After cutting a plumbing access in an outside wall to inspect some freezing pipes, I discovered an unfamiliar batt-type insulation, consisting of a tar-paper bag filled with loose brown fibers. It doesn't look quite as fluffy as the blown-in cellulose insulation in the attic. Is there any chance that this brown substance could be Amosite asbestos? I know if there's any doubt then you can't tell for sure without testing it, but has anyone worked with this type of insulation before? Is this just cellulose or does it need to be tested? The insulation was most likely installed when the walls were redone. I would like to remove the insulation to replace it with fiberglass in hopes it will help stop the pipes from freezing again.
Incidentally, when the walls were redone they used plaster over some cardboard-like substance stamped "Celotex Lath, This Side to Studs." Anybody familiar with this material? What years did they use such a strange animal? I'd like to figure out what year the fire occurred. Thanks.