There are sort of two possibilities, not mutually exclusive. One is that your coop air is problematically humid in general -- the solution is more ventilation. When you say 'two vents on each side', what size vents are we talking about, for what size coop with how many chickens in it?
Another (remember, not mutually exclusive) possibility is that your roof/ceiling is getting seriously cold. If it is metal, I guarantee this is part of your problem; if it is plywood (with or without shingles) then maybe or maybe not. The thing is, the colder the ceiling (or any surface in the coop -- walls, window glass, etc) the more it will condense water vapor or frost out of the air. Which you really DON'T want happening, b/c once the humidity is condensed onto a surface in whatever form, it can't exit the coop via air exchange thru your vents.
I'd seriously consider what I could do to insulate the roof. How exactly to do it depends on its structure. Foamboard is often easiest, with a compatible glue (look on the label of the tube to make sure it is approved for use with foamboard, otherwise it may dissolve its way into the foam!). Extra ventilation might also be necessary, depending on your situation.
Good luck, have fun, hope this helps,
Pat