Tony Hwang:

Styrofoam comes to mind, didn't think of that.

And a general rule for attic insulation: A tight upper-most ceiling plane(no cracks or gaps) plus sufficient insulation = the best cure for drafts.

I crack up when I see folks fall for that plastic saran-crap they place over their windows every autumn, or stuffed draft-stoppers they place at the bottoms of exterior doors! Stopping drafts begins at the top of a structure, not at the ground level.