Sunday, March 18, 2012

Florida Green Roofs, Wind and Fog Fences (Designing For Integrated Wind Issues)

Below are three very short video clips showing wind flow impacts on a small green roof.  Understanding how wind interacts with a green roof is crucial for the designer.  Unimpeded desiccating winds can kill green roof plants ever so quickly, especially on rooftop food plants.

Knowing what type of technologies to employ as wind breaks, or in this case installing a dual function fog net and wind break can help ensure the successes of a living roof project.

The first clip shows a flow of uninterrupted wind two meters above the roof top with speeds of four to five miles per hour or 2.235  meters per second.

The second clip shows wind flow across the roof surface with speeds of two miles per hour, or 0.894 meters per second.

Finally, the third clip shows wind speeds of 0.9 miles per hour or 0.4 meters per second across a living roof surrounded with a fog fence.

All of these readings were taken above the same roof and within two meters of each other.

We have seen a constant wind of one to two meters per second sufficiently desiccate green roof plants so as to kill the vegetation.  Parapets can greatly help but not every building has a parapet, especially residential structures.

Fog fences produce much the same results as a parapet and are cost-effective to install compared to installing a add-on parapet.

Know your roof's wind patterns.  Understanding wind flows across a green roof will increase the chances for long term survival of your green roof plants.

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