Do you know there is an extremely good insulation material that is 95% air? It has the lowest known thermal conductivity of any solid. It is silica aerogel with low density, light weight & unmatched insulating capability. NASA uses it for cryogenic insulation for space shuttle and space exploration. Crayons paced on top of a piece of silica aerogel will not melt in the flame of a blowtorch. Aerogel provides 39 times more insulation than fiberglass. Now used on earth in insoles to keep feet warm.
Examples: Weber Wrist & Ankle Wraps
Toast Feet Foot Warmer Insoles
(see them on this website)