A fastener assembly for affixing insulation blankets to a substrate is provided. The fastener assembly includes an attachment member having a construction for affixing to a substrate as well as a first fastener member preferably in the form of a male threaded stud. The fastener assembly further includes a cap fastener. The cap fastener includes a cap member and a second fastener member preferably in the form of a female threaded extension for threadably affixing to the first fastener member. The cap member has an exterior side and an interior side. The cap member's exterior side preferably has a shape for rotation by a tool. Meanwhile, the cap member's interior side has a circular recess concentric with the cap fastener's female threaded extension. When assembled, the circular recess forms a circular insulating cavity between the cap member and an insulation blanket.