I did an audit last week of a home built in 1992.  The attic insulation looks like a coarse, dark, insulation cellulose.  I haven't run across this type yet and am not sure of the exact name or R-value.  Any help would be appreciated.  See photo.

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Hey, Rob


Based on the photograph that almost looks more like Rockwool than cellulose -- does it have a more irritating fiberglass feel to it?  If so, I'd definitely say rock wool.


Hope that helps,



Thanks for the reply.  It really doesn't have an irritating feel.  Rockwool is pretty consistant in color and texture.  This looks like a recycled material.  Little varied in color and texture.  Also looks like little pieces of cardboard in it.



This appears to be a cellulose type insulation. Recently we have seen more manufactures use recycled cardboard in their manufacturing process because it is less costly, and abundant for them to purchase. It could very well be one of the first cuts at using the cardboard in lieu of newsprint to produce the cellulose insulation.


I hope this is helpful.



Call the DEA!

If you don't see newsprint (letters) and you don't smell iron, it coudl be a blown fiberglass that was made by chopping up batts. 

Rockwool will usually give you an iron taste in your throat even through a mask. 

I haven't heard of the cardboard cellulose stuff before. 

Some cellulose uses ammonia sulfate as a fire retardant and if you get it wet it off gasses ammonia.  Try dampening a little and see what you smell.  Some cellulose uses Boric Acid as fire retardant, and that will not off gas ammonia, so this test is not difnitive, but it is easy & cheap. 

There are cotton batts and cotton blown insulation products in the market, but they are usually denim products, and blue in color.  maybe someone is cutting up Carharts? 

Try setting some on a fire proof surface (dirt) and hitting it with a plumbers torch,  if it melts quick, it is likely fiberglass.  if it just laughs at you it is probably rock wool. if it chars it is probably cellulose.  I am not sure what a cotton batt will do in fire. 

Pat:  I wasn't aware rock wool was a good flame retardent.  Why is that?  Thanks.

i wouldn't call it a flame 'retardant' it is basically spun out iron slag, so it has a melt temp up around 4500 degrees F, and it will not burn.  it also has a very high density, so it is frequently used in commercial work in partitions for sound attenuation. 


thermafiber is a trade name, there may be others.  bear hair is a vernacular name.    


I have seen cellulose go from grey to brown in color with prolonged exposure to light.  i think this is the same as newspaper that browns over time with exposure to light.   


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