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3 open minutes with Joe Harner

Progressive Dairyman Editor Peggy Coffeen Published on 18 July 2018
Cross-ventilation

In the mid-2000s, cross ventilation was introduced as the “dairy housing of the future.” Agriculture engineer Joe Harner and his colleagues at Kansas State University pioneered the concept of these mechanically ventilated, low-profile barns.

Benefits were touted, such as a smaller footprint and year-round temperature regulation to stabilize cows’ core body temperatures, thus positively impacting reproductive performance while minimizing environmental heat and cold stress. However, question marks loomed over the cost to operate and maintain the intense array of fans required to pull air across the width of the building.

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Now, roughly 10 years later, Harner revisits his early work and how cross ventilation has evolved from an emerging idea into one of the common barn design options.

Joe Harner

Joe Harner
Agriculture engineer
Kansas State University

What have we learned about cross-vent dairy barn design and management over the last decade?

HARNER: Most dairymen like the year-round environmental consistency provided by the cross-vent designs. Regardless of [geographic] location, there are more hours per year within the thermo-neutral zone of the dairy cow [in cross-vent systems].

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Producers I have remained in contact with indicate environmental consistency carries over to breeding and milk production and removes many of the seasonal swings. Probably another major change has been the evolution of the concept and adoption of wide-body buildings.

Many dairies today have adopted the concept of the wide body, which is the same style (200 to 500 feet wide and low-profile roof slope) but utilizing tunnel ventilation rather than cross ventilation. If the building is 200 feet wide (eight rows of freestalls), utilizing poly-carbonate panels along the sidewalls, on endwalls and for the ridge cap will result in a significant portion of the building having natural light.

Where do you see this housing style catching on most quickly (geographically, demographically)?

HARNER: Originally, it was anticipated in warmer climates and assumed the evaporative cooling system would help mitigate heat stress. However, more are actually constructed in colder climates to minimize cold climate issues such as frozen manure in alleys.

Typically, in cross vent, there are only one or two alleys that might freeze in cold weather compared to multiple alleys with a naturally ventilated housing system. The frozen manure results in herd health problems due to unevenness of the walking surface.

Cost differences between conventional freestalls and cross vents are minimal in colder climates. In northern climates, there is more investment in facilities or barns due to the enclosures with endwall doors and curtains and insulation. In warmer climates, the barn is mainly a shade structure, so cross-vent barns may be more expensive.

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How have things like evaporative cooling pads and baffles been adapted to make these barns most effective at cooling?

HARNER: As more cross-vent barns are constructed, there are more modifications such as removal of the baffles or evaporative cooling systems. Evaporative cooling systems require treatment of water or soft water to prevent nozzles or pads from accumulating mineral deposits.

Due to the cost of the system, many dairies have opted to install a traditional low-pressure soaker system on the feedline rather than an evaporative cooling system. Similarly, baffles are being removed and replaced by an additional row of fans or an effort to increase air speed across the width of the building. Without the baffles, the challenge becomes moving air into cow space (freestall area) since the air tends to avoid areas where there is resistance.

The ventilation system continues to be modified to accommodate wider buildings or three- or four-row pen configurations. Regardless of modifications being adopted, a key design parameter remains understanding the relationship between fan performance and static pressure. The upper static pressure limit remains at approximately 0.2 inch of water, and adding more fans without more inlet area may have a negative effect on fan efficiency.

How do electrical costs and maintenance costs/requirements stack up compared to other ventilation styles?

HARNER: A general rule of thumb for the early adopters of cross-vent barns was: The additional electrical cost due to year-round ventilation and artificial light was equal to 2 to 3 pounds of milk. (Realize this is milk price-dependent.) The electrical cost for the milk center is the same regardless of housing type. During the summer months, the electrical cost for the fans is similar between a cross-vent barn (400 feet wide) and naturally ventilated buildings with fans over the freestalls and feedline.

The difference is: With a cross vent, an individual can see all of the fans and associated electrical power by viewing one side of the building. So the main electrical cost difference is ventilation requirements during non-heat stress periods and the year-round power requirements for artificial lighting. With improvement in the efficiency of electrical lights, the electrical cost associated with lighting is reduced.

One difference to consider is: With cross vents and adequately designed lighting, the benefits of long-day lighting strategies are probably seen, so the actual cost for the electrical power for lighting may be moot. Most feel the improvements seen from environmental consistency exceed the electrical power requirements. Except for exterior door maintenance, the maintenance cost appears to be similar.

What key improvements have been made in cross vent?

HARNER: The original cross-ventilated buildings had numerous automatic doors for equipment accessing alleys. The doors were frequently damaged by equipment and had to be maintained. Dairies started adding 30 to 50 feet on each end of the building to enable equipment to turn into alleys, resulting in one to three doors on each end. The extra space on each end of the building is a fixed investment, so the more stall inside the building, the lower this fixed investment is per stall.

What do you think are some of the biggest misconceptions out there?

HARNER: Artificial versus natural lighting is frequently a subject of conversation. Regardless of the type of dairy housing system, generally there is a positive correlation in artificially lighted barns between amount of light (more footcandles of light per square foot) and perception of cow performance. While the minimum lighting requirements might be 15 footcandles, generally most people when entering the building with this amount of lighting assume the building is too dark.

Reducing the cost of insulating the cross-vent barns is another area where most feel they can save money. While the low-profile or wide-body buildings are commercial structures, there tends to be more dust, emissions and moisture inside a building used for dairy cows. This results in moisture vapors being trapped between the insulation and roof or dust accumulating on seams as being sealed. In either case, after a couple of years, the insulation begins to separate and fall down, creating more long-term problems.

As previously mentioned, some dairies are eliminating the evaporative pads due to maintenance. The maintenance problems are a result of inadequate or absence of water treatment to remove the hard minerals. Dairies are opting to install more fans to increase the air velocities but not install a low-pressure soaker system at the feedline. Unfortunately, multiple published research articles over the years have stressed the importance of using both water and air in heat abatement.

Research has shown moving more hot air across a hot cow’s body has minimal effect on abating heat stress. With the evaporative pads, the water was used to decrease the air temperature inside the building, corresponding to less heat stress. Without the pads, the water has to be sprayed on the cow’s back to increase the evaporative cooling for the body surface in conjunction with the air velocities. With air alone, the temperature differences between the air and cow bodies is not sufficient during hot weather to increase convective cooling sufficiently to reduce the impact of heat stress.

For a new build, what factors regarding cross ventilation should a dairyman consider?

HARNER: Time requirements for in-pen activities such as cleaning alleys and bedding freestalls. The first pen milked on a shift can have cows returning from the milking center in 10 to 20 minutes. Early adopters of the cross vent quickly helped designers and engineers understand the importance of incorporating a small holding area or pen at parlor exit to allow adequate time to properly perform in-pen maintenance tasks.

Earlier, the topic of insulation was mentioned, and dairymen should be observant to sags, separation or any indication insulation is not in its original position. Finally, the colder the climate, the more critical it is to make sure there are no cold pathways penetrating from the outside to inside of the building. Examples are screws penetrating through the insulation (a screw is a cold pathway) or I-beams or purlins that are uninsulated.

Cold pathways result in moisture condensation problems inside the building due to the warm air inside coming in contact with a cold surface. If possible, dairymen should tour facilities with different types of lighting and purchase a light meter to measure light levels inside a building. Employees should also participate in the tours to make sure they are comfortable working in the environment with the artificial lighting.  end mark

PHOTO: Cross-ventilated barns have caught on in colder regions where they minimize issues like frozen manure in alleys. Cost differences between conventional freestalls and cross vents are minimal in these colder climates. Photo by Patrick Flood.

Peggy Coffeen
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