The invention relates to an additive mixture for addition to a building material covering mixture for forming a composite covering system for the floor, wall, or facade area, which additive mixture reduces the thermal conductivity or thermal dissipation of covering systems, in particular the thermal dissipation through objects and sub-bases coated with the covering system, in such a way that walking on the sub-base provided with the covering system is no longer associated with a sensation of cold feet. This is achieved in that the additive mixture has a proportion of between 50% wt and 95% wt of Muscovite mica.