Earthship Biotecture is a global company offering sustainable design and construction services worldwide. The company is led by Michael Reynolds, the principle biotect and creator of the Earthship Concept. Earthships are radically sustainable buildings. There are different designs of Earthships, adaptable to local conditions, materials, building regulations and climate. Earthships are a type of passive solar house made of both natural and recycled materials, such as earth-filled tyres, designed and marketed by Earthship Biotecture of Taos, New Mexico. Earthships are intended to be "off-the-grid ready" homes, with minimal reliance on both public utilities and fossil fuels. Earthships are constructed to use available natural resources, especially energy from the sun. They are also designed to use thermal mass construction and natural cross ventilation, to regulate indoor temperature.