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Plants Reduce Wind And Fuel Costs
An unprotected home loses much more heat on a cold, windy day than on
an equally cold, still day. Well-located trees and shrubs can intercept
the wind and cut heat loss. Up to one-third of the heat loss may escape
through the walls and roof by conduction. Wind also increases the convective
air currents along outside walls and roof thus increasing heat loss.
Infiltration or air leakage can account for as much as one-third of
heating losses in some buildings. Cold, outside air flows in through cracks
around windows and doors, and even through pores in walls. This produces
drafts that may cause you to compensate by raising the thermostat to
unreasonable levels just to maintain a modicum of comfort. Both windbreaks
and foundation plantings can cut down the penetrating power of the wind.
Windbreak Benefits
Studies of windbreaks show that windbreaks can reduce winter fuel consumption
by 10 to 30 percent. One study in Nebraska compared fuel requirements of
identical test houses which maintained a constant inside temperature of
70 degrees F. The house protected by a windbreak used 23 percent less fuel.
In 1 month, an exposed, electrically heated house in South Dakota used
443 kilowatt-hours to maintain an inside temperature of 70 degrees F. An
identical house sheltered by a windbreak used only 270 kilowatt-hours.
The difference in average energy requirements for the whole winter was
34 percent.
The amount of money saved by a windbreak will vary depending on the
climate of the area, location of the home, and the construction material
and quality. A well-weatherized house with adequate ventilation won't benefit
from windbreaks as much as a poorly weatherized house. In addition to reducing
the force of the wind, windbreaks also can reduce the wind-chill impact
on people outside the house.
Windbreaks can be located to control snow too, reducing the energy required
to remove snow from around homes, buildings, and roads. Make sure windbreaks
are located correctly to have the desired effect on drifting snow.
The height and density of trees determine the amount of protection they
will provide. Windbreaks of 2 to 5 rows of trees and shrubs generally provide
good protection. Evergreen trees provide the best protection, although
low, branching deciduous trees can significantly reduce wind speed. Even
a single row of evergreen trees will give some protection.
Windbreaks reduce wind velocity significantly for a distance of about
10 times the height of the trees. Maximum protection is provided within
a distance of 5 times the height of the trees. Thus a windbreak 30 feet
high protects an area extending as far as 300 feet downwind and some
protection is provided for as far as 20 times the height of the trees.
Foundation Planting
Trees and shrubs planted close to buildings reduce wind currents that
otherwise would chill the outside surface. Foundation plantings create
a "dead air" space which slows the escape of heat from a building.
These plantings also help reduce air infiltration around the foundation
of the house. Evergreen trees and shrubs are thicker and are more effective
than deciduous plants. To be most effective, the evergreens should be planted
close together to form a tight barrier. In summer, the same dead air space
helps insulate your home from hot, outside air reducing the need for air
conditioning.
by Jerome R. Smith
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