The side vents are designed to be fresh air but they do pick up engine heat. I keep mine closed year 'round because the amount of engine heat coming thru in the winter doesn't offset the amount of cold air coming thru and in the summer, I don't want the extra heat either.
I think a part of that design was to prevent a low pressure cell behind the fairing which would cause exhausted radiator heat to be sucked around the corner and into that area where your shins are. It doesn't require alot of air movement to equalize the pressures (similar to what the wind shield vent did for the later model Wings).
I plugged my duct off and did away with the vent...only to re-open the duct and re-route it for pressure equalization later.