Greenhouse Structures and Design
Other Greenhouse Structures
Growing Rooms
Growing rooms, also commonly referred to as plant growth rooms, have been used for many years in Europe. However, their use in the United States has grown with their increased use for germinating seed for plugs and high value specialty crops. Seed trays are kept on ebb and flow benches, which are sub-irrigated several times a day. The temperature (24°C or 75°F, continuously) and the humidity inside the growth room are maintained by a climate control system.
Headhouse
All greenhouse locations should have a headhouse or service building. Large operations may have two or more headhouses. When you plan a greenhouse layout, use this rule of thumb. Make the headhouse equivalent in size to at least 10 percent of the total greenhouse growing area. For example, a certain greenhouse contains 40,000 square feet of growing area. Its headhouse, then, should contain at least 4,000 square feet. This may seem like too much space for a service building, but many important functions are carried out in the headhouse. The following services and operations might be included in a headhouse.
Office
Every operation needs a private area for phone conversations, keeping records, receiving customers, and giving instructions to employees. In larger businesses it can also house the secretary, bookkeeper, and sales staff.
Utilities
The headhouse is a good place to locate the main electric panel and water supply tanks. Its central location with access to the greenhouses keeps wiring and piping distances short.
Restrooms
Depending on the size of the operation, one or more restrooms may be needed. Connection to a sewer system or septic system generally requires a permit.
Lunchroom
An area separate from the work area should be provided for lunches and breaks. This should be partitioned to keep out dust and odors. In large facilities, space for lockers, refrigerator, microwave, and sink is desirable.
Pesticide Storage
If properly designed, the pesticide storage can be placed in the headhouse. The room must have continuous ventilation with makeup air brought in from outside. Identification signs and positive locking are also required. The area for mixing should be nearby.
Storage
Much of the smaller items (replacement parts, hardware, labels, etc.) can be stored where there is easy access and good inventory control. If the headhouse has a high ceiling (14 ft. minimum), a raised storage area above some of the other rooms can be used to hold containers and other light material. Bags of growing mix, peat, etc. are usually stored outdoors or in a vacant greenhouse.
Work Area
The remaining area in the building should be open so that it can be used for a work area. Flexibility is important as the needs change from season to season. In early spring, the space is needed for potting and transplanting. Later, when the plants are grown, more space is needed to assemble orders for shipping. Except in large operations, equipment such as the mixer and pot/flat filler should be portable so that they can be moved out of the way when not in use.
Cold Frames
Cold frames are low-to-the-ground structures consisting of a wood or metal frame with a transparent covering (See Figure 1.15). As their name suggests, they have no heating source except the sun. Cold frames are good when you want to grow cool weather crops in early spring, fall, and even into the winter months. They work well for early planting of summer annuals and seeds, faster rooting of cuttings, starting perennials from seeds in summers, and protecting delicate plants in winters.
Cold Frame Construction
Decay-resistant wood such as redwood, cypress, or cedar should be used, and preferably pressure-treated with wood preservatives, such as chromated copper arsenate (CCA). This compound retards decay for many years and does not give off fumes toxic to plants. Creosote must not be used on wood structures in which plants will be grown, since the fumes released, particularly on hot days, are toxic to plants.
Hot Frames
Structurally similar to cold frames, hot frames are heated with electric heating cables and are primarily used as an inexpensive way to root cuttings. Hotbeds can be used throughout the year, except in areas with severe winters where their use may be restricted to spring, summer, and fall. They are also ideal for overwintering nonhardy seedlings or newly rooted cuttings.
Refrigerated Storage for Greenhouse Harvested Crops
Temperature management of perishable commodities begins with proper handling at harvest. Refrigerated storage is necessary to maintain the quality of the harvested crop prior to use or marketing. Produce is usually cooled to its long-term storage temperature in special facilities designed to rapidly remove produce heat. Forced-air cooling is the most widely adaptable method and is commonly used for many fruits, fruit-type vegetables, and cut flowers. Hydrocooling uses water as the cooling medium and is less widely used than forced-air cooling because some products do not tolerate water contact and because it requires the use of water-resistant packaging.
Click on the following topics for more information on greenhouse structures and design.
