I have what some call a "sun porch" on my coop. The other half of the building is enclosed, insulated, and lighted.
The pullets have spent almost the entire 5 months of their lives on the sun porch (except for time running around on the lawn). The chicken door to the enclosed room was closed. I have been trying to encourage them to move into the warm part of the coop for over 2 weeks, now. It has been freezing here essentially every night over that time.
They have sat on their roost in the sun porch and
looked at the light coming thru the chicken door. I put their food at the door first, then moved it inside. Next, I put their water at the door and then moved it inside.
For 2 weeks, they have had to enter the room for their food and water and I have been giving them a treat just before sundown and sneaking up and closing the chicken door behind them. If I forgot the treat until after it was dark - they'd roost outside and look at the light coming thru the chicken door. I would pick them up and push them slowly out of the darkness thru the door and into the light.
Finally!! Last night, they were standing around waiting for me in the nice comfortable, well-lit room waiting for their treat about 1/2 hour after sundown. Back in there waiting for me tonight - finally!
They can take a lot of cold but up here near 49° North, I was surprised that they were willing to sit out in the darkness when a lighted room was about 2 feet from the end of their nose
. Sunset today was officially at 5:34 pm.
Steve