Beg to differ....

Balaclava needs to be light and display the whole face. It should cover forehead, ears and neck. No problem to put glasses inside. No problem with fogging (at least while the bike is moving).

However, as it gets colder, I also wear a scarf or one of those bike-specific neck scarf thingies that you can pull up and down as needed. Those thing can easily fog up glasses. Which is why I'm constantly pulling it up and down.