the present invention relates to a method intended for heat insulation of a pipe , comprising the following successive stages : depositing , on the outer surface of the pipe moving longitudinally , a thickness of an insulating material made of elastomer having an elastic type behaviour , substantially without irreversible plastic deformation , forming at least one circumferential slot in the thickness of the material , substantially orthogonally to the axis of the pipe , coating the insulating material thickness with a sealed sheath . in a variant , the slot is machined in the thickness of the insulant . the invention further relates to a heat - insulated pipe .