The blinds can either block or enhance the flow of solar radiation. A vestibule is an elegant architectural feature of a building entrance that can also be a practical and effective energy saver. These are, respectively, the passage of conditioned air out of the building and the movement of unconditioned air into the envelope. Busy building entrances can lose much energy, approaching losses from a door open to the exterior all the time. The double set of vestibule doors greatly reduces the flow of air through an entrance.
Automatic operation prevents a clear passage for air flow, since one set of doors is always closed.
Also, the volume of air trapped between the portals acts as a buffer to the transfer of heat through the vestibule. When there is no traffic the trapped volume or air is an effective insulator that increases the thermal resistance of the passageway. Otherwise the glass vestibule can be a source of high energy loss. The single most intensive user of electricity in an institutional facility, such as a school or hospital, is the kitchen. This is especially true of a kitchen in which most of the appliances are electric.