An insulating liner for an article of clothing includes a first layer, a second layer attached to the first layer, and an insulating layer sealed between the first and second layers, wherein the insulating layer is composed of an aerogel material. The first and second layers can be a PVC foam hermetically sealed about the aerogel material by welding. In a preferred embodiment, the insulating liner is a shoe liner that includes a polyester wearing material adhered to the top layer of PVC foam. A method of forming the insulating liner is also provided.