Chapter 9 - Tunnel Ventilation for Hot Weather

Tunnel ventilation is an extremely effective method of cooling broilers during hot weather. Using a 40’ x 400’ example house, six 48-inch fans each providing 18,000 CFM at 0.10 inch static pressure mounted in one end wall are required to tunnel ventilate the house. Increased air velocity produces a windchill effect on birds. The benefits arise from the increased convective heat loss with increasing air velocity. When evaluating the windchill effect in commercial production conditions, it should be kept in mind that air velocities around the birds are approximately 50% lower than the air stream velocity in the open area of the house.

A tunnel-ventilated house requires two ventilation systems and therefore two sets of inlets – winter and summer. The summer tunnel inlets consist of a bank of light trap inlet units. If 56” x 56” units are used, then provide two of these light-trap inlets per 48-inch fan. This is equivalent to 1 ft² of inlet per 450 CFM.

The light-traps would be located in the end of the house opposite the fans. During the winter, sidewall inlets would be used as previously described. Since only about one-third of the fans would be required to cool the house, sidewall inlets would be closed and the large, tunnel ventilation summer inlets would be opened.

Tunnel ventilation is only a hot weather ventilation system. Exhaust fans and air inlets installed in the sidewall are absolutely necessary for ventilation needs during cold and cool weather. Therefore, construction costs of tunnel ventilated poultry housing is more expensive than conventional ventilation. However, considering the effect of good environment on growth rate and feed consumption, tunnel ventilation should be strongly considered in regions subject to hot summer temperatures.

Caution is advised at air temperatures greater than 100°F. At these temperatures, increased wind speed actually causes a heat gain to the birds and any heat loss from the birds is almost entirely evaporative. When interior air temperatures are over 100°F, catastrophic broilers losses could result from operating ‘cooling’ fans without implementation of evaporative cooling.