Insulation, Radiant and Vapor Barriers - Insulate covered porch?

I have a covered porch on the front of my ranch home. Upstairs in the attic, the covered porch area just spills into the rest of the attic that spans the entire length of the house. There is no wall that continues up from the living space below. This area faces east. There is a lot of air that moves into the attic from this area. Shouldn't this area be walled off some how to limit the amount of cold air coming in? Currently, the blown fiberglass just stops short of the porch. I was thinking of some 4 x 8 sheathing. Any recommendations?