White substance on attic insulation

I’m not sure what this white powdery stuff is but it was found only around the flue for the chimney. It was kind of brittle but broke apart fairly easy. Any body ever come across this?

No, I have not seen this before, But it looks like pic 3 has a moisture pattern to it, maybe from a previous roof leak and chemicals leaching out of the cellulose? let’s see what the others say.

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That was my first thought too, Scott. I haven’t seen that before either.

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I would bet on leaching Chemicals, but not sure I did google it and it does mention glucose in the cellulose, But I did not read the entire article.

Boride? …

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Boric acid from chemicals in the insulation being wet and then drying out. Found out last night. Another inspector sent me some pictures of the exact same thing in a few houses he’s had with cellulose getting wet and drying out.


That is what I thought!

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Cellulose insulation is treated with boric acid, to retard the spread of fire. Boric acid releases water to help extinguish the fire.


Don’t leak it, Junior :smiley: It’s loaded with that goodness up to 1/5 by weight. Throw in borate and al sulfate into the mix.

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OK, guys, figure this one out, How did the insulation get wet? :nerd_face: maybe it is not what you think.

In a world of infinite possibilities, anything is possible.

You may not find the answer in a book or on google, only real-life experience may figure this one out. :nerd_face:

Roof decking not being butted tight?

Santa after too much coffee?


It doesn’t snow down here .

Not supposed to be tight.


Condensation from an insufficient chimney flue? Maybe if this is the same attic Jacob had with the single wall flue?

Here is another possibility. The Cellulose I see looks like a type with a glue added (This looks somewhat lumpy and not the normal loose dusty consistency of standard cellulose) This was blown in with water (barely damp). The point of it was to eliminate the dust and also the moisture activated the glue and the cellulose would (tend) to not settle (as much) and therefor would retain the higher R-value of the installed depth not necessarily what you would have after settling. It was also known as “Low Density Cellulose”, Less Material (bag count) but a higher R-value. If you put a little too much moisture with it you would see the Boric Acid as well as the glue ( a Starch) leach out of the material. The other possibility is that the installer may have blown what was actually waist from a previous Spray Applied wall job. (A trick of the trade to use up what was troweled of the walls and would also cut the dust.)

Or it could just be from condensation dropping from the roof. In one of the pictures (below) you see a line directly below the rafter.


200w (4)

Appears to be cellulose insulation saturation compaction. Was the top of the blanket fluffy or have a crusty shell?
Cellulose is treat with boric acid, a white powder, and fire retardant chemicals. The boric acid deters pests and insects.
Could this be leached out chemicals due to aggressive saturation events?

Was the chimney flashed properly? Water had to enter the attic somehow.

I concur to have the insulation tested by a qualified professional.