Good ventilation is indispensable in a poultry house (read more about this in our other blog: The relevance of a comfortable climate in poultry houses ). With the help of mechanical ventilation and air inlets/outlets, it is possible to control the temperature, humidity, airspeed, and CO2 content in the poultry barn, while harmful substances are removed. Too little or too much ventilation results in less efficient poultry growth, unnecessarily high energy costs, and an unhealthy barn climate for both humans and animals. But how do you control fresh air supply for an optimal barn climate?
Closed vs. Free-Range Houses
The easiest way to properly control the climate in a poultry house is to hermetically seal it from the outside world. Using fans, it is then possible to bring the exact right amount of fresh air into the house. If there is a need for more ventilation, for example, because the temperature or CO2 content is too high, you can simply adjust the air inlets or outlets, turn on an extra fan, or increase the speed of a controllable fan. This way, the weather outside has minimal influence on the climate inside the house.
Recently, more farmers are opting for free-range houses. At specific times, pop-hole doors are opened so chickens can walk outside freely. This significantly improves poultry welfare. However, it is crucial to adjust the ventilation system accordingly. In a regular negative pressure system, false air will inevitably be drawn in through these openings, leading to an uncontrolled barn climate.
Negative Pressure vs. Equal Pressure vs. Positive Pressure
An even barn climate requires fresh air to be well distributed throughout the house. This is achieved by strategically positioning air inlets and outlets. Fans can be placed in the air inlets (positive pressure system), the air outlets (negative pressure system), or both (equal pressure system).
Negative Pressure System
Negative pressure systems are by far the most common in poultry houses. In these systems, air is extracted from the house using exhaust fans. Due to the negative pressure relative to the outside air pressure, fresh air flows into the house through air inlets. By adjusting these inlets to match the amount of air being extracted, you can control the incoming airflow. The position of the air inlets determines the angle and speed of the air entering the house. Negative pressure systems are not suitable for free-range houses.
Equal Pressure System
Equal pressure ventilation systems are becoming increasingly popular in the poultry sector. In this system, both exhaust and intake fans are used, maintaining equal air pressure inside and outside the house. While the fans are slightly more economical since they don't need to generate pressure, twice as many fans are required. The advantage of equal air pressure is that the indoor climate remains stable, even when a door is opened. This makes equal pressure systems ideal for free-range houses.
Positive Pressure System
Positive pressure ventilation systems are rare in practice. In this setup, fresh air is blown into the house using fans and extracted in a controlled manner through air outlets. This increases the internal pressure relative to the outside pressure, causing air to escape through every gap. This reduces the likelihood of insects and diseases entering the house, a principle also used in hospitals and laboratories. When a door is opened, air flows out rather than in. Positive pressure systems are suitable for free-range houses. In practice, free-range houses often combine both negative and positive pressure systems for optimal climate control.
More Info
Be sure to check out our other blogs if you'd like to learn more about different ventilation systems or common mistakes in poultry houses. Interested in finding out which Multifan or EMI fans are suitable for poultry houses? Check out our poultry page.
