Heat is transmitted by radiation, by conduction and by convection. A foam jacket blocks heat transmission by preventing convection. A mylar blanket prevents tra

Heat is transmitted by radiation, by conduction and by convection. A foam jacket blocks heat transmission by preventing convection. A mylar blanket prevents transmission by radiation and convection. Yes, it still loses heat to transmission but it isolates rather well. Unsurprisingly, that’s why they are used as emergency blankets.