What is the white insulation?

I’m brand new to the industry and I bought this house a couple of months ago. While I go through the courses, I’m fixing up my house in the process.

The photo shows the insulation in my attic. I know the yellow is fiberglass but I’m kind of stumped on the white insulation.

From the course material, I’ve inferred that the white insulation is probably fiberglass or cellulose. It’s almost looks and feels papery though.

What do the professionals think?

They are both mineral wool.


Do you mind if I ask, how can you tell from a photo?

When I conduct a Google image search of the different types of insulations, they all look very similar in the photos.


Yes, both mineral wool.


Mineral wool is more dense than fiberglass, think of a sheep…

Experience like they said + 35 yrs crawling thru it


Watched a Building Science video by Belinda Carr where she demonstrated that Mineral wool is water-resistant and fiberglass easily absorbs water.

I took a couple of small pieces of insulation and applied water droplets to it and the insulation soaked up the water like a cotton ball.

My question is, does mineral wool have the same water-resistant quality in loose-fill form as its dense-form? Does its water-resistant quality fade over time?

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From Montana that looks like Insulsafe installed with an old hopper.


From Utah…I agree with Walter… it also looks like most likely to be insulsafe, which is a fiberglass manufactured by CertainTeed. technically fiberglass is a mineral (wool), but usually when you refer to mineral wool you will be describing the type made from Steel Slag and most likely it is going to be a dark greyish and sometimes even a greenish tinge to it. Also referred to as RockWool or Rocksall (brand)…mineral wool is just plain nasty to work in/with and best to wear gloves if you are blowing it. However it is probably less dangerous to breath in than fiberglass, especially the very small fibers like the newer higher R-Value per inch Fiberglass that are on the market.