American Society of Agricultural and Biological Engineers

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1 ASAE EP270.5 DEC1986 (R2012) Design of Ventilation Systems for Poultry and Livestock Shelters American Society of Agricultural and Biological Engineers ASABE is a professional and technical organization, of members worldwide, who are dedicated to advancement of engineering applicable to agricultural, food, and biological systems. ASABE Standards are consensus documents developed and adopted by the American Society of Agricultural and Biological Engineers to meet standardization needs within the scope of the Society; principally agricultural field equipment, farmstead equipment, structures, soil and water resource management, turf and landscape equipment, forest engineering, food and process engineering, electric power applications, plant and animal environment, and waste management. NOTE: ASABE Standards, Engineering Practices, and Data are informational and advisory only. Their use by anyone engaged in industry or trade is entirely voluntary. The ASABE assumes no responsibility for results attributable to the application of ASABE Standards, Engineering Practices, and Data. Conformity does not ensure compliance with applicable ordinances, laws and regulations. Prospective users are responsible for protecting themselves against liability for infringement of patents. ASABE Standards, Engineering Practices, and Data initially approved prior to the society name change in July of 2005 are designated as "ASAE", regardless of the revision approval date. Newly developed Standards, Engineering Practices and Data approved after July of 2005 are designated as "ASABE". Standards designated as "ANSI" are American National Standards as are all ISO adoptions published by ASABE. Adoption as an American National Standard requires verification by ANSI that the requirements for due process, consensus, and other criteria for approval have been met by ASABE. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. CAUTION NOTICE: ASABE and ANSI standards may be revised or withdrawn at any time. Additionally, procedures of ASABE require that action be taken periodically to reaffirm, revise, or withdraw each standard. Copyright American Society of Agricultural and Biological Engineers. All rights reserved. ASABE, 2950 Niles Road, St. Joseph, Ml , USA, phone , fax , hq@asabe.org

2 ASAE EP270.5 DEC1986 (R2012) Design of Ventilation Systems for Poultry and Livestock Shelters Developed by joint Structures and Environment-Electric Power and Processing Division Committee on Animal Shelter Ventilation; approved by the ASAE Electric Power and Processing Division and Structures and Environment Division Steering Committees; adopted by ASAE as a Data February 1963; revised June 1966, December 1968, March 1970; revised April 1975 to incorporate and supersede D249, Effect of Thermal Environment on Production, Heat and Moisture Loss and Feed and Water Requirements of Farm Livestock, which was originally adopted by ASAE 1955; reconfirmed December 1979, December 1980, December 1981, December 1982, December 1984, December 1985; revised and reclassified as an Engineering Practice December 1986; reaffirmed December 1991, December 1994, December 1999, December 2001, February 2003; revised editorially March 2003; reaffirmed February 2008, December Keywords: Energy, Livestock, Poultry, Shelters, Ventilation 1 Purpose and Scope 1.1 This information is provided for the convenience of agricultural engineers and other professional persons serving the agricultural industry. It includes basic information and technical data, supported by research, for use in designing and/or evaluating ventilation systems for livestock or poultry shelters. Much of the information presented in Section 3 General Design Information will apply to the design of ventilation systems for any structure housing livestock or poultry. 1.2 In addition to the design and configuration of equipment, hazard control and accident prevention are dependent upon the awareness, concern, and prudence of personnel involved in the operation, transport, maintenance, and storage of equipment or in the use and maintenance of facilities. 2 Definition 2.1 Ventilation as used herein is defined as a system of air exchange which accomplishes one or more of the following: Provides a desired amount of fresh air, without drafts, to all parts of the shelter. A draft is an air speed in excess of m/s ( ft/min) in cool weather (speed depends on animal size). In summer these limits may be exceeded except for small animals. High air speeds, besides causing wind chill, may also create excessive dust levels Maintains temperatures in the shelter within desired limits Maintains relative humidity in the shelter within desired limits for the animal species (see Section 4 Ventilation for Dairy Cows and Calves, Section 5 Ventilation for Beef Cattle, Section 6 Ventilation for Swine, Section 7 Ventilation for Broiler Chickens and Young Turkeys, Section 8 Ventilation for Laying Hens, through Section 9 Effect of Environment on Sheep for relative humidity requirements by species) unless ammonia levels are beyond desired limits for operating personnel Maintain ammonia levels in the shelter at less than 25 mg/m 3 for operating personnel. This limit was set by the American Conference of Government Industrial Hygienists for personnel working no more than four intervals of 15 min each per day in the shelter. The 8 h threshold limit is 18 mg/m 3. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 1

3 3 General Design Information 3.1 Weather data Design temperature. The outdoor design temperature should be selected for the particular area where the animal shelter will be located. The cold weather temperature is normally used for determining heat loss from a building, insulation requirements, minimum continuous air exchange rate and supplemental heating requirements. The summer design temperature is used to determine the maximum required ventilation capacity Cold weather conditions. Cold outdoor air contains relatively small amounts of moisture. As the cold ventilating air enters the building and warms up, it has the capacity to absorb relatively large quantities of vaporized moisture from within the building. Outside design temperature suitable for calculating winter minimum air exchange rates and heat loss through the building components are shown in Fig. 1. Tabular data on outside winter design temperatures can be found in several books and periodicals. Most are derived from the American Society of Heating, Refrigerating and Air-Conditioning Engineers Handbook of Fundamentals or other ASHRAE publications. The 97.5% values are recommended for animal shelter use. Figure 1 Winter (Dec.-Feb.) temperature that is exceeded more than 97.5% of the time Hot weather conditions. In buildings which depend upon mechanical ventilation during hot weather, air exchange must be sufficient to keep the inside temperature only slightly warmer than the outside temperature. Summer design temperatures suitable for calculating maximum air exchange rates are shown in Fig. 2. The design maximum ventilation capacity can be computed using equation and an assumed temperature difference of 1-2 C (2-4 F) or equation , whichever gives the greater exchange rate. Figure 2 Summer dry-bulb temperature data. The dry-bulb temperatures shown will be exceeded not more than 5% of the 12 h during the middle of the day in June to September inclusive (Ausburger, et al.). ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 2

4 3.2 Building requirements Heat transmission through building materials. The rate of heat transmission through building materials depends upon the characteristics of the material. A comprehensive list of heat transmission coefficients of building materials is given in the ASHRAE Handbook of Fundamentals Need for vapor barriers. Animal shelters of the totally enclosed and ventilated type may be subjected to high moisture conditions. For example, a shelter with inside air temperature of 10 C (50 F) and relative humidity of 75% and with outside air temperature of -12 C (10 F) and relatively humidity of 85% will be subjected to a winter vapor pressure difference of approximately kpa (3 in. H 2 O). A vapor pressure difference of this magnitude forces water vapor out through the components of the enclosure. Water vapor transfer is not a problem so long as the saturated vapor pressure gradient within the enclosure components remains above the actual vapor pressure gradient. Condensation will occur at or near the point in the building component where these gradients intersect. The condensate may migrate to other parts of the enclosure due to gravitational force or capillary attraction. Condensed water vapor promotes decomposition of building components and reduces the insulating capacity of many insulations. This situation increases structural heat loss which in turn hinders moisture control by ventilation. To keep insulation dry and free from condensed vapor, a vapor barrier should be applied on or near the side of the insulation with the highest vapor pressure, which is usually the warm side. A vapor barrier is a material with a high resistance to water vapor flow. Vapor barriers should be as continuous as possible. Thus, joints and holes in the vapor barrier should be minimized. 3.3 Ventilation requirements Livestock and poultry produce best when their environment is within an optimum zone. The housing and environmental control system should be arranged to achieve these conditions. Design of the environmental control begins with analysis of the heat flows in the building using equation where Q S + Q E + Q supp = Q M + Q B + Q V + Q stored ( ) Q S = sensible heat loss rate from animals, J/s Q E = heat production rate by equipment, i.e., motors, lights, etc., J/s Q supp = supplemental heat production rate, J/s Q M = heat required to evaporate moisture, J/s Q B = rate of heat loss by conduction through walls, floor and ceiling, J/s Q V = rate of sensible heat exchanged in ventilation air, J/s Q stored = rate heat is stored or released by building material, especially by concrete floors, J/s (This term is zero in steady state analysis.) When a building is ventilated, heat is added or removed. This heat flow rate can be expressed as: where Q V = Mc p T ( ) M = mass flow rate, kg/s c p = specific heat of air, 1005 J/kg K (approx) T = temperature difference between the inside and outside, K Fans are rated by volumetric flow rate, and equation is based on mass flow rate. Ventilation rate should be obtained by multiplying the mass flow rate by the specific volume obtained from a psychrometric chart with conditions chosen to represent those on the intake side of the fan. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 3

5 Each animal produces heat and moisture. Tables 1 and 2 show the production of these constituents for beef cattle, dairy cattle, swine, sheep and poultry. Moisture in the form of latent heat (vapor) and liquid in the waste is produced. Moisture in the liquid form must be vaporized for removal by ventilation, and the heat required for this process is given by: where Q M = mnh fg ( ) m = rate of moisture production in ventilated space, kg/s animal N = number of animals h fg = latent heat of water vaporization, J/kg The mass flow rate of dry air required to remove moisture is found using where M mn = ( ) Wi W 0 M = ventilation rate, kg/s W i = humidity ratio of inside air, kg water vapor/kg dry air W 0 = humidity ratio of outside air, kg water vapor/kg dry air The rate of sensible heat produced by the animals, Q s, is found using data in Tables 1 and 2. Multiply the sensible heat loss rate per animal unit by the number of animal units. Electrically generated heat, Q E, is generally small and can often be neglected. The rate of supplemental heating, Q supp, is either known from the capacity rating of any heaters within the airspace, or it is the unknown to be solved for in equation (when the ventilation rate is known). The rate heat that is conducted through the walls, floor and ceiling of a building can be calculated for steady state conditions using the following expression: where Q B = UAT ( ) U = overall heat transmission coefficient, J/(m 2 k s) A = area of surface to which U and T apply, m 2 T = temperature difference between inside and outside, K Performing a heat balance of all sources and sinks of sensible and latent heat is a necessary first step in design of any environmental control system. The mass flow rate of dry air required to remove heat is found using: QS + QE M = + Qsup p QM c pt QB Qstored ( ) ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 4

6 Table 1 Moisture production (MP), sensible heat loss (SHL) and total heat loss (THL) of livestock based on calorimetric and housing systems studies Building Livestock Temperature C MP g H2O/ kg h SHL W/kg THL W/kg Reference Cattle Dairy cow (Yeck and Stewart, 1959) 500 kg kg kg kg kg Beef cattle (Hellickson et al., 1974) 500 kg Calves Ayrshire male* (Gonzalez-Jimenez and Blaxter, 1962) 39 kg (8 days) kg (14 days) kg (25 days) kg (8 days) kg (14 days) kg (24 days) British Friesian male* (Holmes and Davey, 1976) 47 kg Jersey* (Holmes and Davey, 1976) 28 kg British Friesian male* 2 days to 8 wk (7.9) 2 days to 8 wk (7.3) 2 days to 8 wk (7.3) Cattle Hereford Friesian male* 2 days to 8 wk (7.3) 2 days to 8 wk (6.5) 2 days to 8 wk (6.5) (Webster and Gordon, 1977) (Webster and Gordon, 1977) (Webster and Gordon, British Friesian male* 1976) kg 5 (2.2) (6.8) (8.2) 100 kg kg 10 (4.4) (6.3) (9.3) 100 kg kg 15 (6.2) (4.6) (8.7) 100 kg kg 20 (7.1) (4.4) (9.1) 100 kg Brown Swiss Holstein (Yeck and Stewart, 1960) 16 wk wk wk wk wk wk ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 5

7 Table 1 (continued) Moisture production (MP), sensible heat loss (SHL) and total heat loss (THL) of livestock based on calorimetric and housing systems studies Building Temperature MP SHL THL Livestock C g H2O/ kg h W/kg W/kg Reference Jersey (Yeck and Stewart, 1960) 16 wk wk wk wk wk wk Shorthorn, Brahman (Yeck and Stewart, 1959) Santa Gertrudis 25 wk wk wk wk wk wk Swine Sow and litter (solid floor) (Bond et al., 1959) 177 kg (0 wk) kg (2 wk) kg (4 wk) kg (6 wk) kg (8 wk) Nursery pigs* (Ota et al., 1975) 4-6 kg kg kg kg (single) (Cairnie and Pullar, 1957) (Cairnie and Pullar, 1957) 6-8 kg (single) kg (single) Growing-finishing pigs (solid floor) (Bond et al., 1959) 20 kg kg ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 6

8 Table 1 (continued) Moisture production (MP), sensible heat loss (SHL) and total heat loss (THL) of livestock based on calorimetric and housing systems studies Building Temperature MP SHL THL Livestock C g H2O/ kg h W/kg W/kg Reference 60 kg kg kg Gilts, sows, and boars (solid floor) 140 kg kg Sheep Mature* 60 kg (maintenance diet) (Armstrong et al., 1960) Fleece length Shorn cm cm (1.3 maintenance diet) (Alexander, 1974) Fleece length 12 cm Lambs 1-14 days (Alexander, 1961) (dry no wind) * Figures are obtained from calorimetric studies. Therefore the moisture production in livestock housing systems will be increased with a corresponding decrease in sensible heat loss. Figures in ( ) are g H 2 O/h kg Figures in ( ) are W/kg ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 7

9 Relative humidities. Moisture ventilation rates are proportional to the humidity ratio difference between the inside and outside air (W i W 0, equation ). The magnitude of W i depends both upon temperature and relative humidity. Design relative humidities for most confinement housing systems should be in the desired range for the animal species, but higher humidities can be allowed for short periods (6 to 12 h) when maintaining lower humidities would result in large supplemental heating requirements Types of ventilation systems. Ventilation occurs in a building because of a difference in static pressure between the inside and outside of the building. If the ventilation fan forces air into the building through the air inlets, the static pressure in the building is greater than outside and is commonly referred to as a positive pressure system. If the fan removes air from the structure, the static pressure in the building will be less than that outside, and air will flow in through the inlets. This system is referred to as a negative pressure system. Each system has characteristics that should be considered when deciding which system to use Positive pressure systems. The pressure in the building forces the humid air out through planned outlets, if any, and through leaks in the walls and ceiling. If the air is humid, moisture may condense within the walls and ceiling in winter. This may cause deterioration of building materials and reduce effectiveness of insulation. Since the air is forced from the building, the positive pressure system is well suited to applications where ventilation air must be filtered to prevent contaminants and pathogens from entering the building. The 20 to 30% of the energy used by fan motors that is rejected as heat is added to the building; an advantage in winter but a disadvantage in summer. Table 2 Moisture production (MP), sensible heat loss (SHL) and total heat loss (THL) of poultry based on calorimetric and housing systems studies Building Temperature C MP g H2O/ kg h SHL W/kg THL W/kg Poultry Reference Laying hen Leghorn* (Ota and McNally, 1961) Broilers* 0.1 kg (Longhouse, et al., 1968) 0.7 kg kg kg kg Broilers 0.1 kg (Reece and Lott, 1982) 0.4 kg kg kg kg kg Turkeys Large white* toms 0.1 kg (DeShazer et al., 1974) 0.2 kg kg kg kg kg (Shanklin et al., 1977) hens 8.2 kg (Shanklin et al., 1977) ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 8

10 Table 2 (continued) Moisture production (MP), sensible heat loss (SHL) and total heat loss (THL) of poultry based on calorimetric and housing systems studies Building Temperature C MP g H2O/ kg h SHL W/kg THL W/kg Poultry Reference Worlstad white* toms (Buffington et al., 1974) 2.2 kg 21 light dark kg 21 light dark kg 21 light dark kg 21 light dark hens 1.6 kg 21 light dark kg 21 light dark kg 21 light dark kg 21 light dark Beltsville white* toms (Ota and McNally, 1961) 8.9 kg 18 light dark light dark hens 4.4 kg 18 light dark light dark Broad-breasted bronze* toms (Shanklin et al., 1977) 17 kg 16 kg 17 kg 16 kg hens 9.8 kg 9.5 kg 9.5 kg 9.3 kg 9.1 kg 8.7 kg * Data are obtained from calorimetric studies. Therefore, the moisture production in poultry housing systems will be increased with a corresponding decrease in sensible heat loss Negative pressure systems. Because the ventilation fans are located in the air exhaust, they are exposed to dust, ammonia, other corrosive gases and high humidity. Allowances should be made for reduced fan efficiency as some dust accumulation on fan blades cannot be avoided. Fan motors should be totally enclosed and should be cleaned periodically to prevent overheating. The air distribution system is less complex and costly since simple openings and slots in walls function to control and distribute air in the building. However, at low airflow rates, negative pressure systems may not provide good, uniform air distribution due to air leaks and wind pressure effects Air distribution and intake-infiltration data. Ventilation is accomplished in an exhaust system by reducing the pressure within the structure below outside pressure, causing fresh air to enter wherever openings ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 9

11 exist. Pressure differences across walls in ventilated shelters should range between 5 and 30 Pa (0.02 to 0.12 in H 2 O). The distribution of the fresh air is affected by the location, number and cross-sectional area of the openings. Ideally the amount of fresh air entering a section of the shelter should be a function of the amount of heat and moisture produced by the animals in that particular section. Satisfactory air distribution can be obtained by location of the inlets and by varying intake cross-sectional area to fit the animal distribution. Automated motorized inlet controllers have been developed to adjust the slot intake opening depending on the pressure difference between inside and outside the building. These units adjust the inlet baffle opening in relation to the static pressure difference between inside and outside, thus better controlling the fresh air distribution within the shelter. Another method of intake-distribution uses a fan connected to a perforated polyethylene air distribution tube or a rigid duct which allows a combination of heating, circulation, and ventilation to be designed into one system. Equipment manufacturers should be consulted for proper application of this type of equipment. These air distribution ducts may be used in either negative or positive pressure ventilation systems Inlet design. The rate of air exchange in a building depends upon the ventilation capacity. The uniformity of air distribution throughout the building, however, depends primarily upon the location and size of the air inlet Location of inlet. For many exhaust ventilation systems, slot inlets are used around the perimeter of the ceiling (except at end walls and near the fan). The slots may be continuous or intermittent. A slot wide enough for high air flow requirements during the summer can be partially closed with an adjustable baffle during the winter periods. Air coming from the attic space may be desirable for winter ventilation because of the wind protection and warming effect of the attic but could be undesirable during the summer if flow rate is low and the air experiences appreciable heat gain Size of inlet. The system characteristic technique can be used to design slotted inlet systems and provide understanding of the interaction between slotted inlet systems and fan system. This technique determines the operating points for the ventilation rate and pressure difference across the inlets. Data to graph fan characteristics (airflow rate as a function of pressure difference across the fan) should be available from the manufacturer, and should apply to the fan tested as installed. Data to graph inlet characteristics are available for hinged baffle, and center-ceiling flat baffle slotted inlets (see Fig. 3). For case (a) in Fig. 3, airflow rates are calculated by (Ref. Albright, 1976, 1978, 1979): For case (b): For case (c): where Q = W 0.98 p 0.49 ( ) Q = W 0.98 p 0.49 ( ) Q = W 0.98 p 0.49 (D/T) 0.08 exp[-0.867w/t] ( ) NOTE: Air enters through two sides of the center-ceiling slot inlet system (see Fig. 3c). Airflow per unit of slot inlet length is obtained by multiplying Q (airflow rate per meter length of slot opening) by two. Q = airflow rate, m 3 /s per meter length of slot opening W = slot width, mm P = pressure difference across inlet, Pa D = baffle width, mm (see Fig. 3c) T = width of ceiling opening, mm (see Fig. 3c) ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 10

12 Figure 3 Examples of slotted inlet configurations Another inlet system uses intermittently placed openings, usually rectangular in shape. The airflow rate as a function of pressure difference across the opening should be obtained from the manufacturer since pressure loss due to entrance and discharge coefficients varies with each configuration. Intermittent openings are useful where long building lengths or posts/trusses make continuous slots less practical to construct. Compared to a slot inlet, a rectangular shape will achieve further penetration of the air into the ventilated space since its entraining edge, which is directly related to drag on the airstream, is much less than a slot. In addition to airflow through the inlet, infiltration airflow must be included to provide a true description of the characteristics of the system. Fig. 4 illustrates infiltration rates for two types of dairy barn construction. The infiltration rates can be described as: Tight construction: Very tight construction: I = P 0.67 ( ) where I = P 0.67 ( ) I = the infiltration rate, m 3 /s per 500 kg animal unit Example: A dairy barn, housing 110 animal units (500 kg units) is to be ventilated with hinged baffle, wall flow, slotted inlets (see Fig. 3a). A total inlet length of 140 m is available. The barn is considered to be very tight construction. Combining equations and the total fresh air ventilation rate is described by: Q = (0.154W 0.98 P 0.49)+(0.66P 0.67) ( ) This characteristic equation is graphed in Fig. 5 for the range of pressures characterizing most dairy barn ventilation applications, and for seven inlet widths. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 11

13 Figure 4 Infiltration rates as a function of pressure differential for two example Pennsylvania dairy barns Figure 5 Slotted inlet design example (see paragraph ) system characteristics curves Next, assume a tentative system of fans with their controls staged based on temperature. Assume previous calculations (based on field recommendations) have shown a required maximum ventilation rate of 16.4 m 3 /s in the summer and a minimum continuous ventilation rate of 2 m 3 /s in the winter. Based on these needs, a fan system is chosen with one small fan to operate continuously to provide the minimum ventilation rate, and 4 additional larger fans to be staged thermostatically until all 5 fans operate to provide the maximum ventilation rate. This results in 5 possible modes of fan system operation, which are also graphed on Fig. 5. The increments between the fan stages are not meant to imply an optimum system. In practice it is usually better to make the increment for the lower temperature stages smaller with the final one or two increments quite large. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 12

14 The intersection points of the fan characteristic and inlet (planned and unplanned) characteristic curves indicate potential operating points of the complete system. For the situation shown in the graph, the minimum winter ventilation rate is attainable with the inlets closed completely. Even then the pressure difference will be only 5 Pa making wind effects significant. A minimum pressure difference of 10 to 15 Pa is needed to limit wind effects. The maximum summer ventilation rate can be attained with an inlet opening of 20 mm and a pressure difference of 19 Pa. If inlet width is not automatically controlled by an inside to outside pressure differential sensor, the system characteristic graph provides insight into the strategy to choose proper inlet width Modulation of ventilation rate. A means of regulating ventilation rate must be provided to permit control of temperature and humidity in the building under various climatic conditions and to accommodate variations in size and numbers of livestock. The following basic methods of varying ventilation rate are used, either singly or in combination: Variable-speed fan. Special permanent split-capacitor motors designed for high slip operation permit modulating fan volume smoothly from maximum down to as low as 10% of maximum by regulating the fan speed. Manufacturers should be consulted for actual speed ranges available on their fans. Speed is regulated by varying the RMS voltage to the motor by a variable transformer or solid-state control, either manually or thermostatically. The motors must be direct-coupled to the fan since they do not develop enough torque to start a belt-driven fan at low speed Multi-speed fan. Large fans, 373 W (1/2 hp) and larger, can be equipped with two-speed motors that provide two ventilation rates, the lower one about 60% of the maximum rate. Small direct-driven fans can be equipped with permanent split-capacitor motors with up to 5 speeds Intermittent fan operation. A minimum ventilation rate can be provided for intermittent operation of fans sized for the maximum ventilation rate required for a system. The intermittent operation can be controlled by a percentage timer that typically operates for a set period of time on a ten-minute interval or controlled by a thermostat, or by a combination of the two. Temperature stratification and odor and bacterial buildup can be a greater problem when intermittent fan operation is used, especially during cold weather. Fans should be sized to operate at least 50% of the time with frequent cycles Exhaust fan and thermostat locations. Fans should be located so they will not exhaust against prevailing winds. If structural or other factors make it necessary to install fans on the windward side, it is important to select fans rated to deliver the required capacity against at least 30 Pa (0.12 in. H 2 O) static pressure and having a relatively flat power curve. Without wind protection such as a weatherhood, the fan must be equipped with a motor of sufficient size to withstand a wind velocity of 14 m/s (30 mph), equivalent to a static pressure of 100 Pa (0.4 in. H 2 O) without overloading beyond the service factor of the motor. Since vane-axial or propeller fans normally used as exhaust fans do not operate efficiently or reliably at this static pressure, a centrifugal fan would be necessary. Due to cost and lack of noncorrosive materials on these fans, the wind-breaking weatherhood is a more viable alternative. The fan performance should be examined to determine if its output is maintained fairly consistently through static pressures as high as 31 Pa (0.125 in. H 2 O). Locate each temperature-control thermostat at a point which represents the temperature sensed by the animals. Locate thermostats away from potential physical damage. They should not be placed near an animal, a water pipe, a light, heater exhaust, outside wall or any other object which will affect their action. Because the temperature near the ceiling will be somewhat higher than near the floor, the proper setting of the thermostat should be made with reference to temperature indicated by a thermometer at the level occupied by the animals. A recommended location for the thermostat may often be near the fan exhaust, especially when thermometers are used in the animal microenvironment to determine the final setting of the thermostat Wiring for electric ventilating fans. All wiring must conform to Article 547 and other appropriate articles in American National Standard ANSI/NFPA No. 70, National Electrical Code Emergency warning system. The confinement of animals in high density, windowless shelters in a mechanically controlled environment involves considerable financial risk in the event of power or equipment failure. The failure of ventilating equipment can result in serious impairment of animal health or mortality from heat prostration. An adequate alarm system to indicate failure of the ventilation equipment is highly ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 13

15 recommended for mechanically ventilated structures. An automatic standby electric generator should also be considered. There are many types of alarm systems for detecting failure of the ventilation system. These range from inexpensive power off alarms to more expensive systems for sensing interruptions of airflow, temperature extremes and certain gases. Automatic telephone dialing systems are effective as alarms and are relatively inexpensive for the protection provided. Refer to ASAE Standard S417, Specifications for Alarm Systems Used in Agricultural Structures. Alarm system components must meet the requirements of ASAE Standard S417, Specifications for Alarm Systems Used in Agricultural Structures, and Article 547 of ANSI/NFPA No. 70, National Electrical Code. Each building should have a minimum of two ventilation fans with each one on a separate circuit. If both fans were on the same circuit, the blowing of a fuse or the tripping of a circuit breaker could stop the flow of electricity to both fans. Power failure alarm systems should be capable of monitoring both hot legs of an electrical service. To insure that the selection and installation of an alarm system will be dependable, it is recommended that the assistance of the manufacturer or other qualified person be sought Ventilation for disease control. The airborne route of disease transmission can be blocked by filtering the incoming air and maintaining a positive pressure inside the house. More data are needed, but reported evidence suggests the following: Air filters having an efficiency of 95% (based on ASHRAE Standard 52-76, Method of Testing Air- Cleaning Devices Used in General Ventilation for Removing Particulate Matter) are probably adequate Positive pressure of 60 to 70 Pa (0.25 to 0.30 in. H 2 O) inside the building (relative to outside static pressure) is probably adequate where the outside wind speed seldom exceeds 11.2 m/s (25 mph) To block other routes of disease transmission, it is necessary to decontaminate the building before the livestock or poultry are put in and to prevent organisms from being brought in with the animals, feed and other supplies, or the caretaker. 3.4 Supplemental heating and cooling Supplemental heat. Brooders or heat lamps are usually required for young chicks, ducklings, poults, quail, and pigs, and may be beneficial for calves, lambs, and other young animals that are housed apart from their dams. Various types of heating equipment can be incorporated into ventilation systems if desired. Supplemental and/or primary heating systems must be installed in accordance with applicable codes and the manufacturers installation instructions. Check with other ASAE standards that might apply; i.e., ASAE Engineering Practice EP258, Installation of Electric Infrared Brooding Equipment. Be sure to check with local building code authorities and the insurance carrier to see if other restrictions apply Supplemental cooling. Cooling, although not as commonly used as supplemental heating, can be of economic benefit in hot climates for dairy cows, swine and poultry. Under intensive housing conditions, supplemental cooling may be necessary during heat waves to prevent heat prostration and mortality or serious losses in production and reproduction. The cooling equipment, like heating equipment, may be incorporated into the ventilation system if desired, and can consist of supplemental air movement, evaporative cooling or earth-tempered cooling Air movement. Increased air movement during heat stress conditions can increase growth and decrease water consumption of chicks, improve heat tolerance of chickens, improve feed efficiency of cattle, and increase growth of swine Evaporative cooling. Cooling by evaporation can be applied directly to the animals as with foggers for poultry or sprinklers for swine; or can be used to cool the air, as with pad-and-fan or packaged evaporative coolers for dairy cattle shelters or poultry houses Mechanical refrigeration. Mechanical refrigeration systems can be designed for effective animal cooling but are considered economically impractical for most production systems. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 14

16 4 Ventilation for Dairy Cows and Calves 4.1 Environmental requirements for mature dairy cattle. Mature dairy animals can adapt to wide variations in environment conditions without exhibiting significant production decreases. Small losses in milk production occur within a temperature range of 2 to 24 C (35 to 75 F) with coincident relative humidities from 40 to 80%. Increases in feed consumption occur as temperatures drop below 10 C (50 F) to compensate for added body heat loss. Fig. 6 illustrates air temperature effects on milk yield for Holstein and Jersey cows. The Temperature-Humidity Index, THI, provides a reasonable measure of the combined effects of humidity with air temperature above 21 C (70 F) (Ref. Berry, et al., 1964) such that: where MPD = NL (NL) (THI) (4.1-1) MPD = absolute decline in milk production, kg/day cow NL = normal level of production, kg/day cow THI = daily mean value of temperature humidity index, obtained from the dry-bulb temperature (t db, C) and dewpoint temperature (t dp, C) according to the relation: THI = t db t dp (4.1-1) Below 2 C (35 F) production efficiency declines and management problems increase. Figure 6 Effect of ambient air temperature on milk production in Holstein and Jersey cattle. Relative humidity ranged from 55 to 70% (Yeck and Stewart, 1959). 4.2 Heat and moisture produced by dairy cattle. Table 1 provides an estimate of heat and moisture produced by dairy cattle under conditions with varying ambient temperatures. 4.3 Winter ventilation requirements. Ventilation rates for maintaining heat balances or for removal of excess moisture can be determined using procedure described in paragraph Summer ventilation requirements. Ventilation rates for enclosed buildings should be adequate to hold inside air temperatures within 1 to 2 C (2 to 4 F) of outside temperatures during hot weather. The required ventilation rate is a function of animal size and density, building to paragraph 3.3 for ventilation rate calculation procedures. 4.5 Aids for summer cooling. At temperatures above 21 C (70 F), cooling can increase productivity, conception rates and feed efficiency (see paragraph 4.1). Predicted milk production losses for June September, inclusive, with only shades provided are shown in Fig. 7 for cows of 23 kg/d (50 lb/day) normal production level. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 15

17 Figure 7 Expected seasonal mild production losses (kg/cow) for 122 day summer period for cows of 22.5 kg/d (50 lb/day) production level (Hahn and Osburn, 1969) Evaporative cooling. Adequately designed and maintained systems using wetted pads and fans have potential for economic application in large areas of the U.S. Fig. 8 shows predicted production benefits. System design information is available in University of Arizona Report P-25 (Ref. Stott, et al., 1972). Figure 8 Expected seasonal production benefits from evaporative cooling during 122 day summer period for cows of 22.5 kg/d (50 lb/day) production level (Hahn and Osburn, 1970) Other water cooling methods. Specific heat and latent heat of vaporization of water can be utilized directly for increased animal comfort in hot weather by such methods as spraying with sprinklers or foggers and supplying cooled drinking water Cooling inhalation air. Outside air cooled by refrigeration to 15 C (60 F), supplied to head enclosures at the rate of m 3 /min (25-30 ft 3 /min) per cow, has been shown to benefit milk production for cows in hot environments (Ref. Hahn, et al., 1965) Air conditioning of total space. Air conditioning of dairy cow housing can require 2500 or more J/s of refrigeration per cow, depending on local design conditions and the individual situation. Close attention must be given to air filtration, adequate ventilating air and to maintenance. Feasibility analyses indicate limited application only to high-producing cows in hot humid areas of the U.S. 4.6 Dairy calf ventilation. Moisture and heat production rates differ between calves and mature animals necessitating the use of different system design parameters. Both research and field experience have shown that calves have a high tolerance for temperature variations so long as the variations are not abrupt. Fig. 9 shows the effects of selected environmental temperatures on the growth rate, and Table 1 shows the moisture production ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 16

18 rates for several breeds of dairy calves. Calves are more susceptible to the effects of manure gases and airborne organisms than are mature cows. This must be taken into account when designing minimum ventilation rates. Figure 9 Body weight vs. age of Holstein, Brown Swiss, and Jersey calves at 10 C (50 F) and 27 C (80 F) 4.7 Free-stall barn ventilation. Free-stall barns used to house dairy cattle may be of the cold-enclosed, cold three-sided or warm-enclosed design. Cold barns, barns where no conscious effort is made to maintain a minimum temperature in the barn during winter months, are usually ventilated non-mechanically whereas warm barns, barns that are enclosed and insulated in an attempt to keep interior winter temperatures above freezing, are mechanically ventilated. Research data are not available for the design of mechanical ventilation systems for free-stall barns. However, experience suggests that the broad alleys and associated greater area of exposed wet surface increase moisture evaporation by 10 15% over a tie-stall type barn with narrow gutters, thereby necessitating appropriate increases in ventilation rates to maintain relative humidity levels below 65 70%. Wide free-stall barns and vaulted ceilings make mechanical ventilation difficult. 4.8 Non-mechanical ventilation. Although data herein are primarily directed at providing guidance in the design of powered or mechanically ventilated structures, it should be understood that in many cases dairy cattle structures can be satisfactorily ventilated by non-mechanical ventilation systems (also called nonpowered, gravity or natural ventilation) if appropriate features are built into the structure. This approach has found widespread use in free-stall barns. While some work has been done in this area, most information is based on models and computer simulations. The influence of animal heat on ventilation by non-mechanical means is not yet clearly understood. 5 Ventilation for Beef Cattle 5.1 Definition of the confinement growing of beef cattle: The housing of beef within a structure which is enclosed on all sides (with or without windows or window openings), ventilated, insulated and possibly heated to allow some control of interior temperatures. 5.2 Environmental requirement for beef cattle Temperature. Temperature influences the feed conversion and weight gain of beef cattle. Figs. 10 and 11 show the type of response to temperature found under research conditions where temperature is controlled. Fig. 12 illustrates the effect of temperature on feed requirements Relative humidity. Relative humidity has not been shown to influence animal performance except when accompanied by thermal stress. Relative humidities consistently below 40% may contribute to excessive dustiness, and above 80% may increase building and equipment deterioration. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 17

19 Figure 10 Rate of growth and feed utilization (unit feed per unit gain) of shorthorns (Ragsdale, Cheng and Johnson, 1985) Figure 11 Effects of age and temperature on weight of Brahman, Shorthorn and Santa Gertrudis calves (Ragsdale, Cheng and Johnson, 1958) ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 18

20 Figure 12 Effects of degree-days below critical temperature, -14 C (6 F) on metabolizable energy requirements of a 400 kg (900 lb) beef steer over 150 day period (Webster, 1971) 5.3 Heat and moisture produced by beef cattle. Figs. 13 and 14 give total, latent and sensible heat production values for Ayrshire bull calves ranging in age from 6 to 10 months as affected by temperature and relative humidity. Table 1 provides total, latent and sensible heat production from Shorthorn, Brahman and Santa Gertrudis calves at temperatures of 10 to 27 C (50 to 80 F). These data represent values for the animals on full feed and include heat and moisture transfer effects between the animal environment and a bedded concrete floor. For design purposes the sum of sensible heat from the room and latent heat from the room is the total heat loss from the beef cattle. However, the ratio of sensible heat to latent heat from the beef cattle may be quite different from the ratio of sensible heat from the room to latent heat from the room because of the utilization of some sensible animal heat to vaporize moisture from the floor. The data can be used for normal management practices in solid floor buildings. Daily average temperature should be used in estimating heat and moisture production. Fig. 15 illustrates the effect of ration on hourly heat production at environmental temperatures of 20, 30 and 40 C (68, 86 and 104 F). Figure 13 Effect of temperature of heat losses of three Ayrshire bull calves 6 to 12 months of age. Vapor pressure 1066 Pa, dewpoint temperature 8 C (46 F) (McLean, 1963). ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 19

21 Figure 14 Effect of humidity on heat losses of Ayrshire bull calves 6 to 10 months of age (McLean, 1963) Figure 15 Effect of ration on heat production of a grade steer 20 to 24 months of age. Hay was poor quality. Concentrate was cotton cake and barley meal. Fasting was for 72 h. The + sign indicates addition of 1 kg concentration to ration (Rogerson, 1960). 5.4 Winter ventilation requirements Design values. Inside air temperature, 7 to 18 C (45 to 65 F). Inside relative humidity, 40 to 80% Procedure. For determining ventilation rates for heat balance and moisture removal, see paragraph Summer ventilation requirements Air change rates. Air change rates are adjusted to remove heat produced by the cattle, plus other heat gains, and to minimize inside temperature rise above the outside air temperature. For specific application, the ventilation rate should be calculated based on procedures in paragraph 3.3. Consideration must also be given to air distribution and velocity to aid in animal comfort and feed efficiency. Baffles should be employed to direct airflow at animal level. This may be accomplished by baffled center ceiling inlets or wall baffles. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 20

22 6 Ventilation for Swine 6.1 Environmental requirements for swine. The following physical environment factors should be considered when designing a ventilation system for swine: Temperature. Different size swine have different air temperature ranges for maximum performance (see Fig. 16). Small pigs, up to 18 kg (40 lb), require a much higher temperature than larger pigs. Pigs larger than 18 kg (40 lb) have an optimum feed efficiency when temperatures are between C (50 70 F). Temperatures in excess of 32 C (90 F) will reduce the fertility of sows, gilts and boars. Figure 16 Apparent optimum temperature zone for swine Air movement. Pigs will generally benefit from air movement if the air temperature is between C ( F). Above 39 C (103 F), large rates of air movement will increase heat load on the pig. Pigs prefer still air or, at most, a very low rate of air movement, 0.15 m/s (30 ft/m) when the air temperature is at or below the optimal level for the pig Relative humidity. Relative humidity has not been shown to influence animal performance except when accompanied by thermal stress. Relative humidities consistently above 80% can cause condensation on building and equipment surfaces during cold weather. This condensation enhances pathogenic organism survival and promotes building and equipment deterioration. Relative humidity consistently below 40% may contribute to excessive dustiness Air quality. Contaminants in the air that hogs breathe can influence swine health. These include: Dust. Dust can act as a respiratory irritant, but by itself has not been shown to cause disease in swine. Dust acts as a conveyance mechanism for pathogens to the respiratory tract of animals Pathogens. Pathogenic bacteria and viruses can be transmitted through the air Manure gases. Manure gases, especially ammonia, act to irritate the respiratory tract and defeat the immune response system of animals. Waste agitation below a slotted floor can bring hydrogen sulfide to toxic concentrations for both humans and pigs. These hydrogen sulfide concentrations have exceeded 950 mg/m 3. Studies have shown that animals exposed continuously to levels of about 24 mg/m 3 of hydrogen sulfide develop fear of light, loss of appetite and nervousness. Symptoms at levels between 59 and 238 mg/m 3 have included vomiting, nausea and diarrhea; however, winter ventilation rates designed to remove moisture from the building have been found to maintain the hydrogen sulfide level well below 24 mg/m 3 and closer to 1.2 mg/m 3. A tight structure is especially dependent on the reliability of the ventilating system to remove toxic gases. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 21

23 6.2 Heat and moisture produced by swine. Table 1 provides an estimate of moisture production, sensible heat loss and total heat loss of pigs. Fig. 17 shows the heat loss at various air temperatures for newborn pigs. Fig. 18 gives sensible and latent heat production in hog buildings at various air temperatures for 18 and 100 kg (40 and 220 lb) hogs. These data were collected in a chamber having unbedded, solid concrete floor scraped twice daily. For design purposes, the sum of sensible heat and latent heat from the room is the total heat loss from the hogs. However, the ratio of sensible heat to latent heat from the hogs may be quite different from the ratio of sensible heat from the room to latent heat from the room because some sensible animal heat is expended to vaporize moisture from the floor. The data in Table 1 can be used for normal management practices in solid floor buildings. The latent heat from buildings may increase as much as one-third, (with a corresponding decrease in sensible heat) because of floor flushings, water wastage, temperature, ventilation rate, inside relative humidity, air velocity over the floor surface, and less frequent scraping of floors. Under similar conditions, less moisture is removed from slatted-floor structures. Slatted floors reduce the amount of wet surface exposed to the air compared to solid floors. About 40% as much water is evaporated from a totally slatted floor as from a solid concrete floor, while partial slats (approx. 35% of floor area slatted) produce 75% as much evaporation as solid floors. Daily average temperatures should be used in estimating heat and moisture production from Table 1. Figure 17 Heat loss rate per unit weight of new-born pigs vs. air temperature (Butchbaker and Shanklin, 1964) Figure 18 Room sensible and latent heat production rate in a hog house (solid floor) ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 22

24 6.3 Winter ventilation requirements Minimum ventilation. For determining ventilation rates for heat balance and moisture removal, see paragraph Table 3 shows ventilation rate guidelines for determining fan capacity. Use both calculated rates (see paragraph and Table 3) in determining the actual minimum ventilation rate. If the calculated rate is lower than the recommended value in Table 3, the rate in Table 3 should be used to assure the removal of stale, odorous air. Table 3 Ventilation-rate guidelines for determining fan capacity Species Winter minimum ventilation rate, (m 3 /s sow)10-2 Winter maximum ventilation rate, (m 3 /s sow)10-2 Summer ventilation rate, (m 3 /s sow)10-2 Swine Sow and litter Growing pigs 9-18 kg kg kg kg Gilt, sow, or boar kg kg kg Reference: (Midwest Plan Service 1982.) Winter maximum ventilation. The winter maximum ventilation rate is normally adequate for temperature control as the outside temperature approaches 10 C (50 F). 6.4 Summer ventilation requirements. Air exchange rates are adjusted to remove the heat produced by the hogs plus other building heat gains to limit inside air temperature rise to 1 2 C (2 4 F) above the outside air temperature. Consideration must be given to air distribution and velocity to help animal comfort, sanitary training of animals, and feed efficiency. 7 Ventilation for Broiler Chickens and Young Turkeys 7.1 Definition for broiler/poultry housing: This section applies to structures used for brooding and/or growing of broiler chickens or young turkeys. These structures are generally well-insulated, fully enclosed structures. Some may have curtains over part of the sidewall. The structures permit some modification of the interior environment through use of supplemental heating and ventilating equipment. Supplemental evaporative cooling is often employed. Ventilation can be accomplished by a mechanical ventilation system or a natural ventilation system supplemented by stirring and mixing fans. A common method is to use controlled mechanical ventilation during brooding and/or cold weather and to use natural, curtain ventilation during warm weather when high air exchange rates are necessary. This type of system is currently referred to as flex housing (Ref. Timmons and Baughman, 1983). Lighting programs can be imposed in enclosed structures or in opaque curtain-walled houses. The growth rate of broilers today is considerably faster than just a few years ago. Broilers are currently marketed at 7 weeks of age (1.8 kg). A decade ago broilers required about 8 weeks to reach market weight. A comparison of typical growth rates for broilers for 1967 and 1978 data is presented in Fig. 19. Some of the results presented in the following sections are based on poultry research conducted when growth rates were slower. However, one is able to evaluate the relative effects of temperature, temperature cycles, humidity, light, air movement, etc., on the overall performance of the birds based on the materials presented. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 23

25 Figure 19 Comparison of typical growth rates of broilers in 1967 and Environmental requirements for broilers. Requirements presented herein cover the growing/finishing period (over 4 weeks of age). They reflect the current knowledge of how the immediate environment affects the economic efficiency of broiler meat production, hereafter referred to as performance. Most of the data in this section apply to birds reared on litter floors and may need to be adjusted for birds in cages or coops. Where data are given for only one sex, it should be noted that by 7 weeks of age the average weight of male broiler chickens is about 1.3 times that of females and that environmental conditions tend to exert somewhat greater influence on growth rates of males than of females Temperature. The influence of various constant temperatures on feed efficiency, rate of gain and sensible and latent heat production for mixed sex broilers is given in Figs Feed efficiencies (gain/feed) during growout increase almost linearly with increasing ambient temperatures from 7 to 15.6 C (45 to 60 F). The percentage increase is different depending upon whether the birds are floor reared where huddling behavior decreases low temperature effects (0.42% per C) (Ref. Deaton, et al, 1977) or if the birds are cage reared (1.0% per C) (Ref. Prince, et al., 1961). Growth rates decrease and mortality increases for daily temperatures exceeding 35 C (95 F) (Ref. Griffin and Vardaman, 1970) and growth rates may begin to decrease below 10 C (50 F). Figure 20 Effect of air temperature on body weight of male broilers. Relative humidity 60% at all temperatures except 80% at 8.3 C (Winn and Godfrey, 1967). ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 24

26 Figure 21 Effect of temperature and humidity on male broiler weight (Winn and Godfrey, 1967). Constant low (30-40%) or high (80-90%) relative humidity has little effect on performance if air temperature is below 29 C (84 F). Figure 22 Constant and cyclic temperature effects on growth and feed conversion of male broiler chickens. In Experiments A and B commercial chicks were reared on litter floors at normal brooding temperatures for 3 weeks, then held at the indicated constant temperature or 24 h linear cyclic temperature for 5 weeks. In Experiment C, non-commercial chicks were reared on grid floors for 8 weeks at a normal (N) temperature schedule which started at 32 C (90 F) and decreased 2.8 C (5 F) per week to final temperature of 21 C (70 F) or at one of three 24 h sinusoidally cyclic temperature schedules; e.g., in the N±10 schedule the temperature was varied daily from 5.6 C (10 F) above to 5.6 C (10 F) below the normal (N) temperature for that week. ASAE EP270.5 DEC1986 (R2012) Copyright American Society of Agricultural and Biological Engineers 25