- Microclimate
modification deflects local wind flow toward or away from building
inlets and outlets through strategically placed vegetation and landscape
structures, such as trellises and fences.
- Windbreaks
moderate wind flows on a neighborhood or site scale. Trees are planted
close together, across the path of prevailing winds to redirect
and slow the wind.
Microclimate
Modifications
To capture and
direct airflow into a building, plant trees and shrubs with dense
foliage adjacent to a building, immediately downwind of or above air
inlets. Trellises with tightly spaced lathing can also be located
to create a high-pressure area at inlets, enhancing inward flow.
Where ventilation
outlets are located on the side of a building relative to the prevailing
wind, plant trees and shrubs immediately upwind of air outlets to
create a low-pressure area, enhancing outward flow.
Use a dense planting
of trees, shrubs, and/or trellises with vines at the base of building
facades to dissipate and redirect downdrafts away from building entrances,
patios and sidewalks.
Dissipate high-velocity
winds around the sides of buildings with multi-layered large trees
and shrubs with dense foliage at building corners.
Windbreaks
The effectiveness
of a windbreak depends on its size, porosity, and orientation to prevailing
winds. Windbreaks should be carefully considered in Santa Monica,
since they can interfere with on-shore breezes, essential to natural
cooling and ventilation strategies.
Where required,
windbreaks should form a continuous barrier approximately 10 times
longer than their proposed mature height. Their height should be ~15
ft. for every story of building height.
Windbreaks should
be planted closer to the building than the mature height of the plants,
respecting other site requirements. They should be oriented at angles
to the prevailing wind to direct air toward inlets or away from outlets.
When multiple windbreaks are used, consider planting in a funnel pattern
to direct wind toward the building to increase wind flow where desired.
Windbreaks intended
to dissipate wind for outdoor spaces should be set perpendicular to
the prevailing winds. The depth of the protected area will be approximately
five times the height of the windbreak. (A 10-ft. high hedge will
effectively calm wind flow in the 50 ft. behind it). In this application
the windbreak should allow 15% to 30% of the wind to pass through
to minimize turbulence downwind.
Cautions
- Redirecting
wind flow helps natural ventilation but is not a substitute for
sensitive site planning and building orientation.
- Wind patterns
in an urban context are complex and turbulent. Wind tunnel testing
and computer models can help in planning effective wind modification.
