Rockwool insulation refers to a type of insulation that is made from actual rocks and minerals. It also goes by the names of stone wool insulation, mineral wool insulation, or slag wool insulation. A wide range of products can be made from rockwool, due to its excellent ability to block sound and heat. Rockwool insulation is commonly used in building construction, industrial plants, and in automotive applications.

To make rockwool insulation, minerals and other raw materials are heated to about 2910°F (about 1600°C) in a furnace, through which a current of air or steam is blown. More advanced production techniques are based on rotating the molten rock at high speeds in a spinning wheel, in some ways resembling the way that cotton candy is made. The finished product is a mass of very fine intertwined fibers, bound together with starch. Oil is also added during production to decrease the formation of dust.

The individual fibers of rockwool insulation are good conductors of heat on their own, but rolls and sheets of this insulation are highly efficient at blocking heat transfer. They are often used to prevent the spread of fire in buildings, in light of their extremely high melting point. As with other types of insulation, rockwool can play a large role in reducing energy consumption in homes and businesses. Made of natural materials, rockwool insulation is safe to manufacture and use, when proper guidelines are followed. Decades of research have shown that it poses little to no health risk to humans, including that of respiratory and other cancers.

While it is not attractive to rodents, rockwool can pose problems in other ways, especially if allowed to become wet. Rockwool insulation is able to retain a large amount of water, although gravity will make it slowly drain out, as long as it has a way to escape. This ability to hold water, coupled with the fact that it retains a certain amount of air at all times, has made rockwool a popular growing medium in horticulture and hydroponics. These properties of rockwool allow for good root growth and nutrient uptake. It also provides a good mechanical structure for the plant, keeping it strong and stable.

In its natural state, rockwool has a relatively high pH, which is unsupportive of plant growth. In order for it to be suitable as a medium for growing plants, it must be treated to lower the pH to a more stable and neutral value that will allow the plant to thrive. This treatment involves soaking the rockwool in pH-adjusted water for at least 24 hours before use.