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February 2020

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Luma Bendini

How a building's height affects wind behaviour

Height is a controversial characteristic of a building when the subject is pedestrian comfort. In an era where not even the sky is the limit for constructors, high-rise buildings are criticised for adversely affecting the ground-level wind environment.

Hold on tight to your umbrella! Here are the 3 most important wind effects that make pedestrian life difficult - and 3 ways that architects and urban planners use to avoid them.

Wind effects 

DOWNWASH EFFECT: Faster winds at higher altitudes are drawn down to the floor along the building's smooth facade. When the wind hits the ground, it becomes turbulent and creates vortexes.

 

VENTURI EFFECT: It happens where two or more buildings are close to each other. When the wind travels through a constricted area, velocity increases and pressure drops.

 

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WAKE: On the side sheltered from the wind, a spiraling downward flow creates turbulent wind and environment.

Mitigation techniques 

CANOPY: The overhead roof goes beyond giving shelter against rain or sun, it also migrates the adverse effect of wind on pedestrians.

 

SETBACK: Changes of sectional shapes modify the flow pattern around the construction, therefore air flows smoothly.

 

GRADUAL HEIGHT TRANSITION: Limiting height transitions from one building to another helps increase pedestrian comfort.