Vinnie Bevivino

Seed and Cycle

Hoop Houses During the Summer

How To Use Them With Triple Digit Temperature

Hoop houses are used by small and urban farmers to grow year round and get more food off of a small piece of land.  They’re commonly thought of as a way to make a space warmer and therefore allow the farmer to harvest throughout the winter.  However, hoop houses can make it difficult or impossible to grow in the summer unless you can cool them down.  Its very important to design your hoop house so it is both air-tight to prevent winter drafts yet able to be opened to allow for summer growing.  This article discusses the two common ways of attaching plastic to your hoop house, and ways to use hoop houses in year-round operations that doesn’t slow down when the temperatures reach in the triple digits.

No matter how you attach plastic to your hoop house, the metal frame is always the same.  But, once the frame is built, you have a fork in the road; how you want to vent your hoop house?  There are two main methods.

Tomatoes growing in a hoop house with roll-up sides.

The most common method is attaching a horizontal 2×4 about 4 or 5 feet above your baseboards, called a hip board.  The plastic is attached from hip board to hip board, and hangs below the hip boards to the ground.  The hanging plastic is wound around a metal pole that has a long handle that you can roll up and down.  Venting in warm weather is only through the sides below the hip board, and the open doors on each end wall.  Warm air gets trapped, and air above the hip board is quite warm.  Also, air is vented by wind, so on still days it can still get hotter than desired.

A hoop house with rigid side walls at Growing Power. Note the snow on the roof and the compost piles along outside of the sides.

One variation on the roll-up sides is installing a polycarbonite (corrugated greenhouse plastic) panel below the hip board that is screwed on in the fall and taken off in the spring.  The upside to this is that the rigid polycarbonite is stronger than greenhouse plastic film, and therefore you can mound up mulch or compost along the sides in the winter.  Also, polycarbonite will last longer than the greenhouse film.  However, this option is expensive, as polycarbonite sheets are not just expensive to purchase, but expensive to ship.   It also doesn’t allow for the daily adjustments in venting which can be important during unexpectedly hot days during the early spring.

Vents at the top using the overlapping method. A piece of pallet wood is being used to keep it open.

The second main method to covering a hoop house is with pieces of plastic that are 20 feet wide and as long as the length of your hoops.  These pieces are put parallel to the hoops and attached to the baseboards, and overlap by about five or six feet.  They open at the top by putting a piece of wood in between two pieces of plastic, creating a vent.  The upside is that this causes convection; cool air comes in from the doors and warm air exits the open vents on the top, even on still days.  Also, because the plastic is attached to the baseboards, there’s less of a chance of animals getting into your hoop house.  However, this method makes your hoop house impossibly hot during the hotter months.  Also, putting wood placeholders in your plastic vents takes more time then simply rolling up a side and wears out the plastic.

There still a couple of things to further reduce the heat during the summer months.  When the plastic is still on, you can paint it with Kool Ray, a paint on, water soluble coating for your plastic that makes it more translucent and therefore more shady inside.  You can paint it on the outside and allow the rain to wash it off, or on the inside if you want it to last months at a time.  This is the cheapest way to reduce the amount of light in your hoop house.

Me putting shade cloth on a hoop house.

A better, but more expensive method is using shade cloth.  Many green house supply companies sell custom cut shade cloth in different shade percentages, allowing you to order the precise size with grommets in the correct placement to secure it to your hoop house.  I suggest using 50% shade cloth, unless using it for a wash station or mushroom production, in which 90% is best.  Place a grommet at each hoop and every four feet along the endwalls, and it will withstand the typical summer thunderstorm.  The big benefit of shade cloth over Kool Ray is that you don’t need your plastic on at all, allowing you to actually reduce the temperature when compared to outside temperatures.  This allows you to use your metal frame hold shade cloth, extending your season for cooler crops into the summer months.

So, with all this information, how does an urban farmer make sure that production doesn’t slow down during the summer months?  First, choose either way to cover your hoop house in the winter.  We suggest using roll-up sides, but there’s benefits for each method.  Whatever you choose, plan on taking your plastic all the way off.  The best, but also somewhat expensive way to do this is to use wiggle-wire, a wire that fits into an aluminum track that is bolted to your hoop house.  The plastic goes below the wiggle-wire, and securely holds it.  You can take out the wire and the plastic and not put holes through your plastic like with staples.  Wiggle wire will also hold your shade cloth.

Hoop house with an open endwall.

No matter what, you’ll need end walls that open entirely for maximum ventilation.  Build your end walls with a door-within-a-door design, so that you can have it closed in the winter, but open wide in the summer.

Whatever your method of reducing the summertime heat, you’ll need to water a lot.  If growing in compost and have direct sun, expect to water your farm three if not more times each day.

The moral of the story is that hoop houses were typically thought of as tools for winter growing.  However, unless you take a summer vacation, urban farmers can’t afford to let any part of their farm be anything less then very productive all year round.  With this information, you can see that hoop houses can be a tool for summer growing as well.

One Response to Hoop Houses During the Summer

  1. Pingback: Growing Food, Growing Power: Milwaukee, Wisconsin Urban Farmer Tours the Northeast | The GRID | Global Site Plans

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