In summer, removal of excess heat from a layer house is critical for keeping a flock of hens comfortable and productive.
Heat stress reduces egg size because hens eat too little feed when they are too warm.
Since consumers prefer eggs graded as Large, the prices for Small and Medium eggs are normally discounted. This discount is greater in summer when heat increases the relative number of undersized eggs produced. Heat removal from a layer house is achieved by ventilation. In southern regions of the United States, tunnel ventilation, coupled with evaporative cooling of incoming air, has become accepted as the best way to control layer house temperatures and keep egg size up during the summer. The typical tunnel-ventilated layer house has large air inlets at the center of each long side of the house and banks of fans on each end.