Using a ski helmet for winter biking
I wear a Bern Brentwood with a winter liner in cold weather. It's a certified bike helmet, but designed more like a ski helmet. The winter liner does a great job of keeping my ears warm without wearing any other protection, but doesn't block traffic noise. It is vented, but not well enough that it makes my head cold. It also has a clip in the back for ski goggles if you're using them. With the summer liner it works well for fall and spring, too.