Saturday, March 10, 2012

Green Roofs & Cyclones - A Continuous Vegetated Assemble Design for Hurricane Impacted Areas

The 2012 Hurricane season will be upon us in a couple months, if not sooner.  Cyclones, hurricanes and tornadoes are all important factors to consider when designing a green roof.

Of course no amount of design and construction can preclude extremely high wind damage as we have recently witnessed across the midwestern United States.

Continuous Vegetated Assembly Drawing for Green Roofs in High Wind Velocity Areas

However, common sense tells us that any object on a roof should be permanently fastened in some manner if the building is subject to high velocity winds.  Even then, these extra-velocity winds can rip up heavy items and toss them to the roadway below.

However, though it may be impossible to prevent all wind damage, use of three dimensional geogrid and tri-dimensional non-woven and woven fabrics can provide a platform for green roof plants to anchor themselves in a permanent fashion to the roof.

Choosing the correct bi or tri-axial geogrid for your green roof design can be confusing.  Attaching the geogrid to your roofing system can be even more perplexing.

After years of field trials with a number of popular fabrics, I have seen some work well while others disintegrated under the stress of sunlight or wind or both.

Most are a PPE or other petro-synthetic compound.  Some, more sustainable than the plastics, such as jute and hemp work well under certain conditions yet fail quickly under other environmental factors.

Importantly though, a properly chosen geogrid can not only form the basis for a cyclone resilient roof, but can allow the green roof designer to build continuous vegetated assemblies on slopes.  In fact, I have seen some innovative living walls based on these geogrid fabrics.

The sketch provided here is a depiction of a flat roof continuous vegetated assembly system for hurricane influenced geographic areas.  The three dimensional geogrid can be permanently attached to the roof through a variety of either mechanical of chemical bonding mechanisms.

Keeping plants on a roof is important.  Parapets help.  Good prudence also calls for permanent fastening systems too.

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