Ski helmet = great idea. Similar speeds and similar needs for protection.
I've got an Underarmor headband that works great to keep my ears warm, but its the top of my head and my forehead that are freezing. I have a thin balkava but I honestly don't need the face protection at these temps. I'll look into a cover for the vents. If that doesn't do it, I may be in the market for a ski helmet. I looked online and some of the Giro and other models look very much like bike helmets with fewer, smaller vents and more protection for the ears and nape of the neck.