Vejledning 3 - Isoleringssystemer / Aerogeler
Aerogels
Insulation made of man-made materials
Aerogels are current state-of-art insulation materials made from silica based gel, where the gas replaces liquid components.
Aerogels are formed by crosslinking polymerization reaction and a careful drying phase. The polymerization process forms a solid network surrounded by a liquid (sol–gel). The drying procedure removes the liquid and leaves behind a delicate structure with nanoscale-sized pores.
Aerogels are typically used for insulation material by bonding it with plasterboards. Nevertheless data of aerogels on real on-site performance are rare in the literature.
The review by Jelle (2011) gives values for thermal conductivity as low as 0.004 W/(m K) at pressure of 50 mbar, nevertheless commercially available specimens show typical values for thermal conductivity in the range of 0.013 – 0.014 W/(m K) at atmospheric pressure.
Aerogel is very expensive compared to other insulation materials. Moreover the material has high compression strength and is very fragile. On-going research is to incorporate carbon fibre matrix into the aerogel in order to make the material more susceptible to deformations.
Aerogel render (0.06 m) with thermal conductivity of 0.025 ± 0.002 W/(mK) at 23°C and 50% relative humidity was used as internal insulation in laboratory set up to simulate hydrothermal behaviour of massive wall (0.26 m) during wetting. The wall was set up to simulate the Swiss residential houses built in 1850-1920. The obtained results showed that the water diffusion in the wall has not linear nature and that on average it takes 21-30 days for water front to cross exterior brick. A detailed model of the moisture transport in the massive wall was obtained, to be used for further simulation.