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Are you looking for cost-effective yet
eye-pleasing ways to lower your energy bills? Planting trees, shrubs, vines,
grasses, and hedges could be the answer. In fact, landscaping may be your
best long-term investment for reducing heating and cooling costs, while also
bringing other improvements to your community. |
A well-designed landscape will:
| Cut your summer and winter energy costs
dramatically. |
| Protect your home from winter wind and
summer sun. |
| Reduce consumption of water, pesticides,
and fuel for landscaping and lawn maintenance. |
| Help control noise and air pollution. |
Landscaping Saves Money Year-Round:
| Carefully positioned trees can save up to
25% of a household's energy consumption for heating and cooling. Computer
models devised by the U.S. Department of Energy predict that the proper
placement of only three trees will save an average household between $100
and $250 in energy costs annually. |
| On average, a well-designed landscape
provides enough energy savings to return your initial investment in less
than 8 years. An 8-foot (2.4-meter) deciduous (leaf-shedding) tree, for
example, costs about as much as an awning for one large window and can
ultimately save your household hundreds of dollars in reduced cooling
costs, yet still admit some winter sunshine to reduce heating and lighting
costs. Landscaping can save you money in summer or winter. |
Summer:
| You may have noticed the coolness of parks
and wooded areas compared to the temperature of nearby city streets.
Shading and evapotranspiration (the process by which a plant actively
moves and releases water vapor) from trees can reduce surrounding air
temperatures as much as 9 degrees F (5 degrees C). Because cool air
settles near the ground, air temperatures directly under trees can be as
much as 25 degrees F (14 degrees C) cooler than air temperatures above
nearby blacktop. Studies by the Lawrence Berkeley Laboratory found summer
daytime air temperatures to be 3 degrees F to 6 degrees F (2 degrees C to
3 degrees C) cooler in tree- shaded neighborhoods than in treeless areas. |
| A well-planned landscape can reduce an
unshaded home's summer air-conditioning costs by 15% to 50%. One
Pennsylvania study reported air-conditioning savings of as much as 75% for
small mobile homes. |
Winter:
| You may be familiar with wind chill. If
the outside temperature is 10 degrees F (-12 degrees C) and the wind speed
is 20 miles per hour (32 kilometers per hour), the wind chill is -24
degrees F (-31 degrees C). Trees, fences, or geographical features can be
used as windbreaks to shield your house from the wind. |
| A study in South Dakota found that
windbreaks to the north, west, and east of houses cut fuel consumption by
an average of 40%. Houses with windbreaks placed only on the windward side
(the side from which the wind is coming) averaged 25% less fuel
consumption than similar but unprotected homes. If you live in a windy
climate, your well-planned landscape can reduce your winter heating bills
by approximately one-third. |
Landscaping for a Cleaner Environment:
| Widespread tree planting and
climate-appropriate landscaping offer substantial environmental benefits.
Trees and vegetation control erosion, protect water supplies, provide
food, create habitat for wildlife, and clean the air by absorbing carbon
dioxide and releasing oxygen. |
| The National Academy of Sciences (NAS)
estimates that urban America has 100 million potential tree spaces (i.e.,
spaces where trees could be planted). NAS further estimates that filling
these spaces with trees and lightening the color of dark, urban surfaces
would result in annual energy savings of 50 billion kilowatt-hours—25% of
the 200 billion kilowatt-hours consumed every year by air conditioners in
the United States. This would reduce electric power plant emissions of
carbon dioxide by 35 million tons (32 million metric tons) annually and
save users of utility-supplied electricity $3.5 billion each year
(assuming an average of $0.07 per kilowatt-hour). |
| Also, some species of trees, bushes, and
grasses require less water than others. Some species are naturally more
resistant to pests, so they require less pesticides. Another alternative
to pesticides is integrated pest management, an emerging field that
uses least-toxic pest control strategies. One example is to introduce
certain insects such as praying mantises or ladybugs to feed on—and limit
populations of—landscape-consuming pests. |
| Certain grasses, such as buffalo grass and
fescue, only grow to a certain height—roughly 6 inches (15 centimeters)
and are water thrifty. By using these species, you can eliminate the fuel,
water, and time consumption associated with lawn mowing, watering, and
trimming. Also, recent studies have found that gasoline-powered mowers,
edge trimmers, and leaf blowers contribute to air pollution. |
Climate, Site, and Design Considerations:
Climate:
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.
Temperate:
| 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. |
Hot-Arid:
| 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. |
Hot-Humid:
| 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. |
Cool:
| 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. |
Microclimate:
| 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. |
Sitting 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. |
Shading:
| Solar heat passing through windows and
being absorbed through the roof 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 10 years. 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 areas allow winds to flow around the home, keeping the home and its
surrounding soil reasonably dry. |
Wind Protection:
| 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 30 times 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. |
Planning Your Landscape:
| Before you start landscaping, you must
first develop a plan. The components of your plan could include deciduous
trees and plants, coniferous trees and plants, earth berms, walls, fences,
sheds, and garages. This section will help you create a landscape plan
before you plant around your existing home or before you begin
construction on a new house. |
| Use paper and different-colored pencils to
begin designing your landscape. First, sketch a simple, scaled drawing of
your yard. Locate its buildings, walks, driveways, and utilities (e.g.,
sewer, electric, and telephone lines). Note the location of all paved
surfaces—streets, driveways, patios, or sidewalks—near your home. Then
identify potential uses for different areas of your yard: vegetable
gardens, flower beds, patios, and play areas. |
| Draw arrows to show sun angles and
prevailing winds for both summer and winter. As you sketch, circle the
areas of your yard needing shade or wind protection. |
| Indicate with arrows how you want views to
be preserved or screened. Mark routes of noise pollution you wish to
block. Also, highlight areas where landscaping height or width may be
restricted, such as under utility lines or along sidewalks. |
| Notice yard areas that suffer from poor
drainage and standing water. Some trees and shrubs will not grow well in
poorly drained areas; others will. Note existing trees and shrubs. Plan
for their replacement if they are old or sick and if they provide valued
shade or windbreak. |
| Perhaps you want more defined property
boundaries or less traffic noise. Consider a "living fence" of dense
trees, bushes, or shrubs. Depending on its location and application, this
hedge can be customized to be tall, short, wide, narrow, open, or dense.
Privet is a species of shrub that grows in most parts of the United States
and can serve as a living fence. |
| Areas of lawn not used as picnic or play
areas can be converted to planting beds or xeriscaped areas.
Xeriscaping is a landscaping technique that uses vegetation that is
drought resistant and is able to survive on rainfall and groundwater once
established. Converting a traditional lawn to alternative,
water-conserving grasses or other forms of xeriscaping saves energy and
reduces water consumption. |
| Perhaps you live in an urban area where
yards are small and neighbors close. Your neighbor's yard may be the best
place for trees to shade your south-facing windows. Your yard may be the
best location for their windbreak. Bringing your neighbors into your plans
could benefit everyone involved. |
| The more you identify your goals and
familiarize yourself with your yard's features—current and proposed—the
better your chances for success with your landscaping projects. |
Selecting and Planting Trees and Shrubs:
| Trees and shrubs come in all shapes and
sizes. How you select your trees and shrubs and how you plant them will
directly affect your home's comfort and energy efficiency. You can get
information on regionally appropriate species from your local nursery and
landscaping experts. |
| Trees and shrubs have a life span of many
years and can become more attractive and functional with age. But poor
planning of landscape improvements often creates trouble. Ensure proper
plant placement and minimal maintenance before you plant! |
Shape Characteristics:
| Tree shapes are very diverse think of the
difference in shape between an oak and a spruce. The "Shading" section
under "Climate, Site, and Design Considerations" above discusses how to
use varying tree and shrub characteristics to maximum advantage when
landscaping. |
| The density of a tree's leaves or needles
is important to consider. Dense evergreens, like spruces, make great
windbreaks for winter winds. If you are just looking to impede summer
winds, choose a tree or shrub with more open branches and leaves. Such
trees are also good for filtering morning sun from the east, while denser
trees are better for blocking harsh afternoon summer sun. |
Growth:
| Should you plant slow-growing or
fast-growing tree species? Although a slow-growing tree may require many
years of growth before it shades your roof, it will generally live longer
than a fast-growing tree. Also, because slow-growing trees often have
deeper roots and stronger branches, they are less prone to breakage by
windstorms or heavy snow loads. And they can be more drought resistant
than fast-growing trees. |
| Consider growth rate, strength, and
brittleness when locating trees near walkways or structures. Ask whether
the mature tree's root system is likely to damage sidewalks, foundations,
or sewer lines. The smaller your yard, the more important it is to select
a tree with manageable roots. |
Selecting, Final Planning, and
Purchasing:
| Landscape professionals can help you
choose and locate new trees, shrubs, or ground cover. Share your drawings
and tentative ideas with your local nursery or landscape contractor. As
long as you have defined intended uses and spaces in which planting is
actually possible, a competent nursery or landscape specialist will be
able to help you make decisions. |
| When planting trees, shrubs, hedges, or
bushes, find out how large the mature specimen will grow. In all cases,
determine spacing by the mature sizes. For those plants close to
your house, plan for at least 1 foot (30 centimeters) of extra clearance
between the full-grown shrub and the wall of the home. This will prevent
heavy pruning or damage to home siding in the future. |
| After considering the placement of your
trees and consulting landscaping and nursery professionals, go back to
your drawings or plans and add the new information on species, shape, and
mature-size spacing. This provides a final, pre-purchase review to make
sure that all elements will work well together—in the short and
long term. |
| When you are ready to purchase your trees
and shrubs, avoid buying damaged specimens. Thoroughly inspect the bark,
limbs, and roots to make sure the plant was handled carefully during
growing, digging, and shipping. Reject plant stock with signs of insects
or disease (cocoons, egg masses, cankers, or lesions). |
| After you purchase the plants, be sure to
keep tiny root hairs damp and shaded at all times. The plants will not
survive if these root hairs are allowed to dry before planting. |
| Contact your county extension agents,
public libraries, local nurseries, landscape architects, landscape
contractors, and state and local energy offices for additional information
on regionally appropriate plants and their maintenance requirements. |
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