Tunnel and Cross vented barns employ a series of exhaust fans on one side of the animal house and have a series of air inlets on the opposite side of the barn to provide a controlled air exchange.  Tunnel vented buildings usually have the airflow from gable end to gable end, where a cross vented barn has the airflow running from eve to eve.  Fans are typically in groups of 3 to 6 fans with each group having its own thermostat to control operation. The total number of fans and number of fans in each control group depends on factors like size and geographic location of facility, and type of livestock being cared for. 

Some fans run continuously to remove moisture from animal confinement areas.  Additional fans are used to remove heat as the ambient temperature rises. Tunnel and cross vented barns provide positive and controlled air exchange and have higher energy use and operating costs than naturally ventilated barns.  Another technique used to cool livestock in cross or tunnel vented barns include evaporative cooling on the inlet side of the barn. Sprinkler systems that spray water directly on animals for cooling can be used in either cross-vented or naturally ventilated barns.  Barns with slatted floors should have enough fans evacuating the manure storage pit to create a negative pressure in the pit so that air is not drawn from the manure pit back into the barn.

Resources

• Tunnel Ventilation in Livestock Barns – Ontario Ministry of Agriculture, Food and Rural Affairs
• Tunnel Ventilation for Tie Stall Dairy Barns – Penn State Extension
• Natural and Positive Ventilation – Progressive Dairy
• Cross-Ventilated Barns for Dairy Cows – Dairexnet – Extension
• Low Profile Cross Ventilation Barns – Ontario Ministry of Agriculture, Food and Rural Affairs
• Cooling Costs for Tunnel-Ventilated, Cross-Ventilated Barns – Progressive Dairy
• Barn Ventilation Priorities – Dairy Herd Management