Gardening) Landscaping for Energy Efficiency

8/7/2019 Gardening) Landscaping for Energy Efficiency

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Are you looking for cost-effective yet

eye-pleasing w ays to lower you r energybills? Planting trees, shru bs, vines, grasses,

and hedges could be th e answer. In fact,

landscaping may be your best long-term

investment for reducing heating and

cooling costs, while also bringing other

improvements to your commun ity.

A well-designed landscape will:

Cut your summer and winter energy

costs dramatically.

Protect your home from winter wind

and summer sun. Redu ce consumption of water, pesti-

cides, and fuel for landscaping and

lawn m aintenance.

Help control noise and air pollution.

This publication covers landscaping tips

to save money year-round ; ways that land-

scaping helps the environment; important

climate, site, and design consider ations;

landscape planning; and tree and shrub

selection. You can get

add itional informationon regionally app ropriate

species from your local

nursery and landscaping

experts.

Land scapin g SavesMoney Year-Roun d

Carefully positioned

trees can save up to 25%

of a househo lds energy

consumption for heating

and cooling. Compu termod els devised by the

U.S. Department of

Energy predict that the

proper placement of only

three trees will save an

average hou sehold

between $100 and $250

in energy costs ann ually.

On average, a well-

designed landscape pro-

vides enough energy

savings to return yourinitial investm ent in less

than 8 years. An 8-foot

(2.4-meter) decidu ous

Landscaping forEnergy Efficiency

CLEARINGHOU

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ENERGY

EFFICIENCYAND

RENEWABLE

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Mature deciduous trees provide shade in the summer and su nlightfiltration in the win ter.

This document was produced for the U.S. Department of Energy (DOE) by t he National Renewable Energy Laboratory (NR EL), a DOE n ational laboratory.

The document was produced by the Technical Information Program, under the DOE Office of Energy Efficiency and Renewable Energy. The Energy Efficiency

and Renewable Energy Clearinghouse (EREC) is operated by NCI Information Syst ems, Inc., for NREL / DO E. The statements contained herein are based on

information known to EREC and NR EL at the time of printing. N o recommendation or endorsement of any product or service is implied if mentioned by EREC

Printed with a renew able-source ink on pap er containing at least 50% wastepaper, including 20% postconsum er waste

DOE/ GO-10095-046

FS 220

April 1995

John

Krigger


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(leaf-shedding) tree, for examp le, costs

about as mu ch as an awning for one large

wind ow and can ultimately save your

household hu nd reds of dollars in redu ced

cooling costs, yet still adm it some w inter

sunshine to redu ce heating an d lighting

costs. Landscaping can save you money in

summ er or winter.

Summer

You m ay have noticed the coolness of

parks and w ooded areas comp ared to the

temp erature of nearby city streets. Shad-

ing and evapotranspiration (the p rocess

by w hich a plant actively moves and

releases water vap or) from trees can

reduce surround ing air temperatu res as

mu ch as 9F (5 C). Because cool air settles

near the ground , air temperatures d irectly

un der trees can be as mu ch as 25 F (14 C)

cooler than air temp eratures above nearbyblacktop. Studies by th e Lawrence Berke-

ley Laboratory found summ er daytime air

temperatu res to be 3 F to 6 F (2 C to 3 C)

cooler in tree-shaded neighborhoods than

in treeless areas.

A well-planned land scape can redu ce an

unshaded homes summer air-conditioning

costs by 15% to 50%. One Pennsylvania

study reported air-conditioning savings of

as mu ch as 75% for small mob ile hom es.

WinterYou may be familiar with w ind chill. If

the out side temp eratu re is 10 F (-12 C)

and the wind speed is 20 miles per hour

(32 kilometers p er hou r), the wind chill is

-24 F (-31 C). Trees, fences, or geograp hical

features can be used as windbreaks to

shield your h ouse from the w ind.

A study in South Dakota found that wind-

breaks to the north, west, and east of

houses cut fuel consum ption by an aver-

age of 40%. Houses with windbreaks

placed on ly on the windw ard side (the

side from which the w ind is coming) aver-

aged 25% less fuel consum ption th an simi-

lar but unp rotected hom es. If you live in a

wind y climate, your well-planned land-

scape can reduce your winter heating bills

by ap proximately one-third.

Land scapin g for aCleaner Environment

Widespread tree planting and climate-

app ropriate landscaping offer su bstantial

environm ental benefits. Trees and vegeta-

tion control erosion, protect wa ter sup -

plies, provide food , create habitat for

wildlife, and clean the air by absorbingcarbon dioxide and releasing oxygen.

The N ational Academ y of Sciences (NA S)

estimates that u rban Am erica has 100 mil-

lion potential tree sp aces (i.e., spaces

wh ere trees could be p lanted). NAS fur-

ther estimates th at filling these spaces

with trees and lighten ing the color of dark

urban surfaces would result in annual

energy savings of 50 billion kilowatt-

hours25% of the 200 billion kilowatt-

hours consumed every year by air

conditioners in th e United States. Thiswou ld redu ce electric pow er plant emis-

sions of carbon dioxide by 35 million

tons (32 million m etric tons) ann ually and

save u sers of utility-sup plied electricity

$3.5 billion each year (assum ing an aver-

age of $0.07 per kilowa tt-hour).

Also, some species of trees, bushes, and

grasses require less water than others.

Some species are naturally more resistant

to pests, so they requ ire less pesticides.

Anoth er alternative to pesticides is inte-

grated pest management , an em erging field

that uses least-toxic pest control strategies.

One exam ple is to introd uce certain

insects such as pr aying mantises or lady-

bugs to feed onand limit pop ulations

oflandscape-consuming pests.

Certain gra sses, such as bu ffalo grass and

fescue, only grow to a certain height

roughly 6 inches (15 centimeters) and a re

water th rifty. By u sing these species, you

can elimina te the fuel, water, and time

consumption associated w ith lawn mow -ing, watering , and trimm ing. Also, recent

studies have found that gasoline-powered

mow ers, edge trimm ers, and leaf blowers

contribute to air pollution.

2

Landscaping may be

your best long-term

investment for

reducing heating and

cooling costs.


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Climate, Site, andDesign Considerations

Climate

The United States can be divided into

four ap proximate climatic regions: tem-

perate, hot-arid, hot-humid, and cool. The

energy-conserving landscape strategies

you use should d epend on w hich regionyou live in. These land scaping strategies

are listed by region and in order of impor-

tance below.

Temperate

Maximize warming effects of the sun in

the winter.

Maximize shade during the summ er,

Deflect winter winds away from

buildings.

Funnel summer breezes toward the

home.

Hot-Arid

Provide shade to cool roofs, walls, and

windows.

Cool the air around the home by plant

evapotranspiration.

Allow summer winds to access natu-

rally cooled hom es.

Block or deflect winds aw ay from air-

conditioned homes.

Hot-Humid

Channel summer breezes toward the

home.

Maximize summ er shade with trees that

still allow p enetration of low-angle win-

ter 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 w inds.

Allow the winter sun to reach south-

facing wind ows.

Shade south and west windows and

walls from the d irect summer sun, if

summ er overheating is a p roblem.

Microclimate

The climate immed iately surround ing

your home is called its microclimate. If

your hom e is located on a sun ny southern

slope, it may have a war m m icroclimate,

even if you live in a cool region. Or, even

though you live in a h ot-hum id region,

your h ome may be situated in a comfort-

able microclimate

because of abund ant

shade and dry

breezes. Nearby bod-

ies of water mayincrease your sites

hum idity or decrease

its air temperature.

Your homes micro-

climate may be m ore

sunny, shad y, wind y,

calm, rainy, snowy,

moist, or dry than

average local condi-

tions. These factors

all help determine

wh at plants may ormay not grow in

your microclimate.

3

Carefully positioned

trees can save up to

25% of a households

energy consumption

for heating and

cooling.

Hot-Humid

Hot-Humid

Hot-Arid

Temperate

Cool

Cool

Cool

The climatic region in which you live affects the land scaping strategies you use.

BA-A124001


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Siting and Design

A well-oriented and w ell-designed hom e

admits low-angle winter sun , rejects over-

head sum mer sun, and minimizes the

cooling effect of winter winds. If you

are building a hom e, pay attention to

its orientation.

In the n orthern hem isphere, it is usually

best to align the homes long axis in an

east-west d irection. The hom es longest

wallwith the most w indow area

should face south or southeast. The

hom es north-facing an d w est-facing walls

should hav e fewer w indow s because these

wa lls generally face winter s preva iling

winds. North-facing windows receive lit-

tle direct sunlight.

You m ay be able to design an d orient you r

new house to maximize your hom esitesnatural ad vantages and mitigate its disad-

vantages. Notice your hom esites expo-

sure to sun, w ind, and water. Also note

the location and proximity of nearby

buildings, fences, water bod ies, trees, and

pavementand their possible climatic

effects. Buildings provid e shad e and

windbreak . Fences and w alls block or

channel the wind . Water bodies moderate

temperature bu t increase humidity and

produce glare. Trees provide shade, wind-

breaks, or w ind channels. Pavement

reflects or absorbs heat, dep end ing on

whether its color is light or d ark.

If you r hom e is already built, inven tory its

comfort and energy problems, then u se

the following landscap ing ideas to help

minimize these problems.

Shading

Solar heat passing through wind ows and

being absorbed through the roof is the

major reason for air-cond itioner use.

Shading is the m ost cost-effective w ay

to reduce solar heat gain and cut air-conditioning costs. Using shad e effectively

requires you to know the size, shape, and

location of the moving shad ow that your

shading device casts. Remember that

hom es in cool regions may never overheat

and may not require shad ing.

Trees can be selected w ith app ropriate

sizes, den sities, and shapes for almost any

shad ing ap plication. To block solar heat in

the summ er but let much of it in du ring

the w inter, use d ecidu ous trees. To pro-

vide continu ous shad e or to block heavywind s, use evergreen trees or shrubs.

Deciduou s trees with high, spreading

crowns (i.e., leaves and b ranches) can be

planted to the south of your hom e to pro-

vide maximum su mm ertime roof shading.

Trees with crowns lower to the ground

are more app ropriate to the west, wh ere

shade is needed from lower afternoon sun

angles. Trees should n ot be planted on the

4

North

West

Durin g the summ er, tall spreading trees planted close to the home shade the roof.Broad, shorter trees on the west side b lock afternoon solar heat. A wind break onthe northwest side can shield the home from p revailing winter winds.

If you live in a windy

climate, your well-

planned landscape

can reduce your

winter heating bills

by approximately

one-third.

BA-A124004

To cool the south and w est sides of thehome, reduce paved areas, plant shad e trees,or add a trellis.

BA-A124004

SOUTH


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south ern sides of solar-heated hom es in

cold climates because the br anches of

these decidu ous trees will block some

winter sun.

A 6-foot to 8-foot (1.8-meter to 2.4-meter )

decidu ous tree planted near your hom e

will begin shading windows the first year.

Depend ing on the species and the hom e,the tree w ill shad e the roof in 5 to 10 years.

If you h ave an air cond itioner, be aware

that shad ing the u nit can increase its effi-

ciency by as mu ch as 10%.

Trees, shrubs, and groundcover plants

can also shad e the ground and p avement

around the home. This redu ces heat radia-

tion and cools the a ir before it reaches

your hom es walls and wind ows. Use a

large bush or row of shrubs to shad e a

patio or driveway. Plant a hedge to shad e

a sidew alk. Build a trellis for climbing

vines to shade a p atio area.

Vines can shad e

walls during their

first growing season.

A lattice or trellis

with climbing vines,

or a p lanter box with

trailing vines, shades

the homes perimeter

wh ile adm itting

cooling breezes tothe shaded area.

Shrubs planted close

to the h ouse w ill fill

in rapidly and begin

shading w alls and

windows w ithin a

few years. However,

avoid allowing

den se foliage to

grow imm ediately

next to a home

wh ere wetness orcontinual hu mid ity are problems. Well-

landscaped h omes in w et areas allow

wind s to flow around the home, keeping

the home an d its surround ing soil reason-

ably d ry.

Wind Protection

Properly selected and placed landscaping

can provid e excellent wind p rotection,

which will redu ce heating costs consider-

ably. Further more, these benefits will

increase as the trees and shrubs m ature.

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 northw est of the home are the

most comm on typ e of wind break. Trees,

bushes, and shru bs are often planted

together to block or imp ede w ind from

ground level to the treetops. Or, evergreen

trees combined with a w all, fence, or earth

berm (natural or man -made w alls or

raised areas of soil) can d eflect or lift thewind over the hom e. Be careful not to

plan t evergreens too close to your h omes

south side if you are counting on w armth

from the w inter sun.

A wind break will reduce wind speed for a

distance of as mu ch as 30 times the w ind-

breaks height. But for maximum protec-

tion, plant your wind break at a distance

from you r hom e of two to five times the

matu re height of the trees.

5

Properly selected an d placed evergreen treesand shru bs can shelter the home from winterwind s and red uce heating costs.

To block solar heat

in the summer but

let much of it in

during the winter,

use deciduous trees.

A trellis with a climbin g vine can shade a home andallow air circulation.

BA-A124005

If south wind s are a problem in the winter,plant evergreens far enough away to liftwinds without shading the home.

BA-A124005

NORTH

JohnKrigger


6/8

If snow tends to d rift in your area, plant

low shrubs on the windw ard side of your

wind break. The shru bs will trap snow

before it blows next to your hom e.

In add ition to more d istant w indbreaks,

planting shrubs, bushes, and vines next

to your house creates dead air spaces that

insulate your hom e in both winter andsum mer. Plant so th ere will be at least

1 foot (30 centimeters) of space between

full-grown plants and your h omes wall.

Summ er wind sespecially at nightcan

have a cooling effect if used for hom e ven-

tilation. However, if winds are hot and

your home is air conditioned all summ er,

you may w ant to keep summer winds

from circulating near your home.

Plannin g Your Land scape

Before you start landscaping, you mu st

first develop a p lan. The components of

your p lan could include d eciduou s trees

and plants, coniferous trees and plants,

earth ber ms, walls, fences, sheds, and

garages. This section w ill help you create a

landscape plan before you p lant around

your existing hom e or before you begin

construction on a new house.

Use pap er and different-colored pencils to

begin designing your landscape. First,

sketch a simp le, scaled d raw ing of your

yard . Locate its buildings, walks, drive-

ways, and utilities (e.g., sewer, electric,

and telephone lines). Note the location of

all paved su rfacesstreets, dr iveways,

patios, or sidew alksnear you r h ome.

Then iden tify poten tial uses for differentareas of your yard: vegetable gardens,

flower beds, patios, and play areas.

Draw arrows to show sun angles and pre-

vailing winds for both sum mer and win-

ter. As you sketch, circle the areas of you r

yard need ing shade or wind protection.

Indicate with arrows how you w ant views

to be p reserved or screened. Mark rou tes

of noise pollution you wish to block. Also,

highlight areas w here landscaping height

or wid th may be restricted, such as und er

utility lines or along sidew alks.

Notice yard areas that su ffer from poor

drainage and standing w ater. Some trees

and shrubs w ill not grow w ell in poorly

dr ained a reas; others w ill. Note existing

trees and shrubs. Plan for their replace-

men t if they are old or sick and if they

provide valued shade or windbreak.

Perhaps you w ant more defined p roperty

bound aries or less traffic noise. Consider aliving fence of dense trees, bushes, or

shrubs. Depend ing on its location and

application, this hedge can be customized

to be tall, short, w ide, narrow, open, or

den se. Privet is a species of shru b that

grow s in most parts of the United States

and can serve as a living fence.

Areas of lawn not u sed as p icnic or play

areas can be converted to p lanting bed s

or xeriscapedareas. Xeriscap ing is a land -

scaping technique that uses vegetation

that is drough t resistant and is able to sur-vive on rainfall and ground water once

established. Converting a traditional lawn

to alternative, water-conserving grasses or

other form s of xeriscaping saves energy

and red uces water consum ption.

Perhaps you live in an u rban area where

yard s are small and neighbor s close. Your

neighbor s yard m ay be the best place for

6

Originating in

Denver, Colorado,

xeriscaping is a

landscaping technique

that uses water-

thrifty species which

are often native to

the region. Once

established, they

are able to survive

on rainfall andgroundwater.

This plan d rawing is for a south-facing house in a hot, humid region. Dottedlines indicate potential problem areas. This home is exposed to hu rricane win ds.

BA-A124004

NORTH


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trees to shade your sou th-facing w indows.

Your yard may be the best location for

their wind break. Bringing your neighbors

into your plans could benefit everyone

involved.

The more you id entify your goals and

familiarize your self with you r yard s fea-

turescurrent and proposedthe betteryour chances for success with you r land-

scaping projects.

Selecting and Plan tingTrees and Shru bs

Trees and shrubs come in all shap es and

sizes. How you select you r trees and

shrubs and how you plant them will

directly affect your hom es comfort and

energy efficiency.

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 p roper p lant placement

and minimal maintenance before you p lant!

Shape Characteristics

Tree shapes are very d iversethink of

the d ifference in shape betw een an oak

and a spru ce. The Shad ing section

under Climate, Site, and Design Consid-

erations above d iscusses how to use

varying tree and shru b characteristics to

maximum advantage when landscaping.

The density of a trees leaves or needles

is imp ortant to consider. Dense ever-

greens, like spru ces, make great wind -

breaks for winter w inds. If you a re just

looking to imped e summ er wind s, choose

a tree or shrub w ith more open branches

and leaves. Such trees are a lso good for fil-

tering m orning sun from th e east, while

den ser trees are better for blocking har sh

afternoon summ er sun .

GrowthShould you p lant slow-growing or fast-

growing tree species? Although a slow-

growing tree may require many years

of growth before it shad es your roof,

it will generally live longer th an a fast-

grow ing tree. Also, because slow-growing

trees often have deeper roots and stronger

branches, they are less pron e to breakage

by wind storms or heavy snow loads.

And they can be more drought resistant

than fast-growing trees.

Consider growth rate, strength, and brit-tleness wh en locating trees near w alkways

or structures. Ask wh ether the matu re

trees root system is likely to d amage side-

walks, found ations, or sewer lines. The

smaller your yard, the m ore important it is

to select a tree with m anageab le roots.

Select ing, Final Planning,and Purchasing

Landscape professionals can help you

choose and locate new trees, shru bs, or

ground cover. Share your d rawings andtentative ideas with your local nursery or

land scape contractor. As long as you have

defined intended u ses and spaces in

which planting is actually possible, a com-

petent nursery or landscape specialist will

be able to help you make d ecisions.

When planting trees, shrubs, hedges, or

bushes, find out h ow large the mature

specimen w ill grow. In a ll cases, determ ine

7

Planting Tips

Many su bur ban and ur ban soils need loosening before you p lant. If the soil iscompacted, till it to an area at least five times the d iameter of the root ball.Plant your n ew trees and sh rubs on a cool or overcast day to redu ce the stressof relocating.

Dig a hole in the tilled soil. The hole diameter should be roughly twice thediam eter of the root ball but th e same height as th e root ball.

If your soil is very heavy or sandy, mix quality compost or potting soil withthe soil removed from the hole.

Remove the plant from its container, gently freeing its roots.

If the root ball is surround ed by bu rlap or wire, remove this before planting.

Place the tree or shrub in the h ole so that it sits at its original soil line.

Firmly, but g ently, fill the hole half full of the soil removed from the ho le,and lightly tamp the area around the root ball to remove air pockets.

Water well, then fill the hole to the top w ith soil. Water again.

Build a w atering basin 3 inches to 4 inches (8 centimeters to 10 centimeters)high arou nd the new p lant, about tw ice the diameter of the root ball.

To retain root moisture and reduce weeds, cover the ground around thenew plant w ith 4 inches (10 centimeters) of mulch. Use well-aged organic

materials such as old leaves and grass clipping s, bark, and aged sawd ust orwood chips.

Keep the plant well watered for the first year, but be careful not to drow n it!Watering d eeply tw ice a w eek is usu ally sufficient.


8/8

Source List

The following resou rces prov ide more inform ationon landscaping for energy efficiency.

American Association of Nurserymen (AAN)1240 I Street, NW, Suite 500Washington, DC 20005(202) 789-2900

AAN serves as a network of organizations representing gardencenters, landscaping, an d horticultural interests.

American Society of Landscape Architects (ASLA)4401 Connecticut Avenu e, NWWashington, DC 20008(202) 686-2752

ASLA is ded icated to the advan cement of know ledge, edu ca-tion, and skill in the art and science of land scape architecture.

National Arbor Day Foundation (NADF)100 Arbor Avenu eNebraska City, NE 68410

NADF is a nonp rofit edu cational organization ded icated totree planting and conservation. NADF sponsors NationalArbor Day each spring.

For general information about many kinds of energy efficiencytopics, contact:

The Energy Efficiency and Ren ewab le EnergyClearingh ouse (EREC)

P.O. Box 3048Merr ifield, VA 22116(800) DOE-EREC (363-3732)Fax: (703) 893-0400

EREC provid es free general and technical information to thepu blic on the man y topics and technologies pertaining toenergy efficiency and renewable en ergy.

Reading List

Common Sense Pest Control, edited by C. Timm ons, avail-able from Taun ton P ress, Inc., 1991.

Cooling Our Communities: A Guidebook on Tree Plant ingand Light-Colored Surfacing, H. Akbari, J. Hu ang, andS. Davis, available from Govern men t Printing Office(Document #055-000-00371-8), Superintendent of Docu-ments, P.O. Box 371954, Pittsbu rgh , PA 15220-7954, 1992.

Landscaping Design that Saves Energy, A. S. Moffat an dM. Schiler, William Morrow and Com pany, Inc., 1991.

Landscaping for Energy Conservation, W. R. Nelson, avail-able from th e Building Research Cou ncil, College of Fineand App lied Arts, University of Illinois at Urbana-Champaign, One East Saint Marys Road, Champaign,IL 61820, 1991.

Xeriscape Gardening: Water Conservation for the AmericanLandscape, C. Ellefson, Macmillan Pu blishing Com pan y,1992.

8

spacing by the mature sizes. For th ose

plants close to your hou se, plan for at least

1 foot (30 centimeter s) of extra clearance

between the full-grown shrub and the

wa ll of the hom e. This will prevent heav y

pru ning or damage to home siding in

the future.

After considering the placement of yourtrees and consulting landscaping and

nu rsery professionals, go back to your

draw ings or plans and add the new infor-

mation on species, shape, and mature-size

spacing. This provides a final, prep urchase

review to make sure that all elements

will work well togetherin the short and

long term.

When you are ready to p urchase your

trees and shru bs, avoid buying d amaged

specimens. Thoroughly inspect the bark,

limbs, and roots to make sure the p lant

was han dled carefully during growing,

digging , and sh ipp ing. Reject plant stock

with signs of insects or disease (cocoons,

egg m asses, cankers, or lesions).

After you pu rchase the p lants, be sure to

keep tiny root hairs damp an d shad ed atall times. The plan ts will not sur vive if

these root hairs are allowed to dry before

planting.

Contact your county extension agents,

pu blic libraries, local nu rseries, land scape

architects, land scape contractors, and state

and local energy offices for ad ditional

information on regionally ap propriate

plants and their maintenance requirements

Gardening) Landscaping for Energy Efficiency

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