Aerogels are one of the world’s lightest solid materials, composed of up to 99,8% air by volume. Most aerogels are based on silicium dioxide (SiO2), like glass, but their density is about 1000 times smaller. They are semi-transparent and have a light blue or yellow colour. Aerogels are composed of a dendritic structure made of SiO2 particles of a few nanometers, which are organized together in three-dimensional chains. The pores in between have dimensions in the range of 1-0,01 micrometers. Because of their very high porosity, aerogels have the lowest thermal conductivity values of any solid. They considerably reduce the three phenomena of heat transfer: convection is reduced because air cannot circulate through the (very small) pores; conduction is low because silica is a very poor conductor of heat; radiation can be reduced by adding carbon to the aerogel to absorb infrared radiation. The thermal conductivity of aerogel insulators is approximately two times lower than the thermal conductivity of for example PUR or EPS. This means that a lower insulation thickness can achieve the same energy savings and thermal comfort compared to more traditional insulation materials like mineral wool or EPS.