As North Texans know all too well, we cannot control the weather. However, we do have some power over the “micro-climate” that surrounds our homes.
A well-planned landscape can not only increase aesthetic value and decrease maintenance, it can help to moderate energy use.
Energy conservation and environmental quality are critical issues now and for generations to come as we face the challenges of climate change. While it is not possible to control temperature, wind or precipitation, by using basic Earth-Kind practices we can significantly modify our personal environment, which includes outdoor spaces. In making a few modifications to your landscape, such as adding or moving plants, you will make your home more energy efficient.
SHADE TREES & SHRUBS
Properly placing trees, shrubs, vines and structures in landscapes can keep homes and surrounding areas warmer in the winter and cooler in summer.
Large trees significantly reduce the effect of hot summer temperatures by shading a structure’s roof from the afternoon sun. They can keep a home cooler by as much as 8-10 degrees. Deciduous trees (those that loose their leaves) conserve energy in summer and winter. They shade homes in summer and then warm homes in winter by allowing the sun to filter through their bare branches.
If a home is situated to take advantage of shade from trees on the southern and western exposures, energy expended for cooling can be considerably reduced.
To shade the roof or a wall of a one-story home, place medium to large size trees (at maturity) 15-20 feet from the side or 12-15 feet from the corner of the structure. Smaller deciduous trees/shrubs, such as crepe myrtles and redbuds, can be planted closer to homes and used to shade walls and windows. These plants will provide shade during the summer and allow sunlight to penetrate in winter.
Another way to reduce energy consumption with trees and shrubs is to provide shade for the outside portion of an air conditioner. This practice can reduce the temperature inside a home up to three degrees. However, shrubs planted near compressors should not obstruct airflow or service access.
Plants can protect walls from heat and cold. Vines, shrubs and small trees may be used as espaliers (trained to grow flat against walls) or trained to grow on a wall or trellis. The foliage will insulate walls against summer heat and cold winter winds. Vines can also be highly effective in reducing noise and dust pollution.
Some vines, such as English ivy, have specialized roots that cling to masonry or wood. This type of vine may harm wood surfaces, however, as it tends to encourage pests and hasten wood decomposition. Vines that do not cling to surfaces usually grow by twining; they must have support such as trellises placed close to a structure. Another way to support vines on walls is to place mortar nails in joints between bricks or stones and securely fasten plant stems to the nails with ties.
Deciduous vines, such as Boston ivy and wisteria, allow the sun to penetrate in winter, while giving shade spring to fall. For quick and economical cover in summer, use annual vines, such as morning glory, grown from seed.
Using arbors and other overhead structures can be effective in addressing energy conservation. These structures, either attached or placed adjacent to a home, can shade walls and windows, reducing energy consumption and providing cool, restful sitting areas. When using structures, allow for adequate airflow.
The temperature a few inches above turf or other groundcover plants is often 12-15 degrees lower than temperatures above asphalt or concrete surfaces. Using grass and groundcover plants between homes and paved areas will significantly modify summer temperatures outside structures. Several plant materials are well suited for these applications. For conservation purposes, select species that are drought tolerant.
Texas winds accelerate the rate of air exchange between houses and the outdoors. However, a home that is not protected from air infiltration is more exposed to temperature extremes. Windbreaks obstruct and redirect wind flow. However, impenetrable windbreaks create a strong vacuum, which reduces protection. Living windbreaks, on the other hand, can save up to 23 percent on energy costs. How? Windbreaks composed of living plants allow some of the wind to penetrate, which makes them more effective.
The effective zone of protection for a living windbreak is approximately 30 times its height, although maximum protection occurs in a range of 5-7 times the height of the planting. Therefore, if planting a windbreak 25 feet tall, it should be located 125-175 ft. from the house to be most effective.
For answers to your horticulture questions, please call the Texas AgriLife Extension, Hood County at 817-579-3280 and ask to speak to a Master Gardener or visit the website at hoodcountymastergardeners.org.