Barns & Equipment

We have been hammering away at relieving heat stress on dairy cows for a long time, including how to design, build, modify and manage facilities. Heat stress occurs when the heat generated by the cow and heat received by her from the environment exceeds the amount of heat she can successfully release to her environment. SAAWW is a convenient tool for remembering the critical steps to cut heat stress.

• Shade for dairy cattle (any age) reduces the heat load on the animals from direct solar radiation.

• Air exchange is necessary when cows are inside a shelter to remove hot, stale, humid air and replace it with fresh outside air. A minimum 1000 cfm air exchange per cow is recommended.

• Air moving over cows at a high speed (220 to 440 feet per minute or 2.5 to 5 miles per hour) helps the cow increase the amount of heat she can lose from her body by convective cooling.

• Water is essential for a cow’s bodily functions. During heat stress conditions she needs extra water to enhance her cooling by evaporating it from her respiratory tract and the surface of her body. Plenty of clean fresh water to drink is the first step in any cow heat stress relief process.

• Water can also be applied to a cow’s skin and evaporation encouraged (sprinkling with a breeze) to remove more heat from her body. Passing air through a wet evaporative cooling pad or a fine water mist from a high- pressure misting nozzle will reduce the air temperature (and increase the humidity).

A mild day and a barn with inadequate air exchange (curtains closed or inadequate fans operating) can quickly increase the temperature humidity index (THI) and put a cow under heat stress conditions.

The upper temperature of a cow’s thermal comfort zone is usually expressed as about 77ºF. However, the impact of air humidity on the evaporation rate from the cow decreases cooling as humidity increases. This humidity can be a result of a hot, humid summer day or a hot, humid barn due to warm outside temperatures and inadequate air exchange. Cows can and do experience heat stress every month of the year due to poor or nonexistent ventilation systems.

A heat stress chart (Figure 1*) illustrates the relationship of air temperature and humidity and their impact on the cow’s stress level. A cow can begin to feel mild heat stress between 70 and 85ºF depending on the humidity in the air. At 80ºF and 80 percent relative humidity (RH) a cow in an under-ventilated, humid barn will feel a similar level of stress as a cow at 100ºF and 15 percent RH under a sunshade in the desert.

A dairy that does not respond to warm outside conditions with an appropriate increase in ventilation and drinking water could stress cows any month of the year. Does this happen at your dairy?

Use the chart in Figure 1* to learn the combined effect of temperature and relative humidity on heat stress. Humid, warm nights or barns with insufficient air exchange can be as harmful as higher temperatures when the relative humidity is low. PD

—Excerpts from Penn State Dairy Digest, April 2007

Robert E. Graves, Agricultural Biological Engineering Extension, Penn State University

Spring – time to plant corn, first cutting of hay and spread manure. But before you climb on the tractor seat, think about adjusting your barn ventilation in anticipation of warmer weather. That may be as simple as rolling up sidewall curtains or it may entail the removal of plastic tarps or plywood that protected structures from those brisk winter breezes. Regardless of what it takes, make sure to open up your barns before the hot weather.

The “comfort” zone for dairy cattle is 41 to 77ºF. Temperatures inside poorly ventilated barns could exceed that during the middle of the day even in early spring. Above 77ºF, cows are heat-stressed and dry matter intake suffers leading to a list of problems including reduced milk production, reduced reproductive efficiency and increased occurrence of metabolic disorders.

The effects of heat stress can haunt you for the rest of the year – recall that 1 pound of peak milk translates into 225 to 240 pounds per lactation. For example, 4.5 pounds decrease in peak milk can lower the lactation yield by 1,000 pounds. So make sure you have the capability to cool early lactation cows. Ration adjustments may be needed to compensate for reduced dry matter intake.

A great place to start addressing heat stress is the holding pen and the feed bunk. These two areas of higher cow traffic are prone to heat stress. Look for ways to provide fans and possibly sprinklers on cows at these locations. Below is a list of items to consider as the temperature rises:

• Open up barns (remove sides, roll up curtains) to maximize natural ventilation.

• Clean dust and residue off of fan cages as it can cause drag, which compromises the air-moving ability of the fan. (You would be amazed at how much better a clean fan can function relative to a dirty fan.)

• Ask yourself if any structures around cow housing can be removed or modified to allow for better air flow. Do you really need that ivy-covered corn crib you haven’t used in 10 years?

• Consider installation of a cow sprinkler system. (Your local dairy extension agent should be able to assist you in the design of these systems.)

• Is your feed bunk and holding pen adequately shaded? Is this true at different times of the day as the position of the sun changes? PD

—From Virginia Tech Dairy Pipeline, May 2007

M. Chase Scott, Extension Agent, Virginia Tech

As animal housing continues to move toward larger buildings, the research team at the Bioenvironmental and Structural Systems (BESS) Lab at the University of Illinois is working hard to keep up with industry trends. What this means is that the BESS Lab, which is known worldwide for testing livestock ventilation fans, is checking out larger and larger fans.

“For most new construction, the standard ‘large’ fan is no longer 48 inches, but rather 50 to 54 inches,” said Steven Ford, a research engineer in the U of I Department of Agricultural and Biological Engineering and manager of the BESS Lab. “Airflow rates have increased proportionally, so fan airflow capacities are reaching the limit of our current test chamber.”

Therefore, Ford has taken the lead on garnering industry support to build a larger test chamber.

“We have funds committed from ag ventilation companies in Canada, Michigan, Indiana, Illinois and Alabama,” said Ford, “as well as in-kind equipment donations from companies in Illinois and Wisconsin.”

The BESS Lab first opened in 1990 to provide unbiased engineering data to aid in the design, development and selection of efficient livestock ventilation fans. The lab tests ventilation fans sent to them by equipment manufacturers, or the manufacturers can rent the lab for a day, which Ford said is the most economical option.

“Companies bring their fans to the lab, along with one or two people to assist with the set-up,” he said. “This helps keep costs low and industry participation high, which ultimately is good for the livestock producer.”

Ford estimated that the lab has done more than 3,000 tests over the last 16 years.

“We work with manufacturing companies around the country,” Ford said. “We’ve tested fans from Europe and even Australia. We’re fairly well- known throughout the ag ventilation industry.”

Manufacturers have the option of listing their test data in “Agricultural Ventilation Fans: Performance and Efficiencies,” a biennial publication that provides performance test results of over 800 commercially available fans. This information can be accessed at the BESS website at www.bess.uiuc.edu, or a hardcopy of the book can be purchased through the Midwest Plan Service at www.mwps.org or the National Food and Energy Council at www.nfec.org as well.

Ford pointed to the impact testing has had on ventilation fan performance over the years.

“From 1991 to 2003, the average airflow performance of commercial livestock ventilation fans increased over 15 percent, and average electrical efficiency increased more than 20 percent,” he noted. “Those numbers tell me that manufacturers will improve their product performance when there is an active performance test lab.”

Ultimately, said Ford, the goal is to help producers make more informed choices in ag ventilation systems. “The right fan will reduce odors, minimize the health risk of inhaling dust-laden air and optimize profits,” he concluded. “Efficient ventilation systems are essential to producers.” PD

—Excerpts from University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES) News website

Leanne Lucas, College of Agricultural Consumer and Environmental Sciences, University of Illinois

Since it’s time to cool cows again, it’s time to tune up your cow cooling systems. The first thing is to clean your fans; dirty fans reduce air speed by 50 percent. With the price of energy these days, it is important to keep the fans clean. It is not against the law to clean fans twice a year, especially if you have dusty roads near the barns. The faster the air movement around the cow, the faster the sprinkler water will evaporate from the cow’s skin and the cooler they will be. The cooler the cow is, the more food she will eat and the more milk she will produce. Fans will use the same amount of electricity if they are dirty or clean, so keep fans clean.

The second part of the cow cooling process is the use of water to be evaporated off the cow body to take the heat with it and cool the cow. This means that you only need enough water to get the cow wet to the skin, then turn the water off and the fans will evaporate the water from the cow. Adding too much water reduces the efficiency of this process. The excess water runs off the cow, to the floor and then to the lagoon.

To conserve water, you should adjust your sprinklers to just add enough water to soak the cow’s skin and start to run off the cow. The length of the off cycle should be long enough to let the fans evaporate the water off the cow and then start again. There are some very good sprinkling controls on the market that are easy to adjust and will add more cycles as heat increases.

One of the [2006] Dairy Check-Off Projects was to determine the results of turning sprinklers off on one side of a barn at the Dairy Research Unit at midnight and turn them on again (by timer) for one hour after the cows came back from the milking parlor. Our nighttime cycle for this particular barn is one minute of water every ten minutes. This is a very short cycle compared to most dairies. The water savings was 600 gallons of water per cow from the end of May to the first week in October. On a 1000-cow dairy this will be 600,000 gallons of water saved, 1.2 million gallons on a 2,000-cow dairy.

Remember that the less water you use, the drier the floors and the lower the humidity in the barn. Sprinklers are stationary, cows are mobile. All it takes is a timer in front of the sprinkler controller to shut off the water when cows are in the parlor, laying down, etc. If you don’t have timers on the sprinklers, you are wasting water, have soggy cows and are filling your lagoon.

Less is more. PD

—Excerpts from University of Florida Dairy Update, Vol. 7, No. 2

David R. Bray, Dairy Extension, University of Florida

A Focus on Energy Technical Data Sheet
Animal barns require ventilation to keep cows and other farm animals comfortable and productive year- round. Ventilation provides fresh air, removes excess moisture and helps regulate seasonal temperature swings. The benefits are real and practical; ventilation helps farmers maintain healthy, productive animals.

Ventilation systems vary, depending on the barn configuration, climate zone and the type of animals being housed. For example, a naturally ventilated dairy freestall barn may require stirring fans only on the hottest summer days, while a tunnel-ventilated poultry barn will need the system to operate more regularly.

A ventilation system’s overall energy efficiency and its energy costs will depend on the fan. If you choose the least efficient fan available, you could double your energy costs and obtain less air output from the fan than more efficient models.

Energy efficient fans will reduce energy costs and offer better air output. However, after you choose the right fan, you must also make sure it is installed properly and maintained according to the manufacturer’s instructions. This [article] discusses ventilation fan designs, components, controls and maintenance. It also introduces different fan types and describes their use and ventilation benefits.

All fans are not created equal
Laboratory tests confirm that fan efficiency varies greatly. Tests conducted on high speed agriculture fans at the University of Illinois Bioenvironmental and Structural Systems (BESS) Lab and the Air Movement and Control Association (AMCA) demonstrate that fan choice impacts energy efficiency, operating costs, air output and ventilation effectiveness.

Most fans are rated in two ways:

1. by air volume output in cubic feet per minute (cfm) at a specified static pressure (in inches)
2. by energy consumed, or wattage of electrical consumption (watt)

Combining these two components provides a comprehensive rating for fan efficiency:

X cfm per watt at
X inches of static pressure

For example, a low efficiency fan will have a rating of 17 cfm per watt at 0.05 inches static pressure and a high efficiency fan will have a rating of 20 cfm per watt (or greater) at 0.05 inches static pressure.

Fan components affect efficiency
Shutters and guards can obstruct air flow and increase static pressure. On the other hand, use of a discharge cone reduces a fan’s static pressure. Reductions in static pressure can improve energy efficiency by 12 to 23 percent, depending on fan size. Fans used for tunnel ventilation should also be equipped with a diffuser to improve the energy efficiency.

As a fan’s diameter increases, its energy efficiency increases. Therefore, one large fan is more energy efficient than two small fans. From a ventilation control standpoint, it may be better to have multiple fans that can be staged; this configuration will help you achieve a balance between energy efficiency and efficient control.

Fan motors
The single-phase fractional horsepower (hp) motors used in agricultural fans generally range from 1/3 hp to 1.5 hp. A standard motor of this size range has a typical efficiency of 60 to 75 percent. Most motor manufacturers do not publish efficiency data for single-phase motors, so efficiency is unknown unless the motor is tested.

In the past few years, several companies have introduced high efficiency single-phase motors that increase the motor efficiency to 77 to 84 percent and reduce energy use for the same air output by 11 to 26 percent. Contact your motor supplier for more information on high-efficiency single-phase motors.

If a barn is wired for three-phase electrical power, and fan motors are greater than one hp in size, you might want to consider three-phase motors. Premium efficiency three-phase motors offer higher efficiency (2 to 8 percent) than standard three-phase motors. However, three-phase motors – less than one hp in size – are not readily available.

Fan controls
If fans are used for temperature control, you should install programmable thermostats to control the fans. This automatic control ensures fans are turned on only when needed. Place the thermostats in an area of the barn that will measure its air temperature, but make sure they are protected from possible damage by animals. If you choose to stage fans, set thermostats at progressively higher temperatures to reflect increased heat loads.

Choose a thermostat that is designed for the appropriate environment and make sure the enclosure for the thermostat is rated for moist environments. Keep the thermostat and its enclosure free of dust. Dust will cover it, act as an unwanted insulator and yield an incorrect temperature reading. You should also calibrate thermostats once a year for critical applications to ensure they are working properly.

Wind-fighting fans: Choose the correct air flow ratio
Wind affects fan performance. At some point, most fans will fight winds, but you can minimize this battle. Before installing fans, you should consider the prevailing wind direction and install fans on the downwind side of the barn. This placement is more efficient because the wind will have minimal effect on the fan’s performance. This placement is not always possible, given the barn’s location. And, in many places, wind direction changes continuously. Windbreaks can help, but it takes time to grow trees or vegetation and it may not be possible or desirable in certain situations. Choose fans with a high air flow ratio; a high ratio ensures that fans are less affected by winds than low air flow ratios.

Air flow ratio is defined as the air flow at 0.20 inches static pressure divided by the air flow at 0.05 inches static pressure. For 48-inch fans, air flow ratios range from 0.28 to 0.87 with an average of 0.74. There is little correlation between the ventilation efficiency rating and the air flow ratio; review both ratings when selecting a fan.

Fan maintenance
Any dirt that accumulates on louvers, guards or grills, shrouds or blades will reduce the air moved by the fan. If louvers do not open freely or if dust builds up on safety screens or grills, fan air flow can be reduced by 30 to 40 percent. All fans should be cleaned regularly to improve energy efficiency.

A safety requirement before you begin any fan or motor cleaning task, you must turn off the electricity to the fan and disconnect the unit from its power source. You should clean the accumulated dirt off the louvers and lubricate them with a dry lubricant such as graphite so they will not attract dust and dirt.

Dirt on motors can cause them to run hot, which leads to a breakdown in motor insulation and reduced motor life. A vacuum cleaner and a stiff brush will work best to clean motors, but for heavy deposits, a plastic scraper may be helpful. If the fan’s motor is totally enclosed and has a water-tight wire connection, you could use a power sprayer to clean the fan.

Loose belts can cause belt slippage, reduce air flow by up to 30 percent and shorten belt life. You should check and re-tension the belts monthly if the fan does not come equipped with an automatic tensioning device. This maintenance chore rarely gets performed as frequently as recommended by manufacturers. Therefore, most fan manufacturers offer V-belt self- tightening devices for new fans. Some of these devices can be retrofitted on existing fans to reduce maintenance costs and ventilation disruptions.

Finally, if your ventilation system is set up with emergency backup power or another ventilation system, test it regularly.

Summary of fan selection tips

• You should consider many parameters when determining the size and number of fans required for ventilation.

• Generally, larger diameter fans will be more efficient than smaller fans.

• Fans with a discharge cone will be more efficient than those without.

• Motor efficiency will affect energy use and the motor’s speed can affect efficiency and noise levels.

• Fan blade tip speeds greater than 4,500 feet per minute will create excessive noise levels. To keep noise levels low, fan revolutions per minute (rpm) should be less than 720, 480, 360 and 320 rpm for fan sizes of 24 inches, 36 inches, 48 inches and 54 inches, respectively.

• Machete or straight and teardrop blade designs are more efficient and accumulate less dust than cloverleaf-shaped fan blades.

• The clearance between the fan blade and the housing will affect efficiency and the static pressure at which the fan is capable of operating. Large clearances will allow air to leak back past the fan blade and housing. If the entrance of the housing to the blade is smooth and rounded, it will reduce the turbulence and drag of the air as it enters the fan blade air foil.

Fan types – stirring fans
Stirring fans move air within a structure to maintain a uniform temperature, eliminate dead zones and increase air velocity to cool animals. Currently, no energy efficiency data is available for stirring fans.

Two types of stirring fans are used to ventilate animal barns:

• high speed fans
• high-volume, low-speed (HVLS) paddle-type fans

High speed fans
High speed fans can be very simply designed. Some have a motor with a blade connected to the motor shaft and a grill to protect the blades. Others include box-type fans in which the motor and blade are supported by a shroud (the same type fan as is found in tunnel ventilation, but without shutters or diffusers). These box fans may or may not have a grill.

In a dairy freestall barn, high speed fans are typically installed over the feeding alley or over the center cow beds to provide cooling. Fans are generally spaced at a distance of ten feet for each foot of fan diameter. Therefore, 48-inch fans would be spaced at 40 feet, while 36-inch fans are typically spaced at 30 feet. Stirring fans are also commonly used in greenhouses and crop storage facilities to provide uniform temperatures and keep condensation from forming.

High-volume, low-speed (HVLS)
HVLS fans have been used in the agricultural market since the late 1990s. They should be installed in buildings with high ceilings, such as dairy freestall barns. HVLS fans are large paddle-type ceiling fans that range in diameter from 8 to 24 feet; dairy freestall barns typically use HVLS fans with diameters of 16 to 24 feet. The fans are mounted horizontally to push a column of air down to the floor. As the air movement is impeded by the floor, the air moves out in a radial pattern away from the fan.

These fans are the most energy-efficient units available today. A 24-foot HVLS fan will move as much air as six high-speed fans and consume only 1/6 the energy. In a typical four- or six-row dairy freestall barn, the fans are placed over the feed alley every 35 to 60 feet, depending on the fan size. Current owners have described other advantages, including drier floors, less flies, fewer birds in the barn and reduced noise.

HVLS fans come with a variable speed controller to adjusts the fan speed. Some dairy farmers are using the fans at slower speeds to keep the air from stagnating during the cooler months.

Critics of this technology are concerned that the air velocity over the cows is too low to provide effective cooling if the fans are placed down the feed alley. Feed manger lockups, cows and stall dividers all impede the air movement from the center of the barn to the outside walls of the building.

Misting systems to augment ventilation
Misting water into the air or onto the backs of dairy cows can increase the effectiveness of ventilation cooling. Studies have shown that combining misting with stirring fans provides a significant decrease in heat stress when compared with fans alone. Generally, these systems mist water over cows’ backs for a period of one to three minutes. Then, the misting is shut off for 12 to 25 minutes, while fans help to evaporate the water.

You should not mist dairy cattle in humid conditions, such as Wisconsin’s summer months, without using fans. If the water does not evaporate fast enough, wetting the cow can increase heat stress rather than decrease it. PD

—From 2006 Professional Dairy Producers Annual Business Conference Proceedings

Dairy cattle housed in freestall barns are normally separated from the feed delivery area by some sort of barrier. Barriers are important as they prevent cattle from walking and defecating on the feed.