Monday, March 12, 2012

Green Roof Design on A Rabbit Hutch, Urban Permaculture

We are taking our one acre of land here in the middle of downtown Jacksonville and working to develop an intense permaculture site.  Though we've worked with plants all our lives,  animals are relatively new to us.

This year we'd add twenty seven chickens (no roosters!) to the greenhouse and honeybees on the rooftop but we started with two rabbits,  Jack and Ruby.

Jack and Ruby are not destined for the stew pot as we've already named them.  However they produce a prodigious amount of droppings and the way their hutches are built about one and one half meters above the ground, allows for collection of the pellets into the earth worm composting bin constructed underneath.

Jack's Green Roof Hutch
We hope Jack and Ruby will eat all the organic greens we have left over from the garden and produce lots of fertilizer.

Naturally their hutch had to have a green roof and what a better opportunity to test a new type green roof system?

The green roof needed to be structural, capable of spanning the gap across the top of the hutch enclosure that was approximately one meter wide and three meters long.

Lightweight, Extensive and Structural Green Roof for Rabbit Hutch
Atlantis Corp's 52mm panels were chosen for the main structure.  At 52mm thick the panels provide plenty of root room for an extensive green roof.  The 52 mm panels are quite versatile, are structural in design (a full size fire truck can park on them without crushing the panels)  and are made from post-consumer recycled automobile battery casings among other recycled polypropylene.  They were originally designed as underdrains of pervious pavers but my good friend Felipe Kovacic has found many other ways to utilize the 52mm panel, including living walls, green roofs and much more.  For a marvelous look at what Atlantis' visions of Green Cities can be, check out their website here. 

Included here is a living wall section I constructed earlier this year using the panels along with a non-woven geosynthetic material.

52mm Living Walls

Because the 52mm panels are modular,  I assembled several of them into two panels of the desired size (one panel for the front slope and one panel for the rear slope) A 20 mil HDPE liner was attached to the underside of the panels using standard zip-ties.

The roof had to be lightweight.  Taking advantage of extra shelf space in one of our greenhouses the entire rabbit hutch was to be positioned where once sat plant trays.  Weight limits were important and fat rabbits are heavy.  So rather than filling the 52mm panels with a lightweight soil mixture we embedded the panels with a non-woven geosynthetic material.

Over the last couple of years I've been fascinated by the use of non-woven geosynthetics as growing medium, especially those made from post-consumer recycled plastics.

Of course I ultimately prefer burlap, hemp of other natural fabrics and I do believe ultimately as an industry, the green roof movement must move away from plastics towards natural materials.

Yet with plenty of synthetic materials available on the market it is important to test the capabilities of recycled containing system components.

One of the benefits of using non-woven geosynthetics is the capabilities to distribute water throughout the soil system through 'wicking' actions.  The material is extremely lightweight and supports the very thin layer of organic material added to the top for the plants to germinate within.

Plants love the non-woven geosynthetic material.  I've successfully used the fabric in floating wetlands (we have a large study in progress with the University of Florida as we speak to determine the capabilities of aquatic plants to remove N and P from stormwater ponds) and also in street side wetlands that clean stormwater and double as beautiful landscape units.

The material has also been the basis for many living walls we've done.  Plant roots grow throughout the fabric as if the fabric were soil.  The extremely large surface area of the fabric (think about the surface area of velcro) allows for microorganisms to grow and convert N2 into NH4 and NO3, cleaning water and making nutrients available for plants.  You can find aerobic, anaerobic and anoxic conditions all within a piece of the fabric in the field.  Patrick Blanc and his living wall work should be given credit for his pioneering work with growing plants in fabrics.

Also added to the panels were a couple lengths of threaded rod to ensure the system stayed together.  We have hurricanes in Florida and I always over-design any outdoor system because I was raised in Miami and have witnesses the damage tropical cyclones can do (the threaded rod is not really necessary in most non-cyclone prone locales).

Finally the panels were planted with garlic and a C3 type ground cover mix we've designed to serve as a 'pest-insect' natural control.  The plants will provide plenty of green beauty,  white flowers and snack food for the rabbits.

The photos here depict the panels after about one week from planting and the C3 mixture has sprouted.  The garlic sprouts are also peeking through the soil mixture.

Within a couple weeks the rabbits should have a very green roof.

The entire system was easy to assemble, very light weight and set perfectly on top of the hutch frame.  A cedar 2 x4 with a half diameter of plastic drainpipe was used for the ridgecap between the front and rear panels.

This system would be ideal whereever lightweight, structural capacities were needed, such as;
  • a structure slated for retrofit
  • sheds
  • large stretches of commercial buildings where foot traffic is to be expected
  • garages
  • residences and more
Though personally I like flexible mats for extensive green roof systems, I am impressed with the recycled content of the 52mm panels and the structural capabilities the system allows.

I'll be adding wildflowers this spring, too.


Lushe said...

Love to get some more photots of your green wall. Did you put onto the rabbit hutch as well.


Kevin J Timothy said...

It seems like you've set to where it doesn't need much maintenance. It looks totally self-sufficient. This is great stuff here, man. Its always good to see others making it their business to be environmentally responsible.

We have a Rex rabbit (which is what actracted me here) but I can tell already that I'll be back to this very informative blog. So, I take it that Jack and Ruby likes garlic?

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