Abstract: Structural support members are surrounded with a cover that insulates the outer envelope of the support member. The cover may be made of an elastomeric material sufficiently flexible to permit the cover to be physically installed about the structural member. The structural member and cover may also be provided with interlocking means that will retain the cover on the support member once it is installed. Disclosed is a skylight framework formed of a plurality of spaced rafters joined by a plurality of crossbars wherein the rafters and crossbars each include an elongated central support member having a cover member that surrounds the outer envelope of the elongated support member except for a central fastener opening.