Livestock Buildings is part of a series of Efficiency Checklists and Topics that can help you to assess all areas of your farming operation for energy efficiency and find ideas to save energy and reduce costs. For links to other articles in the Efficiency Checklists and Topics series, see Additional Resources at the end of this article.
Confined livestock structures need ventilation to remove heat and moisture and maintain air quality. The amount of ventilation needed varies depending on air temperatures inside and outside the building, amount of moisture to be removed, odors to be controlled, and the heat produced by the animals and equipment.
To reduce energy requirements for ventilation equipment, determine the number of fans needed to do the job and operate only those fans for as short a time as possible. For example, less ventilation is usually required in winter than in spring or fall and much less than in summer. Summer ventilation needs are usually high due to heavy heat loads. Winter ventilation needs are usually low because buildings need only enough air exchange to remove moisture and maintain air quality. Fan efficiency is reduced if obstructions are located near or in front of fans.
Several advances in technology have improved energy efficiency for livestock buildings such as efficient space heating, heat lamps, creep pads, and more energy efficient milking equipment.
Questions to ask:
- Are fan blades, motors and housings clean?
- Can you use natural ventilation rather than electrical fans?
- Are ventilation fans the right size for the number of animals in the building?
- Would automatic controls improve the efficiency of your application?
- Would zone heating and ventilation systems be appropriate?
- Would an air-to-air heat exchanger be appropriate?
- Is insulation and ventilation adequate to prevent condensation problems?
- Are the heating systems for the livestock facility properly adjusted and sized?
- Are thermostats accurate and located so that they are not affected by drafts and direct sunlight?
- Is more building insulation necessary?
- Are you using the appropriate and most energy efficient technology for your livestock operations?
Facts and Actions: Livestock Buildings
- Keeping dust off fan components helps motors operate cooler and prolongs their life. Clean fan blades move more air. Dirt, chaff, and animal hair clinging to protective guards reduce air flow. Dirty louvers and shutters that don’t open fully can reduce air flow by 40 percent. These should be cleaned and lubricated with a dry lubricant such as graphite so more dirt is not attracted. Loose fan belts can slip and reduce air flow by 30 percent. Fan belt tension and condition should be checked semi-annually. Install self tensioning devices on fans if possible to reduce the chore of tightening belts.
- Ventilation inlets need to be cleaned annual and adjusted for proper operation if they are adjustable.
- Natural ventilation uses airflow passages that allow clean air to enter a building and displace stagnant or dirty air. The difference in building pressure and atmospheric pressure, caused by wind passing over the building and by thermal buoyancy of air, creates the air movement. Using natural ventilation wherever possible will save energy by reducing the number of ventilation fans needed for an air exchange. Natural ventilation is typically used on open-sided buildings with curtain sidewalls and open roof peaks such as dairy freestall barns. The curtain sidewall can be closed during cold or inclement weather to protect the animals.
- It is important to size fans correctly for building ventilation. Fans that are larger than necessary waste energy and produce a cold air blast in the winter, while undersized fans will not adequately exchange building air. Air inlet size should be equal or larger than that required for the fan capacity, or the fans will operate at a higher static pressure than necessary and use additional energy.
- Automatically controlled ventilation systems reduce unnecessary fan operation and provide more uniform climate control. Variable speed controllers can be used to control the amount of air exhausted by slowing or increasing the speed of a single fan based on the building temperature.
- Select fans that are energy efficient. Fan efficiency is measured in cubic feet per minute per Watt (cfm/Watt) and reflects the air moved per energy consumed at a specific static pressure. There is a two-fold difference between the best and worst performing fans; therefore, if you make a poor choice, ventilation costs could be twice what they would have been if you had chosen the proper fan.
BESS Lab - University of Illinois is a source of independent test data for agricultural ventilation fans and has online access to fan test results. The recommended minimum efficiency for a fan 36 inches or larger is 20 cfm/Watt at a static pressure of 0.05 inch of water. Higher cfm/Watt values indicate more efficient fans.
- Fans with diffuser or discharge cones are 12 to 26 percent more efficient than fans without them.
- Large diameter fans are more efficient than smaller diameter fans. One method to get the energy efficiency advantage of a large fan and the usefulness of several small fans is to install a variable speed controller on a large fan with a temperature sensor. The fan speed can be changed at preset temperature points to reduce over-ventilation while maintaining temperature. The fan will act like a bank of small fans; as the temperature increases the fan speed will increase. When the fan runs at slower speed, the energy use is reduced by the cube of the percentage of full speed. For example: a fan running at half speed (0.5) will move half the air flow it would at full speed but use only about 15 percent of the energy required if the fan were operated at full speed (0.5 x 0.5 x.0.5).
- Significant energy savings can be achieved through zone climate control. The savings come from heating or ventilating only rooms or areas of buildings that are used or need more climate control.
- Insulation in livestock confinement buildings is necessary to reduce heat loss and condensation on walls and ceiling. Insulation should be protected from damage by birds and rodents.
- Beef and dairy calves may not require supplemental heat unless they are born in very inclement weather. A “hot box” or small room with radiant may be useful for this purpose.
- Baby swine and poultry require very precise temperature and humidity regulation that is normally engineered into the building; however, additional or spot heat can be provided if required. Certain safety precautions need to be considered. Some energy saving options:
- Heated creep pads for swine are more energy efficient than heat lamps and more evenly distribute the warmth.
Hovers provide small enclosed areas which capture heat and reduce drafts to provide a comfortable environment for baby pigs. This allows the overall building temperature to be kept lower.
- Radiant heaters can be used to heat larger areas. They warm the animals and objects in the building without directly heating the air, which reduces heating requirements.
- Hydronic floor heating will also reduce energy needs because it produces a microclimate near the floor where the animals are located rather than heating the whole volume of air in the building.
- Boilers or furnaces should be serviced and cleaned at least annually to ensure efficient operation. Depending on the amount of use, it may be cost effective to replace an older, less efficient heating system with a newer high efficiency unit with efficiencies of 90 percent or greater.
- Replace incandescent bulbs with compact fluorescent lamps or linear fluorescent fixtures, and mercury vapor lamps with high pressure sodium or pulse-start metal halide lamps.
Midwest Plan Service publications Low cost agricultural publications available through Iowa State University:
- Beef Housing and Equipment Handbook, Midwest Plan Service, MWPS-6. Fourth Edition, 1987.
- Dairy Freestall Housing and Equipment, Midwest Plan Service, MWPS-7. Seventh Edition, 2000.
- Swine Farrowing Handbook, Midwest Plan Service, MWPS-40. 1992.
- Sheep Housing and Equipment Handbook. Midwest Plan Service. MWPS-3. Fourth Edition, 2002.
- Horse Facilities handbook. Midwest Plan Service, MWPS-60. 2004.
- Heating, Cooling and Tempering Air for Livestock Housing, Midwest Plan Service, MWPS-34, 1990.
- Natural Ventilating Systems for Livestock Housing, Midwest Plan Service, MWPS-33, 1989.
- Mechanical Ventilating Systems for Livestock Housing, Midwest Plan Service, MWPS-32, 1990.
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Contributors to this Article
This publication was adapted from the Farmstead Energy Audit, North Dakota State University Extension.