I recently had an experienced insulation
contractor take a look at the attic insulation
that is under the floor boards of the 1920’s
Colonial I purchased in August.
Based on the home inspection done before I
purchased the house, I was told that the existing
insulation was cellulose and that I should have
some additional insulation (blown-in or batts)
added to fill the space beneath the boards.
The contractor, however, examined the existing
insulation and said that it is not conventional
cellulose insulation and, moreover, couldn’t
really say what the stuff is or, more
importantly, how good an insulator it might be.
It’s whitish, fiberous, roughly 3-4″ deep, but with a lot of fine
white powder throughout. He thought that perhaps
it’s a poorly mixed batch of some sort of cellulose having a
high concentration of boric acid or such. It’s
not known when the insulation was added because
it appears that at one time the rafters were
insulated. There are remnants of a dark brown
wooley insulation in places on the rafters as
well as a bit on top of this white stuff that fell through the
cracks of the floor boards.
Before having the white stuff removed and
replaced, I (and the contractor) would like to
identify it if possible. We’re not thinking about toxicity but rather insulation effectiveness.
I put a scoop into a small black container and
photographed it (attached). Any ideas as to what it is
and whether it would be advisable to have it removed
before adding blown-in cellulose?
Replies
Looks sorta like rock or mineral wool insulation. A little tough to tell.
Unless it's somehow migrating into the house (by breaking down into fine particles and working their way throgh cracks/gaps in boards), I'd leave it in place and blow in additional cellulose.
Not positive but it could be rockwool. I would leave it alone and dump cellulose on top. Since you dont know what it is you really dont know its toxicty lelvel. Digging that stuff up is going to stir up a lot of dust, not worth it in my opinion.
Marc,
Welcome to Breaktime!
If you click on your name above (where it says "To: marcwd"), you will open your profile.
We would appreciate it if you could fill some of that in, especially where you are located!!
Thanks!
For what it's worth, I vote with Mongo and Reinvent. Leave whatever it is alone and blow cells on top.
Rich Beckman
Another day, another tool.
Thanks for all the replies. Based on your suggestions, I will likely leave the existing stuff in place.
I'm curious, though -
Assuming the stuff is rock wool or mineral wool, what's the composition of these insulations and what's their relative effectiveness compared to cellulose?
Would the attic floor insulation have been likely added at the point when the rafter insulation was removed? (Added info FWIW: the previous owner pulled out a huge fan that had been mounted on the floor boards. The fan pulled warm air out of the house through a hallway ceiling vent and forced it out through a huge louvered opening in the side of the attic.)
Finally, is it surprising that an experienced insulation contractor wasn't familiar with the rock or mineral wool (or whatever it is) ? How common was the use of this stuff?
bump
I can't tell if its rockwool or not.
Here's a link from a previous thread on rockwool.
http://forums.taunton.com/tp-breaktime/messages?msg=50352.21jt8
Thanks for the link. The few pictures I've seen online show rockwool to be a brownish color. The stuff I've got in my attic is a greyish-white fibrous product with a high content of white powder throughout. I'm going to send the photo to a guy at NAIMA to look at.
Before I have cellulose blown over it (under the floorboards), I'd like to be reasonably sure that the stuff (whatever it is) isn't junk as an insulation.
Probably rock wool, but you name it and it's been used as insulation at one time or another. Could be something like textile mill lint, some sort of byproduct of processing cotton or flax, etc. If you really want to know, an "industrial hygienist" can probably identify it (for a fee).
In general, the insulating ability of an inch of "fluffy" material is pretty much the same, for all types of "fluffy" material. The main difference has to do with the porosity of the material -- the more porous, the more air can infiltrate through and the worse it is as an insulator.
The other issue would be how much it's likely to compress when more insulation is added on top. If it compresses flat it won't contribute much.
Thanks, Dan. The stuff doesn't appear to be nearly as compressable or fluffy as cellulose. Much more dense and granular.
Then that sounds like some sort of rock wool. It's basically blast furnace slag, and can come in all sorts of colors and textures, depending on the furnace.
The other possibility would be vermiculite. But it has visible flakes in it that look like slivers of mica, and the overall texture is more like cat litter.
Dan, I think that your description of vermiculite would rule it out.
I'm not at all familiar with blast furnace slag; would it likely contain a fine white powder? I thought, perhaps, that the powder might be Borax, but that wouldn't need to be added to furnace slag, right?
As I said, rock wool comes in many forms. The variety I've seen most often resembles fiberglass, but is finer fibers, a different color, and much stiffer. It will shed a sort of powder that is kind of coating the individual fibers, and is also brittle and can be ground to powder if handled too much.There is a vague danger that what you have is asbestos. You need to eliminate that possibility before you move forward.It might be worthwhile to pay for the industrial hygienist.
I second the motion by Mongo exactly.
Looks like a type of mineral wool.
Leave it intact and simply add celluloise over it.
I want to thank everyone again for the responses. Based on your suggestions, I will leave the existing stuff in place. Among other advantages, that will save me the estimated $1,000 to have it removed.
Now I have to reassess whether to have cellulose blown into the remaining 2-3 inches of space under the floorboards. The contractor said that the cost (~$1/sq ft) is largely independent of the amount of material added. In other words, the labor involved predominates.
I second DanH on the asbestos possibility. I would have a small sample evaluated by an abatement company, for peace of mind.
Me too on the asbestos possibility. The picture looked like the same stuff we used in the Navy to insulate steam lines.
I'm surprised to hear from so many about the concern of asbestos. From what I've read, the only instance of asbestos found in loose insulation was in vermiculite. This stuff does not have the characteristics of vermiculite.
I suspect that asbestos is a long shot but in an 80 yr old house, who knows what may have been done over the years. Since the stuff is loose, I would err on the side of caution.
Checking for asbestos is cheap, and can save you in the long run if. Asbestos was used in all sorts of applications. I think it is unlikely that it is asbestos carrying, but I would certainly check.
The thing is, it looks like something like crumbled asbestos pipe insulation, and the description of the OP isn't inconsistent with that. If he comes in and adds other insulation over the top he's quadrupling any cleanup problem that asbestos might present.Better to play it safe.
Dan, I'm somewhat familiar with asbestos pipe insulation; I've abated some myself from the steam pipes in the basement. The pipe insulation is a "crunchy" consistency and greyish. The stuff in the attic is much softer and white in color. Though it's not bad advice to have it checked, I don't believe it's asbestos-containing material.
I just got the report back from a testing lab. The stuff contains no asbestos.
Further, I was told it’s roughly one-half cellulose fiber, one quarter mica, and a quarter "mineral grain." I have confidence in the asbestos conclusion, but I’m not fully convinced about the compositional analysis.
Sounds like the stuff they swept up off the floor.
Maybe "perlite" mixed with cellulose. Perlite has a mineral source and has been used as loose insulation. Crumbles to a fine powder.
Go to: http://www.perlite.net/
If it is Perlite, it would have to have been in a fine powder form before it was combined with the other stuff. No hard pebble-like pieces at all. Just a fine white powder along with some soft, fibrous material.
I'm a little skeptical of the cellulose conclusion from the lab. One of the insulation contractors who looked at a sample of the stuff tried to ignite it with a propane torch. Apparently, it didn't even smolder.