I have a similar situation in that the yard light is about 30' from the coop. I put in a clear vent cap that's 18" wide so I could get some light in the coop as well as two clear sheets on the roof. I have guineas as well as chickens and ducks. I had found that thus far they don't seem to mind, true I don't know how they would behave if the light was off. I do have two or three confused roosters that will crow at about 2-3AM for about 5-6 minutes but I don't know if this is a result of the yard light or their own confused brain. The chickens and guineas go in the coop at dark and in the evenings that I'm late closing them up their still all inside. The ducks want to stay out on the water in the pen but go in when I herd them. I have found that the uncovered metal sheeting is probably more of a stressor than anything else thus far. I am lining the interior with cardboard to, 'tone it down'. I believe if the coop were bigger the unlined interior wouldn't resonate the energy as much but it is what it is!!! My 5 ducks are laying regularly and the four hens (To regular size and two bantam's) have cut back but are still laying. I may have to block the yard light to give them a break from laying. But it is all wait and see for now. In summary, coming from the first year Fowldad, I've had to cover the clear sheeting up to cut down on the heat in the summer but that's been about it. As far as ventilation, the floor is open, 3/4" mesh, the ridge cap not sealed, fan on a thermostat and I open the down wind window. May ad more later, wait and watch the humidity. I hope this helps.