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The Planet

The Air Up There

October 30, 2008

Writer Malcolm Gladwell sits down with environmentalist Amy Norquist to discuss one of the most unsung and low-tech green solutions out there: green roofs.

In Europe, quiet and clean diesel engines cruise for 40 or 50 miles on one gallon of gas. Geo-thermal heating and cooling systems cost about as much as a new furnace, and can be installed by anyone with a backyard. Yet stateside, industry leaders insist we just aren't ready for widespread-and simple-strategies to curb our habit of wasting energy.Malcolm Gladwell: What is a green roof, exactly? Does it look like you've got a patch of prairie on your roof?Amy Norquist: A green roof is simply a roof that is partially or fully covered with plants. Typically the sort of silver-bullet plant of green roof is called sedum… Part of what's so cool about it is that because there are so many varieties, it covers the whole spectrum of aesthetic design. If you have a very modern house and you like the look of succulents and cactus, you can pick sedum that looks that way. Or you can have sedum that flowers at different times of the year, or in different colors. There is sedum that turns a bright purple in the fall, and there is sedum that flowers white. What they all have in common though is that they are drought tolerant.MG: How do you install it? AN: Well, first you want to make sure your roof is waterproof. So you don't want to just put a green roof on top of shingles, for example. You want a single-ply waterproof membrane. You have a drainage layer, a filter fabric, growing medium (soil) and plants. The growing medium can be anywhere from 2 to 16 inches depending on what type of green roof you have.MG: Lets walk through the benefits. As a homeowner, why would I want to do this with my roof?AN: You are going to save money in heating and cooling costs, because the green roof acts as an insulation layer. It is also going to look beautiful and more and more cities are offering financial incentives to building owners who install green roofs.MG: So it's the equivalent of going up into your attic and adding another layer. AN: Exactly.MG: Can we be more specific about the insulation benefits? AN: The insulation properties, especially in summer, can reduce energy needs by 50% or more. It the winter, it helps keep the indoor temperature more constant. If you look at a typical one-story home, and the temperature outside is between 75 and 90 degrees, it's going to be on average 7 to 10 degrees cooler inside.MG: Seven to ten degrees? That's astonishing! AN: It is astonishing. So summertime benefits are huge, which means that your payback time for the costs of installation can be as short there is two to three years-depending on the energy costs where you live.MG: And I have a feeling that the two-to-three-year period is going to shrink as energy costs increase. AN: Bingo.MG: Does the slope of the roof make a difference? It doesn't have to be flat, does it?AN: It's just a matter of tinkering with the system. People have put in green roofs on a 45-degree slope. You really can do a green roof on most any roof as long as you have a waterproof base and the structural capacity is adequate.MG: So if I have the standard American, 2,500-square-foot house, what is it going to cost me?AN: In addition to roofing the house, you are going to spend between $10 and $50 a square foot depending on the depth of [the soil], the plant you choose, and the complexity of design. So if you have a 3,000-square-foot house, and you are putting in a green roof, you might spend $30,000. That would be for everything-labor and materials. The other great thing to remember about green roofs is that they actually double the life of the roof membrane because you don't have the degradation of the roof due to the sun and [weather]. So that $30,000 investment is going to last you a lot longer than a similar investment in a conventional roof. There have been some green roofs in Europe that are 100 years old, and they are still okay.MG: Does it get unruly up there?AN: Not really. These are plants that don't require a lot of water so as a result they are not big and booming. That being said, there are varieties of sedum that grow as high as 11 inches. So if you want something that looks a little wilder, you can certainly try it.MG: Tell me a bit about the history of this idea. How long have people been putting in green roofs?AN: For thousands of years.MG: I take it that in parts of Europe, it is quite common?AN: Yes, green roofs are most common in Germany, [where] certain municipalities actually require green roofs at this point. Also, there are many in the Netherlands. The airport in Amsterdam actually has a large extensive green roof.MG: Are there parts of the U.S. where it is taking off?AN: Chicago, Portland, and Seattle are leading the way, as are Baltimore, D.C., and Philadelphia. They are also catching on in Los Angeles … and here in New York City.MG: Did anyone ever run numbers if every roof in New York City was green? Do we know what impact that would have?AN: We know that if 50% of the buildings that could build a green roof did, it would be the equal in additional green space of something like 16 Central Parks. It would save the city something like $100 million in waste water cost per year. And it would drastically reduce the number of combined sewerage overflow, meaning there wouldn't so much raw sewage that gets poured into the Hudson and East Rivers.MG: So you have this technology, and there are three arguments for it: an aesthetic argument, an economic argument, and an environmental arguments. Which of those three do you think is the most powerful with the public?AN: I think it comes down to the economics, with aesthetics and the environment tied for second. New York is proposing a tax abatement which would be given to building owners who install green roofs. When and if that is approved by the state legislature, it will have a big impact with consumers.MG: The American homeowner has eagerly embraced all kinds of ideas that make their home more beautiful while they save money. But this has been around forever, and we have been slow to embrace it. Why do you think that is?AN: I think because it is a pretty big psychological change. It's having something  growing on your roof. People are accustomed to thinking of that part of their house as being sterile.MG: If you can dream up one thing that would make speed up the adoption of green roofs, what would it be?AN: I think given the state that green roofs are in right now, government incentives are critical. It can be local, state, or federal. I think most people right now need a little push-just like they do for solar power and other energy-saving measures.MG: So many of these environmental interventions have the same economic profile, which is they require large upfront investments which are recouped over time. And that's a different way of thinking. If I go to a bank and try to borrow $30,000 for a green roof, is that something banks are open to? AN: Yes. A bunch of banks are starting to do this kind of lending, either as individual loans or as part of mortgages [because] the math works out. If you amortize that $30,000 over 20 years, it becomes a very easy investment to make. Something else that factors in is that the real estate industry has gotten into figuring out how much value is created when you add green components to your home or business.  It's pretty high. There is a pretty big increase-between  8% and 25%-in terms of the value of the home.MG: Is the nonresidential market here potentially more important?  AN: There is a lot of newfound cachet in marketing green buildings. One particular company has thousands of properties in Manhattan. They want Greensulate to go around with them and see which of their buildings are good candidates for green roofs, and then run the numbers on what their energy savings would be over time. There's also been interest from municipalities. I did an op-ed for the New York Times which talked about how much the city could save if they employed green roofs instead of trying to re-engineer their entire sewerage system.MG: Are there a lot of people out there like you, pushing this idea?AN: I'm afraid that so far there are very few people who have started green roof or green wall companies. It's a brand new industry.MG: Describe to me what a living wall is.AN: A green living wall is a similar concept. It can be interior or exterior, but you are planting plants in panels or growing them from the ground and training them up the wall. Green walls have some of the same benefits of the green roof: They improve air quality, decrease storm run-off, and insulate the building. And I have one client who is putting up a number of parking lots in Manhattan and their projects are going to be a lot more popular and have less impact on the neighborhood if you see green walls instead of solid concrete slabs. I think for me the coolest use of a green walls in the dense urban setting. They can transform a block or neighborhood.LEARN MORE greensulate.com
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