Crafting comfortable broiler barns

In all regions, no matter if it’s extremely cold and or hot and humid, house design is critical to ensure optimal air flow for bird cooling and comfort. When designing a modern broiler house, the first factor to consider is the optimum floor area for the best return on investment. 

New longer and wider houses challenge the ventilation system’s ability to produce uniform conditions across the house. Secondly, providing the correct air exchange and speed to keep the birds comfortable is important, but also consider the impact of rising energy on costs. 

Ventilation supports a good start
The primary goal of the broiler farmer is to stimulate feed consumption from chicks arrival on the farm to processing. The first seven days are the most important. The brooding period sets the precedent for good performance and extra effort will be rewarded in final flock performance. 

To ensure a good start, the grower must provide an environment that ensures optimum intake of feed and water. The perimeter ventilation system in conjunction with a circulation fan system, can be argued as the most important system in the modern broiler house. It ensures efficient air exchange and temperature management without creating excessive air movement at chick level. 

Until broilers have full feather development, they are very sensitive to air speed, which will directly impact activity and feed consumption. Choice and installation of a high-quality inlet is often overlooked by growers in hotter regions. Price rather than the impact on early performance is often the driver of equipment choice that ultimately only represents about three per cent of total capital cost. Consider that for every one gram of bodyweight improvement in the first week, will translate to an additional five grams or more at processing.

The other most challenging period is the grow-out phase (after 25 days). When the birds are fully feathered and stocking density is increasing rapidly, temperatures at bird level will increase running the risk of high body temperatures. The more heat that is removed from the birds, will lower the birds’ body temperature and make them more likely to consume feed. 

Designing and building a ventilation system for good performance
Capital investment is often driven by the need for high returns on investment or fast paybacks. Access to good quality equipment, government import tariffs and freight costs can limit choice. Investment decisions may be made without optimizing design and air flow requirements needed to ensure optimum bird performance and financial return. In today’s low margin environments returns depend on achieving performance in line with genetic targets. These are some essential design considerations:

• Good quality perimeter inlets for the minimum and transition ventilation stages for tunnel type housing, or in the case of cross ventilated houses, for both minimum and temperature control stages.
• The installation of the correct number of perimeter inlets. 
• Adequate static pressure control, by thorough sealing of houses. All new projects should be commissioned only after a house pressure test.
• Fan choice should be based on efficiency – not cost! Fan choice will be the most important equipment decision, especially in hot climates.
• The roof and/or drop ceiling insulation is one of the most important aspects of any new house project. 

The biggest challenge for tunnel ventilated houses longer than 120 m is maintaining an acceptable temperature pickup from the front to the back of the house, or commonly referred to as the ∆T, during the summer months with big birds. The level of bird comfort ultimately drives daily feed consumption. Even temperature distribution the length of the house will ensure uniform feed intake and processing weight uniformity.

To manage heat, consider the structure materials
The amount of heat the air collects moving down the length of the house will depend primarily on three factors:

• Metabolic heat added by the broilers;
• How quickly the air in the house is exchanged; and
• Thermal properties of the house.

Heat flows through surfaces from hot to cold, entering the house through the ceiling, side walls and curtains. The higher the resistance to flow or higher the R value of the surface, the lower the emissivity.

As well as entering the house through all surfaces, heat is also produced by the birds which are by far the greatest contributors to heat load. The value of an insulated roof or drop ceiling cannot be underestimated, as it is vital to bird comfort and operational costs. 

For example, improving ceiling R value from an R2 (simple plastic drop ceiling with no insulation) to a R10 should improve the ∆T by 1 or 2°C. Improving the ∆T will reduce the tunnel fan or air exchange capacity needed to achieve the goal of having an absolute maximum of 2.8°C temperature pickup on the hottest day of the season with the biggest birds. A broiler house should have a minimum insulation in the roof of R 10 in tropical regions, but in a region with cold winters this value needs to be in excess of R20. 

Providing an environment conducive to feed consumption is crucial for brooding success.
Photo: Alltech

Ventilation keys to keep the house cool
Heat is removed from the house by rapidly exchanging the air in conjunction with evaporative cooling in the form of evaporative pads or fogging systems. If the temperature difference between the birds and the surrounding air is minimal, heat removal from the birds will be low. By increasing the temperature differential with evaporative cooling, bird heat removal will be increased. The evaporative cooling system will provide at best a maximum of 20 per cent of the cooling capacity for the broiler. 

In a tunnel ventilated house air speed or wind chill effect is by far the greatest contributor to cooling, in the form of sensible heat removal. In a house with only cross ventilation, maximizing the air exchange rate and having an perimeter inlet that can force air movement towards the birds is important. 

Achieving significant airspeed requires very high operating static pressure and a multi-directional design of perimeter inlet.

Removing metabolic heat from birds depends on a fast air exchange rate and creating good airspeed at bird level. In a well-designed tunnel ventilated house an air exchange rate of approximately 40 to 45 s is common. 

In the colder regions with only cross ventilation, the air exchange rate should be close to tunnel ventilated houses for those few days in summer where temperatures rise above 28°C.

Unfortunately, a good air exchange capability alone in hot weather will not guarantee bird comfort. Air speed is the most important component, so many new houses built in colder climates are being designed with some tunnel ventilation capacity. 

The major challenge is the design of the tunnel inlet. Very wide houses, (> 25 m), pose a significant challenge to achieving air speed uniformity during tunnel ventilation. If tunnel speed is < 1.5 m/s, the tunnel inlet can be installed in the front wall of the house. Tunnel speeds higher than 1.5 m/s require u-shaped tunnel inlet which can negatively impact airspeed uniformity across the width of the house. 

In very wide houses, the airspeeds along the house sides tends to be significantly lower than down the center. Higher air speeds through the side wall tunnel inlet forces most of the tunnel capacity to move down the center ultimately creating higher speeds in the center.

Summary
Correct house design will support optimal air flow for bird cooling and comfort, during both hot and cold weather when stocking density is at its highest. Birds that are comfortable will consume more feed than hot birds. Likewise, energy efficiency is improved in a house that is designed correctly. Well-ventilated houses support good flock performance, health and welfare outcomes and, in turn, provide the biggest return on investment. 

Optimizing bird comfort and performance

Here are some key things to consider when tailoring ventilation and airflow for broiler comfort.

• Critical House Design: Regardless of climate extremes, house design plays a pivotal role in ensuring optimal air flow for bird cooling and comfort.
• Floor Area Optimization: Modern broiler house design begins with maximizing floor area for optimal return on investment.
• Ventilation Challenges: Longer, wider houses pose ventilation challenges, necessitating careful consideration of air exchange and speed to maintain uniform conditions.
• Brooding Importance:  The initial seven days set the precedent for broiler performance, emphasizing the importance of providing an environment conducive to feed consumption.
• Perimeter Ventilation: Perimeter ventilation systems, alongside circulation fans, are crucial for efficient air exchange and temperature management, particularly in sensitive early stages.
• Inlet Quality High-quality inlets are essential, especially in hotter regions, impacting early performance and overall flock success.
• Investment Considerations: Investment decisions should prioritize design and airflow requirements to ensure optimal bird performance and financial returns in low-margin environments.

Andrew Bourne is global genetic excellence – environmental specialist with Cobb-Vantress.