Are you wanting a permanent solution or just something to get you through the winter?I was think of putting 1 pen at a time in the big yard.
The shed is plastic, it's not fiberglass. I was thinking about the insul-boards but am afraid the chickens will try and eat it. and I thought about covering the board with a tarp but worried about moisture build up. Cant use that spray foam around chickens, they will eat it... Mine do anyway. But thanks for the ideals.
If winter only, you could put some straw bales around the outsides.