Cellulose insulation fire test 1 © Daniel FriedmanCellulose Building Insulation Fire Resistance Informal Test Report

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Fire resistance of cellulose insulation:

This article illustrates and describes the fire resistant properties of cellulose building insulation materials. This document assists building buyers, owners or inspectors who need to identify building insulation materials and also people who need to recognize both asbestos materials (or probable-asbestos) in buildings as well as materials unlikely to contain asbestos - all by simple visual inspection.

In these articles we provide photographs and descriptive text various kinds of building insulation along with description of the characteristics of each material.

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What is the Fire Resistance of Fire-Retardant Treated Cellulose Building Insulation?

Cellulose Fire Test No. - Home Depot sample

Cellulose insulation fire test 1 © Daniel Friedman Cellulose insulation fire test 2 © Daniel Friedman

Anyone looking closely at cellulose insulation can often see recognizable bits of newsprint in this chopped fibrous gray insulating material. Walking through a major home improvement center recently we picked up some loose fill cellulose insulation that fell out of a package of new cellulose insulation being purchased by a client. Our photos (above) show what it looked like when we put a little of this insulation on a ceramic dish in the sink in our forensic lab.

We were curious to know how fire resistant this random sample of new cellulose insulation would be in response to a very simple test.

Watch out: DO NOT TRY THIS IN YOUR HOME - you could start a fire.

Cellulose insulation fire test 1 © Daniel Friedman Cellulose insulation fire test 1 © Daniel Friedman

Using an ordinary butane cigarette lighter and in safe lab conditions over a sink with water and fire extinguishers at ready (Photo above left) we heated the cellulose insulation for 60 seconds in direct flame. The temperature to which we exposed our cellulose insulation sample was perhaps hotter than the insulation might experience if it were in contact with a light bulb, but possibly no hotter than if it were in contact with shorting electrical wiring or an overheating aluminum branch wiring circuit connection.

There was a very brief tiny flame as a piece of plastic-coated newsprint in the insulation caught fire. The plastic on this newsprint probably resisted treatment by the fire retardant chemical and that fragment burned easily - and momentarily. Other than that small fragment, the insulation charred, smoked, but would not support combustion.

Cellulose building insulation manufacturers should avoid accepting plastic or water-resistant coated papers into their insulation manufacturing process, or at least be sure that water resistant paper is present only at such trivial quantities (as indeed it was in our test sample) that the cellulose insulation will not support combustion after treatment.

Cellulose Insulation Fire Test No. 2, National Fiber Corp. (Cel-Pak & Nu-Wool)

Deborah Falkow, owner of MetroNY Insulation, provided us with a sample of cellulose insulation produced by National Fiber Corp. (Cel-Pak & Nu-Wool) for further testing in 2010. According Ms. Falkow, Cel-Pak and Nu-Wool have an 83% recycled content, primarily over-issue newsprint and other ground wood paper sources. The paper is fully fiberized (reduced to cellulose fiber) and infused with borate, a naturally occurring mineral. Borate gives cellulose [insulation] a Class A fire rating."

Cellulose insulation fire test © Daniel Friedman Cellulose insulation fire test 2 © Daniel Friedman

Watch out: DO NOT TRY THIS IN YOUR HOME - you could start a fire.

In our test lab we observed:

Microscopic Comparison of Typical vs. "Fully Fiberized" Cellulose Building Insulation

Our photos compare sample of cellulose insulation collected from a Home Depot brand (below left) and National Fiber's "fully fiberized" cellulose insulation (below right). As you can see, fragments of newsprint remain recognizable in both samples (notice the "Y" and other letters at left and the "e" character at right.

But in our photos below, both taken at similar levels of magnification in the stereo microscope, the National Fiber Corp. cellulose was visibly much more fragmented into individual cellulose fibers. The number of discernable paper fragments per cubic centimeter was notably fewer than in the Home Depot sample.

Cellulose insulation fire test © Daniel Friedman Cellulose insulation fire test 2 © Daniel Friedman

Notice: although our lab and the author (DF) are trained in forensic microscopy, our forensic lab has no certification for fire testing or fire rating of materials. Judgment of degree of fiberization and remaining paper fragments, while obvious on direct physical examination, was nonetheless subjective because no quantitative fiber count nor count of particles by size was attempted.

In sum, our amateur "fire tests" demonstrated in two cases with two different cellulose insulation products (1. Home Depot brand, 2. National Fiber Corp. (Cel-Pak & Nu-Wool)) that our samples of new cellulose insulation would not support combustion. But take a look at NAIMA's findings just below.

NAIMA's Fire Resistance Testing of Cellulose Insulation

According to the North American Insulation Manufacturers' Association, the chemical treatment of cellulose insulation does not make cellulose insulation "non-combustible" nor does it prevent smoldering type ignition of the material. Cellulose insulation is tested for fire resistance using ASTM C-739.

It has also long been our opinion that the chemical retardant treatment, however effective it may be, may deteriorate over time or especially if the insulation is exposed to water - say from a roof or wall leak. NAIMA has a similar view.

In sum according to NAIMA "fire retardant treated cellulose insulation" is not necessarily completely fireproof [PDF]

But then, a chief competitor of cellulose insulation, fiberglass insulation products are also not exactly fireproof - the kraft paper to which lots of fiberglass insulation is affixed to ease installation (and provide somewhat of a vapor retarder), for example can be set afire and it is possible that some of the binder resins may support combustion.

ASTM C-665 is the test standard for fire resistance of mineral fiber batts and rolls, and ASTM C-764 is the fire test standard for loose fill mineral insulation.

In industry speak, fiberglass is considered a mineral fiber along with rock wool or mineral wool insulations.

Manufacturers of Cellulose Insulation

Some of the cellulose manufacturers registered by NIST include


Continue reading at CELLULOSE INSULATION FIRE RESISTANCE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



Or see INSULATION R-VALUES & PROPERTIES for an extensive table describing the properties of different insulating materials used in buildings.

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