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Trees are the primary means of energy conservation in landscapes. They can have a canopy large enough to shade roofs, reducing cooling costs and increasing comfort.
The best locations for deciduous trees are on the south and east sides of a house. When these trees drop their leaves in winter, sunlight can reach the house to help in heating it. Note: even without leaves, trees can block as much as 60 percent of the sun, making placement of trees critical to their effectiveness.
Evergreen trees on the north and west sides afford the best protection from the setting summer sun and cold winter winds.
If large trees are to be planted, it is best to select those that have a moderate growth rate rather than fast-growing varieties. Moderate-growth trees are sturdier against storm damage and generally more resistant to insects and disease.
A tree that will reach a medium to large size should be located 15 to 20 feet from the side of a house and 12 to 15 feet from the corner. Smaller trees can be planted closer to a house and shade walls and windows.
Shrubs or small trees can be used to shade outside air conditioning or heat pump equipment, improving its performance. For good airflow and access, plants should be at least three feet from the compressor.
Vines for Shading
Vines provide shading for walls and windows. Some vines such as English Ivy will cling to any wall surface and can harm wood surfaces. Trellises placed close to the walls can be used to support vine growth without touching or marring the walls. Evergreen vines will shade walls in the summer and reduce the effects of cold winds in winter.
Arbors
Arbors are a traditional cooling method used worldwide. Positioned along the sides of the house, an arbor will reduce temperatures by allowing air to pass through and be cooled by the evaporation at the plant's leaves. Arbors are also effective shading devices.
Evergreen shrubs and small trees can be planted as a solid wall along the north side of the house to provide a windbreak. The most effective windbreaks have limbs that extend to the ground. Two to three rows of evergreens or five to six rows of deciduous trees should be used.
The effective zone of protection for a windbreak can be 30 times the height of the trees. However, the maximum protection occurs within five to seven times the tree height. For example, if the windbreak will be 25 feet tall, it should be placed 125 to 175 feet from the house.
Groundcover and/or turf can also reduce temperatures. The temperature above a groundcover will be 10 to 15 degrees cooler than above a heat-absorbent material such as asphalt or a reflective material such as light-colored gravel or rock. Heat-absorbent materials will also continue to radiate heat after the sun has set. It is best to either minimize the use of such materials near the house or shade them from direct sun. |