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... payback time is even less. Along with savings on your utility bills, a mature landscape with energy-conserving shade trees can, by some estimates, increase your property's value by as much as 15 percent. Of course, arbitrarily placing these same energy-conserving plants can also increase your utility bills. The more solar-dependent your home is (that is, if it has a solar-water heater, a passive space heater, or an attached greenhouse), the more vulnerable it is to haphazardly placed trees and shrubs. The old-fashioned idea that an energy-conserving landscape means a thicket of trees along a homes southern wall is not only ineffective, but often counterproductive.
For landscaping to work, it is hard to over-emphasize the importance of properly placing trees for both shade and wind protection. For example: A homeowner in Pittsburgh who plants trees for shade will save $ 20 per year in cooling costs with just a 30 percent increase in tree cover. So far so good. But when these same trees block out the winter sun, they can increase heating costs by $ 25 -a net loss!
Design the s e Pittsburgh landscape for both winter wind-shielding and summer shading, however, and the homeowner saves the same $ 20 per year in cooling, and an additional $ 40 during the heating season. It is possible to block wind in order to keep house warmer in winter, or scoop the prevailing breezes toward the house to cool your home and yard in summer. Deciding which to do is easy: attack whichever utility bill is higher. In many areas, the prevailing winds are different in summer and winter, allowing you to landscape for both. The most common way to sculpt air currents is to plant a windbreak of trees. A windbreak wont fit into every yard.
To be effective, a good windbreak for blocking out winter winds must be at least eleven times longer than its mature height. (8) This keeps the wind from whipping around the ends like a speedy back-eddy. A wild cherry plum tree called the holly-leaved cherry (Prunus ilicifolia) works well in many parts of the country. It can grow up to 30 feet, or be pruned as low as 10 feet, meaning a windbreak of 110 to 330 feet long. (Using oak trees, which can reach a height of 75 feet, means a windbreak thats 825 feet long obviously not an option for your typical suburban lot! ) A second rule-of-thumb states that windbreaks should extend at least 50 feet beyond both sides of the house. (7) On the issue of height: The windbreaks mature height should be one-fifth to one-fifteenth the distance to your house. (Put another way: The distance from your house to the windbreak should be five to fifteen times the trees height. ) For example, an 8 -foot hedge can provide a measure of protection up to about 80 feet downwind. Plan your windbreak so that the mature height of the trees is sized to the area you wish to protect. A windbreak works best when its length is perpendicular to the prevailing winds. And it neednt have an angled slope of short to taller trees to be effective.
In fact, a vertical, narrow windbreak often works best at lifting the strongest winds over the largest sheltered area. Allowing some air to pass through a windbreak actually reduces the winds speed over the greatest distance and makes the best diversion. A solid windbreak causes a dead space directly in front of it, allowing some of the wind whipping up over the tops of the trees to then shoot down, creating a blustery vortex in the very area youre trying to protect. With a permeable windbreak, some wind can slip through to form layers of air. This blanket of air (called laminar air) helps keep blustery winds aloft after passing over the top of the windbreak. Remarkably, the most effective windbreaks are actually 50 percent permeable.
Other important considerations include: it is necessary to be sure to talk to a local nurseryman about the best windbreak trees for used soil and climate; use evergreen trees for winter and summer protection. Deciduous trees buffer only summer winds. It is also necessary not to leave any large gaps in the windbreak, such as a driveway. The wind will funnel through the opening at a speed up to 20 percent greater than normal. (3) Make sure the windbreak is far enough from the house that it wont cast a shadow on south-facing windows during the winter. Hilly property requires careful observation of the winds patterns. Predicting the winds flow over complex topography cant be done with simple, two-dimensional drawings.
Contact an experienced landscape architect or designer to help you with the guesswork. If you want to help cool your home or garden in summer, reverse the windbreak principles outlined above. Funnel afternoon breezes toward the house or patio by placing two windbreaks or hedges more or less parallel to the prevailing summer breezes. But make sure they are planted at angles from each other, so the space between them is wider at the end farthest from the house and narrower near it. (See Funneling Summer Wind, p. 48. ) Like a funnel, the wide opening forces the breeze toward the narrow opening. This will increase the velocity of breezes by as much as 20 percent, enabling you to channel the air through your homes open windows.
In dry summer climates, channeled breezes can pick up some moisture as they pass over a moist brick patio, chilling the air via evaporative cooling. Placing trees for summer shade and winter sunshine is often more complicated than youd think. Many people assume summer shade trees should be planted close along the south-wall. But a study conducted in Sacramento, California, determined that all homes (both solar and conventional) pay more for energy year-round when either deciduous or evergreen shade trees are planted along the southern side of the house.
Some varieties of trees even doubled the energy costs over homes without trees. The reason to that is the fact that even the bare branches of a deciduous tree can actually block as much as 60 percent of the winter suns warming ability. This study found that the closer the shade trees are planted to a house, the higher the yearly utility bills. For 90 percent of the country (all but the most northern reaches), heres how to determine what area should be left free of shade trees: On a scale drawing of your property, draw two dotted lines due (magnetic) south from both the southeastern and southwestern corners of the house. (3) Next, starting from the same corners of the house, draw solid lines at 45 -degree angles to the east and west of the southeast and southwest corners of the house, respectively. One solid line will be east of the southeastern dotted line, and the other will be west of the southwestern dotted line. The area south of the house between these two solid lines should be free of trees or shrubs tall enough to shade the wall and the roof during any time of the year.
To beat summer heat, dont forget the eastern and western sides of the house- especially if they have lots of windows. A study conducted in Mesa, Arizona, found that the eastern and western walls absorb the most amount of summer sun. This is because the sun is directly overhead in summer, and eaves on southern windows can block a lot of the light that hits them. In contrast, the sun shines directly at eastern windows as it rises and directly at western windows as it sets. When it comes to reducing heat gain, shading the eastern wall was almost fifteen times more effective than shading the southern wall.
Even shading the western wall was six times more effective than the southern wall. While these numbers may vary considerably in places other than Arizona, eastern and western windows help overheat a house in the summer more than most people realize. To determine where to plant western and eastern facing shade trees, first look at your old utility bills or get weather records from the National Climatic Data Center, and figure out which week in summer is usually the hottest. Then, using sun charts at the local library, determine the suns angle in mid-afternoon on those days. Use this angle to chart the angle of the planting from the house. (5) For example, the hottest period in St. Louis, Missouri, is usually the last week of July, when the mid-afternoon sun is 75 degrees high in the sky.
Thus, all trees should be planted no closer to the house than a line 75 degrees on either side of the dotted lines marking true south. The major drawback to using shade trees for comfort is the time it takes them to grow large enough to have a real effect. Many shade trees won t have real impact until their second decade. Perennial vines, which take just two or three years to cover a trellis as tall as the houses walls, can work almost as well as shade trees for eastern and western walls.
The trellis shouldnt be under the eaves of the house; any hot air that might build up between the trellis and the siding wouldnt be able to vent out the top. Edible perennial vines for summer protection include grapes, chayote, kiwi, and passion fruit. Evergreen ornamental options include honeysuckle, jasmine, potato (not the plant that gives Idaho its tuber fame), trumpet, and hardenberg ia vines. (5) Annual vines grow even quicker than perennial vines and can cover a large area by mid- to-late summer. Annual vines are also well suited for use very close to the walls of the house. A wooden lattice trellis will lend a measure of shade from the very start. Keep the trellis at least a foot away from the house to allow enough air circulation to keep the siding free of mildew and rot.
You can plant vigorous, fast-growing edible vines such as scarlet runner beans, winter squashes and luffa squashes, or ornamental vines such as morning glory, hyacinth bean, and moon flower. You can also plant small trees or large shrubs near an existing air conditioner so it is shaded during the hottest months of the year. But make sure none of the foliage of falling leaves and twigs interferes with the AC fan or the flow of air. During the oppressive heat of summer and blistering cold winds of winter, landscaping can become another comforting layer of protection from the weather. You were born with a protective covering of skin; clothing adds another layer of comfort; the insulated skin of the house provides yet another measure of defense; and, finally, you can enjoy an energy-conserving shelter of attractive foliage wrapped around your home. These are just the most basic, broad strategies available to energy-efficient landscapers.
The most effective way to use these strategies (and more subtle ones) will vary greatly from region to region and even vary from property to property within a region. The same advice holds for recommended plant species. During a walk in the woods youve probably noticed that some spots are more pleasant, soothing, and comfortable than others. By understanding the forces of nature and putting them to work for you, you can create those conditions in your own yard- for the good of the earth and your wallet. Bibliography: 1) J. Goldemberg, T.
B. Johansson, A. K. N.
Reddy and R. H. Williams, Energy for a Sustainable World (New Delhi: Wiley (Eastern), 1988), 517 pp. 2) H. S. Geller, Promoting Energy Conservation in Developing Countries (Washington DC: American Council for Energy Efficient Economy, 1990). 3) A. Mckillop, Energy Sector Investment in LDCs: the credibility gap widens, Vol 14, No 8, August 1986. 4) W.
Finley. Landscaping for Energy Conservation. Garbage, Jun/Jul 2003, Vol. 5 Issue 3, p 44. 5) G. S. Dun and M. F.
Fels Planning for Planting, in T. B. Johansson, B. Bound and R. H.
Williams, Energy Efficient End-Use and New Generation Technologies and Their Planning Implications (Sweden: University of Lund Press, 1989), pp 353 - 388. 6) M. Kosmo, Money to Burn? The high cost of energy subsidies (Washington DC: World Resources Institute, 1987). 7) J. Goldemberg et al, Energy for a Sustainable World (New Delhi: John Wiley, 1988). 8) H. S. Geller, J.
Baroque de Holland and M. J. Marquis, Opportunities for Conserving Electricity through Landscaping! Regulations or Accords, paper presented at the 5 th National Energy Congress, Rio de Janeiro, October 1990.
Free research essays on topics related to: energy conservation, study conducted, prevailing winds, eastern and western, energy efficient
Research essay sample on Eastern And Western Prevailing Winds
