A window includes a vacuum insulating glass (VIG) window unit in a window frame. The window frame includes at least one vacuum insulated structure (VIS) for improving the insulating functionality of the frame, so that the frame can adequately insulate the periphery of the VIG unit. Such windows may be used in residential and/or commercial window applications for buildings. The use of a window frame having at least one VIS is advantageous in that allows for improved window frame thermal performance and a narrow frame design if desired for improved aesthetics.

A window assembly may include a vacuum insulated glass unit and a frame assembly. The vacuum insulated glass unit may include first and second glass substrates defining a space therebetween that is at a pressure lower than atmospheric pressure. One of the first and second glass substrates may include a vacuum port extending outward therefrom. The vacuum port may define a passage in communication with the space. The frame assembly supports the glass unit and may include a base member and a glazing member. The base member and the glazing member cooperate to define a slot in which an edge portion of the glass unit is received. The glazing member may include a cavity receiving the vacuum port.

A fenestration assembly includes a fenestration frame having a frame core. The frame core includes a core exterior face and a a core interior face. A core wall of the frame core includes filament reinforced polymer, and the core wall extends between the core exterior face and the core interior face. One or more core cavities are within the frame core and surrounded by the core wall. At least one insulation scaffold is seated within the one or more cavities. The insulation scaffold includes one or more scaffold walls and scaffold cavities bordered by the one or more scaffold walls. Engagement feet are coupled with the remainder of the insulation scaffold, and the engagement feet are engaged against the core wall.