The zero-concept has no need for external heating energy. It typically employs active systems to utilise solar heat and spill energy from lightning and other internal sources.

An extensive amount of research work has been carried out for the concept, but apart from the generation of warm tap water in the warm and moderate climate zones, the final breakthrough has not yet taken place.

We participated an international research project, that resulted to a '5% energy house' in Pietarsaari, Finland