Climate, Site, and Design Considerations
The United States can be divided into four approximate climatic regions: temperate, hot-arid, hot-humid, and cool. The energy conserving landscape strategies you use should depend on which region you live in. These landscaping strategies are listed by region and in order of importance below.
Maximize warming effects of the sun in the winter.
Maximize shade during the summer.
Deflect winter winds away from buildings.
Funnel summer breezes toward the home.
Provide shade to cool roofs, walls, and windows.
Allow summer winds to access naturally cooled homes.
Block or deflect winds away from air-conditioned homes.
Channel summer breezes toward the home.
Maximize summer shade with trees that still allow penetration of low angle winter sun.
Avoid locating planting beds close to the home if they require frequent watering.
Use dense windbreaks to protect the home from cold winter winds.
Allow the winter sun to reach south-facing windows.
Shade south and west windows and walls from the direct summer sun, if summer overheating is a problem.
The climate immediately surrounding your home is called its microclimate. If your home is located on a sunny southern slope, it may have a warm microclimate, even if you live in a cool region. Or, even though you live in a hot-humid region, your home may be situated in a comfortable microclimate because of abundant shade and dry breezes. Nearby bodies of water may increase your site's humidity or decrease its air temperature.
Your home's microclimate may be more sunny, shady, windy, calm, rainy, snowy, moist, or dry than average local conditions. These factors all help determine what plants may or may not grow in your microclimate.
Siting and Design
A well-oriented and well-designed home admits low-angle winter sun, rejects overhead summer sun, and minimizes the cooling effect of winter winds. If you are building a home, pay attention to its orientation.
In the northern hemisphere, it is usually best to align the home's long axis in an east-west direction. The home's longest wall with the most window area should face south or southeast. The home's north-facing and west-facing walls should have fewer windows because these walls generally face winter's prevailing winds. North-facing windows receive little direct sunlight.
You may be able to design and orient your new house to maximize your home site's natural advantages and mitigate its disadvantages. Notice your home site's exposure to sun, wind, and water. Also note the location and proximity of nearby buildings, fences, water bodies, trees, and pavement -- and their possible climatic effects. Buildings provide shade and windbreak. Fences and walls block or channel the wind. Water bodies moderate temperature but increase humidity and produce glare. Trees provide shade, windbreaks, or wind channels. Pavement reflects or absorbs heat, depending on whether its color is light or dark.
If your home is already built, inventory its comfort and energy problems, then use the following landscaping ideas to help minimize these problems.
Solar heat passing through windows and being absorbed through thero of is the major reason for air-conditioner use. Shading is the most cost-effective way to reduce solar heat gain and cut air-conditioning costs. Using shade effectively requires you to know the size, shape, and location of the moving shadow that your shading device casts. Remember that homes in cool regions may never overheat and may not require shading.
Trees can be selected with appropriate sizes, densities, and shapes for almost any shading application. To block solar heat in the summer but let much of it in during the winter, use deciduous trees. To provide continuous shade or to block heavy winds, use evergreen trees or shrubs.
Deciduous trees with high, spreading crowns (i.e., leaves and branches) can be planted to the south of your home to provide maximum summertime roof shading. Trees with crowns lower to the ground are more appropriate to the west, where shade is needed from lower afternoon sun angles. Trees should not be planted on the southern sides of solar- heated homes in cold climates because the branches of these deciduous trees will block some winter sun.
A 6-foot to 8-foot (1.8-meter to 2.4-meter) deciduous tree planted near your home will begin shading windows the first year. Depending on the species and the home, the tree will shade the roof in 5 to 10years. If you have an air conditioner, be aware that shading the unit can increase its efficiency by as much as 10%.
Trees, shrubs, and groundcover plants can also shade the ground and pavement around the home. This reduces heat radiation and cools the air before it reaches your home's walls and windows. Use a large bush or row of shrubs to shade a patio or driveway. Plant a hedge to shade a sidewalk. Build a trellis for climbing vines to shade a patio area. Vines can shade walls during their first growing season. A lattice or trellis with climbing vines, or a planter box with trailing vines, shades the home's perimeter while admitting cooling breezes to the shaded area.
Shrubs planted close to the house will fill in rapidly and begin shading walls and windows within a few years. However, avoid allowing dense foliage to grow immediately next to a home where wetness or continual humidity are problems. Well-landscaped homes in wet area sallow winds to flow around the home, keeping the home and its surrounding soil reasonably dry.
Properly selected and placed landscaping can provide excellent wind protection, which will reduce heating costs considerably. Furthermore, these benefits will increase as the trees and shrubs mature. The best windbreaks block wind close to the ground by using trees and shrubs that have low crowns.
Evergreen trees and shrubs planted to the north and northwest of the home are the most common type of windbreak. Trees, bushes, and shrubs are often planted together to block or impede wind from ground level to the treetops. Or, evergreen trees combined with a wall, fence, or earth berm (natural or man-made walls or raised areas of soil) can deflect or lift the wind over the home. Be careful not to plant evergreens too close to your home's south side if you are counting on warmth from the winter sun.
A windbreak will reduce wind speed for a distance of as much as 30times the windbreak's height. But for maximum protection, plant your windbreak at a distance from your home of two to five times the mature height of the trees.
If snow tends to drift in your area, plant low shrubs on the windward side of your windbreak. The shrubs will trap snow before it blows next to your home.
In addition to more distant windbreaks, planting shrubs, bushes, and vines next to your house creates dead air spaces that insulate your home in both winter and summer. Plant so there will be at least 1 foot(30 centimeters) of space between full-grown plants and your home's wall.
Summer winds especially at night can have a cooling effect if used for home ventilation. However, if winds are hot and your home is air conditioned all summer, you may want to keep summer winds from circulating near your home.