A closure is configured for use with a portable cryogenic container or dewar, such as a dry vapor shipper (DVS). The closure has advanced insulating properties which enhances cryogen residence time and also minimizes negative effects on residence time when the dewar is placed on its side, such as during shipping. The closure includes a gas vent in the form of a fluid passage which is particularly sized to minimize thermal leakage and located away from the closure-to-neck interface. Embedded electronics can detect, record, and/or communicate information pertinent to a condition of the storage container in which the closure is installed.