Landscape Design for Energy Conservation
As energy costs continue to increase we need to look for various, imaginative and logical ways we can reduce the amount of energy we consume. Often overlooked is how trees and shrubs surrounding our homes can affect the temperature of our living spaces. Trees and large shrubs can even modulate the intensity and quality of light entering through windows. We can decrease the amount of fuel used in lawnmowers, edgers, spin trimmers, leaf blowers and hedge trimmers and the air and noise pollution they create, by reducing or eliminating high maintenance turf areas and hedges.
Computer models used by the Department of Energy predict that just by planting trees in the proper places you can save 25-30% in heating and cooling costs.
In our climate, keeping your southern exposure open for the greatest solar heat gain is the most important way to reduce heating costs. We built a greenhouse on the south side of our house to provide passive solar heating as well as for propagating and growing plants. We angled the glass so that it would be perpendicular to the sun’s rays at noon on the spring and fall equinoxes. On sunny days, I can just open the door to the greenhouse and allow the heat in—I often do not even need to turn on the furnace on cool, but sunny fall or spring days!
For people that live in windy areas, planting a windbreak can also reduce heating costs. Most of our winds originate in the west from the Pacific Ocean, but every microclimate is different due to varied landforms. The most effective windbreaks are evergreens, with branches that grow close to the ground. They are best planted at a distance from your home that is 2 to 5 times the mature height of the trees. For a more interesting, and natural-looking design avoid a single-species—”soldiers in a row” hedge, instead, try a mixed species planting!
Foundation plantings also help to insulate your home by creating dead air spaces.
For cooling, one or more deciduous shade trees on the west side of your home can make a big difference in your comfort during the hottest part of the summer. For maximum benefit, the crown of the tree should shade your house, especially any windows during the hottest part of the afternoon. I used a sun chart for our latitude to determine that on July 22nd, at 2:30 pm– the sun would be 60 degrees west of true south at an angle of 50 degrees from the horizon. Therefore, the best position of a shade tree would be at an angle of 60 degrees west of south, from the point where you want the most shade on your house. The distance should be about ½ to 2/3 the mature height of the tree, perpendicular from your house (if it lies on a north-south axis). For example, a Red Maple that grows to about 60 feet should be planted 20-30 feet perpendicular from the house or about 25-35 feet along the hypotenuse of the triangle from the spot you want shade.
Trees are nature’s air-conditioners. Most (except for some desert plants) are inefficient in the use of water. As trees draw water up though straw-like xylem cells and use it in the process of photosynthesis, they must open small pores (stomata) in their leaves to take in carbon dioxide, and release oxygen. During this gas exchange, water vapor is lost to the outside air. This process, called transpiration, produces a cooling effect.
With the careful design of your landscape, you can save money and help the environment by reducing your family’s carbon footprint!
(This article was first published in the Peninsula Gateway on Aug 26, 2009 as Work on your Landscaping to Help with your Energy Efficiency in your Microclimate.)