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How to Tell Rock Wool From Vermiculite

Melissa Busse

While many types of insulation are considered harmless, other types may affect your health. Vermiculite insulation was once commonly installed in homes and is now considered dangerous, since it is often contaminated by cancer-causing asbestos. Another commonly used insulation, rock wool, is thought to be safe.

There are many types of insulation found in homes; some are more dangerous than others.

To identify which type of insulation exists in your home, it is important to learn the differences between rock wool and vermiculite.

  1. Observe the texture of the insulation. Vermiculite insulation is loosely packed and granular in appearance, often resembling small pebbles. The size of the pieces may vary from 1/8 inch in diameter to 1/2 inch. Rock wool is made up of soft fibers, rather than loose particles, and has a cottony appearance.

  2. Observe the color of the insulation. Vermiculite insulation is made up of gray or brown particles that may be sprinkled with bits of reflective gold or silver mica. Rock wool can be either white, off-white or brownish white.

  3. Slip your protective gloves onto your hands. With your gloved hands, feel the texture of the insulation. Vermiculite insulation feels granular between your fingers, almost like small pieces of gravel. In contrast, rock wool feels like dense wool.

  4. Tip

    If you are still unsure of the type of insulation in your home, contact a professional to help you. EPA.gov features photos of vermiculite insulation to help you better identify it in your home. If you find vermiculite insulation in your home, the Environmental Protective Agency advises to leave it alone as opposed to removing it. Covering the insulation with more insulation can be done by the homeowner, but removing it must be done by a professional.


    Asbestos is considered very dangerous to your health. Always take great care when dealing with vermiculite that may be contaminated with asbestos.

    If you are concerned that the insulation in your home may be vermiculite, do not attempt removal by yourself. Disturbing the insulation could cause asbestos-tainted dust to contaminate your home.