JUL 2019, Luma Bendini
What is Pedestrian Wind Comfort?
The way wind is experienced on ground level affects pedestrian comfort, safety and even the financial returns for the building and the surrounding commercial activities.
What are the wind speeds and direction on that location?
How does flow behave around that architecture?
How much wind is too much wind?
The questions above are a basic guideline for conducting a Wind Comfort study. The answers consist of combining meteorological data, with aerodynamic information, and a comfort criterion.
The perception of wind at the ground level is mainly influenced by wind speed and wind direction. The way wind is experienced affects pedestrian comfort, safety and even the financial returns for the building and the surrounding commercial activities.
To address those issues in an architectural project, understanding Comfort Criteria is a must. A Comfort Criterion is a standard by which pedestrian comfort is defined.
A wide range of different wind comfort criteria exist. Most of them are based on a maximum allowed exceedance of a speed threshold. In other words, the criteria set a threshold wind speed. And then says how much can wind speeds go beyond that threshold.
That is because a light breeze can be experienced for a longer time, without being uncomfortable. But being exposed to a high wind speed for a long time can be uncomfortable and even dangerous.
Let’s put it into practice, the next videos will show 2 commonly used comfort criteria with practical examples.
Lawson-based Criterion
Lawson is one of the most used criteria to assess wind comfort at ground level. Lawson criterion assumes that wind speeds exceed its average velocity less than 5% of the time considered.
The picture below shows Wind Comfort on that location during the Quarter 4 - visualizations set to 2 meter height. The average wind velocity reaches from zero to 2,5 meter per second for up to 5 days the color will be shown in dark blue. When the wind registers speeds from 8 to 10 meters per second less than 5% of the days in a quarter, the color will be shown in green. Each color represented a wind speed range and is recommended for a specific activity.
Davenport-based Criteria
The Davenport Criterion is a comfort classification divided into specific activities. It analyses how comfortable is to practice an activity at a certain location.
The color scheme displays how often the wind exceeds the limit of 5 meters per second. The longer the average wind speeds exceed this limit, the more uncomfortable the activity is assumed to be.
The pictures bellow shows an analysis for a specific activity, occasional sitting. The wind speeds are higher than 5 meters per second up to 53% of the time considered. In this case, the time considered is a quarter of the year or 3 months.
This high probability of stronger winds makes that area uncomfortable for occasional sitting. And it can be even dangerous, as shown by the red spots.
Within Ingrid Cloud, Davenport Criterion also shows the same analysis for other activities such as sitting, strolling or jogging.
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