Living windbreaks (trees and hedgerows) have been used for thousands of years. They were primarily used as a stock and predator barrier, but as any sheep about to lamb knows, it is warmer behind a hedgerow. The main reason: less wind-chill.
Some of the first serious windbreak research started in the dustbowl years in the U.S. Midwest. Years of removing trees, and of finely tilling the soil had created a classic wind erosion problem. To analyze the effect of windbreaks, the researchers built small fences using laths. Some of the technology was borrowed from snow fences which had been in use since the 1850’s and were undergoing a revival in popularity at the time.
Both fences controlled the wind. The difference was that where snow fences slowed the wind to allow the snow to settle out, erosion control fences slowed the wind to stop the soil lifting in the first place. The researchers varied the spacing of the laths then measured the effects on the wind and the erosion of the soil. They discovered that solid fences were not the best solution- they needed some porosity.
Wyoming snow fence
This information made it difficult for others who were looking at tree windbreaks as the porosity varied with height, from season to season, and even with windspeed as many leaves “feather” in strong winds.
In time it became apparent that windbreaks could dramatically increase crop production because of the change in several parameters important to crop growth. These are summarized in the Growth Optimization section.
In the early 1980’s the kiwifruit boom created a need for artificial windbreaks.
The first kiwifruit were sheltered because the hairs on the fruit were rubbed off if the vines were shaken by the wind. This devalued the fruit. Scientists then discovered that the growth and fruit production of the vines were very sensitive to windspeed too, so windbreaks were quickly accepted as an essential part of a viable kiwifruit orchard.
When kiwifruit became popular, established growers made enormous profits while supplies were very short. Wanna-be growers could not wait for tree-shelters to grow so they built artificial windbreaks of every type imaginable covering thousands of acres. Many blew down.
Engineers working for the New Zealand government were asked to investigate the failures and develop design guidelines for reliable shelter.
The Ultra Span windbreak systems by WeatherSolve Structures Inc. are based on these guidelines. The designs have been further refined following analysis of their structures after storm events. The biggest test was on about 200 acres in South Florida that had weathered (with varying levels of success) the 150mph plus winds of Hurricane Andrew in 1992.
Windbreaks are now in use in many situations throughout the world. Some of them may not seem so at first glance, but the aerodynamic design fundamentals are the same.
You will find examples of many of these structures elsewhere on this site.
- In agriculture and horticulture, conventional windbreaks are used for crops from apples to zucchinis; including items as diverse as pasture, wheat, strawberries, carembolas, lettuce and grapes.
- Snow fences are windbreaks designed to slow the wind enough to allow the snow to settle out.
- Groynes on eroding beaches use the same principles to slow the movement of water along a beach and allow the sand the water carries to be deposited.
- Golf Driving Range fences are just very porous windfences.
- Tennis-court surrounds are used as a windbreak as well as a visual screen.
- Nursery growers have shadehouses to keep the sun off their plants, but also to stop the wind blowing them over.
- Green-house owners erect windbreaks in front of their houses to reduce the amount of wind damage in a storm, and to cut heat losses from the houses.
- Industrial sites use windbreaks to keep the wind from blowing dust onto their neighbours.
- Dockyards use windbreaks to cut wind-drift of paint and to increase temperatures for extended painting periods.
- Mines use windbreaks to retain valuable ore on their stockpiles.