Solid phase change materials, such as CARBOWAX.RTM. polyethylene glycol 8000, are encapsulated in a condensation polymeric shell to provide heat storage material for use in such things as solar heating devices. The phase change material is put into particulate form and then is coated with a reactive monomer, such as ethylene diamine. Then the monomer coated particulates of phase change material are reacted with prepolymers, such as isocyanate-terminated polybutadiene diol, to form elastomeric, condensation polymeric shells. The polymers have elastomeric (flexible) segments which are the prepolymeric portions. The encapsulated phase change material has little or no significant loss of its latent heat of fusion due to its encapsulation.