This study assesses a wall element designed with natural materials only. It was designed with the vision of zero CO² emissions. A traditional life cycle assessment yields CO² emissions greater than zero. However, the results are significantly better than those from traditional wall elements. Furthermore a dynamic life cycle assessment yields negative CO² emissions. This is due to the high use of straw as insulation material. The straw is a fast growing bio-based material and it is shown, that these types of materials have high benefits, regarding CO² in the atmosphere.