There are a two facts to remember when it comes to hot weather and tunnel-ventilated houses: First, the birds in the house will, over time, migrate towards the tunnel inlet end of the house if not prevented from doing so. This is true whether talking about broilers, broiler-breeders, pullets, or turkeys. It is basically in their nature to walk into a breeze. It doesn’t matter whether it is a dark house, cool cell house, fogging pad house, fogging nozzle house, or for that matter a naturally ventilated house with a large number of circulation fans blowing in one direction. The second fact is that if the birds are allowed to migrate performance will definitely suffer.