UTILIZATION OF PLASTIC COVERED GREENHOUSES FOR ANIMAL HOUSING

UTILIZATION OF PLASTIC COVERED GREENHOUSES FOR ANIMAL HOUSING John W. Bartok, Jr. Extension Professor, Emeritus Natural Resources Mgt. & Engr. Department University of Connecticut Storrs CT 06269-4087 Abstract: Plastic covered greenhouses offer an attractive alternative for housing dairy, beef swine and small animals. Their lower cost as compared to conventional wood frame structures has increased their popularity across the U.S. and Canada. Advantages include less animal stress and disease problems, better environment control, less pollution and lower taxes. Plastic is used for the covering, shading and fencing. This paper will review structure selection, building codes, glazing, construction techniques and ventilation methods. Keywords: Plastic greenhouse, animal housing, natural ventilation. Introduction: Greenhouse structures have many applications on farms for housing animals including dairy calves, cows, beef animals, swine and small animals. Their low initial cost, ease of erection, low taxes and insurance and good weather protection make them suitable for use throughout the U.S. and Canada. Continual improvements in film plastic make this material attractive as a covering for greenhouses. The structure consists of a steel tubing frame covered with one or two layers of plastic, either clear or white. During the summer temperature is controlled by covering the roof with a tarp or shade cloth and opening the side and endwalls to allow natural air movement. During the winter, the side and endwalls are partially closed to reduce drafts and the heat from the sun modifies the inside temperature during the day. Greenhouse selection: A free standing greenhouse can have a quonset (hoop), gothic or gable roof shape. The quonset is usually the least expensive to build and easiest to erect. In northern climates, the gothic style is preferred as the steeper roof pitch allows snow to slide off easier. If roll-up sides are to be installed, select a shape with a vertical sidewall to reduce the rain penetration when the sidewalls are open. Also select a design with a high ridge to give greater temperature buffering and air movement. 241

The frame materials for commercial greenhouses is round or rectangular, galvanized steel tubing. Size and wall thickness determine of the tubing determine its strength. Frames are usually spaced 4' - 6' apart. For farmers who have access to native lumber, plans for rigid frame, wood greenhouses are available from the author at the Natural Resources Mgt. & Engr. Dept., University of Connecticut, Storrs CT 06269-4087. Several sizes and shapes are available. Cost of a wood frame greenhouse barn is usually less than a comparable metal frame greenhouse especially if on-farm labor is used. When compared to gutter-connected greenhouses, free-standing greenhouses are easier to construct, less expensive, good for non-level sites and easier to ventilate. A gutter-connected greenhouse is a series of gable or quonset arches connected together at the gutter level. Individual bays vary from 12' to 40' in width and have a clearance of 8' to 16' at the gutter. Bays can be put together to get any width of building. When selecting bay width consider the layout of the interior in relation to animal pen location, movement of animals and access for feed supply equipment and manure removal. A gutter height of 14' or 16' allows better air movement and provides more temperature buffering of the air. Gutter-connected greenhouses have the advantage of greater labor efficiency as all operations are under one roof. It also makes better utilization of the land. Provisions need to be made to handle rain water and snow melt from the gutters. It is important to select a greenhouse with a design wind and snow load adequate for the location where it will be built. Many horticultural greenhouses have low design loads as the structure is expected to be heated to a minimum of 50 deg F during the winter. These greenhouses should not be used in areas were heavy snow loads occur. When building a greenhouse be sure to follow the manufacturers recommendations for the foundation. Metal posts driven into the ground may not provide adequate uplift resistance in a heavy wind. Concrete piers or metal plates may be needed. Floors: The level of the floor should be higher than the ground outside to prevent runoff water from entering. The floor should provide support for the animals, drainage of liquids and be easy to clean. For calf installations, a gravel floor, 6" to 8" thick has worked well. A polypropylene weed barrier is sometimes used to separate the gravel from the underlying soil. Either a manure pack can be developed or the manure can be cleaned when the calf is removed. Sawdust, shavings or straw are common bedding materials. 242

Concrete floors are necessary in barns used to house cows and in milking parlors to support the stalls and make clean-up easy. At least a 6" thickness is needed in areas where tractors will be operated. In swine structures used for grow-finish, a 15' to 20' long concrete pad is placed on one end for feeders and waters. This is normally located on the end away from the prevailing summer wind. Plastic cover: Clear or white polyethylene plastic is the common roof covering material. The clear plastic allows about 87% light transmission and the white about 30%. Use a 6- mil thickness, greenhouse grade with a 3 or 4 year life. If covered with a shade cloth during the summer, the life may be extended to 6 years or more. Materials that contain a wetting agent will reduce dripping but this is generally not necessary if good ventilation is maintained. Two layers that are air inflated by a small, continuously operating squirrel cage blower will reduce flapping noise and keep the film taut to reduce tearing of the plastic. Attachment to the frame can be with aluminum extrusions or a double furring strip. On free standing greenhouses, the attachment of the plastic is made to a wood or metal rail located several feet above the ground to allow roll-up sides to be used. During the summer the sides are open and a fence material, galvanized wire mesh or plastic fencing is used to enclose the lower half of the frame. During the winter the sides are rolled down to give wind and rain protection. Site considerations: Before selecting a site, check with local zoning and building officials to see what regulations apply. Orientation is one of the keys to a successful greenhouse barn. As the summer heat is the greatest environmental factor to contend with in much of the U.S., a location that intercepts the summer breezes is very important. Generally the structure should be located so that the summer wind is not blocked by buildings, trees or other obstructions. A distance of at least 50' to any obstruction is needed. Wind pressure is more important than the difference in temperature between inside and outside in moving air through the structure. For freestanding greenhouse barns, the best orientation in most situations is facing one endwall to intercept the prevailing summer winds. In the Northeast and Midwest this is usually facing south. Endwalls should be open and sidewall plastic rolled up. 243

For larger gutter-connected greenhouses, the direction is not as critical. Usually both endwalls and sidewalls are open during the summer. Removal of rain and snow from the site is also important. Swales or underground piping can be used. A free-standing greenhouse should be spaced at least 10' from another greenhouse or other building. This allows space for snow to collect without crushing the sidewalls. In a gutter-connected greenhouse, the water and snow-melt is collected by the gutters. Down spouts should be sized for the expected maximum rainfall. These should be connected to a cross drain buried below the floor. Water can be directed to a wetland, drainage ditch or man-made containment pond. Year-round access for tractors and equipment should be provided. Bedding and manure have to be handled and animals moved to other facilities. All through the planning process, provisions should be made for expansion. Land should be available for additional greenhouses or expansion of existing houses. Water, electrical and environment control systems should be installed with expansion in mind. Utilities: A year-round supply of portable water is essential for animal and sanitation needs. In northern areas it should be supplied through frost-free hydrants. Electric service is needed for lighting, pumps motors and feed handling equipment. A 60 amp service is adequate for most calf and swine facilities as the major use is in room lighting. For dairy barns and milking centers a 200 amp, 230 volt entrance is minimum. Environment control: The temperature inside a greenhouse barn in northern climates can vary from -30 deg F during the winter to over 100 deg F during the summer. Ideally it would be best to limit the high temperature to the outside ambient. Observations in Connecticut showed that temperatures inside a free-standing hoophouse were maintained at no more than 3 deg F higher than ambient at animal level during 90 deg F weather. Polypropylene shade material is commonly used to reduce the temperature during the summer. A shading level of more than 90% is generally used. This material costs from $0.10 to 0.20/sq ft. It is usually fitted with grommets and held in place with bungy cords. Some farmers have used a solid plastic tarp with good results. 244

Roll-up sides allow air movement across the structure. This system consists of a pipe or conduit attached to the bottom edge of the plastic. A handle or winch raises and lowers the plastic which is attached to the rail with extrusion or furring strips. Strapping, rope or conduit is used to keep the plastic from bellowing out in the wind. The plastic is usually permanently attached for the winter. Fans are generally not needed for ventilation. Exceptions to this might be where there is little natural wind, where the structure is very long or where the sides are closed such as in a milkhouse. If needed, they should be installed properly to get efficient air movement. In the winter it is important that adequate ventilation be maintained to keep moisture at acceptable levels. It is a natural tendency for producers to restrict ventilation to keep the warm air inside the structure to provide some heat for the animals. Because of the tight covering, this moisture can become excessive causing wet litter and result in increased disease potential. The greenhouse barn should be operated as a cold structure not a warm barn. Animal concerns: Animal health in greenhouse barns has proven to be very good. Studies have shown that death loss and respiratory problems have been minimal The interior layout for a greenhouse barn should fit the animals that are to be housed. Individual and group pens are common for calves, heifers and swine. Free stalls or stanchions may be used with dairy animals. For calves, the greenhouse barn offers a better transition for animals to go from one stage to another. Young calves from day old to weaning are usually housed in pens made out of wire mesh or fencing. Size varies from 4' x 6' to 4' x 8'. These are spaced so that calves can't touch each other. At the weaning stage, calves are moved to community pens holding up to 6 animals. These pens need to be stronger with good support for the wire. Wood or steel posts are often used. Heifers, 3 to 6 months of age are held in larger pens with wood or steel fencing. Some installations have an access aisle down the center of the greenhouse for feeding and manure removal. For milking animals, freestall construction is used. Concrete floors and scrape alleys are added to make animal movement and manure removal easier. Provisions for feed and water should be made. Equipment similar to what is used in conventional facilities works well. 245

Protection of the sidewall plastic is important to prevent damage. Wire fencing works well. Metal fences may be needed in traffic areas or where animals can reach the plastic. For swine housing, a pressure treated post and lumber kneewall up to 4' high is sometimes used. The greenhouse is built on top of the kneewall. Freestanding Greenhouse Barn 246