Granular Minerals Insulation

Hello All,

My wife and I purchase a house from the 1930's. Is a semi detach brick house. Long story short I removed part the sub-floor in one of the the bedrooms. The bedroom is located on top of the garage. From what I assume the insulation looked like vermiculite. I took two samples to have it tested for asbestos. The results from the samples were negative for asbestos and vermiculite. So, can someone help me figure out what insulation was used in the sub-floor? The insulation is loss, rocky and sandy. I have attach pictures and result of the test. The email from the lab technician stated:

"Both samples contain no asbestos.
Note: these are not Vermiculite insulation samples. These are (burned?) debris materials.."

Thanks,
Hupdy

 

Kind of looks like clinkers from old coal furnaces.

 

"These are (burned?) debris materials." that sounds closer than anything I can think of. From the looks, given the all clear report, I would clean that stuff out and fill with a better insulation. I like Roxul.

Bud

 

Did people use this type of material for insulation during the 30's? Was it the norm?

 

I could see people who lived in the depression era think that it would be a good use for an otherwise discardable material. its already paid for and its probablt better than nothing at all.

 

It could be a slag material. Is it lighter than normal rock?

If it is lighter it could be some type of a slag/dross product. Some of the waste materials from smelting iron ore have been used and subjected to higher temperatures (up to 2000F.) The lighter foam, when subjected to the high temps, makes a great insulator. Even the heavier slab excess is expanded by the high temperature, expands. It is often crushed into a lightweight aggregate that insulates and has great fire resistance. - Similar materials like clay, shale and slate are used to make lightweight concrete that is used for structural purposes in concrete, concrete block and some precast. The UL fire rating (protection) for materials with this are higher than the common aggregates. It was one of the first manufactured lightweight aggregates.

It is eventually crushed to a desired size for use in different applications.

Just a guess and the particles could vary in color, depending on on moisture of the raw ores, but generally, they are tinted with reds and browns within the grays.

Dick

 

As others have stated, could certainly be some slag material or perhaps even coal ash .

Since it is over the garage and under the subfloor, we might assume it was there from the original construction as it would be difficult to add the material later.

Have you had an opportunity to check other insulation in the structure? This could have been installed as a fire proofing application since the garage was below living space.

 

The structure of the garage is concrete. This house has lath and plaster, but so far I did see fiber glass insulation in one of the bedrooms. I am pretty sure the res of the house is not well insulated.