What is the best drainage mat for a green roof on a Brooklyn Brownstone? That is the burning question in our minds right now. Price, recycled materials, water retention, water drainage and shipping distance are some of the considerations in our search for the ideal mat.

Robie Anson is Eco Brooklyn’s current R&D guy for green roofs. Here is what he found today:

I found a drainage layer with deeper reservoirs and a root barrier built in. I e-mailed but didn’t get a response, so not sure on pricing, but it looked good: http://www.tremcoroofing.com/fileshare/specs/WaterDrain_GRS.pdf.

American Hydrotech makes a drain layer for extensive/intensive roofs that appears to retain even more water: http://www.hydrotechusa.com/product_data/PDS-GR30.pdf (nearly 3 times that of the Tremco product). This looked like it might work too (and be cheaper) but there’s no info. on water retention. Again, no pricing info.

JDrain makes some products that I think would work and may be cheaper (esp. if we use the standard 400 series, rather than the GRS) — I’m just not clear on water retention for the 400. (For the GRS, retention is not as high as the AH GR30.) Check here for options: http://www.j-drain.com/sub-product.php.

The search continues…..