Originating in aerospace-industry laboratories to insulate rovers on Mars, aerogel is the definitive solution to the problem of thermal bridges and thickness constraints. It insulates in a single centimetre as much as traditional materials do in four.
Silica aerogel is obtained by replacing the liquid of a silicon gel with a gas, creating a solid structure that is up to 99.8% air. Its pores (20-50 nanometres) are smaller than the mean free path of air molecules at atmospheric pressure. The molecules become literally trapped and, unable to move or collide, heat transmission by gaseous convection is reduced to zero (Knudsen effect), guaranteeing a lambda conductivity of just 0.015 W/mK.
In its pure state, aerogel is a hyper-fragile glassy fragment. To make it usable in construction, it is infused into flexible glass-fibre or PET meshes (the so-called blankets). This produces rolls 5-20 mm thick, very easy to glue. Being an inorganic material, aerogel is completely water-repellent yet highly vapour-permeable, preventing mould and keeping its insulating performance unaltered even in conditions of extreme humidity.
Standards
European and international references applicable.
Physical properties
Usage environment
When cutting aerogel blankets, amorphous silica dust is released. Although not fibro-toxic or carcinogenic, it is a powerful mechanical desiccant for mucous membranes. Use of safety glasses, gloves and P3 dust mask is mandatory during cutting.