. In DC you can take it to household hazardous waste.

    In pre-pandemic times you could buy a kit on Amazon for DIY asbestos removal that was a Tyvek suit, N95 respirator, gloves and booties. I triple bagged the tile in contractor bags and threw the PPE in the last bag. While working I kept a spray bottle of soapy water handy and sprayed each tile before removing to try and capture the dust.

    1. Tacocat99 | | #31

      Im going to grab that stuff tomorrow and make it my project for the week since Im off the next 5 days. Going to peel off some of the fully laminated tiles first and do a sniff test after soaking them down. Think the loose tiles might have had a bad reaction to the carpet cleaner before I removed the carpet, or the dawn dish soap mop water I casually tossed on the floor.

      Would like to figure out why the main bedroom is fine but the guest bedroom tiles are acting weird for my own sanity. Assuming the chemical cleaners had a bad reaction to all the loose tiles in the guest bedroom since the main bedroom tiles are all still strongly bonded to the floor and smell fine.

    2. Tacocat99 | | #38

      Any tips for removal? Most of the tiles in the center popped off easily but the outside edges are fully laminated to the floor. Currently using putty knife+hammer, and a heat gun when the adhesive is stuck to the tile.

      I saw some guides say that soaking the floor with water at least 2 hours prior can help loosen tiles, some even mention a day. Not sure if this would apply to a wooden subfloor.

      1. Tacocat99 | | #39

        Nevermind. Soaked the floor overnight and all the tiles popped off easy. Only took about 2 hours to do the main bedroom vs the 5 for the guest. Tiles in bags, inside boxes, and going into the shed while I wait for my trash authorization to be approved. I was unable to remove about 10 sq feet of tiles since one of the closets was built after the fact, above the tiles. I was going to try and remove it but the framing was complicated and a couple of the walls were drywall rather than the wood paneling like I originally assumed. I did find a working metal outlet behind one of the wood panels. I razor cut the tiles to the wall and plan on chalking the edges and then using sealing foam on the inside walls to cover it up.

        After the room dries im going to hepa vac the floors and walls, followed by moping the walls. The subfloor is this really flimsy 1/8 plywood so im going to tear that out instead of trying to remove the tar paper. It was deteriorating at the edges from my carpet shampoo a couple months ago and started to rot out even more after soaking the floor. Looks like massive deck boards underneath.

        About 2 days ago I had a violet reaction after carrying down my linen and my matress, so apparently shampooing my carpet had no point other than making my life hell for the last 3 months from causing all the hidden vat tiles to delaminate and plage my room. So learned Im not allergic to my cats, probably just extremely sensitive to laundry detergent.

        Thanks for all the help, I really appreciate it. If anything I mentioned above seems like a dumb idea please let me know. I'm kinda dumb about home repairs.

  13. Deleted | | #30


  14. Expert Member
    Zephyr7 | | #33

    It's entirely possible some cleaning solvent reacted with the old mastic and that's what is causing your problem. I have had problems specifically with Formula 409 cleaner causing issues with some types of vinyl -- not smells, but chemically altering the vinyl so that it is permanently tacky. My point is that the reaction may be permanent, so if it's its bothering you, removal of the problematic material is the only sure solution.

    Note that the tile adhesive often has asbestos in it, not just the tile. Keep that in mind while working. You're usually alowed to just encapsulate the asbestos, but removal is a better long term option if you can do it.

    BTW, try a trick from the telecom world: use some shaving cream to keep the dust down. We do this in datacenters when drilling holes in floor tiles (which are concrete panels wrapped in steel). The shaving cream traps all the dust, even shards from the hole saw, and keeps things clean. We have to be very careful to keep dust down in these facilities, which are essentially low end clean rooms. Keep regular stuff moist, but use the shaving cream on things that are more "energetic" -- stuff you have to snap, drill, break off, or chisel away. The shaving cream is better at trapping stuff than water or soap solution.


    1. Tacocat99 | | #34

      Ill buy some shaving creme for the tact strips I need to yank out. The testing I did indicated the tar paper was abestos free and it was just in the tiles.

      Both the tiles and black mastic downstairs have abestos but I plan on encapsulating that since it hasnt caused any strange odor issues.

  15. Nick Defabrizio | | #36

    These types of situations can be difficult to remedy when different materials/chemicals mix or offgas to create noxious situations. And once you are sensitized to it, it takes very little to cause a reaction.

    Years ago I sprayed sporocedin mold killer (phenol) on masonry and then a short time later spot sprayed with a mold bleach based solution. This caused a reaction that required us to evacuate the house. Years later, after a dozen scrubbings, sealing w paint and constant ventilation I still got an allergic reaction after stepping in that room. Others thought I was nuts! Finally I personally tore out the block and replaced the wall. I can still smell a little but no longer get sick. Even innocuous chemicals can cause bad reactions when they mix, and they are rarely tested in such mixed situations. This is why I advocate to reduce the use of many synthetic products in homes, particularly tight homes.

  16. Deleted | | #37


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