Dow Cornings foam Glass insulationis used in the petrochem industry where high temperature heating fluis such as Dowtherm or Therminol are used. There have nbeen instances where the fluid has leaked into fibrous insulation. The increase in surface are has resulted in spontaneous combustion of the fluid.
Visit the Therminol website for more details.
I can only assume that whoever has specified FoamGlas is concerned from this aspect. Before changing it check your PI policy. Sharing knowledge is a way to immortality