Yeah, I haven't started digging yet...holidays interfered with that. Polycarb panels and we only just caulked all the seams/edges. I didn't have a clue about this until I read the forums. Wish I had known when we were putting ours up, but still, better late than never. We have straw bales on the outside perimeter and we use the water cooler bottles painted black and filled with water to help heat it as well. Every little bit helps.
