Bird health and production are significantly impacted by air quality, humidity and temperature. Mechanical ventilation systems play a crucial role in maintaining indoor air quality and disease control, but the current systems have limitations, particularly in caged-layer facilities.
These limitations are acutely felt in the Midwest, where hot, humid summers present challenges for its numerous poultry producers, especially in manure-belt layer houses.
Lingying Zhao, PhD, an agriculture air quality specialist and Extension educator at The Ohio State University, and her team researched current systems and designed an innovative ventilation system that addresses health and heat concerns. During a May 2025 University of Georgia webinar, she shared her team’s findings and their new design.
Ventilation issues
Large layer houses can house 100,000 to 200,000 hens in stacked cages and have automated systems for feed and water delivery, egg transport and manure removal, but they struggle to maintain uniform temperatures with current ventilation systems, Zhao explained. Cross ventilation and tunnel ventilation are the most common methods, but both have their disadvantages.
In a cross-ventilation system, air enters a layer house through inlets located under the eaves or on the ceiling and exits through exhaust fans on the side walls. This creates uniform airflow inside the house but doesn’t effectively remove heat in the summer.
Tunnel systems are the most common and address excess heat in most of the house, but problems still exist. In tunnel systems, fresh air enters a layer house from one end and is exhausted by fans located at the other end. This creates a wind-chill effect with high-speed airflow across the birds, making them feel cooler and reducing heat stress.
With tunnel systems, as air travels toward the exhaust, it absorbs heat and moisture generated from the hens. However, tunnel ventilation creates an uneven indoor environment, with differences in temperature, humidity and air quality throughout the house. Zhao noted that the air nearest the outlets will be hotter, have higher humidity and contain more pollutants, which results in hens nearest the outlets being at a higher risk for heat stress and experiencing decreased performance.
Uneven temperature presents problems
Due to the high stocking density of layer houses and hot, humid summers, heat stress remains a concern, even with state-of-the-art tunnel ventilation systems, Zhao pointed out. She explained that poultry are happiest and healthiest within a very narrow window of temperature fluctuation. They maintain their temperature at 105° F (41° C) to 107° F (42° C), experiencing heat stress easily if their temperature rises.
Heat-stressed birds spend less time feeding and moving and more time drinking, resting and panting. Egg production also suffers with decreased production rate, reduced egg quality and increased hen mortality.
Virus spread and disease outbreaks are also impacted by airflow. “The mixing of air by ventilation systems facilitates the transmission of viruses among hens and speeds the spread of the disease,” Zhao noted.
New design advantages
Providing comfortable and safe indoor environments for hens in large layer houses is complex. Ventilation systems must address heat stress and disease outbreaks, both of which cause significant economic loss to producers.
Zhao and her team developed an upward airflow displacement ventilation (UADV) system for commercial manure-belt layer houses that reduces heat stress and disease outbreaks, preventing economic loss.
An upward airflow is formed inside the house, and air is removed without passing through other cages, Zhao explained. In their design, fresh air is uniformly supplied from air ducts located beneath the cages. This air collects heat from the hens, along with air pollutants, and is then pulled upward in the aisles. Exhaust fans on the roof then pull the air out of the house.
“This ventilation design provides efficient removal of heat, moisture, air pollutants and viruses. It is the shortest pathway for the removal of contaminated air, compared to existing tunnel and cross ventilation systems,” she said.
The design and testing to date of the new UADV system have been evaluated using a computational fluid dynamics model developed by The Ohio State University. The simulations demonstrated that, compared to existing tunnel ventilation systems, the new UADV system provided more uniform thermal conditions with less heat stress, Zhao stated.
“The UADV system enhanced air-exchange efficiency in the cage zone by 129% in the summer and 46% in the winter. It also provided a more uniform indoor thermal environment, with 38.2% fewer heat-stress areas in summer and 9.6% fewer cold-stress areas in winter,” she explained.
Additionally, the system limited pathogen transmission in layer houses, according to the simulation data.
Zhao stated that her team has submitted a provisional patent application for this new ventilation design. However, she said that further research is needed to test the system in on-farm scenarios.
