Ventilation and temperature management is a key componenet in the production of healthy broiler chickens. In the last several years, chicken houses have gone from a couple of fans and drop curtains to today's setup of multiple fans , cool cells, vent doors and curtains or solid walls.  Some farmers prefer drop curtains.  The curtains can drop in an emergency such as power failure accompanied by failure of the farm's generator to function, but they are less efficient in the use of costly propane.  

Sollid walls save on fuel costs, and provide for more efficient air flow, but can compound problems during a power failure accompained by a generator malfunction.  Some farmers have "walled up" the north side of the broiler houses, leaving the south side with curtains.  Some integrators (Tyson, Sanderson, etc.) prefer solid walls and may require them for a farm to qualify for top pay from the company.