Not sure why you think you 'nailed' me....<scratcheshead>....<shrugs>Here I made sure that I didn't step on @azygous 's toes and I nailed my friend @aart ! I don't know why your heating plate wouldn't work just as well outside, aart....seems to me that as long as the chicks can get warm and the area where the pen is located is free of direct drafts, they'd do very well.
My 'pseudo heat plate' could work outside,
just wanted to be sure I made the disclaimer that I hadn't used it outside,
and offer a different configuration to the 'cave'.
Not sure I will ever use it outside either, I have a Cadillac of a brooder, kinda of like the chicks inside the house,
and would probably have to have a spider web of extension cords to use it in my coop(which I hate-fire phobia) already too many of them out there.