Great looking barn, Birdguy! It is wonderful that the good weather has held out so long so that this can be completed before the snow builds up!
My husband and I are converting a horse stall in the our steel sided barn to a chicken coop (the previous owners of the property had horses). Could you show a picture of your pop door or mention how you are planning to insert it? Are you having workers install the pop door or are you doing it yourself?
Our barn is not insulated like yours, but I am trying to figure out aside from cutting a pop sized door in the metal siding, what sort of flashing etc. should go around the pop door. Someone we talked to mentioned putting J channel around the pop door, so I am doing research on that. We plan on having a secure run outside of the chickens pop door like you mentioned.