Ventilation Systems: Which is Right for your Facility?
Not sure which ventilation system is right for you? Below we discuss the three most common types of ventilation systems; natural ventilation, tunnel ventilation, and cross ventilation.
Natural Ventilation was used by the Egyptians and the Romans to cool ancient buildings by design. The basic concept behind natural ventilation is that heat rises. If you give the warm air a place to escape at the highest point of the structure, it will exit. In the process of exiting, it will create a very slight negative pressure in the building which in turn draws in fresh air from outside. This works well when the air outside is colder than the air inside, but when that is reversed the entire functionality of the system falls apart. Summertime ventilation can be inadequate when it is hot outside and there isn’t any breeze to be found. Fans placed on the inside of the barn to keep air moving can help cool cows, but fail to draw in an acceptable quantity of fresh air to reduce gases and pathogens to an acceptable level. Lack of control is the biggest downfall of a naturally ventilated structure.
To address the issues with Naturally Ventilated barns, many farms turned to mechanical ventilation. Tunnel Ventilation got its name from the shape of most early freestall structures, which were necessarily longer than they were wide. If you installed fans on the narrow end and allowed air to enter at the other end, it essentially flowed through the “tunnel”. The advantage of tunnel ventilation is the ability to control the quantity of air moving through the structure, and it requires less fans to achieve a desired velocity than if you put them on the side of the building. Typically, however, the stalls are perpendicular to the airflow, so very little air makes it down in between the animals to maximize their cooling comfort.
Cross Ventilation is the opposite of tunnel ventilation. Fans are placed on the long “sides” of the building and the air is drawn from the other side, usually through a curtain. The advantage of cross ventilation is that the air now flows in the same direction as the stalls. This allows air to get down between the animals and better cool them in hot conditions. Baffles can be placed at the center of the head-to-head stalls and the air is forced down under the baffle, right where the cows are standing or lying providing high-velocity air for their comfort.
Different projects have different environmental conditions, different desired outcomes and different input constraints, so no one type or style is perfect for every situation. Knowing there are different ways to approach cow comfort needs is the first step to choosing the correct one for you.