I'm in central New York. We had a very wet summer. I have had two situations with fogging and I think there are two available reasons, and the thing is to figure out which is which. First, it could be you need more openings - but it may be you need to change the configuration of your openings. Second, it might be that when you've observed fogging, the humidity everywhere is very high, and it wouldn't make a difference what you did.
So the first scenario: yes, the fogging could be too high humidity in there. What I would suggest is think about it like coop ventilation. Because it's possible that the entire top open doesn't actually move air very well if it sits, trapped in there. So you might want to think about somewhere lower down to open that offers a way for air to move in and help push / draw the air up and out. But of course you don't want it directly blowing on anybody.
This is my approach, because I am in a fairly exposed location with very strong winds. I've got a lot of unbroken tarp on one side because my main exposure is northwest. But it isn't total. I've had to make some interior wind blocks, "diversions" where the breeze comes in, but then has to change direction, and hopefully slow, and doesn't blow directly through on the gang, but goes up and over them, or along the inside wall (I try to minimize strong breezes that way, but there are some). Then the upper side exits (East and South) are quite open. I don't have an "open sided" run, because we get such swirling snowy gales and it would let too much snow in. I don't want to shovel in there! But the biggest openings are on the East and South upper walls (what works for me).
The second scenario: this summer I hung some small clear plastic tarps like clothes on a clothesline, hung out in the wide-open forage area that's covered by aviary netting on greenhouse frames here and there and completely open on the sides. This was so that when it rained they might wash clean (it worked, sort of). They were summertime windbreaks and I was going to use them elsewhere when I winterized the runs. When I went out there on several days, everything was fogged, yes the run, but also and especially the tarps hung in the open. They remained foggy for hours. It was just so wet this summer here.
Just my two cents. Good luck!