Green roof

I hit the zoo a few weeks back to check out the new Asian Trail exhibit. It looks great. Lots of time, effort, and money were spent. Too bad they didn't spend more on animals. Well, there's a couple of sloth bears, some pandas, couple of red pandas, a few other things. Lots of educational material. I just expected more critters for all the work they put in.

On one of the buildings they put a green roof. It's at a level that you can see it as you walk down a ramp which is what most green roofs lack. This picture shows a green roof shortly after being planted. The plants should expand nicely.
Click to enlarge

I thought I'd written more about green roofs. Apparently not. So here's the summary. A green roof is a flat (or at least flat-ish) roof that you grow plants on. Your house occupies area that could be used by plants. Even unoccupied your house leaves a thermal footprint that reflects heat and warms the air. By putting plants on the roof you help cool the area, clean the air, clean the rainwater, and insulate your house.

If you put much thought into it you're gonna start worrying about roots poking through the roof, mold, mildew, rot, water damage, etc. Well, there's ways to avoid those problems. You build the green roof in layers. One to waterproof, one to block the roots, one to insulate, one to retain moisture, one to drain, one to filter the water, and, of course, dirt. They're becoming popular in DC where many of the building are nearly flat row houses. There's a few organizations you can contact to help. There's probably some in your area, too.

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From the bottom up, this is what the Building Museum had for the green roof in their exhibit.
Monolithic Membrane6125-ev roofing membrane
Hydroflex 30 protection course and Root Stop root barrier
Dow styrofoam insulation
moisture retention mat
Gardendrain and Floradrain drainage layers
Systemfilter filter fabric