Abstract: A reflective insulation blanket of folded flexible metal foil having dead air spaces between a principle member (20) and one or more outer members (22) and (24). The blanket being held apart in spaced relationship with one or more pairs of expanders (28) terminating with a mounting flange (26) at each end. A pair of retaining clips (36) cooperate with each other to hold the blanket in place against building structural members (30) and (32). Each clip having an elongated base (38) folded over upon itself (40) to provide a retaining section terminating with a pair of radial arcuate surfaces (42) and (48) with an angular abuttment point on the extreme end. The clips (36) embrace the structural members (30) and (32) at the leg and compressably engage and retain the mounting flange (26) of the blanket against the web of the building structural members.