Evaluated Alternative Durable and recyclable insulation material ROCKWOOL stone wool insulation is based on volcanic rock. Stone wool is non-combustible which means it can help stop the spread of a building fire and does not contain any chemical flame retardants. In addition, if it is exposed to fire it will not give off any significant amount of toxic smoke. Extremely durable, stone wool lasts more than 65 years without any loss of thermal efficiency, non-combustibility or dimensional stability. It can also be endlessly recycled at a growing number of locations, helping to reduce the amount of construction waste going to landfill.