Cultivate Success: Master Your Hoop House Design for Year-Round Harvests
The Fundamentals of Hoop Houses: Cultivating an Extended Growing Season
Hoop houses, often referred to as high tunnels, are structural marvels designed to protect crops and significantly extend their growing seasons. These plastic-covered arched structures are tall enough for comfortable human access and function similarly to unheated greenhouses, polytunnels, or cold frames. While they don't offer substantial temperature increases at night without sunlight, they remarkably foster vigorous plant growth and yield high-quality produce. Typically unheated, crops within are cultivated directly in the soil. Many modern hoop houses feature a double-layered plastic covering, with an air blower maintaining inflation between the layers. This design enhances insulation, bolsters resistance against wind and snow loads, and prolongs the lifespan of the plastic by preventing wear and tear. A double-layered hoop house can maintain internal temperatures approximately 8 degrees Fahrenheit warmer than outside during winter nights, provided there are no strong winds. For regions like Zone 7a, the soil temperature inside rarely drops below 50 degrees Fahrenheit, highlighting the effectiveness of these structures in creating a more hospitable growing environment.
Strategic Site Selection: Maximizing Solar Exposure for Optimal Growth
Establishing your own hoop house requires careful planning, with site selection being paramount. Begin by evaluating potential locations on your property during midwinter when the sun is at its lowest angle and shadows are longest. Hoop houses rely heavily on solar energy, necessitating a site that receives maximum sunlight during the winter months. Avoid areas prone to shading from obstructions. For instance, at Twin Oaks Intentional Community, an initial site chosen for its winter sun exposure was later adjusted for better drainage. However, this shift inadvertently placed a third of the hoop house in shade after 2:30 p.m. due to a cluster of loblolly pines. The trees were eventually removed to optimize sunlight. Ideally, hoop houses are oriented with their ends facing east and west, and longer sides facing south and north, to capture the most sunlight. While some suggest different orientations for southern regions, particularly for warm-season crops, a north-south alignment of rows is preferable for tall, vining plants to ensure uniform lighting.
Soil Quality and Drainage: Foundations for a Thriving Hoop House
The success of a hoop house hinges on fertile and well-drained soil. While soil improvements can be made over time, starting with severely poor conditions like a boulder field, gravel pit, or heavy clay is ill-advised. An ideal site would have a slight lengthwise slope of about 1 percent, running east to west or west to east. Steeper slopes might be suitable for temporary structures like Haygrove tunnels but are not recommended for permanent hoop houses. Minor adjustments of a foot or two over 100 feet are manageable, but significant alterations should preserve existing topsoil. Resources like the Natural Resources Conservation Service (NRCS) website offer valuable guidance and grant opportunities through initiatives like the High Tunnel System Initiative. Effective drainage is also crucial for managing rainwater runoff from the roof. Solutions can range from horseshoe-shaped V-profile moats to extended plastic roof coverings that direct water away, or even guttering systems on hipwall lumber to collect rainwater for irrigation, though this often requires pumping due to low catchment barrel placement.
Practical Considerations for Hoop House Placement: Accessibility and Protection
Beyond sun exposure and soil, several practical factors influence optimal hoop house placement. Protection from strong winds, ideally at a non-shading distance, is vital. A site with good frost drainage, rather than at the bottom of a slope, is also beneficial. Proximity to water and electricity is another key consideration. Connecting to the grid is often the most straightforward option, especially for powering inflation blowers, which consume minimal electricity. Locating the hoop house near your home, barn, or primary work area allows for easier monitoring and access for quick tasks. For winter harvesting, having a nearby packing shed prevents crops from freezing during transit. While most hoop houses are unheated, if wood heating is desired, planning for firewood access or an underground pipe from a remote furnace is necessary. Once you experience the benefits of one hoop house, the desire for more often arises. When planning multiple structures, maintain at least 10 feet between side-by-side hoop houses, or more if heavy snow is common. In northern regions, a structure must be at least twice the height of any building to its south to avoid shading.
Optimizing Hoop House Dimensions: Size, Efficiency, and Layout
Determining the ideal size for your hoop house involves assessing your cultivation goals and market demand. Growers rarely regret having a hoop house that is "too big." Heights can range from 6 to 17 feet, widths from 10 to 30 feet, and lengths up to 100 feet, constrained by the standard dimensions of plastic film. Consider the surface-to-volume ratio: a greater volume can be achieved with a relatively small increase in surface area. Since material costs are linked to surface area, it's generally more cost-effective to build as large as is practical. However, narrower structures (e.g., 20 feet wide) require less bracing than wider ones (e.g., 30 feet), potentially making a narrower, longer hoop house more economical for the same total area. A 100-foot length is often the maximum without needing forced airflow to ensure adequate ventilation. High windows in the end walls help release warm, stale air without chilling plants at ground level. Soil and air serve as heat reservoirs during sunny days, releasing warmth at night to benefit plants. Larger volumes of air and soil contribute to better heat retention. Smaller structures retain less heat, and edge beds are typically colder. Pioneering high-tunnel grower Steve Moore suggested that a 28- or 30-by-96-foot hoop house offers optimal heat efficiency. When planning bed layouts, align the hoop house width with your preferred bed dimensions. For example, a 30-foot-wide hoop house can accommodate five 4-foot-wide central beds and two 2-foot-wide edge beds, with 1-foot-wide paths. Ensure beds are not wider than comfortable cultivation, and if using a cultivating tractor, match bed width to the wheel axle spacing.
Selecting the Right Framework: Durability and Safety Considerations
When planning your hoop house, the choice of framework material is crucial. While PVC piping might seem like a budget-friendly option, it's not recommended for large hoop houses due to its insufficient strength, rapid degradation in sunlight, and adverse reactions with polyethylene sheeting. Furthermore, PVC's production, incineration, and disposal processes release dioxins, posing significant health risks. Bending your own steel tubing, though possible, is labor-intensive for large-scale projects. For most growers, investing in pre-shaped galvanized steel tubing is a worthwhile expenditure. The cost of commercial frames is often justified by their consistent curves, precise fit, and correct lengths, ensuring structural integrity. A well-designed hoop house can quickly pay for itself, often within the first year. Factors like snow loading and wind force necessitate careful consideration of hoop spacing. While 6-foot spacing may suffice for snow loads up to 9 inches, 4-foot spacing offers enhanced resilience against heavier snowfalls and stronger winds, especially in light of changing climate patterns. For instance, at Twin Oaks, historical weather data revealing 32-inch snow depths and 60 mph winds influenced a decision for closer hoop spacing, resulting in a hoop house that has stood strong for 15 years. Growers commonly report that winds exceeding 75-80 mph can compromise hoop house structures, emphasizing the importance of robust construction. Additionally, for further insights into optimizing hoop house productivity, resources like "Hoop House Intercropping in Spring" offer valuable information.
Hoop House Shapes: Functionality and Environmental Adaptation
The shape of your hoop house significantly impacts its performance, particularly in relation to environmental conditions. Gothic-shaped structures are more effective at shedding snow compared to the rounded Quonset design. Gothic shapes also provide greater headroom over a larger area and offer improved sun angles, which is beneficial for plant growth. However, if you are bending your own tubes, a round shape is typically easier to achieve. Determining the necessary sidewall height is also important. To comfortably work the edge beds, you'll likely want to be able to stand upright, so factor in the standing room needed about 2 feet in from the sidewalls. These design choices contribute to both the structural integrity and operational efficiency of the hoop house, ensuring it meets the specific needs of your growing environment and cultivation practices.
Choosing the Right Supplier: Quality, Strength, and Budget Alignment
When selecting a supplier for your hoop house plans, shipping costs for heavy materials can be substantial, making local suppliers a practical consideration. Different brands offer varying levels of construction quality. Beyond examining cross-bracing and end-bracing, scrutinize the gauge of the steel tubing. Regions prone to significant snow, ice, and wind require a more robust structure. Gothic arch designs inherently offer greater strength than Quonset shapes, and 4-foot hoop spacing provides superior stability compared to 6-foot spacing. Similarly, a double-layered plastic covering offers enhanced strength over a single layer. Weigh these factors against your budget and risk tolerance. While growers often rebuild after a tunnel collapse, it's crucial to minimize the risk of crop loss. For movable hoop houses, ensuring thorough anchoring is critical, as strong winds can easily dislodge them. Some growers initially plan for frequent relocation but find it inconvenient, leading to annual movements instead. If you intend to hang items from rafters or train plants on wires anchored to them, confirm with manufacturers that the frame can support the additional weight. Many frames are not designed for this; in such cases, installing a separate, in-ground support framework is a viable alternative.
Layering for Efficiency: Single- vs. Double-Layered Hoop Houses
The choice between single- or double-layered plastic significantly impacts a hoop house's heat retention and overall performance. Single-layered plastic offers minimal nocturnal heat retention, resulting in indoor temperatures closely mirroring outdoor conditions. In contrast, double-layered plastic provides an 8-to-10-degree Fahrenheit temperature difference, which is crucial for winter crop growth, especially for plants like spinach and kale that thrive when temperatures exceed 40 degrees. The initial investment in double-layered plastic is often offset by increased yields from faster-growing crops. Additionally, double-layered plastic enhances structural integrity against wind and snow or ice loads by distributing weight across the entire structure. For example, a double-layered hoop house in Iowa withstood 80 mph winds due to the "bubble" effect preventing plastic ripple. While double-layered plastic may slightly reduce light transmission (a 1% reduction in light often leads to a 1% reduction in yield), this must be weighed against potential yield losses from colder nights in a single-layered structure. Research by Nick Calabro of Klerks Hyplast on Photosynthetically Active Radiation (PAR) light transmission through various film combinations provides valuable data. At Twin Oaks, a combination of standard 6-mil outer plastic and infrared (IR) inner plastic, featuring condensate control, has proven effective. Other options include Solarig from Robert Marvel, a woven poly film touted for its durability and high diffused light transmission, reducing plant burning and increasing photosynthesis. SolaWrap, a newer bubble-wrap-like material, offers double-layer advantages without inflation, providing 83 percent light transmission and diffusion. Double plastic typically requires an inflation system, but for remote sites or where grid access is costly, off-grid power solutions like solar with batteries, air-driven motors, or wind power can be employed. Alternatively, plastic foam blocks attached to bows can create an air gap for insulation without inflation, though this doesn't offer the same structural strength benefits. Thoughtful planning and construction of a hoop house, tailored to specific needs and environmental conditions, will establish a valuable and long-lasting asset for any agricultural enterprise.