In order to insure maximum bird cooling during hot weather, it is crucial that evaporative cooling pads are properly sized. Pad area should based on the total amount of air moved by the tunnel fans, not the size of the house (Table 1). The greater the fan capacity of a house, the more pad required. If not enough pad is installed in a house, the amount of air the fans move will be decreased. As the amount of air the fans move decreases, wind chill decreases and the temperature difference between ...the pad and fan ends of the house will increase. For instance, if we reduce the pad area by 25% in a tunnel ventilated house with fogging pads the cooling produced by the pads will be reduced by 20%, air flow will be reduced by 10% or more, the wind chill effect produced by air moving down the house will be decreased three degrees or more, and the temperature difference at the fan end of the house can increase by as much as 20% (Table 2).