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Musings of an Energy Nerd

Smelly Fiberglass Batts

The glue used in Owens Corning EcoTouch batts has generated a few odor complaints

Image 1 of 3
The glue is bio-based, but not necessarily odor-free. Owens Corning has received enough complaints about the smell of EcoTouch fiberglass batts that the company has released a statement addressing the product’s distinctive “aroma.”
Image Credit: Owens Corning
The glue is bio-based, but not necessarily odor-free. Owens Corning has received enough complaints about the smell of EcoTouch fiberglass batts that the company has released a statement addressing the product’s distinctive “aroma.”
Image Credit: Owens Corning
Owens Corning has been sending this letter to contractors complaining that EcoTouch fiberglass batts have a strong odor. According to Karyn, this roll passes the smell test.
Image Credit: Martin Holladay

I first heard about the problem of smelly fiberglass batts from Michael Maines, a builder and GBA blogger who lives in Portland, Maine. Maines sent me an e-mail saying, “The latest problem with fiberglass insulation is that it smells like burnt brownies!”

I’ve collected a half dozen reports of this problem, all centering on EcoTouch brand fiberglass batts manufactured by Owens Corning. Two years ago, the company switched from a formaldehyde-based glue (or binder) to a new glue described as a “bio-based” binder.

The batts smell like burnt cookies

Descriptions of the problematic odor vary. The odor has been compared to burnt cookies, burnt cotton candy, and burnt glue.

I interviewed two contractors who have had this problem. The first person I interviewed was an insulation contractor who was very forthcoming, but who prefers to remain anonymous. “It smells like something you burned in the oven,” my informant told me. “It’s a sugary smell — not a bad smell. The smell usually goes away if you air it out. But in this case, it just didn’t go away. They waited for the smell to go away before they put up the Sheetrock, but the smell never went away.”

At first, the contractor assumed that the smell came from another product. “It was a flash-and-batt job, and when I heard about the smell, I was worried that the problem was the spray foam,” he told me. “But it turns out that the spray foam didn’t smell. They were smelling the fiberglass. The Owens Corning rep came. He said, ‘We will pay to take it out and have it replaced.’ The owner didn’t want any more Owens Corning insulation, so after the smelly batts were removed, they put in Roxul. I know that this is not the first time it has happened. In one case they had to take down some Sheetrock. This whole job was a headache for me. I had to spend 5 or 6 hours with the owner, hand-holding, and I don’t want to deal with it again.”

The next person I interviewed was Peter Rice, a builder and designer in Maine. He hired an insulation company to install 10-inch-thick Owens Corning batts in the basement ceiling of a new home. On January 22, Rice told me, “The smell is quite noticeable.” Two weeks later, I called Rice again, and he told me, “The smell has not gone away. I’m going to ask to have the insulation removed and have it re-done. It’s been at least three weeks since it was installed. If it hasn’t outgassed by now, I don’t know when it will.”

Headaches and other symptoms

A little web surfing turned up a few similar complaints. A post about EcoTouch insulation on the Fine Homebuilding website by someone using the screen name Rabbitdog99 included this report: “I’ve had this in my attic for about 2 months and the odor has permeated into my living space. It gives me headaches, makes my eyes water, gives me a funny taste in my mouth. I will be having it removed. Before using this, I would recommend that you go to the local home improvement store that sells it and sit in their insulation aisle for a while. If you don’t like the odor, or you get a headache, or your eyes start watering, don’t buy it.”

An anonymous post on the Home Depot website reports, “They changed their glue and it SMELLS HORRENDOUS. … This new EcoTouch Pure Fiber Technology insulation is HORRENDOUS! We tried to insulate a wall with it last night, and right out of the bag it has a HORRENDOUS ODOR — smells like burnt glue, burnt chemicals, or burnt cotton candy, like a burning sweet smell that is overpowering — very, very strong. My husband used 3 batts, thinking the smell would dissipate. NO, it DOES NOT! … We had to rip out the three batts that he had done and move all of the unused insulation to the garage. It was so strong of a smell that it started to make my throat close up on the right side. No, I am not being dramatic. Whatever they have done, it is horrible, and I think they know it.”

Getting rid of the formaldehyde

Owens Corning switched the glue used in their fiberglass batts for the best of reasons. The new product was developed to meet the needs of those asking for a formaldehyde-free product.

According to Frank O’Brien-Bernini, an Owens Corning vice president and chief sustainability officer, “The new binder was introduced a couple of years ago. We have totally converted our entire product line to this product.”

O’Brien-Bernini admits that you can smell the binder when you open a fresh bag of insulation. He reminded me that old-fashioned formaldehyde-based glues also have an odor — one that is sometimes compared to cat urine. “Our prior insulation also had an odor to it that was far less pleasant,” O’Brien-Bernini said. “When we started developing this product, we did an aroma test. Most people said the new aroma is far preferable to the aroma of the prior product.”

In response to smell complaints, Owens Corning releases a statement

Owens Corning has been receiving enough complaints about the fiberglass batt odor that they have released a statement on the issue (see Image #2, below).

The statement notes, “Recently, we have been making our insulation products with a bio-based binder ingredient. This use of natural ingredients supports OC’s commitment to making our products and our production facilities more sustainable. The use of natural ingredients can sometimes cause different scents when installing the product. This scent is very similar to the smell of baked goods. This scent is normal for bio-based materials, and will dissipate after a few days. … Owens Corning stands behind its products and will cover the costs of replacing any products that do not meet customer needs.”

Only 31 complaints?

During the manufacturing process, fiberglass batts are cured in an oven. The burned-cookie smell is blamed on overbaking. According to O’Brien-Bernini, only a small percentage of batts have a lingering odor. “Just like if you bake cookies, if you overbake them you can get a baked cookie smell that can be quite a durable smell that sticks around for a long time,” he told me. “There were over a million installations of this product last year, and we have had only 31 complaints. That’s an extremely small number. But when it is installed in a closed building, and when the product has been overcured and overcooked, it has an odor that can be disturbing. In general, it clears out when it is aired out a little bit.”

Environmental conditions at the factory can affect how long the product needs to be baked. “When it comes to overbaking — we usually term it ‘overcuring’ — there are a number of reasons why that can happen,” O’Brien-Bernini told me. “One analogy would be, if you are baking cookies on a moister day than the last time you baked them, you might have to adjust the baking time. There are all kinds of environmental variables that can impact the manufacturing process.”

What’s the binder made of?

Owens Corning representatives were reluctant to tell me what their new binder is made of. On the Owens Corning website, the glue is described as a “bio-based binder.”

When asked what the binder was made of, O’Brien-Bernini was vague. “We don’t want to say what plants the binder is made from, but it’s made from carbohydrates,” he said. “It would be like something you bake in your oven.”

According to the company’s Environmental Product Declaration for EcoTouch insulation, the binder contains carbohydrate polyol, polycarboxlic acid, a cure accelerator, a surfactant, vegetable oil silane, and pink colorant.

Maltodextrin and modified starch

I gleaned more information when I discovered the Owens Corning patent application for their binder. The patent application notes, “The present invention relates generally to fibrous insulation and non-woven mats, and more particularly, to a binder for use in manufacturing fibrous mineral insulation such as fiberglass and non-woven mats that is bio-based, contains no added formaldehyde, is crosslinked through phosphate di-ester bonds, and is environmentally friendly.”

The Owens Corning patent covers an insulation binder “comprising a polyol and a phosphorus crosslinking agent derived from a phosphonic or phosphoric acid, salt, ester or anhydride to form crosslinked phosphodiester linkages. The polyol is polyvalent, but may be monomeric or preferably polymeric; and may be synthetic or natural in origin. Carbohydrate polysaccharides are exemplary polyols, including water-soluble polysaccharides such as dextrin, maltodextrin, starch, modified starch, etc.”

There are strong hints in the patent application that the basic raw ingredient for the binder is maltodextrin. The patent application notes, “It is yet another advantage of the present invention that maltodextrin is readily available and is low in cost. … It is a feature of the present invention that the maltodextrin can form an aqueous mixture that can be applied by conventional binder applicators, including spray applicators.”

Maltodextrin is a white powder that is added to sodas, candy, canned fruit, cereals, and instant pudding. Maltodextrin can be manufactured from many grains; in the U.S., maltodextrin is made from corn.

Just because the Owens Corning binder is probably made from maltodextrin, however, doesn’t mean you would want to eat it. The patent application also notes, “The binder composition … may also include one or more members selected from a catalyst, a coupling agent, a process aid, a crosslinking density enhancer, an extender, a moisture resistant agent, a dedusting oil, a colorant, a corrosion inhibitor, a surfactant, and a pH adjuster.”

In other words, the binder is not exactly (in O’Brien-Bernini’s words) “like something you bake in your oven.”

“We love this binder”

Owens Corning has no plans to reformulate its fiberglass glue. When I asked O’Brien-Bernini whether the product would be reformulated, he answered, “No. We love this binder. We love the material. It is a terrific product in terms of its environmental attributes. It has a high recycled content, and it’s a bio-based material. It’s exactly what we are after. We are committed to this. We will resolve this aroma thing. I’ll remind you that the traditional fiberglass product was not without odor issues.”

According to O’Brien-Bernini, the odor problems will be licked by improving the manufacturing process to avoid overcuring the batts. “Any customer product complaint concerns us,” he told me. “We are working to drive this to zero defects. We are continuing to work on this. We feel like we are making strong progress against this.”

What if your batts are smelly?

In most cases, the odor associated with EcoTouch batts goes away in a day or two.

I asked O’Brien-Bernini what he would tell a builder who contacted Owens Corning with an odor complaint. He said, “If there is an issue with an odor, we might say, ‘Let us know if you still smell something tomorrow.’”

This is not a simple story with a clear moral

Unlike some of my blogs — for example, my story about the “insulating paint” salesman who insulated his own house with useless paint — this is not a morality tale.

Owens Corning is to be commended for developing a formaldehyde-free binder for their fiberglass batts. According to all evidence, most EcoTouch batts do not have an offensive odor. (After I visited the fiberglass aisle at a local Home Depot and put my nose close to EcoTouch fibers in several packages, I concluded that the odor of the batts was extremely faint.)

In the rare cases when smelly batts have been shipped from the factory and installed in homes, Owens Corning has reacted appropriately. The company has taken responsibility for the problem and satisfied their customers. The company’s reaction is in stark contrast to reports of stonewalling by manufacturers of smelly spray foam insulation.

If Owens Corning is able to determine why their ovens occasionally “overbake” their batts, and can come up with improvements to their manufacturing methods, this problem may go away.

Martin Holladay’s previous blog: “A Chat With Henry Gifford.”

Click here to follow Martin Holladay on Twitter.


  1. Hein Bloed | | #1

    There are mineral based
    There are mineral based binders used for the very same purpose.

    No need for formaldehyde or "bio".

    Keep in mind what is supposed to rot (organic material) will rot. Be it oil or resin.

  2. Florian Lorenz | | #2

    Sugar in the walls?
    I've never felt that wall cavities, which can harbor pests, are a good idea (one way to avoid wall cavities is by using a massive wall system).
    Installing insulation that uses a binder based on a sweetener (e.g. for beer) into wall cavities amounts to building a bed & breakfast for roaches and other insects. Whatever the terminator, who will inevitably have to be called, sprays to get a handle on bug city will likely be no less harmful than the non "bio" based binder initially used.
    Maybe it really is time to stop using fiberglass batts (as others have suggested because of the difficulty of installing them properly).

  3. User avater GBA Editor
    Rob Wotzak | | #3

    No complaints here
    I recently installed quite a few EcoTouch batts in my home (meticulously and with a tightly air-sealed layer of XPS behind them) , and you're right--it did smell like burnt cotton candy! Luckily, the smell went away as soon as I covered it up with drywall. Let's hope the lingering smell others are seeing is an isolated problem that shows up less frequently as quality control is improved. I imagine it's in Owens Corning's best interest to make things right.

  4. greenhouse437 | | #4

    Homeowner testing materials in advance
    "...I would recommend that you go to the local home improvement store that sells it and sit in their insulation isle for a while. If you don’t like the odor, or you get a headache, or your eyes start watering, don’t buy it.”

    That's actually a great idea for spray foam as well if there was a place homeowners could go to be around large blocks of newly installed foam to test any allergic or other negative reactions to it before they have it installed in their house.

  5. User avater
    John Semmelhack | | #5

    The pink stuff is pretty rare
    The pink stuff is pretty rare in my area, but on each of the 4-5 jobs (large multi-family apartment buildings) in the past two years where I've seen Owens Corning fiberglass batts installed, it's smelled terrible...burnt coffee-flavored cotton candy sounds about right. I cringe each time I go into a building and see pink.

  6. John Brooks | | #6

    Smelly Batt
    Smelly Batt, Smelly Batt what are they feeding you?
    Smelly Batt, Smelly Batt it's not your fault.

  7. Steven McCarthy | | #7

    owens-corning eco batts
    I recently tried some OC r-19. When I rolled out the product to cut it, it lay there like r-11. I let some lay over night and in the morning it still looked like R-11. Then when I cut it, the asphalt like adhesive that bonds the kraft paper to the fiberglass stuck to my knife blade and the blade stopped cutting. It was always below 20 degrees F during this work and maybe that caused the problem but I had no problem with the Knauf insulation. I think the Knauf R-19 would actually fill a 2 x 8 cavity. I will not use Owens-Corning insulation.

  8. Gregory Worrel | | #8

    googled to find this post
    I am a regular reader here, but it was a google search that led me to this article. My search was "bagged fiberglass insulation basement smells." I have been trying to determine the source of the strange odor in my basement for several weeks. I had two bags of R19 ecotouch insulation sitting in my basement that I was planning to stuff up in my open joists. It was for acoustic purposes in my home theater area rather than for its insulation value.

    It was only yesterday that I determined that the smell was coming from the fiberglass. It is a strange smell that I first thought was coming from the dehumidifier which was next to the batts. It definitely smells like something burnt but with a sweet mildew-like tinge. It is not subtle or easy to dismiss. But not headache inducing or anything like that, at least for me. I never noticed the smell when I first put it down in the basement about 10 months ago. It was only in the recent summer weather that the odor became noticeable. This calls into question the idea that it is merely a manufacturing issue that goes away in time.

    Of course, the insulation was still sitting in the bags on the cement slab basement floor. But the relative humidity never gets above 55 with the dehumidifier and I don't think the temperature ever got above 80.

    I've already used most of one bag of 3.5" r-11 Sound Attenuation Batts doubled-up in some of the joists. What I am doing is creating a full-ceiling "bass trap." The plan is to staple landscape fabric to the underside of the joists and then cover with some stretched black fabric. So it will only be enclosed in air-permeable fabric. That will either allow it plenty of opportunity to air out, or blanket me in the smell. I will leave up what I've used so far but the unopened bags are going back. If the smell persists it is not a huge job to take down what I have up so far.

    Any word on smells from other formaldehyde-free brands of fiberglass? Roxul is an option but much more expensive.

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