There may be multiple reasons for that.
Here is a link to a post about roosts. @aart said it quite well.:thumbsup
https://www.backyardchickens.com/threads/proper-design-of-roost-bars.1197058/post-23176470
Read the complete thread and make your own decisions. :old :idunno
Build a Poop board shelf, on north wall all the way to the window. Then build your roost on top of the poop tray, elevated about 8 inches.
Your chickens will be out of draft currents even if the pop door is not closed.
Your poop board should have a vertical 2 x 4 on the open end, (end...