Blowing sleet won't keep you inside when you have the Castelli WS Balaclava.
I cannot breath though it when my mouth or nose is covered, like I can with my PI balaclava. Because no air can pass thorough when I exhale the warm air vents out the sides and onto my sun glasses, which of course steams them up.
The neck cover is a nice touch, and it is warm -- and if you wear it with a light bandana you can breath though, you can keep warm.
Apparently this is a problem with any super warm balaclava - I was just looking for a bit more ear warmth.