Ventilating the world’s largest cage-free layer house

With the U.S. egg-laying industry potentially moving toward 100% cage-free production, new housing systems are being tested to find what methods make the most sense economically while providing for bird health and welfare.

Recently, an Iowa egg producer constructed a unique two-story, cage-free house for 540,000 hens. (Deven King)
Recently, an Iowa egg producer constructed a unique two-story, cage-free house for 540,000 hens. (Deven King)

With the U.S. egg-laying industry potentially moving toward 100% cage-free production, new housing systems are being tested to find what methods make the most sense economically while providing for bird health and welfare. Recently, an Iowa egg producer constructed a unique two-story, cage-free house for 540,000 hens.

Inside the outer skin of the building, walls and roof, are four housing enclosures or rooms. These rooms are arranged as two stacks of two, which are placed side by side with air space in between the two stacks and over the top of the stacks to serve as a plenum for air movement from outside the building to the inside of the rooms. Each room is 100 feet wide and 640 feet long and houses 135,000 hens. Each room has five zones. The exterior dimensions of the building are 220 feet by 640 feet.

The birds can move across the 100-foot width of the room, but each room is divided by fencing into five compartments that are 128 feet long. This type of aviary system is called a Bolegg Gallery created by Vencomatic.

Building ventilation

This ventilation system was designed by a group of people working with several organizations. Ventilation experts at equipment suppliers Munters and Valco, managers for the egg production company responsible for building the new systems and engineers from Henning Construction.

The layer house temperatures for ventilation are set between 68 and 78 degrees Fahrenheit. Set temperature is based on flock age and feed consumption. 

Building ventilation was automatically controlled with a PMSI Command III environmental control system from Poultry Management Systems Inc.  Openings for the inlets are controlled according to the ventilation stage and the house static pressure using this system.

Air is introduced through the plenum using air inlets and hemisphere fans during cooler temps.

Both floors of the laying house are equipped with six 36-inch sidewall fans and 30 51-inch sidewall fans mounted in six exhaust fan banks on the outside wall.

Light traps, made custom for this system, are installed between birds and the sidewall fans. Single-speed fans are controlled by static pressure and air temperature and are placed strategically to maximize the outcome of the regulated ventilation airflow. There are 13 ventilation stages.

There are 52 propane-fueled forced air heaters in the entire house (13 per room). Each room has three heaters in the blower room to heat the recirculated air. This air is not only used for keeping the birds warm, but it also dries the manure on each belt. Sizing and placement of the heaters were critical for generating optimum comfort. A heater that is too big results in inefficiency, and one that is too small might not have enough heat to maintain the desired room temperature.

This building uses elevated airspeed for cooling rather than an evaporative cooling system.

Upper floor

The east rooms of the second floor (Room A) and first floor (Room B) are ventilated differently.

Fresh air enters Room A from the attic through the eave inlets surrounding the whole perimeter of the house. It then comes into the room through ceiling inlets mounted over two of the six aisles of birds. In cooler weather, 198 ceiling inlets per upper unit of the house are open. Slot inlets for the interior wall of the plenum are used in hot weather or when maximum ventilation is desired.

Ceiling Inlets

Fresh air enters Room A from the attic through the eave inlets surrounding the whole perimeter of the house. It then comes into the room through ceiling inlets mounted over two of the six aisles of birds. (Deven King)

Lower floor

Room B has no ceiling inlets. Instead, fresh air enters the room from 75 inlets on the east outside wall with hoods and light traps. There are an additional 147 inlets on the west interior wall to be used during cooler temperatures. Like Room A, Room B also has continuous slot inlets for warmer weather.

Light Traps

Light traps, made custom for this system, are installed between birds and the sidewall fans. (Deven King)

The west side of the house mirrors rooms A and B.

An initial analysis of the system

Brett Ramirez, Ph.D., assistant professor in the Department of Agricultural and Biosystems Engineering at Iowa State University (ISU) took an in-depth look at the ventilation system on the east side of the building located in Iowa.

Cage Free Laying House Side View

The east rooms of the second floor (Room A) and first floor (Room B) are ventilated differently. The west side of the house mirrors the east.

Together with his team, Ramirez was able to reduce heating fuel usage through the identification of improper ventilation control parameters.

“Each facility requires individual tuning of settings and, with the enormous amount of data available in modern ventilation controllers, troubleshooting and optimization are much simpler to perform and achieve,” he said.

Through the team’s evaluation, they also found that “house-level sensible heat production was determined to be greater than previous values found from cage-free barns.” Ramirez explained that this finding will affect future cage-free housing supplemental heat and ventilation design.

The classical understanding of how animals lose heat suggests that, as temperature increases, sensible heat production decreases; however, air temperature, relative humidity, and airspeed all affect the thermal comfort (heat loss) of the birds, he said.

“So, in this facility, with high airspeeds, we measured a little decrease in heat production as temperatures increased, suggesting the ventilation system was adequate in maintaining the birds in their thermoneutral zone,” Ramirez said.

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