Sustainable Landscaping
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Plants and the Wind
Wind affects house energy use most importantly in winter. As the air is cold at that time, it seeps into cracks and openings in the home, allowing warm air to escape. However, this is not really a problem in the summer. On the contrary, breezes in summer tend to have a desirable cooling effect.
Wind affects plants by causing them to lose water through transpiration. If plants lose water too quickly, their stomates will close, which prevents photosynthesis from taking place, as the leaves can no longer take up carbon dioxide. In extreme cases, this can cause stunted growth. In winter, evergreen plants can lose too much water during windy conditions, causing them to dry out, and may lead to winter dieback.
Plants can modify the wind in three ways: wind breaks, or wind screens re-direct the wind over an area, plants can trap cold air as it moves downslope, and tree funnels can channel breezes in the desired direction.
Trees are used to break the wind in usually open areas, such as houses or buildings in a rural environment. Much heat energy is lost in exposed buildings in winter due to the wind. with good protection on three sides of a building, energy savings may run as high as 30%. In addition to cost savings, this also contributes to a reduction of carboon emissions from power plants.
Windbreaks can reduce the velocity of wind up to 20%. Thus, a 20mph wind can be reduced by 4 mph, to 16mph; a 30mph wind can be reduced to 24mph, and so on. The zone of protection extends a distance 15-20 times the height of a plant screen.
To design an effective windbreak, plants are placed perpendicular to the prevailing wind. A variety of plants are used, providing different heights and different densities, so that some air can filter through.
In urban environments, the wind is usually much less of a problem. As a matter of fact, still air is often more stagnant and uncomfortable. It is possible to use plantings designed as a wind funel, that can help to channel and direct the wind, allowing a cooling effect as it moves through. Air flow is also beneficial for disease avoidance.
Berms can also be used to divert the wind in the desired direction. A berm is soil that has been mounded up. It is often kidney shaped or elongated, covered with mulch, groundcovers, and shrubs and trees. Berms can also help to block an unsightly view.
SOURCES AND REFERENCES:
Iowa State University. 1997. Farmstead windbreaks: planning. ISU University Extension. Pm-1716.
Nowak, D. J. and D. E. Crane. 2002. Carbon storage and sequestration by urban trees in the USA. Environ. Pollution. 116: 381-389.
Wilson, J. S. and S. J. Josiah. 2004. Windbreak design. Nebraska Cooperative Extension G96-1304-A. http://ianrpubs.unl.forestry/g1304.htm. Viewed 4/4/2005.
Wind affects plants by causing them to lose water through transpiration. If plants lose water too quickly, their stomates will close, which prevents photosynthesis from taking place, as the leaves can no longer take up carbon dioxide. In extreme cases, this can cause stunted growth. In winter, evergreen plants can lose too much water during windy conditions, causing them to dry out, and may lead to winter dieback.
Plants can modify the wind in three ways: wind breaks, or wind screens re-direct the wind over an area, plants can trap cold air as it moves downslope, and tree funnels can channel breezes in the desired direction.
Trees are used to break the wind in usually open areas, such as houses or buildings in a rural environment. Much heat energy is lost in exposed buildings in winter due to the wind. with good protection on three sides of a building, energy savings may run as high as 30%. In addition to cost savings, this also contributes to a reduction of carboon emissions from power plants.
Windbreaks can reduce the velocity of wind up to 20%. Thus, a 20mph wind can be reduced by 4 mph, to 16mph; a 30mph wind can be reduced to 24mph, and so on. The zone of protection extends a distance 15-20 times the height of a plant screen.
To design an effective windbreak, plants are placed perpendicular to the prevailing wind. A variety of plants are used, providing different heights and different densities, so that some air can filter through.
In urban environments, the wind is usually much less of a problem. As a matter of fact, still air is often more stagnant and uncomfortable. It is possible to use plantings designed as a wind funel, that can help to channel and direct the wind, allowing a cooling effect as it moves through. Air flow is also beneficial for disease avoidance.
Berms can also be used to divert the wind in the desired direction. A berm is soil that has been mounded up. It is often kidney shaped or elongated, covered with mulch, groundcovers, and shrubs and trees. Berms can also help to block an unsightly view.
SOURCES AND REFERENCES:
Iowa State University. 1997. Farmstead windbreaks: planning. ISU University Extension. Pm-1716.
Nowak, D. J. and D. E. Crane. 2002. Carbon storage and sequestration by urban trees in the USA. Environ. Pollution. 116: 381-389.
Pitt, D. G. J. Kissida, and W. Gould. 1980. How to design a windbreak residential landscaping. Amer. Nurseryman. Vol. 152(10): 10-11.
US DOE. 1988. Landscaping for energy efficient homes. U.S. Dept. of Energy, Conservation and Renewable Energy Inquiry and Referral Service. Silver Spring, MD. 8 pp.
Wilson, J. S. and S. J. Josiah. 2004. Windbreak design. Nebraska Cooperative Extension G96-1304-A. http://ianrpubs.unl.forestry/g1304.htm. Viewed 4/4/2005.
PHOTO COURTESY OF NY NRCS USDA
