While sarking is just a vapour barrier, reflective insulation is both a vapour barrier and an insulation material in one application. Typical reflective insulation includes the encapsulated air cell structure (bubble), or higher performance cross-linked foam with foil surfaces on either side, whereas sarking is only a single layer of foil.
Because of this structure, reflective insulation has significant conductional resistance properties while sarking does not have any resistance to conductional heat transfer. Designed primarily as vapour barriers, most sarkings do not have highly reflective foil surfaces which greatly limits their ability to reflect radiant heat. A good quality reflective insulation’s plain foil surfaces reflect up to 97% of radiant heat, effectively reducing the amount of heat entering a building throughout the day and saving you energy costs.