The structural architecture is completed, on one side, with iron tubes symbolising a tangle of trunks: two are the pillars, two are the downspouts for channelling and recovering rainwater and the others have a mere aesthetic purpose. Floorings and internal and external claddings are made of highly resistant fully-vitrified ceramics, provided with outdoor anti-slipping surface. They are produced through sustainable processes conferring a wood and nature-like effect with patterns of extraordinary dramatic result. The external lighting system features a twilight sensor and gives great visibility to the outdoor area and entrance, beyond providing a bottom-up light illuminating the tree, which is integral to the architecture. The building includes different areas, i.e., outdoor, bedroom, and bathroom, and a mechanical room to accommodate all installations. The end of the module, where the curved surfaces are, is intended to accommodate tanks and equipment for rainwater recovery and management of incoming and outgoing water. GREEN_ZERO is a dynamic and customisable system able to meet every client’s need, keeping however intact its building and functioning principles.