{
    "document_id": 12962,
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        {
            "id": "p53.1",
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            "text": "45",
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        {
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            "text": "IX. Controlled Environment Growing",
            "attrs": {
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        {
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            "text": "Types of Greenhouses",
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            "text": "Free-standing greenhouses come in a variety of shapes and sizes (Figure 24). Choice of greenhouse depends on snow load and wind speed of a particular location. Free-standing greenhouses are less"
        },
        {
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            "order": 5,
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            "text": "expensive than larger structures and are easier to optimize environmental parameters for different crop species. If multiple stand-alone structures are used, increased sanitation protocols are required to prevent insect pest and disease issues from being transferred between structures by workers."
        },
        {
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            "type": "figure",
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            "attrs": {
                "block_label": "image",
                "embedded_text": "FIGURE 24\nDifferent styles of greenhouses"
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        },
        {
            "id": "p53.7",
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            "bbox": {
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            "text": "Gutter-connected greenhouses provide a more efficient use of space and reduced overall heating costs during winter compared to stand-alone structures (Figure 25). The upfront cost of this greenhouse style is high and may be cost prohibitive for growers on a limited budget."
        },
        {
            "id": "p53.8",
            "order": 8,
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            "text": "Lean-to greenhouses have one wall that borders a building. Light reduction is not severe if the dark wall is the north wall. These types of structures may be useful for decoupled aquaponic systems, as environmental parameters can be controlled independently in each structure."
        },
        {
            "id": "p53.9",
            "order": 9,
            "type": "heading",
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            "text": "Greenhouse Covering Options",
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            "attrs": {
                "block_label": "image",
                "embedded_text": "FIGURE 25\nGutter connected greenhouse"
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            "text": "Greenhouse coverings come in a variety of materials, including glass, rigid plastic (fiberglass, polycarbonate, or acrylic), and plastic films. The appropriate choice depends on your climate zone and budget. Regions with a colder climate will require the covering to provide increased insulation and low heat transfer measured by the R-value and U-value, respectively. The R-value measures how well the material insulates. The higher the R-value, the more insulation the material provides. The U-value quantifies heat transfer and describes how much heat is lost or gained. Materials with a lower U-value will be more energy efficient. Approximately 75% of plastic used for covering greenhouses in the U.S. is air-inflated double-"
        },
        {
            "id": "p53.12",
            "order": 12,
            "type": "text",
            "bbox": {
                "l": 68.4,
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            "text": "layer polyethylene plastic. 6ml polyethylene plastic covering is inexpensive and has an R-value of 1.4 and a U-value of 0.5 (high insulation capacity and energy efficient). A single layer fiberglass covering is moderately expensive and has an R-value of 0.83 and a U-value of 1.2 (moderate insulation capacity and not energy efficient) (Table 11). Choosing the right material for your climate zone is critical to reduce heating costs during winter. Energy cost is the second greatest production expense, just behind labor."
        }
    ],
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        "first": [],
        "last": []
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