An opening in a vapor barrier membrane interior to a ceiling can be sealed by a flexible enclosure. A planar member of the enclosure can be bonded to the inner side of the membrane. The enclosure is formed with a cavity that can encompass a ceiling mounted electrical device. A fastener is joined to the planar member permits bonding thereof with an interior surface of the membrane by manual application of a compressive force. The fastener may comprise a removable release liner covering an adhesive.