Is the secret heat or light? Do I place a heater in the roost area? Or do I need to cover the whole coop in plastic and keep it all warm for the winter? Or supply a warmed area immedietly around the roost box that is heated but not heat the whole 36x24 fenced area? Or do I need to add a light inside the roost area to wake them up earlier? Sunrise is 7:30 am Sunset is 6pm Or is it a combination of Light and heat?