Wednesday, February 16, 2011

Alternative Drainage Systems for Green and Living Roofs

Green Roofs have existed for as long as man has here on Planet Earth in one form or fashion.

Today we see the majority of green roof drainage systems created and manufactured from petroleum based chemicals.

Notably, there is a difference in using recycled content in a plastic and reusing the plastic.

Recycling recently has come under varying levels of scrutiny with respect to the morality of low overseas sweat-shop type wages in both the recycling facility and then the low wage, sweat-shop plastics molding facility.   Certainly though the idea of recycling plastics is a good idea.

Reusing plastics, on the other hand is quite sustainable.  Reusing available materials, as is a focus of the many green building programs, prevents materials from ever reaching the landfill without an additional step of shipping overseas, grinding, melting and re-molding.

Issues with reusing plastics include; consistency and quality control,   The same issues exist with re-ground and re-molded plastics but on a different level - one easier to quantify in technical terms.

Kent Thompson, a Green Roof Professional here in the states commented on the Capitol GreenRoof Discussion board about a demonstration green roof using reused drainage material.  Kent writes:

"Currently, I'm building a demonstration roof with upside down nursery flats filled with styrafoam packing peanuts (not the newer biodegrable variety) as the drainage layer.  Both of these materials were diverted from the waste stream.  I doubled up the flats for extra durability during installation.  The flats have several holes drilled in each side and are imperfectly adhered to the waterproof membrane to facilitate drainage. "

I added several thoughts, including; published an article about a zero C eco-village where egg cartons were used as drainage in the green roof.  The article can be viewed at 
Another interesting 2005 article briefly discusses the historical use of reeds and tar for green roof bases
Country Smallholding published information about historical roofing materials, including reeds and waterproofing & drainage for old turf roofs here:
I admire your initiative to try the inverted trays & peanuts.  Excellent effort - keep us updated on the results.
Dusty Gedge of is a great resource - he is in the UK and has knowledge of most European efforts.
If you are on twitter - check out  Green Roofs in France - I know they are very familiar with reed construction and are doing a small green roof with reed drainage system now.  Some water reeds are said to last 50-80 years. 
I really appreciate everyone's comments here and hope for more as it is very beneficial to my understanding.
Transparency is always the best approach.  If we use plastics for green roof systems and those plastics are molded in low wage shops and contribute significantly to local pollution somewhere across the globe, we should acknowledge that.
If the plastics are recycled locally and sustainably we should acknowledge and applaud those sustainable results.
If the plastic drainage systems are virgin petroleum based we should acknowledge that too.
Asking ourselves the hard questions always leads to success and improvement.
As I stated many times before, I am not ready to give up on plastic components.  I still use plastic systems and am very happy with the performance.  
Yet it would be nice to be able to rightfully be proud the green roof system was constructed in a sustainable manner.
As always, we look forward to your comments and emails.

Happy Green Roofing! Kevin

1 comment:

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