I have stupid insulation question. 
We are in Texas. We are building a new open air coop with a metal roof. I'm concerned about insulating the roof from the hot Texas sun. What would be the cheapest way to accomplish this? Could I use old feed bags stuffed with hay for roof insulation? Are their drawbacks to this?
Who can give me some great ideas?

We are in Texas. We are building a new open air coop with a metal roof. I'm concerned about insulating the roof from the hot Texas sun. What would be the cheapest way to accomplish this? Could I use old feed bags stuffed with hay for roof insulation? Are their drawbacks to this?
Who can give me some great ideas?