Automatic door opener
My coop is similar to yours in that I have a vertical wooden pop door that slides up and down. I bought a ChickenGuard. Attached it to the existing door via a pulley. I love it. The best purchase I ever made.
** Since you are in Michigan I would recommend the "Extreme" version, same one I purchaced, made for extremes in tempatures and can lift up to a 8 lb door. **
Edited by Dom'sHEns - 5/8/16 at 10:08pm
We've had it for about a year and other than the string breaking once, it's very dependable.
Edited by ChickenMammX4 - 5/9/16 at 6:14am