The present disclosure encompasses provides thermal stabilizer compositions comprising a phase change material admixed with a support material such as a diatomaceous earth, and a nucleator. The present disclosure further encompasses a heat insulation blanket for reducing heat transfer between adjacent spaces, comprising at least two plies of thermoplastic sheet material in superposed relationship and a seal, wherein the seal connects the plies of sheet material to form a cell containing a volume of a thermal stabilizer comprising a phase change material, a support material such as a diatomaceous earth, and a nucleator.