(xV* 0F K Division of Agricultural Sciences UNIVERSITY OF CALIFORNIA :» I HOUSING FOR POULTRY H |L 1L IL H ilil An LTC house with package evaporative coolers installed on the roof. The exhaust louver is continuous along both sidewalls. S. A. HART W. O. WILSON P. J. LERT CALIFORNIA AGRICULTURAL it Station CIRCULAR 526 WHAT IS LTC HOUSING? An LTC poultry house is one in which light and temperature can be modified h\ the grower. Control of these two factors can increase egg pro- duction, reduce bird mortality from summer heat, and minimize winter environmental problems. This publication discusses considerations in- volved in designing and operating LTC housing. GLOSSARY OF TERMS USED Anemometer An instrument for determining air velocity. BTU British Thermal Unit; it takes 1 BTU to raise the temperature of 1 pound (about 1 pint) of water 1 degree Fahrenheit. Dry-bulb temperature. . .The temperature measured by a regular ther- mometer. Evaporative cooling .... Cooling in which the dry-bulb temperature is re- duced while the wet-bulb temperature remains constant. Water is evaporated, and the heat ab- sorbed by the water as it evaporates cools the air. Evaporatively-cooled air contains more water vapor than it did originally; thus, its relative hu- midity is higher. Foot-eandle A measure of light-intensity. Heat conductivity The rate at which heat moves through the walls and roof. The units are BTl per square foot per minute per degree Fahrenheit. Psychrometer An instrument for measuring dry- and wet-bulb temperatures. Wet-bulb temperature . . Temperatures measured by a thermometer that has a wetted "sock'' around it. Theoretically, evap- orative cooling can reduce the dry-bulb tempera- ture of the air to the wet-bulb temperature. In actual practice, air is usually cooled to within about 2 degrees Fahrenheit of the wet-bulb tem- perature. An ltc house must be cool in summer, adequately ventilated in winter, and capable of being totally darkened. Cool- ing is the most important of these prob- lems and the most difficult one to solve. Evaporative cooling is the method usually used for cooling LTC houses; refrigera- tion-type air conditioning is expensive and unsatisfactory because dust from feed and feathers gets into motors and air filters. Two systems of evaporative cooling are available: package coolers and pad- and-fan coolers. Package coolers have cooling and blowing equipment in one unit, and air is cooled before being forced into the house. The pad-and-fan system employs wetted pads on one side or end of the house, and exhaust (or suction) fans on the other; these fans blow out- ward and create a slight vacuum within the house, thus drawing air through the pads and through the house. Package units are simple to install and relatively easy to incorporate into the light-tight design of LTC housing, but because they discharge a high-velocity air blast the individual coolers must be located properly for cooling to be uni- form. Pad-and-fan coolers are more eco- nomical both in first cost and in opera- tion, and generally do a slightly better and more uniform cooling job. Pad-and- fan cooling systems are somewhat sensi- tive to wind, however; if the wind is blowing against the fan it can seriously reduce the volume of air being moved through the house. Again, pad-and-fan units are generally more difficult to in- corporate into the light-tight design of LTC houses. ESTIMATING THE SIZE OF COOLING SYSTEM NEEDED Interior temperatures of LTC housing depend upon three things: • the heat coming into the house through roof and walls • the heat given off by the birds • the amount and temperature of air being moved through the house to remove the heat from the above two heat sources In a well-designed house, the average air temperature will be about 5 degrees Fahren- heit higher than the temperature of the cooled entering air, and this entering air will be about 2 degrees Fahrenheit above the wet-bulb temperature (see GLOSSARY) . Heat coming into the house The heat load from the outside depends on the area of walls and roof, the amount of insulation, and the difference between inside and outside temperatures. The formula for this part of the total heat load is: Quantity of heat (in BTU per minute) = area of heat transfer x heat conductivity of roof x temperature difference between inside and outside of house (1) Area of heat transfer can be taken as 1.25 times the floor area (this allows for wall and sloped roof surfaces) . Heat conductivity values for various types of construction [3 are given in the table on page 12. Average temperature difference between the inside and outside of the house is obtained by subtracting 7 degrees Fahrenheit from the difference between the design dry-bulb and design wet-bulb temperatures. Design temperatures for California areas are given on page 5. Heat given off by birds The formula for this part of the heat load is: Quantity of heat (in BTU per minute) = number of birds x heat- production per bird per minute (2) An adult chicken produces 0.124 BTU per minute per pound of body weight, or 0.62 BTU per minute per average hen. Young birds weighing 3 pounds or less produce 0.15 BTU per minute per pound of body weight. Turkeys and other large birds give off 0.10 BTU per minute per pound of body weight. Total heat load The sum of the above two separate heat loads on the LTC house is the total amount of heat that must be removed by the cooling system. Cooler capacity To determine the amount of air that must be supplied to the house each minute to keep the inside temperature low (about 7 degrees Fahrenheit above the wet-bulb temperature) the following formula is used: ~ , , . r . Total heat load Looter capacity in cubic teet per minute = _ _ -^ — r 0.086 (a cubic foot of air absorbs 0.086 BTU when it is warmed 5 degrees Fahrenheit) . (3) As an example, let us calculate the cooling requirement for an 8.500-chicken LTC house, 50 feet wide by 200 feet long, in the Fresno area; the house has a sheet-metal roof with interior sheeting of %-inch insulation board. We first determine the quantity of heat coming into the house. The area of heat transfer is 1.25 x 50 x 200, or 12,500 square feet. The heat conductivity (table, page 12) is 0.0033 BTU per square foot per minute per degree Fahrenheit. As shown on page 5, for the Fresno area the design dry-bulb temperature is 105 degrees Fahren- heit, and the design wet-bulb temperature is 74 degrees Fahrenheit. Subtracting 7° from 105° — 74° gives 24° Fahrenheit. Using these figures in formula (1), we have: Quantity of heat coming into the house = 12,500 x 0.0033 x 24, or 990 BTU per minute The quantity of heat produced by the chickens is obtained by multiplying the num- ber of chickens (8,500) by their individual heat production (0.62 BTU per minute per hen). Using formula (2), we have: Quantity of heat from chickens = 8,500 x 0.62, or 5,260 BTU per minute Adding heat from outside to heat from birds gives: Total heat load = 990 + 5,260, or 6,250 BTU per minute The cooler capacity (in cubic feet per minute) required to remove this heat is obtained by dividing the total heat load by 0.086. Using formula (3), we have: Cooler capacity = ' , or 72,700 cubic feet per minute O.Ooo [4] This is the cooler capacity needed. Because it is impractical to use one cooler as large as called for in this example, smaller units are preferred. Cooler manufacturers specify how much air their package units or their fans will move under two conditions: free air discharge, and capacity against %-inch (of water) back-pressure. (The capacity against V8-i ncn back-pressure is usually 75 to 85 per cent of the free air discharge.) There is a considerable back-pressure buildup in an LTC house due to the light trap entrance and exhaust, and because of friction as air goes through the pads. It is therefore important to choose the size and number of coolers or fans needed on the basis of their rated capacity against %-inch back-pressure. u W^F Summertime design dry-bulb temperatures in degrees Fahrenheit are shown above, left; design wet-bulb temperatures are on right. Actual outdoor temperatures will occasionally be greater than these values as buildings heat up more slowly than surrounding air, but these design tem- peratures are the most useful basis for evaporative-cooling systems. [5] VENTILATION Air in an LTC house must be changed frequently, even when it is not being cooled, in order to provide oxygen, re- move moisture, and lessen odors. One cubic foot of air per minute is sufficient for a 5-pound chicken, and chicks and pullets in hovers need only 0.5 cubic feet per bird per minute. Winter ventilation for turkeys should be 2 to 3 cubic feet per minute per bird. (In the sample problem, summer air requirements were 8% cubic feet per minute per chicken.) Adequate ventilation for winter can be obtained by operating only part of the cooling system, or operating all of it only part of the time. LIGHT CONTROL WITHIN THE HOUSE Not all houses need to be made light- tight, as cooling alone may sometimes be sufficient. When light control is required, however, the house and its cooling-venti- lating system must be specially designed. Preventing light leaks in the house itself is best achieved by using a "double-wall" building; the outside structural wall and roof cut out most of the light, and the interior wall or wall-covering surface cuts out the remaining light. No change in construction is necessary for the outer wall. The inner wall, made of insula- tion board, plywood, or similar large paneling material, can be nailed to the insides of the studs or posts (opaque plas- tic film and construction paper are some- times used for the inner wall) . The evaporative-cooling system must be baffled to allow air flow without light entrance. It is relatively easy to pre- vent such entrance at a package-cooler attachment ; the pads of the cooler cut out some light, the configuration of the blower cuts out more, and an interior duct can often be designed to cut out any remain- ing light and distribute inlet air to best advantage. The inside of the duct (and of all light traps) should be painted a dull black. It is also advisable to dye the pads of the cooler with common clothing dye (a package of black dye can be added to the recirculation water) . Light-tight air exhausts are also needed. Exhaust areas must be large enough that air velocity through the (Below, left) Fan end of pad-and-fan house. Louvers, which shut down when fans are off, act as safety guards when fans operate. House is not light-controlled. (Below, right) Interior of pad- and-fan house showing pad end. exhaust is no greater than 500 feet per minute. The formula for determining this area is: Exhaust area (in square feet) = cooler capacity 500 (4) Substituting figures from the example problem, we have 72,700 Exhaust area: 500 , or 145 square feet This is the net area across the flow of the air; the area taken up by studs, posts, and baffling must be allowed for in figuring the size of the exhaust. Light traps and air-velocity limits must also be designed for pad-and-fan LTC houses. The pad area must be large enough that the maximum velocity of the air through the pad is 150 feet per min- ute or less. This will allow the air to be- come thoroughly cooled when passing through a pad 2 to 2% inches thick, and will also prevent excessive pressure loss. The formula for determining the pad area is: Pad area (in square feet) = cooler capacity 150 (5) Using the figures from our example prob- lem, this becomes Pad area 72,700 150 or 485 square feet This is also net area ; posts, studs, and the water distribution and collection equip- ment take up additional area. The lower illustration on page 8 shows a pad-and- fan system layout for the house described in the sample problem. The 485 square feet of pad area is divided into two pad units; each end pad should have over-all dimensions of about 6 feet by 48 feet. The light-tight baffle preceding the pad area must be designed so that the velocity in it does not exceed 500 feet per minute. These light traps can be made from plywood, sheet metal, or similar smooth material, and should be designed so that most sur- faces are vertical — this will help keep feed dust from accumulating on the sur- faces where it reflects light. Easy access for cleaning is desirable. The fan that exhausts the air in a pad- and-fan system must also be light-trapped. This can be done best with a sheet-metal shroud. (Below, left) Light-tight shroud on a roof fan. This design would also be satisfactory for a fan in a sidewall. (Below, right) Interior air-duct for deflecting discharge of a package cooler. Duct also helps reduce amount of light entering house. -- ADDITIONAL DESIGN CONSIDERATIONS Cooling, ventilation, and light control must be combined properly if the LTC house is to be efficient. Air paths within the house must be considered: a short path i> apt to create dead air spots and uneven temperature; a long path requires the air to move at high velocity, with con- sequent excessive pressure loss and re- duced cooling capacity. An air path of 100 to 150 feet is generally satisfactory. If the air has to turn a corner on enter- ing or leaving the house, its velocity should be less before turning than it is after, in order to obtain even flow of air across the width of the path. It is desirable (and for litter houses it is essential) that the air exhaust be close to the ground so that dust will be more readily removed. When LTC houses are adjacent to one another, the exhaust of one should not be the inlet air of the other, nor should two discharge fans blow directly against each other. Prevailing wind Light-tight exhaust louvers Package coolers m .J 15" .J my-^^-y^/'^'---'--»y.-^ ■-■-■-■-■ ■ Measuring air flow from package cooler with an anemometer. to 80 per cent of the cooler design capacity (based on Vs-inch static pressure), and that the average temperature is about 7 degrees Fahrenheit above the air entrance temperature. Air flow rates less than 75 or 80 per cent of design, and interior tem- peratures higher than expected, are prob- ably due to improper equipment, con- stricting light traps in the ventilation sys- tem, low motor-voltage, slip in the belts between fan and motor, or clogged pads. OPERATING THE LTC HOUSE The cooling system of an LTC house is usually controlled by a thermostat, either alone or in conjunction with a time switch, and fans or blowers are usually on a separate circuit from the water sup- ply. Thus, blowers may ventilate the house, but cooling can be started only if necessary. When the system is turned off, water to the pads should be shut off before the blowers are stopped so that the pads will be dried out by the air drawn through them; this prevents microbial growth. Almost all LTC cooling systems recir- culate water through the evaporative cooler pads, so it is essential that there be a constant bleed-off of a small quantity of water to prevent mineral incrustation of the pads, salting up and burning out of the recirculation pump, and increased corrosion and disintegration of the whole cooling system. This bleed-off need not be large — 1 gallon of water per hour for each 1000 cubic foot per minute of cool- ing capacity will do. Some recirculation pumps have a built-in bleed-off connec- tion; if not, one can easily be attached. The LTC cooling system will also ven- tilate the house in fall winter, and spring; with such use, pads should be left in place but not wetted. Only a minimum air flow is needed for ventilation, so some of the motors can be disconnected or all the equipment can be run for a few min- utes hourlv. [10] MAINTENANCE OF Keep air duets and light traps free from dust and feed. Adjust sagging pads, as they allow un- eooled air to pass through the gaps, thus raising temperatures in the house. Cooler pads should he hosed down monthly to remove dust and feathers which reduce air flow. Since washdown water collects in recirculation tanks or sumps, these should be drained and cleaned at the same time. The water-distribution system should be checked frequently and clogged holes cleaned out with an ice pick to avoid in- sufficiently and unevenly wetted pads. If chemical control of algae and slime growth on the pads or in the recirculation sump is needed, use a weekly treatment of 1 cup of ordinary bleach (or special alga- cides available from swimming-pool sup- ply companies) per 100 gallons of cool- ing-system water. Copper sulfate (blue- THE LTC HOUSE stone) should not be used, as it corrodes metal parts of the cooling system. Pads should be replaced every year; using pads for a second year may cause a house to run as much as 5 degrees warmer. Use aspen fiber or expanded paper pads, as excelsior does not wet through thoroughly. Motors should be kept free from dust and water, oiled as indicated by the manufacturer, and operated at rated volt- age and amperage. A standby generator is highly desir- able; power interruptions will stop both the cooling system and the lighting within the house, with possible loss in egg pro- duction or of birds. Safety Precautions Safety guards should be placed on ex- posed sides of fans. Electrical safety codes should be carefully observed. IS INSULATION DESIRABLE? In the example problem given previ- ously, the roof consisted of sheet metal and %-inch insulating board having a heat conductivity of 0.0033 BTU per square foot per minute per degree Fahr- enheit. The heat load coming in through roof and walls was 990 BTU per minute. If no insulation had been used and the roof surfaces were sheet metal, the heat conductivity value would be 0.011 BTU per square foot per minute per degree Fahrenheit (table, page 12). The heat load through the roof and walls would then be, from formula (1) : Quantity of heat = 12,500 x 0.011 x 24, or 3,300 BTU per minute. The difference is 3,300-990, or 2,310 BTU per minute. The additional evaporative cooler re- quirement to remove this additional heat is obtained from formula (3) : Cooler capacity ( additional ) 2,310 0.086 or 27,000 cubic feet per minute. Evaporative coolers cost $20 to $30 per 1,000 cubic feet per minute of cooler capacity installed, and power costs about $1 per year per 1,000 cubic feet per min- ute cooler caapcity. Thus it will cost be- tween $540 and $800 more in initial costs for the larger cooler capacity, and about $30 more per year in power cost and maintenance. The cost of insulating should be com- pared with the cost of increased cooler capacity. About 15,000 square feet of %.- inch insulation board is needed for this 50 x 200-foot house. The cost of insulat- ing is between 5 and 8 cents a square foot, installed, or $750 to $1,200, with little or no annual upkeep cost. On the basis of straight economics the decision can be made either way. Insulation does help in wintertime, and may help to light-trap the house. [in Heat conductivity values for typical LTC house roofs Roof construction Heat conductivity ( RTU per square foot per minute per degree Fahrenheit) Sheet metal (aluminum or galvanized steel) 0.0110 Sheet metal, with interior sheathing of plywood or plastic film 0.0070 Sheet metal, with interior sheathing of %-inch insulation board, air space between metal and board 0.0033 Sheet metal, with 3-inch insulation batts laid against the metal (no air space) with or without sheathing to hold batts in place 0.0013 Sheet-metal roof and separate insulated ceiling, attic space pro- vided with air circulation 0.0010 Wood-deck roof, tar-paper cover, no insulation 0.0067 Wood-deck roof, tar-paper cover, %-inch insulation board on inside, with or without air space between insulation board and roof decking 0.0027 Wood-deck roof, tar-paper cover, 3-inch insulation batts laid against underside of roof deck, with or without sheathing against insulation 0.0010 THE AUTHORS: S. A. Hart is Associate Professor and Associate Agricultural Engineer at the Agricultural Ex- periment Station, Davis; W. O. Wilson is Professor and Poultry Physiologist at the Agricultural Experiment Station, Davis; P. J. Lert is Associate Agriculturalist. Agricultural Extension Service, Santa Clara County. MARCH, 1964 Cooperative Extension work In Agriculture and Home Economics College of Agriculture, University of California, and United States Departmenl of Agricultur co-operating. Distributed in furtherance <>f the Vets of Congress of May 8, and June 30, 1"1». George B. Alcorn. Director, California Agricultural Extension Servici 15m-:V64(E3300)VL