This means six times safer than the usual reinforced concrete or brick walls offer. The ceiling ratings are even better.
Why? Wood burns well when it is thin and in contact with plenty of air. However, a thick block of wood hardly burns at all. It chars fairly slowly, approximately 0.5-0.7mm per minute. In a Holz100 house, every ceiling, wall and floor is a thick, fire-resistant block of wood that serves as firewalls.