Help Mother Nature help you save energy
Tuesday, August 19, 2008 3:51 PM PDT
By Joel M. Lerner
Special to The Washington Post
Printable version
E-mail this articleWASHINGTON — A well-researched landscape design can help lower energy costs and put homegrown food on the table. Nature allows us to save money while being environmentally conscious.
Focus on alleviating or harnessing the power of the sun. Your house should be shielded from the heat of direct sunlight in summer, while the sun shines on plants such as vegetable gardens. When deciduous trees that provide shade in summer lose their leaves in fall, sunlight can warm the house.
Tracking the sun and the prevailing winds on your property throughout the year provides information that will help you design according to plants’ needs. Plantings can offer aesthetics, energy efficiency and food. The best designs use trees, shrubs, vines, annuals and perennials.
Trees are interesting, low-maintenance and a naturally effective overhead element, an important part of the energy-efficiency formula. When planted properly, they provide comfort, conserve energy and cut fuel costs. Properly placed shade trees can reduce summer cooling bills by 25 percent and provide a canopy to define your property.
Afternoon is the hottest time of day, with the sun in the southwestern sky. To cut air-conditioning costs, deciduous trees should be planted to shade your house during this time.
Plant trees to shade the walls, not just the roof. Roofs in today’s homes are well insulated, and most of your air conditioning is lost through windows and walls. So place trees on the southern, southwestern and western sides of your house.
In winter, keep the southern, southwestern and western sides free of obstacles that might block radiant heat from reaching walls and windows. Don’t use evergreen trees because they will block the winter sun. Plant trees about 20 to 25 feet from the house and at least 25 feet from each other. It depends on the mature size of the tree you choose.
You can also shade your air-conditioning unit or heat pump to conserve energy. According to the American Nursery and Landscape Association, shading an air-conditioning unit can ease strain on the compressor and lengthen its life. By shading heat pumps, you can save up to 3 percent on energy. Plant a flowering tree or shrub near the unit, taking care not to block air circulation.
Deciduous vines on trellises will also give shade to south- and west-facing walls. Do not use evergreen vines. They won’t allow the sun to warm the walls as well in winter.
Vines that lose their leaves can serve a function similar to that of deciduous trees. While not nearly as effective, they grow more quickly. In as little as five years, some vines, such as trumpet creeper (Campsis radicans) and five-leaf akebia will grow large enough to shade a portion of your house. Plant vines so they climb on the southern and western walls of a brick or masonry house. On wooden houses, train vines on trellises next to walls to prevent decay from vines holding too much moisture.
Insulate with evergreens. Dense plantings of evergreen shrubs will provide insulation against cold air by creating a dead-air zone adjacent to the external walls. This can reduce the infiltration of cold air through walls. Plant shrubs on the northwest- and north-facing walls. To establish insulating plants on the north side, you must have a bright wall with no trees overhead. Install shrubs that are somewhat shade-tolerant, such as hollies, boxwoods and yews.
Vegetable crops will benefit from some enclosure to protect them from wildlife damage. Fences are the best enclosure. The fence should not act as a windbreak, because air circulation helps maintain healthy plants, including berry bushes, strawberries and fruit trees. Good air circulation dries foliage quickly after rain and discourages the spread of fungal diseases.
Joel M. Lerner is president of Environmental Design in Capitol View Park, Md., and author of “Anyone Can Landscape”(Ball 2001). Contact him through his Web site, www.gardenlerner.com.
Past Month's Most Commented Stories