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Livestock production encompasses various aspects that significantly influence animal health, welfare, and overall productivity. Ventilation is a crucial element in both livestock and greenhouse facilities, as it regulates temperature, humidity, and air quality. Static pressure plays an important role in any ventilation system. Understanding static pressure is crucial for designing efficient ventilation systems because it helps determine how much resistance the system faces as air flows through inlets, vents, fans, and other components.
This article explores the role of static pressure in livestock and greenhouse production, stressing its importance for efficient ventilation, animal welfare, and maintaining optimal levels. It highlights static pressure as a key factor and advises growers to assess it carefully to ensure both animal welfare and operational efficiency.
Static pressure
Static pressure is the pressure exerted by air or a fluid such as water when it is still or moving steadily within a closed space. A simplified example is a cup of water. Static pressure is the force the water applies to the walls of the cup. The pressure stays the same throughout the water, no matter how fast it moves, because it comes from the water molecules bumping into the inside of the cup.
In livestock and greenhouse facilities, static pressure refers to the pressure differential created by ventilation fans between the interior and exterior of the building.
Static pressure is important for regulating airflow through ventilation systems, including fans, curtains, and inlets. By carefully managing static pressure, producers ensure that fresh air is evenly distributed throughout the barn. This not only promotes energy savings for equipment like fans but also reduces the accumulation of harmful gases, creating a healthier environment for animals.
How static pressure works
Two tubes are connected to an instrument called a manometer, which measures differences in pressure between locations. The manometer shows these differences by making the fluid move towards the lower-pressure area. To measure pressure changes caused by exhaust fans, one tube is placed inside the building and one is placed outside, causing the fluid to rise accordingly.
Ideal static pressure levels
The appropriate static pressure for operating ventilation in a livestock or greenhouse facility is determined by factors such as the building’s size, design, layout, and purpose, as well as conditions such as temperature and humidity. Producers typically measure static pressure in inches of water (sometimes abbreviate as inWC or simply WC) when evaluating the pressure difference. Maintaining a consistent static pressure difference between the inside and outside of the building helps ensure steady airflow throughout the building.
Inches of water, sometimes called inches of water gauge, is sometimes abbreviated as inWC or simply WC.
For more information, see the Wikipedia article.
Swine
Swine are sensitive to temperature changes. Proper ventilation, controlled with the help of static pressure, is essential for maintaining ideal temperatures within swine facilities. This is especially true in hot and humid areas or during harsh weather conditions. This is critical for preventing heat stress, which can impair growth rates, reduce feed intake, and lower reproductive success in pigs.
The ideal static pressure range is usually between 0.05 and 0.12 inches of water. If the pressure goes below or above this range, it could mean there is not enough fresh air coming in or there is too much restriction in the ventilation system. So, it’s important to keep an eye on the static pressure to make sure the ventilation system is working well and the pigs are comfortable.
Poultry
Static pressure plays a crucial role in regulating airflow and temperature in poultry houses. It ensures efficient heat removal and adequate ventilation in hot weather to prevent overheating. Maintaining proper temperature levels reduces stress on the birds and enhances growth rates and feed conversion efficiency. Also, the width of the poultry house influences the required static pressure and the size of inlet openings. Wider houses require in higher pressures and larger openings compared to narrower ones.
In poultry houses, especially in cold weather conditions, the optimal static pressure is usually between 0.05 and 0.25 inches of water. For layers, the recommended range is 0.10 to 0.25 inches. For broilers, it is between 0.05 and 0.15 inches. These specific ranges help ensure effective ventilation tailored to the needs of the birds.
Dairy
Dairy cow barns are typically designed to meet or exceed industry standards, helping ensure the safety and well-being of the cows — think “cow comfort”. However, if the exhaust fans operate at too high a rate because of high static pressure levels, it leads to increased operating costs.
When static pressure is too low, it means there is not enough force to move air properly through the ventilation system. This usually causes warm air to stay up high and cold air to stay down low, disrupting airflow. On the other hand, if static pressure is too high, fresh air will not mix well with the existing air, causing inefficient ventilation. That is why it is crucial to maintain the right static pressure for effective ventilation and optimal conditions for dairy cows.
A standard static pressure level in dairy barns is generally maintained at less than 0.15 inches of water column. Levels exceeding 0.20 inches of water column are considered undesirable as they can lead to inefficient ventilation and increased energy usage.
- Static pressure measures how different ventilation system components affect airflow within a system.
- The right static pressure helps ensure that incoming air mixes and warms up properly before reaching the desired level.
- It is important to recognize that static pressure is not the only factor determining the creation of good airflow. The direction of the incoming air is equally important.
Greenhouses
Static pressure is beneficial for controlling airflow in greenhouses, helping ensure that hot air is effectively removed and replaced with cooler air as needed. This is important for preventing overheating, especially during sunny periods, that can harm plants and hinder their growth.
In greenhouses, the ideal static pressure difference is typically around 0.05 inches of water, with a suitable working range of between 0.03 and 0.13. These values help maintain optimal airflow without causing drafts or inefficiencies in the ventilation system.
Ventilation and fan considerations based on static pressure
- Make sure fans you are considering have been independently tested for airflow and efficiency at different static pressure levels.
- Static pressure does not indicate how much air enters the building; it indicates how much negative pressure the fans generate as they draw fresh air through the inlets. In other words, it is related to the velocity (speed) of incoming air but not directly to volume.
- Fan capacities are rated for a specific static pressure. As static pressure increases, the volume of air a fan can move (measured in cubic feet per minute, abbreviated as cfm) decreases.
- Negative static pressure is a barrier to airflow through a system and creates inefficient ventilation.
- A mechanical ventilation system attempts to maintain a static pressure balance.
- Fans can generate either positive or negative static pressure, depending on their configuration and role within the ventilation system. In some applications, fans are designed to create positive pressure to push air into a space, while in others, they create negative pressure to pull air out of a space.
Conclusion
Livestock and greenhouse production rely on good, efficient ventilation to maintain optimal conditions. Despite the importance of static pressure within the ventilation system, it is often overlooked as a factor. Recognizing the role of static pressure in your ventilation system can guide you to improve your system’s efficiency and effectiveness, which, in the end, can reduce costs, increase productivity, and make your operation more profitable.
Phason Controls has two controllers that can control ventilation systems using static pressure measurements: AutoFlex Connect and the SPC-2.
AutoFlex Connect controls ventilation systems according to temperature, but it can also measure static pressure and use those readings to influence or modify the settings when the static pressure readings are out of range.
The SPC-2 (Static Pressure Control) operates inlets or curtains according to static pressure only and does not measure temperature.
