In order to produce a high performance thermally insulating rendering, a dry blend is provided that consists essentially of: —60 to 90 Vol.-% of a hydrophobized granular silica aerogel; —0.5 to 30 Vol.-% of a purely mineral binder; —0.2 to 20 Vol.-% of an open-porous water-insoluble or slowly water soluble additive having an accessible pore volume from 10 to 90 Vol.-%; —up to 5 Vol.-% reinforcing fibers; and—up to 5 Vol.-% of processing additives. After mixing the dry blend with water, the slurry thus formed can be applied to a surface or shaped to a self-supporting body using an overpressure without adversely affecting the thermal insulation properties.