Foam glass gravel is made from recycled glass. This can withstand high loads, is pressureresistant, and does not rot. The material is also categorised as non-flammable (building material class A1). The thermal insulation properties of the foam glass gravel are based on the inclusion of air in the countless closed cells of the insulating material. For example, foam glass gravel has proven its effectiveness in perimeter insulation as it withstands extreme conditions in the ground with pressurised water.