Sunday, April 3, 2011

Florida Green Roofs & Rooftop Permaculture in Arid and Cyclone Prone Areas

Recently, one of the original field trial green roofs was temporarily removed to allow for installation of a solar hot water system piping.  The roof's slope was approximately 7/12 and originally the lightweight extensive mat system was installed over the existing asphalt shingles (with a root barrier/waterproofing liner).  The green roof system used a soil media comprised of primary organic mixtures, had a variety of sedum, succulents and native Allium species planted (A. canadense and others).
Florida Green Roof, MetroVerde Extensive Mat System

The sedum and original Aptenia struggled over time, eventually giving way to the A. canadense, primarily due to fungal attacks during the steamy hot, humid summer months (not necessarily rainy just high water vapor months).

Once removed the underlying roof appeared to look the same as the day the green roof was installed seven years ago, free of water damage and quite nicely preserved.

The green roof system was a simple.ost-effective system defying all odds and wagging-tongues - (don't use high organic soil media, the roof is too sloped, can't put a green roof over asphalt shingles, a nature-irrigated green roof will not survive, etc...).   The system easily survived several tropical cyclones, one rainfall event where we had eighteen inches of water in over two days (Tropical Storm Fay), extended periods of brutal drought and more).  The roof never had additional soil or plants added to it.

 Once the solar piping was in place the intent was to  add a recycled section of old, heavy duty chain link fence to the wall under the roof and plant and grow luffa gourds in the gutter, allowing them to cascade down over the guter edge across the chain link living wall fencing. I can hear the wagging tongues now - growing plants in gutter!
Florida Green Roof, Luffa Gourds in Gutters


Importantly, over the years of watching the roof preform the plants adsorbed and drank most of the rainfall events - especially any rain less than one inch (most of our afternoon rainstorms here are les than one inch) rendering the gutter useless.  The gutter was useless in the eighteen inch plus rainfall event too.  Though I would not do this on a commercial application, we do push the limits at the nursery to see what systems can do.  I am confident the green roof system we've replaced on the roof will handle any and all precipitation events, even with the luffa planted in the gutter, and just as the organic matter did not clog and wash out or decompose as predicted or the roof wash off during tropical cyclones, the luffa planted gutter - filled with a fast draining soil media will pleasantly surprise us.

The luffa is deciduous and will allow winter sun to hit our masonry walls, adding heat in the cooler months yet shading out summer solar radiation.

So with skyrocketing food prices in the grocery markets, a food based schema was designed for plantings.  The original mat, removed during the solar renovation process was replaced, adhered using a low VOC roofing glue.
Florida Extensive Green MetroVerde Green Roof, Mat installed
Once the mat was in place and inspected the soil media was added.   This is the process where the greatest leap of faith occurs for me.
Florida MetroVerde Extensive Green Roof Soil Media
A leap of faith because placing soil on a quite steep roof surface seems to be a futile approach, one probably washing off during the first rain storm, covering outside walls with a muddy mess.  Of course we watch the weather predictions as would any roofer and don't start if rain is predicted for a couple days.

The soil media is a fine material, free of aggregate - important when designing in a cyclone prone area.  Our soil media specifications call for microscopic sharp, geometric edges capable of locking together and when roots are added to the blend a highly stable, well-drained monolithic system is created.  The trick lies in initially adding fast growing C3 plants to bind all together then incorporating a purposeful evolution to a blend of more C4 and CAM plants to allow for drought tolerance and wind resilience.
Florida Extensive Green Roof, Matt's Wild Cherry Tomatoes


Since I love Wild Cherry Tomatoes and cannot get enough of them I decided on Matt's Wild Cherry Tomatoes to accompany the luffa's.  This wild breed produces more delicious cherry tomatoes than any other variety I have seen.  I am expecting thousands and thousands of cherry tomatoes this year.
Florida Green Roof, Food Roof, Rooftop Permaculture by MetroVerde


Cherry tomatoes are ramblers and will cascade down alongside the luffas, down the living wall so I won't have to actually climb the roof to fetch the round red scrumptious fruits.
Florida Green Roof - Rooftop Permaculture
Expect update photos as the luffa's and tomatoes grow and fill in the living wall, cascading down from above, providing us and countless hungry insects, birds and other Urban Jax Core wildlife with fresh organic nectar, food and beauty.

I'll add a video clip of a hard rain too, to show how well the drainage actually works.

2 comments:

Anonymous said...

Hi, this is a great idea! I live in Louisiana in an older home with an asphalt roof that does not have proper insulation. I am looking for an ecological way to reduce cooling costs in the summer. A green roof is one of the options I am considering. (Not sure if the neighborhood association will like it, though. We'll see.) Is there any way I can obtain the same kind of mats you used? What kind of liner did you use as a root barrier and how many layers did you use?

Kevin Songer, J.D. said...

I'm curious about neighborhood associations in older neighborhoods - never seen any before - usually they are historical preservation groups - can you tell me what part of LA you live in? Structural issues would be a concern. You'd need an architect to certify the existing roof would hold the additional weight. Green Roofs can really provide moderation to roof temperatures! And they are ecological! Kevin