HOUSING
PIH-92
pork industry handbook
COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA
Energy Conservation in Ventilating and Heating Swine Buildings
Authors
Robert L. Fehr, University of Kentucky
Raymond L. Huhnke, Oklahoma State University
Reviewers
David Shelton, University of Nebraska
William White, Jones, Michigan
Howard Williams, Boyd’s, Maryland
Energy Inputs
Energy is used in swine facilities for operation of fans, lighting, feed handling, creep heaters, water heaters and supplemental space heaters. This fact sheet will consider ways to save energy used for operation of the ventilation system including supplemental space heaters. Before considering ways to save energy, however, remember that most ventilation systems were designed to use energy to reduce the management required. In most cases, reducing energy use will increase the level of management required. Energy inputs used in swine production facilities are normally less than 5% of the total cost of farrow to finish production. Some methods of saving energy may increase other production costs, such as feed requirements, enough to offset any monetary savings. Even though energy expenses are a small percentage of the total production cost, there are ways to reduce energy use without adversely affecting feed use or animal performance. However, the primary objective of a ventilation system is to provide a productive environment for the animals.

Environmental Control
Ventilation Principles
It is important to understand how ventilation systems operate because ventilation rate has a major impact on energy use for supplemental heating. Ventilation systems are designed to vary air flows from minimum ventilation rates in the winter to maximum ventilation rates in the summer (Table 1).

These ventilation rates vary because there are different needs for ventilation at different outside temperatures (Figure 1). Ventilation rates are varied to: limit temperature rise during hot weather, control temperature during mild weather, control humidity during cold weather, and control odors and gases.
Table 1. Total Per-head Ventilation Rates for Confinement Swine Building During Various Times of the Year.
	Cold weather	Mild weather	Hot weather
		—cfm—	
Sow and litter	20	80	500
Pre-nursery pig (12-30 lbs.)	2	10	25
Nursery pig (30-75 lbs.)	3	15	35
Growing pig (75-150 lbs.)	7	24	75
Finishing hog (150-220 lbs.)	10	35	120
Gestation sow (325 lbs.)	12	40	150*
Boar (400 lbs.)	14	50	180*
* Use 300 per sow or boar in breeding facilities due to low animal density.
When the outside air temperature is above the desired inside air temperature, the best the ventilation system can do (without a cooling device) is to limit the temperature rise in the air as it passes through the building. The air temperature will increase because of the heat being added to the building by the animals, lights, creep heaters, motors, etc. As the outside air temperature decreases below the inside air temperature, temperature control is achieved by altering the ventilation rate until the heat losses, such as ventilation air and building surfaces, equals the heat gains listed previously. As the ventilation rate decreases to control temperature, the relative humidity in the building will increase. The humidity increase is caused by the lack of sufficient ventilation air to carry out the moisture produced by the pigs in the building. When the humidity level becomes too high, the ventilation rate must be increased to balance the moisture removed by the ventilation air with the moisture produced in the building. At low outside temperatures, the ventilation rate to control humidity is greater than the rate to control
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture Cooperating. H. A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. We adhere to the policy that all persons shall have equal opportunity and access to our programs and facilities.