Thursday, December 9, 2010

Lightweight Nature-Irrigated Extensive Green Roof Florida

Photos here are of an extensive green roof in Jacksonville, Florida.

33kg per M2 - 8 lbs per SF lightweight green roof
One of the important requirements for the roof was the weight restrictions.  Because the existing roof was flat and the center distance the existing rafters were placed on, the architect specified a green roof system weighing less than 8 lbs/SF - 39.2 kg/M2 live load saturated with water.

Insulation and TPO were added per the design and the green roof system installed.

Non-irrigated - nature based irrigation for green roofs
The green roof system is a woven polyethylene (UV resilient) mat with a soil media especially designed to move water off the roof.

Metroverde Extensive Green Roof Florida
Existing roof contours create a slight swale or low spot where stormwater runoff would accumulate during large rain events.  Certain green roof plants where chosen for the areas where rainwater might be expected to accumulate.  These plants were chosen based on their ability to survive on natural rainfall, dew and fog.  Additional considerations factoring into plant choice were: the ability to grow under both extended wet and extended dry conditions; wildlife value, evergreen color, simplicity in form and root systems that would adapt to growing horizontally rather than vertically.

The Yucca filamentosa is an excellent shallow soil plant because of the roots habit of growing horizontally.  Many times this plant can be seen growing in natural areas with very shallow or rocky soils.  Click here for a Floridata plant sheet describing Yucca filamentosa, also know as Adam's Needle.

Yucca filamentosa will grow upright when provided with adequate soil depth.  The plant is ideally suited for green roofs because it also possesses the ability to acclimate its habit and height to a more "bonsai" form when limited by shallow or rockier soils.

Another excellent green roof trait the Yucca filamentosa possesses is the low stomata to leaf surface ratio - the S/LSR ratio equation we typically use in green roof plant suitability determinations.

Average soil media depth of the green roof is approximately 1".

The roof is subject to moderate shade, especially on the southern end.  Sunlight exposure is greatest between the hours of 10:00 am and 4:00 PM.

After seventeen months in the field the roof is looking good and the plants are well established.

As always, feel free to email us with your questions and comments here.

Happy Green Roofing!


1 comment:

Steve said...

what a great idea! really like this post and your blog!

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