3rd International Poultry Meat Congress

How Tunnel Ventilation Works
The goal of tunnel ventilation is to keep birds comfortable in warm to hot weather by using the
cooling effect of high-velocity airflow. The tunnel setup is especially suited to warmer areas and
where larger birds (5-8 pounds) are being grown. Tunnel systems are designed first to handle the
expected need for heat removal, providing the air exchange rate needed to exhaust excess house
heat in hot weather.
The tunnel setup also provides wind-chill cooling, moving air as in a wind- tunnel through the
length of the house. A velocity of approximately 500 to 650 feet per minute is needed for most
effective wind-chill cooling.
The wind-chill effect created by high-velocity air can reduce the effective temperature felt by
fully-feathered birds by as much as 10-12 degrees F. The graph below shows estimated effective
temperatures that result with different air velocities, for 4-week and 7-week birds.
As the illustration shows, caution must be used in tunnel ventilating with younger birds, since
they experience greater wind-chill effect for a given air velocity. Note that the “effective”
temperature can only be estimated, not read from a thermometer or calculated. Bird behavior
must be the guide to judging the right number of fans to turn on to create the air velocity and air
exchange rate needed to keep birds comfortable.
The high-velocity airflow of the tunnel setup makes it well suited to adding evaporative cooling.
This can be done either with in-house foggers or with evaporative cooling pads placed outside
the air inlets. This real cooling of incoming air, on top of the “effective” cooling produced by
wind-chill, can keep birds performing well even in very hot weather. Used alone, the wind-chill
effect of tunnel ventilation becomes less pronounced as air temperatures rise much above 90°F,
and above 100°F the air begins to warm instead of cool the birds.
How Transitional Ventilation Works
The transitional ventilation setup is a hybrid system that enables a grower to provide effective
negative-pressure ventilation in conditions where neither minimum nor tunnel ventilation would
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