Green Roofs, From the Ground Up
As I’ve previously noted, green roofs are thriving, with 2.4 million square feet of green roof planted between 2006 and 2007. But with this growing interest in green roofs has sprung the myth that they’re simple, DIY projects.
Not so, cautions Marni Horwitz, a green roof specialist in New York City. Last week, I visited her at a green roof she installed at the Wild Project, an arts venue on the Lower East Side of New York. There, she gave me a ground-up lesson in green roofing—and why you can’t go it alone:
All green roofs require the same first step: hire a structural engineer to evaluate how much additional weight the roof can support. From this, you can determine how much soil to use and what kinds of plants will flourish. The roof at The Wild Project has a 40 pounds per square foot capacity. Marni opted to use 4 inches of soil at 25 pounds per square foot, enough for sedum, a fast-spreading plant with small roots that is widely used by green roofers, but not for most food-producing plants.
Green roofs are built in layers, which you can either put down yourself or order in modular form. For this roof, Marni installed a modular system by ELT Easy Green, a Canadian company. The first layer is a waterproof membrane, which sits flat against the roof deck. On top of this, there’s a root barrier, a synthetic fabric that prevents roots from penetrating the membrane. Next comes a drainage board, whose egg-crate shape stores water in cups—a reserve that nourishes roots during drought. Excess water, which adds weight to the roof and can over-saturate the soil, escapes through holes in the bottom. The last layer is a bioblanket, a mixture of organic and synthetic fabrics that retains the drainage board’s moisture, and prevents soil from running off the roof. Marni also recommends green roof systems by G-Sky and LiveRoof.
Marni ordered soil from Rooflite, a brand she likes for its nutrient- and compost-rich blend. Marni also recommended GaiaSoil, which is made of 80 percent recycled Styrofoam, which is light enough for five inches per square foot on a roof with a 10-pounds per square foot loading capacity.
But after the hard work of installation, green roofs require little care. “The whole roof is designed to be self sufficient,” she said. “But these little plants will still take our hot, dirty air and turn it into cool, clean air. It’s an amazing service they do for us.”
How do you green your home? Let us know by emailing houses@dwell.com.
Not so, cautions Marni Horwitz, a green roof specialist in New York City. Last week, I visited her at a green roof she installed at the Wild Project, an arts venue on the Lower East Side of New York. There, she gave me a ground-up lesson in green roofing—and why you can’t go it alone:
All green roofs require the same first step: hire a structural engineer to evaluate how much additional weight the roof can support. From this, you can determine how much soil to use and what kinds of plants will flourish. The roof at The Wild Project has a 40 pounds per square foot capacity. Marni opted to use 4 inches of soil at 25 pounds per square foot, enough for sedum, a fast-spreading plant with small roots that is widely used by green roofers, but not for most food-producing plants.
Green roofs are built in layers, which you can either put down yourself or order in modular form. For this roof, Marni installed a modular system by ELT Easy Green, a Canadian company. The first layer is a waterproof membrane, which sits flat against the roof deck. On top of this, there’s a root barrier, a synthetic fabric that prevents roots from penetrating the membrane. Next comes a drainage board, whose egg-crate shape stores water in cups—a reserve that nourishes roots during drought. Excess water, which adds weight to the roof and can over-saturate the soil, escapes through holes in the bottom. The last layer is a bioblanket, a mixture of organic and synthetic fabrics that retains the drainage board’s moisture, and prevents soil from running off the roof. Marni also recommends green roof systems by G-Sky and LiveRoof.
Marni ordered soil from Rooflite, a brand she likes for its nutrient- and compost-rich blend. Marni also recommended GaiaSoil, which is made of 80 percent recycled Styrofoam, which is light enough for five inches per square foot on a roof with a 10-pounds per square foot loading capacity.
But after the hard work of installation, green roofs require little care. “The whole roof is designed to be self sufficient,” she said. “But these little plants will still take our hot, dirty air and turn it into cool, clean air. It’s an amazing service they do for us.”
How do you green your home? Let us know by emailing houses@dwell.com.
Posted by: Audrey Tempelsman on Jun 16, 08 at 10:11 PM PDT
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Posted by sewimsiz on 10/27/08 11:24PM PDT
Careful of your source, we know Marni and her expertise is experience from an outdated book at best......ask to see the rest of her portolio....it dosent exist....drop me an email and I will show you pics of the so called expert
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Posted by zombo08 on 09/29/08 11:09PM PDT
Posted by zombo08 on 09/29/08 11:09PM PDT
I spotted a very small green roof on Gardeners World TV programme this week.
http://www.gardenersworld.com
Posted by Andy on 07/13/08 12:11PM PDT
Whats the smallest size for a green roof? Could I put one on my workshop?
http://workshopshed.blogspot.com
Posted by Andy on 06/20/08 01:20AM PDT
Thanks for the every interesting post. I've linked to you from my blog: http://greeninstore.blogspot.com
Posted by Michael Moran Alterio on 06/18/08 08:06AM PDT
this is so great...would love to get this going in my building.
Posted by sean on 06/17/08 05:55PM PDT
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