Factors Affecting Moisture in Poultry Houses

Posted by Jones-Hamilton Co. on Apr 29, 2020
Jones-Hamilton Co.

Managing moisture levels in poultry houses is a vital part of producers’ efforts to improve performance and minimize a wide range of potential problems.


As birds grow, they convert feed and water into the energy needed to gain weight. This is a very inefficient process, however, and roughly 80% of water consumed is released in the house environment either through defecation or respiration. In addition, water is introduced to the environment as the result of poor insulation, improper ventilation, and cleaning processes, thereby compounding the challenge.

Ventilation is the most important tool in managing the in-house environment for ideal bird performance as it works to bring in just enough fresh air to dilute ammonia and other noxious gases while removing excess moisture. With current bird growth rates, minimum ventilation rates need to be roughly 20% higher than they were ten years ago. In general, to control house moisture levels, approximately 2.5 million cubic feet of air must be exchanged daily during the first week of a flock. That number increases to 40 million cubic feet by the end of the flock. However, no formula takes the place of careful oversight and management of flock needs.

The Impact of Equipment Maintenance on Ventilation

The condition of house and ventilation equipment can significantly impact the efficiency of a ventilation program. Dust or feather-covered fans, including shutters and screens, experience significantly reduced air moving capacity. When relative humidity levels rise or condensation occurs and dust becomes wet, air flow is impeded even more.

In addition, fans may not be able to reach optimal or target rotation speeds, which has a far greater impact on ventilation efficiency than many producers realize. For example:

  • Fan rotation 10% slower than target reduces air moving capacity of fans by 5-10% in low pressure houses (>0.05”)
  • Fan rotation 10% slower than target in higher pressure houses (0.15”) reduces air moving capacity of fans by 10-20%. As the same pressure, fan rotations decreased by 20% decreases fan output by up to 40%.

Fan shutters that do not open or close completely are also a sign of dust buildup or excessive house pressure. Shutters or vents that remain partially open regardless of the number of fans running is a sign that cleaning is needed. 

For optimal performance and moisture removal, be sure to:

  • Regularly grease fan bearings
  • Tighten or replace fan belts, as needed
  • Remove dust and feather build-up on fan blades, fences, etc.

Support for Fast, Efficient Cleaning

SWASHDUST-REPEL™ plays an important role in this process as it repels moisture to change the way dust adheres to a surface and decreases the amount of overall dust buildup. With SWASHDUST-REPEL™, dust is easier to remove, thereby decreasing cleaning time. Less dust buildup allows fans to operate at maximum efficiency. For those who use water to clean fans, less water is needed to achieve the same level of clean which is better for the house environment and the long-term performance of fan motors.

Looking Beyond Fans and Inlets

While it’s natural to start with fans, shutters and inlets when examining moisture removal challenges, it’s also important to recognize other elements that can impact the level of moisture or efficiency of moisture removal in a poultry house.

For example, house tightness and inadequate insulation can greatly impact the amount of moisture in a house. Insulation impacts the level of supplemental heat needed in colder weather and affects ventilation requirements year-round.

In addition, insulation can impact condensation which can greatly increase the moisture introduced to a house environment. Where there’s a temperature differential, there’s condensation; where there’s condensation there’s dust that sticks to surfaces — most often seen on drinking lines, cables, pulleys and air inlets and fan blades. With moisture, dust becomes more mud-like and becomes very difficult to remove.

Houses must also be tight with carefully managed airflow patterns. If air comes into a house through cracks or loose areas, rather than inlets, it will not be properly warmed. Warm air has greater moisture-holding capacity, which lowers relative humidity. One sign of improper airflow patterns which have the potential to increase house moisture is caked litter.

Water lines are another prime variable to introduce excess moisture and should be carefully managed to ensure appropriate line height for bird age/size, slope and pressure so that water is not leaking into litter. Dust buildup on waterlines is a big nuisance and is difficult to remove.

Manage Ventilation, Manage Relative Humidity

With equipment clean and in good working condition, focus next on house management aimed at maintaining the desired relative humidity levels in poultry barns. Read more on that in our next blog >>



SWASH™ is owned by Jones-Hamilton Co., a leading provider of science-backed solutions to the animal agriculture industry. Led by industry veterans who understand the challenges faced by producers, the SWASH™ team is dedicated to providing reliable, high-quality chemicals backed by dependable customer service and knowledgeable technical support. Our team knows that every penny matters and works continuously to ensure value, maximize efficacy, and enhance the bottom line.


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