Abstract: A microporous insulation material contains an ingredient which exhibits a phase transition and functions to maintain temperatures attained by an object shielded by the microporous insulation material, during exposure of the microporous insulation material to a high temperature environment, at an acceptable level over a given period of time. The insulation material is especially suitable for insulating flight data and voice recorder systems. The microporous insulation material contains inorganic particulate material; endothermic compounds, (optionally) an opacifier, inorganic fiber and preferably, a dry resin or other binder. The inorganic particulate material can comprise only hydrophilic material or both hydrophilic and hydrophobic material.