Landscape Shading
Solar heat absorbed through windows and roofs can increase your air conditioner
use. Incorporating shading concepts into your landscape design can help reduce
this solar heat gain, reducing your cooling costs.
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° F (5°C). Because cool air settles near the ground, air temperatures directly
under trees can be as much as 25°F (14°C) cooler than air temperatures above
nearby blacktop.
Using shade effectively requires you to know the size, shape, and location of the
moving shadow that your shading device casts. Also, homes in cool regions may
never overheat and may not require shading. Therefore, you need to know what
landscape shading strategies will work best in your regional climate and your
microclimate.
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 dense 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.
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. Slow-growing trees can also be
more drought resistant than fast-growing trees.
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 5–10 years. If you have an air conditioner, 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 also 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.
Solar heat absorbed through windows and roofs can increase your air conditioner
use. Incorporating shading concepts into your landscape design can help reduce
this solar heat gain, reducing your cooling costs.
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° F (5°C). Because cool air settles near the ground, air temperatures directly
under trees can be as much as 25°F (14°C) cooler than air temperatures above
nearby blacktop.
Using shade effectively requires you to know the size, shape, and location of the
moving shadow that your shading device casts. Also, homes in cool regions may
never overheat and may not require shading. Therefore, you need to know what
landscape shading strategies will work best in your regional climate and your
microclimate.
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 dense 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.
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. Slow-growing trees can also be
more drought resistant than fast-growing trees.
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 5–10 years. If you have an air conditioner, 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 also 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.
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