Richard wrote, wood wool is also called rock wool and is a loose fiberous material made from Paper like fiber(hence wood). Sometime it is in a bat form but is always damaged by moisture.. . Richard I don't know much about wood wool but it my experience rock wool is not made from wood products at all. It is made from asbestos, a naturally occurring, long fiber form of the mineral silica that is found in rock. Hence the term Rock Wool. I imagine that wood wool is indeed made of wood fibers but all the rock wool I've seen is in fact asbestos. I have removed tons of this stuff as it was used quite frequently as insulation in older houses. It is impervious to water and will last just about forever. Possibly since asbestos has been banned some entrepreneur has marketed a form of wood wool and called it rock wool so that people would think that it has the water resistance of the original asbestos rock wool. I don't know, that is just speculation. I just wanted to point this out in case somebody found some rock wool somewhere. I did not want them to think that it was made of wood then find out later that they had been dealing with asbestos. I hope this helps! Later!