RWebb -- utility audit would likely be somewhat humorous in this house. It was built in 1927, lit on fire during the Great Depression, then apparently repaired by a three-armed homunculus. I'm slowly working my way through the process of modernizing this thing, but I suspect that an energy audit would tell me that I'm losing heat through everything that I haven't touched yet.
But thanks for the idea.
Shutting down the attic in the winter isn't going to be practical; that'll be the kids bedrooms, so they'll have to be inhabitable all year round.
I opted against the vents in the ceilings. They're good in the summer, in that they move some fresh air up through the ridgeline, which helps to keep roof temps down and can prolong the life of the roofing. However, in winter, that's a layer of fresh moving air instead of a layer of insulation. So I opted for 2" of EPS foam instead of 2" of roof venting.
StomachMonkey -- I'm curious what heat reflecting stuff you put in your roof that worked so well. The stuff I put in didn't seem to have any effect. I didn't exactly do the science experiment, but I certainly couldn't tell the difference until I started putting the foam and fiberglass in.