Finally starting my walk in coop. Want to follow?

[Brahma Chicken5000]

I’d block off the openings on the front with wood that you can remove during the summer. Leave the back vents open for air exchange and so that moisture doesn’t build up.

 

[aart]

It's hard to say how much 'breeze' you're feeling, and if it will reach the roost.
Hanging some flagging tape around, up high(front and back) and near roost, can help assess the air movement.

One thing you can do, is to staple up cardboard to the bottom of the rafters over the roost. They should go from the top of the wall and out about 2 feet. That will keep most drafts off the roost and just redirect the air flow rather than blocking it.

 

[blackdog043]

It's hard to say how much 'breeze' you're feeling, and if it will reach the roost.
Hanging some flagging tape around, up high(front and back) and near roost, can help assess the air movement.

X 2 ^^^^^

You could also use wide ribbon to hang. I'm betting that the breeze is not even hitting the roosting area very much to have any effect on your ladies.

 

[Cryss]

The poopboards and roosts are about waist high or a bit above. It's a cool day unless you are in the sun. I was wearing a summer dress. I was standing in the middle of the coop when I was hit with a cold shot of air, then again as the breezes blew outside. I felt it on my arms and knees. I guess the front end of the slanted roof exposes too much of the eaves catching breezes like a kite, shooting the chilly air through the vents between the roof beams straight inside the coop like blowing through a straw. We loosely and hurriedly tacked feed bags to the venting roof beams to redirect the draft. We'll see how it goes.

 

[blackdog043]

The breeze has to be strong enough to ruffle the chickens feathers, to really effect their warmth. That's a strong breeze hitting them. If you ever played hangman as a kid, make something similar and put it on your roost bar. Hang a piece of tissue, mimicking the height of a roosting chicken and see how much it blows. It's gonna have to move pretty good, if it's gonna ruffle feathers. You could use one of those banana hanging things if you have one and hang a tissue on the hook. Hope you get what I mean to do.

I have a lean to roof like yours, except the open eves are only 12" long on front and back, I never block them off. The roost bar is about 20 inches below the back eve. I have 2 fly papers hanging in the coop and yes they get blown when wind comes through, but it doesn't stay strong enough to bother the chickens on the roost bar. Any breeze coming from the back eve, pretty much goes over their head. I don't get as cold as NW Jersey, but we do get below freezing at times.

 

[aart]

The poopboards and roosts are about waist high or a bit above. It's a cool day unless you are in the sun. I was wearing a summer dress. I was standing in the middle of the coop when I was hit with a cold shot of air, then again as the breezes blew outside. I felt it on my arms and knees. I guess the front end of the slanted roof exposes too much of the eaves catching breezes like a kite, shooting the chilly air through the vents between the roof beams straight inside the coop like blowing through a straw. We loosely and hurriedly tacked feed bags to the venting roof beams to redirect the draft. We'll see how it goes.

Was the coop door closed?
That can make a difference, both in allowing air to flow in the doorway and as an 'exit' for air coming in the upper vents.
You felt it on your knees/arms...but where exactly was the breeze coming from?
Do your prevailing winds come right at the large front overhang?

 

[Cryss]

Door was closed. I felt it at my knees coming from above as it traveled down from my arms. I have never been able to figure out which way prevailing winds blow. I want a rooster weather vane for the top of my coop.

 

[aart]

I have never been able to figure out which way prevailing winds blow.

Do you watch the weather radar?
Which direction does most of it come from...that would be your prevailing wind direction.
Here it mostly comes from the west.

 

[Cryss]

Do you watch the weather radar?
Which direction does most of it come from...that would be your prevailing wind direction.
Here it mostly comes from the west.

No, I've never followed wind on radar. Temperatures and precipitation seemed all I needed to know. I mean, yeah, I know where it comes from when weather reports say we're getting a nor'easter. So now, will prevailing directions change with seasons? Or will I have to check it daily?
Yeah, I'm very ignorant on this subject, just never gave it any thought or knew it was a thing to concern myself with.

 

[aart]

So now, will prevailing directions change with seasons?

Maybe.
I'm just a natural world geek, thus a weather geek.