In laser fusion plasmas, most of the absorbed laser energy can go into the generation of suprathermal electrons, which potentially can preheat the pusher and/or fuel. An approach of using a vacuum to shield the pusher or fuel against these energetic electrons is discussed in some detail. Both qualitative and quantitative kinetic calculations governing vacuum insulation in plane and spherical geometry are developed. The principal effect of vacuum insulation is to convert an electron time scale to an ion time scale.