Ed,
Installing a "green" roof is not as simple or inexpensive as you make it  
sound. There are many large corporations that are installing green roofs and all  
are extolling their benefits, but as a roofing professional, I can tell you 
that  the nightmares these systems cause and or will cause down the road are 
not worth  the effort. Plant roots by nature are highly invasive and can 
penetrate most  roofing materials used today. Installing a "green" roof requires many 
layers of  materials including those for proper drainage.
A simple solution which is currently mandated in CA and a few other states  
is to apply white roofing materials (Cool Roofs) which can reflect as much as  
88% of the suns energy. These are the most common roofing systems that I tell 
my  customers to install.
The days of black roofing systems are just about over for flat roofs. Some  
areas are now experimenting with cool shingle roofing systems. Knowing that not 
 everyone wants to have a white shingled roof in this country, manufacturers 
are  working to create shingles that will reflect the UV bands that create 
heat in  roofing systems. In many Mediterranean countries, white roofs are all 
that you  see. Apparently they know something that we should have figured out 
years  ago.
 
Rummy
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