Yes, the louvered vent covers that you (
@Dazz172 ) posted should go where the rain might hit them, they'll keep water out but let air in and out.
The other vent opening I suggested would be under cover of the run roof,
so can just be an open hole...but covered with HC for safety.
Too much ventilation, never..... too strong of drafts blowing on roosts in winter, yes.
Here's a pretty good discussion of such:
http://www.backyardchickens.com/t/1048597/ventilated-but-free-of-drafts
BUT that coop is so small that it's tough make it anywhere near perfect.
I looked up your annual temps and they seem pretty mild on average.
Oh, had another thought, raising the roosts a few inches and reducing the amount of bedding in nests might help.....or you might just have to block nests every evening as
@rosemarythyme suggested.