I'm not sure where you're located but do you find it's too "open" in the winter. There's a lot of ventilation. I wonder if it's too much when it gets cold out. I guess you felt like you needed the winterizing panels...
I'm in KS and my coop is unprotected (no trees or buildings near by), and it gets WINDY here, year round, so yes we definitely needed the winterizing panels. I really like how the ventilation in the henhouse is all overhead. I did add Premier1 Ultrascreen to the openings on the back (under the roof) to blunt the N wind. It's removable, so will only be up during wintertime. The Ultrascreen still allows air flow, but makes it so the strong wind isn't swirling around in the henhouse (
see this thread). My winterizing panels also don't go all the way to the roof - I leave around 2' of it at the top open for airflow (and added Ultrascreen to those open areas too). It did get cold when we had that super freezing week before xmas, and a few of my hens got some mild frostbite (I think from drinking, not from moisture in the coop, as it stayed very dry), and a few had to be brought into the garage to thaw the ice that accumulated on their backs from the condensation on their own breath. But they all survived (including 3 month old chicks!), and if they can make it through that cold snap, I think we'll be good from here on out!
I was wondering if we need a closing door. Is there a problem just leaving it open for them to come and go as they please?
You can technically leave it open since the entire structure is protected with HWC. I just sleep better knowing they are locked up and "out of sight." I'd prefer they get in the habit of sleeping in the coop where foxes, coyotes, racoons, etc can't be eyeballing them all night.
The ladder would have to be directly on the inside of the coop so they can get down when the bedding is low. Would it be bad for the wood on the legs of the ladder to sit in the deep bedding while the layers keep getting higher? I wonder if it would warp and decay.
I used pressure treated wood to make the ladder from the henhouse to the run because of this. And the one inside the coop was scrap from the other ladder. It was probably the easiest part of the whole project, so if it rotted and we needed to replace it, it's a quick fix. Also doesn't have to be a ladder made of wood. With only 12" to cover, you could just stack some cinder blocks or bricks to make "steps" (and add/remove as needed based on bedding height).
Someone mentioned that I probably don't need a poop board. Are you glad you added it?
YES YES YES. Can't imagine not having it. I put a thin layer of PDZ on it and scoop it every other day or so. They don't all end up "hitting" the board because they sleep in weird places, but I'd say 80% of the poop ends up on the board (and then scooped out and put into my compost bins, which I then use in my garden). One surprise bonus of the poop board was it gave me a bit of storage underneath. I was mad I didn't get to keep the storage above the nesting boxes, but realized I could put containers of food/treats/grit/etc under the poop board, and the hens leave it alone and it doesn't get pooped on.