What Is A Hoop House?


Whether you are a new or experienced gardener, you might be wondering what a hoop house is, and what they are used for.  I was wondering the same thing, so I did some research to find out.

So, what is a hoop house?  A hoop house is a semi-circular tunnel structure, used to grow plants in a protected microclimate.  A hoop house allows you to control the temperature, humidity, and ventilation inside the structure by using doors or flaps.

Let’s take a closer look at hoop houses, including what they are for, how they work, what they are made of, and how much they cost.  We will also see how hoop houses are different from greenhouses, and when you might want to choose each one.

What Is A Hoop House?

A hoop house (also called a high tunnel or polytunnel) is a rectangular tunnel structure with a semi-circular roof.  It is tall enough to walk in, so that you don’t need to hunch over.  In fact, many farmers build hoop houses that are tall enough to accommodate farming equipment inside.

A hoop house is warmed by the sun and cooled by the wind, and it also has a door and vents that can be opened or closed as needed.  This allows you to create a “microclimate” inside of the structure to grow a particular crop based on its need for temperature, humidity, and ventilation.

sunlight through forest
A hoop house is warmed naturally by the sun, and usually does not contain any heating or cooling equipment like a greenhouse would.

You can also use cloches or row covers inside a hoop house to provide an additional layer of insulation to protect plants from cold.

For more information, check out my article on how to protect plants from cold and frost.

You can also choose different materials for the “skin” or walls and ceiling of the hoop house, depending on how much light you want to let in to the structure.  You can change the skin depending on the season, to protect sensitive plants from too much light when the sun is strong.

A hoop house is usually 14 to 21 feet (4.2 to 6.4 meters) wide, and they can be as long as a few hundred feet (100 meters).  Hoop houses are often portable and perhaps modular, so that they can be moved easily to cover crops that need protection.

For more information, check out this article on hoop houses (polytunnels) from Wikipedia.

What Is The Purpose Of A Hoop House?

A hoop house has several purposes, all of which are aimed at helping gardeners and farmers to get a better yield per acre of land.

A hoop house can be used to extend the growing season by warming the air and soil inside the structure.  Temperatures inside a hoop house are warmer than the outside air, often by 4 to 6 degrees Fahrenheit (2.2 to 3.3 degrees Celsius).

This makes a hoop house a good place to harden off seedlings in the spring, especially if you live in a cooler climate with a shorter growing season.

A hoop house is also helpful for keeping plants alive that could not otherwise survive the winter, by protecting them from cold, wind, rain, and hail.  A hoop house can even serve to protect livestock from winter weather.

pigs in hoop house
A hoop house can be used to protect plants or animals from the weather. Image by Brian Johnson and Dane Kantner. Image from: https://commons.wikimedia.org/wiki/File:Pigs_in_hoop_house,_Polyface_Farm.jpg

In addition, a hoop house helps to control moisture levels in the soil and humidity levels in the air.  On dry, windy days, you can close the doors and flaps of the hoop house to prevent water from evaporating out of the soil.

Finally, a hoop house can be used as a shade house if you use different material for the skin, or covering.  For example, you can use material that does not allow much light or heat through to grow cool weather crops, such as lettuce, when temperatures rise in the summer.

A hoop house lets you manipulate the inside environment to create a microclimate.  This microclimate will have the perfect temperature, humidity, ventilation, and light levels to grow a particular crop.

How Do Hoop Houses Work?

A hoop house works similarly to a greenhouse.  The sun’s light goes into the hoop house through transparent covers (ceiling and walls), heating up the soil and air inside.

greenhouse
A hoop house works just as a greenhouse does, by trapping heat from sunlight in the air and soil.

The heat then becomes trapped inside the hoop house, taking longer to escape and keeping the air and soil inside the structure warmer than outside.

Think about how warm a car or house can get on a sunny day with no clouds, even if it is windy outside, and you will have a better idea of how a hoop house works.

A hoop house also allows air to circulate via doors and openings in the structure, which can be opened or closed to allow for changes in temperature or humidity.

What Are Hoop Houses Made Of?

Hoop houses are made of many different materials, including metal, wood, and plastic.

hoop house
Image by Dwight Burdette. Image from: https://commons.wikimedia.org/wiki/File:Interior_of_a_Hoop_House_on_the_Farm_at_Saint_Joe%27s,_Superior_Township,_Michigan.JPG

A common way to start building a hoop house is to drive metal poles into the ground at a 30 degree angle, pointed towards the top of the hoop house.

From there, put lengths of hollow plastic pipe over the metal poles, bending them to form the curved tunnel of the hoop house.  Lengths of new 2-inch diameter PVC pipe are recommended for this step.  Older lengths of PVC pipe are more likely to become brittle with age, and are more likely to crack or break instead of bending.

Once the PVC semi-circles (hoops) are in place, use lengths of wood for baseboards along the ground.  This wood will form an outline around the entire hoop house structure.

Next, run tubular braces along the length of the hoop house (attached to the PVC hoops) for extra support and irrigation.

Then, attach a plastic greenhouse cover to the structure to act as a skin.  Be sure to install this plastic cover when there is no wind, and make sure you have helpers available.

It is recommended that you use a polyethylene greenhouse cover, treated with a UV inhibitor.  These are guaranteed to last 3 years, while an unprotected plastic cover will break down within a year due to sunlight damage.

Finally, you can use plywood or greenhouse plastic to make the walls to close in the ends of the structure.  Make sure to mark a space on the plywood or plastic for a door, and cut it out before attaching the ends.

For more information, check out this article from New Mexico State University on building a hoop house.

How Much Does A Hoop House Cost?

A hoop house costs anywhere from $0.75 to $3.00 per square foot, so a larger hoop house will cost more.  Of course, costs will vary depending on the material used for the hoop house, and whether you perform the construction labor yourself or hire someone to help.

To get an idea of the materials you will need, you can check out this article from New Mexico State University.  Note that the prices listed are from 2005, so while the materials are still valid, the prices will not be.

You can also check out this article from the University of Arkansas on constructing a metal hoop house and this article on hoop house prices and types from the USDA.

What Is The Difference Between A Hoop House And A Greenhouse?

So far, it sounds like hoop houses and greenhouses are very similar.  However, there are several key differences between a hoop house and a greenhouse.

First of all, a hoop house usually has no heating element or ventilation fan, instead relying on sun and wind to heat and cool the air and soil inside.  A greenhouse is often heated and cooled by fans or a heating unit.

Also, all of the plants in a hoop house are grown directly in the ground.  The plants in a greenhouse may be grown in the ground, or they may grow in raised beds, pots, grow bags, trays, or other containers on tables or benches within the greenhouse.

greenhouse
A greenhouse, like the one shown here, will often have plants grown on raised beds, tables, or benches. A hoop house grows plants directly in the ground. Image by Dwight Burdette. Image from: https://commons.wikimedia.org/wiki/File:Interior_of_a_Hoop_House_on_the_Farm_at_Saint_Joe%27s,_Superior_Township,_Michigan-2.JPG

In addition, a hoop house does not use reflective ground cover, since all of the plants are growing in the ground.  A greenhouse will often contain reflective ground cover to reflect reflects heat onto seeds growing in trays on raised tables.

Finally, a hoop house is much more affordable than a greenhouse.  Since a hoop house does not contain heating or cooling elements, it does not need an electrical connection.

Furthermore, there is no need to spend additional money on benches, containers, reflective ground covers, or other gardening equipment, since everything in a hoop house is grown in the ground.

For more information, check out this article on hoop houses from the BTL Liners website.

How To Pollinate Flowers In A Hoop House

There is one more thing to remember about hoop houses: the plants inside still need to be pollinated in order to produce fruit and vegetables!  If the hoop house is always closed off, there is no way for this to happen.

bee on blueberry flower
You need to open the doors or windows of your hoop house to allow bees and other pollinators inside if you want your flowers to yield fruit!

To solve this problem, open the door or window of the hoop house on a warm day to allow bees inside.  You may also want to plant some attractive flowers nearby to bring the bees to the area, where they can easily find the hoop house.

One exception is self-pollinating plants, such as tomatoes.  You can hand pollinate tomatoes with a toothbrush (among other things), without help from bees or other pollinators.

For more information, check out my article on how to hand pollinate tomato plants.

Conclusion

By now, you know what a hoop house is, and why you might use one in your garden.  You also have an idea of what materials to use to build a hoop house.

I hope you found this article helpful.  If so, please share it with someone who can use the information.  If you have any questions about hoop houses, please leave a comment below.

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

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