What is a Hoop House or Tunnel?
A Hoop House is a polyethylene tunnel in the shape of a semi-circular, square or elongated shape. The interior heats up from the sun and warms the plants, soil and other things inside the building faster than it can escape. The warm air is retained in the building by the roof and the walls.
Like other forms of gardening protection, it protects your plants from harsh weather, such
as wind, snow, sleet and hail. It can also protect them from intense heat and bright sunlight in the summer months. It allows you to grow fruits and vegetables off season. They are often used in floriculture (flower farming) and nurseries.
In a tropical climate, where temperatures can soar, foggers/misters are used to reduce the temperature. The droplets are evaporated immediately to the open air so it doesn’t increase the humidity levels in the tunnel.
Some hoop houses are large enough that you can drive cultivating and planting equipment through them. This it makes it much nicer for the large farmer. The very high tech Hoop Houses, even have heating systems and soil heating systems to purify the soil of unwanted bacteria and viruses.
Types of Hoop Houses and Tunnels
Designs vary, but they usually all have steel hoops covered by greenhouse grade plastic. Roll-up sides for ventilation and sit on the ground. It’s like a big bubble to protect your plants.
High tunnels have upright post that are driven into the ground about two to three feet. This should provide enough stability to hold up in wind storms. The hoop houses that rest on the ground need to be anchored down with ground augers with chains. The augers also go deep into the ground and should be spaced evenly throughout the tunnel. No matter how well the tunnel is anchored you must keep the end and sidewalls closed in a high winds.
Caterpillars’ and low tunnels- Narrow single bay tunnels, often barely tall enough to stand in. They’re intended as temporary protection because they can’t hold up to the wind and snow, unless they’re secured tightly. Sometimes farmers will improvise by using rebar, plastic sheeting, row covers and other materials. They‘re also used inside the higher tunnels as an added protection in the winter months. Please note it is very possible the cover will freeze to the ground in the winter if used outside of the Hoop House, making it nearly impossible to harvest your winter crops.
Quonset or Hoop House-They can have rounded sidewalls, with the hoops beginning and ending on ground level or the hoops can sit on straight walls. The straight walls allow for taller plants in the rows along the wall and easier to get to your plants. You can stand, making it easier on your back.
The rounded roof style can collect more snow, than some styles so you need to place the hoops close enough together to hold the weight of the snow. Four foot spacing should be strong enough for many high tunnels.
Ventilation is controlled by raising and lowering the walls, so length of the tunnel isn’t an issue.
Gothic Style- These have a peaked roof and helps the snow to slide off better. They tend to be taller than the Hoop House, which makes the temperature more stable in warm months. This higher structure requires bracing for structural support.
Multi-bay Tunnels- Multi-bay, high tunnels are very popular in California and Europe. They’re used to cover larger acreages than the other types. They’re also large enough for tractors and cultivating equipment and tall enough to easily cover fruit trees. These have several spans of arches connected by a common “gutter” at the roof seem. They don’t have braces and aren’t intended to hold up in the high winds or snow. Not meant for the home gardener.
Things to Consider about Hoop Houses and Tunnels
Mobility- They can be moved but with the post in the ground 2-3 feet being 4 feet apart, it wouldn’t be an easy task. Tunnels that sit on the ground can be moved to fresh soil annually with less effort, however are more vulnerable to wind damage.
Snow/Wind- If you live in the North with a lot of snow, I would consider the Gothic types, unless you plan on removing the plastic every year. The climates with not much snow only have to worry about the wind factor.
Drainage- A shallow trench or slight slope along the edges will help with the water from coming in the sides.
Pros and Cons of a Hoop House
Pros-You can still plant your crops in bad weather, because you are inside. You can have “out of season” crops, enjoying fresh vegetables year round. Temperature is easily managed due to the sides rolling up and a larger space than with cold frames. Protection from pesty animals also, such as birds. You can buy them in kits to make sure you have the proper supplies.
Cons- Not easily moved. Internal temperatures can rise quickly on cool sunny days and damage or kill plants unless sides have been rolled up to allow for ventilation. Plastic covering will only last a few years unless you use more expensive greenhouse plastic.