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Index : Shading
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- 2. Shading for Comfort and Energy Savings - Top
- Proper shading of homes can make a big difference in comfort both indoors and outside. It can also equate to big savings in energy consumption. On average, shading can reduce air conditioning costs by $200 in the months from May through September.
Shading of the home can best be accomplished with a combination of landscape plants. Trees can shade large expanses of walls, paved areas such as driveways, and roof of a home. Shrubs and vines also do an excellent job of shading walls. When exposed to full sun, walls transmit 3 times the amount of heat as do shaded walls. Roof areas exposed to sun transmit 2 times the amount of heat compared to shaded sections of the roof.
The greatest heat reduction and energy savings can be had by shading west-facing walls. That's because afternoon temperatures are highest and the suns rays fall most directly on west-facing walls. The next greatest impact is obtained by shading the morning sun on east-facing walls. Because the Summer sun is high in the sky, south-facing walls are not as exposed to strong sunlight, so the benefit from shading is less, but still significant.
Trees should be planted close enough to the house to shade, but not so close that they cause damage to the structure. Determine the mature size of the tree or trees you intend to use for shading. To excellent reference books for our area are ‘Landscape Plants for Dry Regions' by Jones & Sacamano, and ‘Plants for Dry Climates' by Duffield and Jones.
If a tree has a mature spread of 30 feet, it should be planted about half the mature spread, in this case 15 feet from the house. Trees can be planted closer to driveways, walks and patios. This will allow the canopy to spread out and shade these heat-absorbing surfaces. Keep in mind that some trees, such as mesquites, have large roots and can lift sidewalks and driveways if planted too close.
The best type of shade trees to use on south, east and west-facing walls are deciduous varieties. They shade during the Summer but loose their leaves in late fall, allowing the warming rays of the sun to heat the home in the Winter. Some excellent deciduous shade trees for Tucson include; Fan Tex Ash, Texas Honey Mesquite, Desert Willow, Indian Rosewood, and Chinese Pistache.
Shrubs can be placed in the same fashion as trees, by using the mature spread to determine spacing from the house. Vines can be grown on trellises a foot away from the wall. The dead air space created between the vines and the wall of the house will cause hot air to be funneled up, out and away from the house.
Shrubs and ground cover plants can be used to shade large expanses of heat-absorbing rock mulch. In addition to shading the ground these plants also help lower air temperature around the home through evaporative cooling.
As plants absorb water from their roots, they emit moisture through pores in their leaves called stomata. By this process plants and the air around them is cooled. So the more plants there are around your home, the more evaporative cooling will take place.
In addition to shading the house and the ground around it, place plants to shade the air conditioner. The strategic placement of just one or small trees can cool the air around the unit by 6 or 7 degrees F, and increase it's efficiency by as much as ten percent. Just make sure the placement of the plants doesn't block the flow of exhaust air from the unit.
Shading can be obtained quickly with the planting of shrubs, vine and ground covers. But trees can also provide shade in a relatively short period of time. Even small trees planted from 5 or 15 gallon containers can provide significant shade in just a few years. The key is providing adequate water for these young trees to grow.
To speed growth of trees, watering can be increase during the Spring and Summer seasons. For instance, it's generally recommended to water established Mesquite trees monthly during hot, dry periods. But if trees are watered two or three times monthly, their growth rate can be greatly increased.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona,
520-626-5161. - Updated: May 23, 2004
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