Environmental regulations and problems with nearby neighbors. Windbreaks are barriers used to reduce and redirect wind. They usually consist of trees and shrubs, but they may also be made up of perennial or annual crops and grasses, fences, or other materials. The reduction in wind speed behind a windbreak modifies the environmental conditions, or microclimate, in the sheltered zone. Within this protected zone, the structural characteristics of a windbreak, especially density, determine the extent of wind speed reductions.
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 that passes through. Low pressure develops on the leeward side of very dense windbreaks. The 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.