Landscaping can significantly reduce the costs of heating and cooling the home. Some well-placed shade trees, evergreens and shrubs not only look great, but also keep the house cool in the summer and warm in the winter.
Not much solar energy enters our homes through the walls and roof because of the insulation. Sun shining through the windows accounts for about half of the unwanted heat in a house during the summer. Twice as much solar energy enters through the east and west windows as the south windows, particularly if there is a roof overhang on the south side of the house.
The sun and wind both affect the temperature of residences in winter. A substantial amount of warmth can be gained from the sun shining through a southern facing window in the winter when the sun is low in the sky. East and west windows can also provide solar energy gain in the winter. The solar energy from the windows may provide 4-18% of the total energy needed to heat the home. Although, escaping warm air, along with cold wind penetrating a home, increase the heating costs and account for 24-39% of the heating requirements.
How to Utilize Landscape to Save Energy
When planting trees for energy conservation, try to:
- • Create windbreaks to block harsh winter winds, generally using evergreens and different sized shrubs.
- • Enlarge the deciduous tree canopy in specific areas to either shade or not obstruct the solar energy.
Commonly, the harsh winter winds come from a different direction than the cool summer breezes. Begin by placing an effective windbreak on the side of the house where the winter winds prevail. This can provide shelter for the home from cold winds, and therefore reduce heating energy costs.
When a windbreak is planted correctly, a larger area of relatively calm air is formed downwind from the windbreak.
To be effective, the windbreak should contain trees and shrubs that are the right height, thick enough, and in a long enough row to protect the house. The most proficient windbreaks will made of at least one row of dense evergreen trees whose branches extend to ground level. Windbreaks are planted in rows perpendicular to the wind direction.
For us in the Midwest, the windbreak will run to the north and west of the home. A windbreak that permits 50-60% of the wind to penetrate (such as plant material) is superior to a solid barrier (such as a solid fence) because it creates a larger area of protection on the leeward (downwind) side.
Smaller yards do not have space for large evergreen trees, but the canopy of tall deciduous trees can provide a great deal of protection. To be effective, mature trees should cover at least half the canopy space. This will provide some defense from winter winds, and a significant amount of shading from hot summer sun.
Deciduous shade trees should be planted due west and east of windows. Shade trees in these locations will shade the late morning and afternoon sun, which produces the most heat to homes in summer. Be sure to research and choose the right tree for the location, it should grow within 20 feet of windows and should grow to a mature size of at least 10 feet higher than the windows they are shading.
Trees planted to the south of the home will have an opposing result on energy savings. In the summer, the midday sun is high, almost directly overhead. The resulting shadow of a tree will fall directly under the tree, and miss the house, providing no shading. Alternatively, in winter, when the sun is at a much lower angle, the branches will shade to the house, rather than letting the full solar heating benefits get through. Mature deciduous trees in summer block 60 to 90% of the sun. In winter, a mature tree’s branches and twigs will block approximately 30 to 50% of the sun.
In addition to shading the house, trees or shrubs should be planted to provide shade to air conditioners. Be aware of where the fans discharge on the unit, as this could cause drying and death to the herbaceous screen. Keeping the surfaces of the air conditioner allows it to run more efficiently.
Foundation plantings of shrubs and small trees can also considerably reduce energy costs. In addition to reducing the amount of wind that hits a home, shrubs planted next to the house can provide insulation as it creates a dead airspace next to the foundation. Plant the shrubs so at mature size there will be approximately 1 foot of space between the plants and the building wall.
If drifting snow is a problem in the yard, windbreaks of trees and shrubs can act as living snow fences to control the location of snowdrifts. Lower shrubs planted on the windward side of the windbreak will trap snow before it blows next to the home. Winds will funnel around the ends of a snow fence. If possible, the row of plants should extend beyond the snowdrift area. A minimum of two rows of deciduous shrubs and/or one row of evergreens are most effective for snow control.