The Importance of Minimum ventilation

• When outside temperatures are below 5 °C the inlet pressure drop, and opening size will need to be increased. The ability of the incoming air jet to attach to the ceiling depends on the temperature differentials between outside and inside the house. • Always use a smoke test to ensure that the incoming air reaches the centre of the house. Smoke tests should only be done when the outside temperatures are significantly colder than inside, and when there is no wind. • Inlets need to open enough to achieve the required static pressure and airflow. Depending on inlet design, a minimum opening of 2.5 to 5 cm is required to ensure cold air reaches the centre of the house. • Inlets should be installed as close to the ceiling as possible – about 30 cm below the eaves provided there is no interruption of airflow.

• It is common for cables to stretch and twist and can cause variability in perimeter inlet openings. Inlets closer to the drive unit are open more than those at the end of the house. This can be minimized by ensuring a sufficiently sized counterweight or spring. • Guide pulley position and size is very important for efficient closing and sealing of inlets. • All inlets require wind proofing covers on the outside of the house. The inlet cover should be at least 30% more than the cross-sectional area of the inlet to minimize air restriction. These inlet covers also help to reduce natural light entering the house. When it comes to minimum ventilation, there is rarely a one size fits all solution. However, by applying the information from this article together with good stockmanship, such as making daily adjustments to minimum ventilation based on air quality, humidity, and bird behaviour, will greatly assist with providing an optimum environment to achieving excellent bird performance.

• In open truss houses, the angle of the inlet opening must be such that the air is not directed onto a purlin which will redirect the air down to the floor. • Any obstructions (electrical conduit/concrete or wooden beams) should be removed because they interrupt the air flow, forcing air to the floor. • In the case of existing obstructions, a directional flap can be used on top of the inlet and/or a solid “air ramp” to aid the air in passing the obstruction. • When using a negative pressure ventilation system, it is not the placement of the fans which dictate uniformity of air distribution but rather the placement of the inlets. • To achieve uniform air distribution, inlets should be evenly spread throughout the house and open the same amount. • Houses over 100 m (330 ft) should have the inlet drive units installed in the centre of the side wall to reduce any inlet opening variation. Solid 5 to 8 mm (0.2 to 0.3 in) steel rods eliminate any stretch and twisting.

About this author Brendan Graaf is a broiler specialist with 10 years of experience in the poultry industry. He services the EMEA region. Brendan holds a bachelor’s degree in Animal Science and a master’s degree in Poultry Science.