A sports boot shell of which at least a part of the wall is composed of a sock covered with a rigid material in plastics material, wherein the sock includes, on its inner surface, an insulating means limiting losses of heat by radiation, which may be a polyurethane coating that includes aluminum particles or aluminum pieces bonded on the inner surface. The process for manufacturing such a boot comprises the step of lasting the sock prior to injection-overmolding of plastics material in order to form the wall of the shell.