Here's a picture of the run and the coop. I have 6 hens and one rooster. Most of the time I let them sleep on the roof it they want too, and if I think they have to be inside I keep the door to the wooden part open and close the door to the miniature run that's part of the coop. I also have an example of some ventilation I've installed, that's their nesting box. I also have hardware cloth which I shaped to fit directly on the wooden doors, to act as vents too.
The vented nestbox is very well done!
What you need is venting at the roof peak -- up in the top triangle. You can cut a piece out there on each end and replace it with hardware cloth. Since it's under the cover of the run roof you won't have to worry about rain getting in.
7 birds should have this for space:
- 28 square feet in the coop,
- 70 square feet in the run,
- 7 linear feet of roost
- 2 nest boxes
- and 7 square feet of ventilation, best located over the birds's heads while they're sitting on the roost.
Do you put tarps up on the sides of the run in the winter? As long as they always have a place safe from wind and free of snow they should be perfectly happy to go outside in the cold.