"Isokern manufactures high-end modular fireplaces made from the most energy-efficient material on earth, volcanic pumice. The Icelandic pumice used in all Isokern components has incredible refractive properties that reflect heat back into the room instead of absorbing like other site-built concrete, metal, and masonry fireplaces.  

An Isokern Fireplace can be installed in less than a day, is less expensive than a traditional masonry fireplace, and will last a lifetime. Fireplaces are available in wood-burning and gas, vented and vent-free, and can be used indoors or outdoors."