SOLUTIONS HEADING

What are some effective windbreaks?

A very effective windbreak shrub is made by planting two rows of evenly spaced trees, with the trees staggered between the rows. Perfect Plants has a large selection of trees suitable for windbreaks and privacy screens. These include broad leafed evergreens as well trees with needlelike leaves.

How much wind can a wood fence withstand?

In fact, all of our privacy fences up to 6 feet tall have been engineer tested and can be installed to withstand high winds.
How to Guide: High Wind Installation.

Largo Privacy Fencing120 MPH sustained winds with gusts up to 137 MPHT&G Privacy Fencing110 MPH sustained winds with gusts up to 130 MPH.

Effect of height ?
Windbreak height [HI is the most important factor determining the downwind area protected by a windbreak. This value varies from windbreak to windbreak, and increases as the windbreak matures. In multiplerow windbreaks, the height of the tallest tree-row determines the value of H.
On the windward side of a windbreak, wind speed reductions are measurable upwind for a distance of 2 to 5 times the height of the windbreak [2H to 5H). On the leeward side (the side away from the wind), wind speed reductions occur up to 30H downwind of the barrier. For example, in a windbreak where the tallest trees are 30 ft, lower wind speeds are measurable for 60 ft to 150 ft on the windward side, and up to 900 ft on the leeward side. Within this protected zone, the structural characteristics of awindbreak, especially density, determine the extent ofwind speed reductions.

Effect of density ?
Windbreak density is the ratio of the solid portion of the barrier to the total area of the barrier. Wind flows through the open portions of a windbreak, thus the more solid a windbreak, the less wind passes through. Low pressure develops on the leeward side of very dense windbreaks. This low pressure area behind the windbreak pulls air coming over the windbreak downward, creating turbulence and reducing protection downwind. As density decreases, the amount of air passing through the windbreak increases, moderating the low pressure and turbulence, and increasing the length of the downwind protected area. While this protected area is larger, the wind speed reductions are not as great. By adjusting windbreak density different wind flow patterns and areas of protection are established. In designing a windbreak, density should be adjusted to meet landowner objectives, Awindbreak density of 40 to 60 percent provides the greatest downwind area of protection and provides excellent soil erosion control. To get even distribution of snow across a field, densities of 25 to 35 percent are most effective, but may not provide sufficient control of soil erosion. Windbreaks designed to catch and store snow in a confined area usually have several rows, and densities in the range of 60 to 80 percent. Farmsteads and livestock areas needing protection from winter winds require multiple row windbreaks with high densities. The number of rows, the distance between trees, and speciescomposition arefactors controlling windbreak
density. Increasing the number ofwindbreak rowsor decreasingthedistance between trees increases density and provides a more solid barrier to the wind. The species chosen for the windbreak wlll determine height as well as density. and will influence the length of the sheltered area. The interactionof height and density determines the degree of wind speed reduction, and ultimately the length of the protected area. For agiven height, the protected area usually increases asdensity increases. However, if density isbelow 20 percent, thewindbreak does not provide useful wind reductions. If density is above80percent,excessiveleeward turbulence may reduce windbreak effectiveness beyond 8H. Thecross-sectional shape ofwindbreaks with equal densitieshasminimal influence onwind velocities within 10H'ofthe leeward side of a barrier. Beyond 10H,straight sides provide slightly more protection
than slanted sides, becausemore wind passes through the trees. and extends the protected area fartherto the leeward.

Effect oforientation ?
Windbreaks are most effective when oriented at right angles to prevailing winds. The purpose and design of eachwindbreak is unique. thusthe orientationof individual windbreaks depends on the designobjectives. Farmsteadsand feedlots usually need protectionfrom cold windsand blowing snow or dust.  Orienting thesewindbreaks perpendicular to the troublesome winter wind dlrection provides the most useful protection. Field crops usually need protection from hot, dry summer winds, abrasive,wind-blown soil particles, or both. The orientation of thesewindbreaks should be perpendicularto prevailing winds duringcritical growingperiods. Successful field windbreaks should be designed to fit within the hhgoperation. Consideration should be given to reducing wind erosion, providing crop protection, increasing irrigation emciency and improving wlldlife habitat, Windbreaks protect fall-seeded small grms like wlnter wheat that may need protection from summer and winter winds.To controlsoil erosion, wfndbreaks should be planted to block the prevailing
winds during the timesof greatest soil exposure-wlnter and early spring. To recharge soilmoisture with dri!ibg snow, windbreaks should be placed perpendicular to the prevailing winter winds. Although wind may blow predominantly from one direction for a season, it rarely blows exclusively from
thatdirection. As a result, protection is not equal for all areas on the leeward side of awindbreak. 

Effect of length ?

Although the height of awindbreak determines the extent of theprotected areadownwind, the length of a windbreakdeterminesthe amount of total are receiving protection. For maximum efficiency, the uninterrupted length of awindbreak should exceed the height by at least 10:1. Thisratio reduces the influence of end-turbulence on the total protected area. The continuityof awindbreak also influences its emciency. Gaps in awindbreak become funnels that
concentratewind flow,creating areas on the downwlnd side of the gap in which wind speedsoften exceed open field wind velocities (Figure 3).Where-there are gaps, the effectiveness of the windbreak isdiminished. Lanes or field accessesthroughwindbreaksshouldbe located to minimize thiseffector if possible avoided al together.

Microclimate modifications ?

The reduction inwind velocity behind a windbreak leads to a change in the microclimate within the protected zone. Temperature and humidity levels usually increase decreasing evaporation and plant water loss. Actual temperature modifications for a given windbreak depend on windbreak height, density, orientation, and time of day. Daily air temperatures within 10Hleeward of a windbreak. are generallyseveral degrees higher than temperatures in the open. Beyond 1OH,air temperatures near the ground tend to be cooler during the day. On most nights, temperatures near the ground in sheltered areas (OHto 30Hlare slightly warmer than in the open. However, on very calm nights, sheltered areas may be several degrees cooler than open areas. Soil temperatures in sheltered areas are usually slightly warmer than in unsheltered areas. Taking advantage of these warmer temperatures may allow earlier planting and
germination in areas with short growing seasons. In the area next to an east-west windbreak soil temperatures are significantly higher on the south side due to heat reflected by the windbreak. Relative humidity in sheltered areas is 2 to 4 percent higher than in open areas, depending on windbreak density. Higher humidity decreases the rate of plant water use, soproduction is more efficient than in unsheltered areas. However, if the windbreak is too dense, and humidity levels get too high, diseases may become a problem in some crops. Heat loss due to wind-chill is reduced on the leeward side of a windbreak. Moderation of the chill factor is most important in farmstead and livestock windbreaks where humans and other animals readily notice increased energy efficiency. Most windbreak benefits come about indirectly because of changes in the microclimate of the sheltered zone.One exception is the direct benefit of reducing wind speed to control soil erosion. A well designed windbreak can reduce soil erosion to near zero within 10H of the leeward side of the tree row.

Summary
Windbreaks reduce wind speed on both the leeward and windward sides. The resulting reductions in wind speed lead to moderation of the microclimate in these protected zones.With careful planning, and in consultation with local professionals, these changes in microclimate can be used to create desirable environments for growing crops, raising livestock, and protecting the living and working areas.

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