Cellulose building insulation examined under the microscope can point out its key identifying properties such as plant fibers and paper fragments.

This article series illustrates and describes the properties of cellulose building insulation materials.

Cellulose Insulation Under the Microscope

Modern cellulose building insulation is basically chopped newsprint, usually treated with a fire retardant chemical. As you can see in the photos above, it looks like fluffy gray papery material. The lighter colored chips may be wood fragments that have been added to this mix.

Definition of Cellulose Insulation or LFC: Loose-fill cellulose insulation (LFCI) is a fibre or fibrous or granulated insulation material derived from paper, paper stock and/or wood, leaf or stalk strings with or without binders. - Materials for Energy Efficiency and Thermal Comfort in Buildings, 2010 sciencedirect.com/science/article/pii/B9781845695262500098

Photos above and below: cellulose insulation in the attic of a 1975 home in Tuolumne County, California, courtesy of an InspectApedia reader K who provided samples for examination in our forensic microscopy lab in 2023.

[Click to enlarge any image]

On 2023-06-23 by (mod) - Cellulose Insulation: newsprint + wood/plant fibers under the microscope

Here we include photographs of the "mystery insulation" discussed earlier this year. This looks to us like a cellulose building insulation that combines shredded paper or newsprint - classic "cellulose insulation" combined with a high percentage plant fibers, possibly shredded wood.

Above, in the sample bag provided by our reader, the insulating material appears densely packed, combining paper fragments with another dense wooly material. Packed it looks tan-gray in color.

Watch out: note to readers: don't send a large volume of unknown material like this to your test lab. It's unnecessary.

Even a single cubic inch of representative material is plenty.

Large volumes are more difficult to handle and may be unsafe. Some forensic microscopy labs will simply throw away such samples or may charge extra for handling them as more trouble is involved in order to be safe.

Below, opened outside the building, we see that the insulation is gray in color and resembles classic cellulose insulation except for its unidentified filler.

Below we show the beginning of slide preparation for examination of this sample - first under the stereo microscope, then at high magnification under a forensic microscope.

At right on the microscope slide you can see an unambiguous example of shredded paper.

Below we show that same paper fragment extracted from the cellulose insulation and examined under the stereo microscope at about 100x magnification.

Below we see this insulating material at 1200x magnification first in transmitted light ...

and below, in polarized light, showing that in addition to paper fragments we have a high percentage of shredded plant fibers.

And finally, just below we see at the center of the slide a wood fragment with pores (center of photo) characteristic of softwood, possibly fir or pine.

Similar insulation is examined

at

• BALSAM WOOL BATT INSULATION
• CELLULOSE, WOOD, PLANT Identification by Microscope where we illustrate similar wood pore details in a sample of eucalyptus wood under the microscope.
• FIBER & HAIR IDENTIFICATION
• WOOD FIBRE INSULATING PANELS

On 2023-05-08 by KK

Thanks so much for helping me out with identifying this mystery insulation at our 1975 home in Tuolumne County, California.

Let me know the address and I'll send in a sample for you to check out under the microscope. - KK

[Done as illustrated above - Ed.]

Cellulose Insulation Details Under a Magnifying Glass

As we illustrate below, even without a forensic microscope, a simple hand held lens can help you identify key features characteristic of cellulose insulation.

In each of these photos you can clearly see bits of newsprint. Chopped, recycled newspaper is a common ingredient in cellulose building insulation as it makes use of recycled materials.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-07-21 by inspectapedia.com.moderator (mod) - blown-in cellulose wall insulation might be "dense-pack" ... or not.

@Chris H,

Thank you Chris, that's very generous;

You have contributed by asking a question and posting a photo in a public forum where it may help other readers;

Eventually we migrate these Q&As up into the website article or onto its FAQs page.

So in essence you've supported the website by contributing content to it. That's invaluable to us and to other readers.

Indeed we have worked hard for over twenty years to make information at InspectAPedia.com accurate, in-depth, and without bias, so I am of course very grateful when a reader reports that our website has been useful.

To that end, I would much appreciate hearing any comments, critique, suggestions, or further questions that you may have about any of our diagnosis/repair articles.

We are dedicated to making our information as accurate, complete, useful, and unbiased as possible: we very much welcome critique, questions, or content suggestions. Working together and exchanging information makes us better informed than any individual can be working alone.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.

Content contributors, even if it's just a small correction, are cited, quoted, and linked-to from the appropriate additional web pages and articles - which benefits us both. A brief summary about InspectAPedia.com can be read at https://inspectapedia.com/Admin/About_InspectApedia.php

Best wishes, and thank you again

On 2021-07-21 by Chris H

@inspectapedia.com.moderator, really appreciate the quick response! How can I donate to your site?

On 2021-07-21 by inspectapedia.com.moderator (mod)

@Chris H,

You're on the right page: the insulation in your photo is cellulose, as we see in this closer-look.

I'm not sure we'd call what we see "dense pack" - it doesn't look dense in that location;

Blowing in insulation into any building will have mixed results as the installers encounter blocks to the insulation insertion that they can't see - such as fire blocking between wall studs, diagonal bracing, or even wiring and plumbing routed in walls.

You're on the right page: the insulation in your photo is cellulose, as we see in this closer look.

If you want to be thorough, in cold weather have a detailed thermal inspection to identify spots of heat loss.

On 2021-07-21 by Chris H

I purchased a home that is going through renovations and have noticed that it has the insulation depicted near the light switch in the attached photo, blown into every wall.

After walking around the outside of the house, I can see what looks like ~2" plugs in the exterior wall every foot or so. Is this dense pack cellulose? It's packed in the wall pretty tightly.

The home was originally built in 1906 and is in the US. I did remove a piece and it chars pretty quickly with a standard bic lighter. Really appreciate the guidance.

...

Continue reading at CELLULOSE INSULATION FIRE RESISTANCE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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Suggested citation for this web page

CELLULOSE INSULATION UNDER the MICROSCOPE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING INSULATION

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