Bike helmets are designed to vent in the hottest temps and work well in those conditions. I think the best type of cold weather gear is what skiers wear. Yesterday we had a nice storm with 1 1/2 feet of snow. I spent the day skiing into a brutal north wind causing wind chills of 0 F and was completely comfortable wearing a fleece lined wool hat and ski goggles with balaclava and ski gloves. Now that I've had cataract surgery and no longer wear glasses for cycling, driving or skiing, fogging is not a problem. Moving lower, a fur jock strap may be ideal, but for the very coldest temps I've hand sewn a strip of wind-block fleece in the crotch of a pair of bottoms. I've put platform pedals back on the bike and will wear as warm a boot as necessary. Cold weather cycling is not like regular cycling so dress up for it just as in hot temps we dress down.