With more and more areas of the country facing water restrictions and high energy costs,
professional landscapers and homeowners alike are turning to cost-effective yet eye-pleasing
landscape designs to aid in lowering both water and energy consumption. According to one
government study, winter heating bills may be reduced by as much as 15 percent, while summer
cooling energy needs may be cut by as much as 50% by landscaping with energy and water
conservation in mind.
As far as heating and cooling your home, there are three basic ways your home loses either
heated or cooled air:
Air Infiltration - passage of air through cracks and around doors
Heat Conduction - conduction of heat through the materials of which your home is built
Solar Radiation - heat transmitted into homes by penetration of the sun's rays
Designing with conservation in mind requires taking your particular climate into
consideration. In the United States, climate can be divided into four climate regions:
temperate, hot-arid, hot-humid and cool.
Below are some points to keep in mind while planning your landscaping.
For the Temperate Climate:
- Maximize warming effects of the winter sun
- Maximize shade during the summer
- Deflect winter winds away from your home
- Funnel summer breezes toward your home
For the Hot-Arid Climate:
- 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
For the Hot-Humid Climate:
- Channel summer breezes toward your 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
For the Cool Climate:
- Use dense windbreaks to protect your home from cold 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
Everyone's climate also involves microclimates. For instance, even if you live in a cool
region, if your home sits on a sunny southern slope, you may be located in a warm microclimate.
So you must take your individual situation into consideration also.
Three basic landscape applications that save energy are:
- use of shade trees
- windbreaks
- and foundation plants
Trees will reduce summer temperatures significantly. If you can shade the roof of your
home from afternoon sun, you can reduce inside temperatures by as much as 8 to 10 degrees F.
Deciduous trees (those that lose their leaves in the fall) allow for the warmth of the winter
sun to filter through and warm in the winter but provide shade in the summer. Shade trees
placed on southeast and west exposures will reduce your summer cooling needs.
Although it is tempting to plant trees that are fast-growing, that truly is not always
your best choice. Trees that grow at a more moderate rate usually live longer, are less likely
to break in storms, and are often more resistant to insects and disease. You can always
increase a tree's growth rate with good care. Be sure to ask your local extension service
for a list of good shade trees for your area and make note of how fast and how large a
tree will grow when making your choice. Smaller trees can be planted closer to the house and are used for shading walls and
window areas.
Porches, arbors, pergolas and trellises are other options for obtaining shade. Oftentimes
these are good choices to provide immediate shade for walls, windows and decks or patios. A
trellis covered with a vine can protect walls from both heat and cold. The foliage cover
insulates the wall against summer heat and cold winter winds. Trees, shrubs and vines
are also effective in reducing dust and noise pollution. An arbor or pergola, whether located
adjacent to your home or farther out into the landscape, can be very effective conservators of
energy. If located adjacent to your home, they can provide shading of walls, windows and
decks reducing heat and glare while at the same time providing a cool, restful sitting and
viewing area.
If your home has an air-conditioner, you will want to shade the unit. Now, this doesn't
mean cover it up. It needs ventilation. But shading your cooling unit can increase its
efficiency by as much as 10%.
Our next area to consider while planning our landscape is protection from the wind. If
you live in a city, this is not as great a concern as those of us living in rural areas.
Unless, of course, you are in a new subdivision with little vegetation. While hedges
have been used for many years, with higher fuel costs coming into play, their
value is becoming more apparent. Savings of up to 23% have been recorded when comparing
a completely exposed home to one that is landscaped to minimize air infiltration.
For the southern and eastern areas of the United States, summer winds normally flow
from the south or southwest and generally produce positive effects. Tall trees on the
south or southwest can reduce temperatures while allowing the breeze to pass beneath and
through the foliage canopy. The western and northwestern areas of the United States
will most likely experience summer winds from the west and southwest.
A windbreak will obstruct and redirect the wind. As the wind strikes the obstruction,
it will move over, around or through it. The amount of protection on the leeward (facing
the direction toward which the wind is blowing) side of the windbreak is dependent on the
height and length of the windbreak. An impenetrable windbreak creates a strong vacuum on
the protected or leeward side, which reduces the protection. A windbreak that consists of
living plants will allow the wind to penetrate, which makes them more effective. Evergreen
trees and shrubs planted to the north and northwest of your home are the most common windbreak.
Trees and shrubs planted together can impede wind from ground level to the treetops. To
calculate the distance away from your home for a windbreak, it should be 2 to 5 times the
mature height of the trees you are planting.
It is important to note that winds, although somewhat predictable, are different for
every situation. So before planting or chosing your site, test and record your wind flow.
This will aid in chosing your site and maximizing your windbreak's effectiveness.
Last on our list is the use of foundation plants. Shrubs can be used closer to the home
for winter protection. Plant so that there is at least 1 foot of space between full grown
plants and your home's walls. This creates a dead air space that will insulate your
home in both winter and summer.
Trees, shrubs and groundcover plants that shade the ground and pavement around your
home reduces heat radiation and cools the air before it heats your home's walls and windows.
A hedge can shade a sidewalk, while a trellis with climbing vines can shade a patio or
deck. Trellises with vines or window box planters or hayrack planters with trailing vines
will cool your home's perimeter while allowing cool breezes to flow around your home.
No truly efficient landscape design would be complete without taking into consideration
water conservation, but I'm afraid I may have been too long-winded as it is, so that will
be a topic for another newsletter. But for those of you anxious to learn, many water
departments around the country have information available for your specific area and are
a great source of information on this topic.
