ISOLFONDO is a lightweight, biocompatible insulating subbase, pre-packaged powder for interior and exterior use, according to standard UNI EN 13813. ISOLFONDO is free from cement or compounds belonging to the clinker group. It consists of a mixture of pure mineral sands, expanded with low specific weight, screened with continuous grain size arc from 0 to 5 mm. The only binder present is ST ASTIER Pure Natural Hydraulic Lime NHL 5 according to standard UNI EN 459-1. The lime NHL 5, white, is produced by baking siliceous limestones at temperatures below 1250°C and reduced in powder by only the breakdown of calcium oxide, without the addition of pozzolanic materials or hydraulic binders of any kind.