The combustion chambers in Aduro stoves are insulated with vermiculite plates rather than traditional chamotte tiles, as vermiculite insulates approx. eight times better than chamotte. Vermiculite creates and maintains a higher temperature in the fire, which results in a cleaner combustion. The insulation tiles also protect the exterior surface of the stove against overheating and heat damage.

Vermiculite is a light material that cannot burn, but it can crumble and crack due to incorrect firing or wear and tear.

Vermiculite can crumble when the concentration of carbon monoxide is too high in the combustion chamber. The carbon monoxide reacts with some of the minerals and binders in the vermiculite, which causes the vermiculite to crumble.


An excessive concentration of carbon monoxide in the combustion chamber can occur due to an imbalance between supplied oxygen and the amount of firewood in the combustion chamber. A classic example is to fill the stove with firewood at night and shut down the air supply at the same time. A high concentration of carbon monoxide can also be caused by firing with other materials than wood, which we would always advise against.

If the insulation stones/vermiculite plates in you stove crumbles, we recommend regulating the balance between air intake and the amount of wood.

Since damaged vermiculite plates can cause poor combustion and, in worst case, damage the stove, you should replace the damaged plates with new ones. Original spare parts can be found and bought in the Aduro webshop.

Related FAQ: ”Why do the insulation tiles (vermiculite) in the combustion chamber crack?"