First Winter with Chickens - Vent Too Big?

[PowerChanS]

Please ignore the tumblers.
I have 9 pullets in a 6x8' metal shed with a modified door to include a vent.
The vent is roughly 2.5' x 3.5' - I was worried that the summer heat is going to cook them alive. Turns out it's densely shaded so they were fine.
My concern now is the winter. Should I cover up the screen at least partially to prevent cold draft? How much should I leave open for humidity concerns?
Temperature in my area gets down to about mid 20s, with occasional chills that hits mid 10s.
Also, the opposite wall has the automatic gate to the run - should I keep it closed once the chickens stop hanging out due to the weather?
Appreciate all helpful comments in advance!

 

[PowerChanS]

 

[nuthatched]

Can wind hit then in the roosts?

 

[PowerChanS]

Currently, yes. The highest of 3 bars is roughly at the midpoint of the vent. When the temperature reached 29F a couple nights ago, I did notice the chickens not using the roosts. Maybe because of the draft?

 

[nuthatched]

Currently, yes. The highest of 3 bars is roughly at the midpoint of the vent. When the temperature reached 29F a couple nights ago, I did notice the chickens not using the roosts. Maybe because of the draft?

I would cover with plexiglass , all but the top 6".

 

[PowerChanS]

I would cover with plexiglass , all but the top 6".

sounds like a plan! Thanks for the input