Insulation materials, thermal cellular glass

Thermal insulators comprise an equally broad range of materials. Such inorganics as mineral fibers, magnesia, aluminum silicate, cellulose, and glass fibers are widely used for steam and hot-water pipes, furnaces, and blown-in home insulation. Organic products that are effective include plastic foams (polyurethane, polyvinyl chloride, polystyrene) and cellular rubber. There are a number of materials that may be called double insulators, since they have both electrical and thermal insulating properties,... 

Air is a unique case, as it is the only gaseous material in actual use as an insulator. Its dielectric constant is 1.0058, far less than that of any other dielectric material, and it has low thermal conductivity as well. It is particularly effective when trapped within a solid network, as in wool, cellular plastics, or glass fibers, or as an interlayer between wall panels. 

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