Evacuated insulation panels filled with pyrogenic silica powders: properties and applications

The thermal conductivity of pyrogenic silica powder boards mixed with a silicon carbide opacifier is measured as a function of gas pressure and of temperature. At room temperature and gas pressures around 1 to 5 mbar the thermal conductivity is about 0.004 W m(-1) K-1. At a mean temperature of 300 degreesC the evacuated panel has a thermal conductivity well below 0.010 W m(-1) K-1, because of the silicon carbide opacifier. Several square metres of vacuum panels have been encapsulated in laminated aluminium envelopes and tested as thermal insulations for building facades.