Long term investigations with 20 mm thick micro-porous Silica VIPs, which were wrapped into a metallized high barrier film, show that the gas pressure at ambient temperatures does not rise more than 1 mbar per year.(see Fig. 3)
That means the increase of the gas pressure after 50 years is about 50 mbar. This corresponds to a rise of the thermal conductivity to a maximum of 0.008 W/mK. That means, that the life time of a 20 mm thick VIP can be up to 30 years. A dry ambient condition for the VIP is very important, because high humidity can influence the film of VIPs.
Accordingly the life time of a 10mm VIP is reduced to half the time compared with a 20 mm VIP. For 40 mm VIPs the life time is doubled.
Increase of Gas Pressure
Fig. 3