The Air Up There
- Posted by: GOOD
- on October 27, 2008 at 3:27 pm
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.
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DISCUSSION: 42 Comments
“borrow $30,000 for a green roof” …Hello. How about planting a vine plant like ivy (there are many varieties of leaf size and flowers) and train it to grow up a pole or a trellis a few feet from your house walls and then about two or three feet above and parallel to your roofs 45-degree slope. You can cut this back as desired. Start from seed, buying wood poles or several pre-made trellis and maybe some expert labor should put you below $3,000
Victor P, Pomona CA
i think what they were saying was you need a water proof roof so that you can lay down soil for the plants, i think they meant like a actual garden you would place on the roof. The soil would keep the roof insulated and the plants provide the shade. You water the plants keeping the soil wet/damp… etc.growing ivy can still get inbetween your siding and roof, causing gaps even if they are on a trelis, you cant guarantee you can get in there to cut it back enough to prevent, and they grow rapid in the spring and summer time in some areas.
This has got to be a joke, right? Taking care of a bunch of plants on a roof is about the most hazardous thing I can think of doing, Take a fall and possible kill yourself to save a few bucks on your heating bill???
While the benefits to green (or vegetated) roofing systems are impressive, this is quite simplistic. If you are going to consider a green roofing system, you MUST consult a local structural engineer and/or a roofing consultant (http://www.rci-online.org) before you get started. The majority of vegetated roofing systems are too heavy to put on an existing residential structure. Vegetated systems also contribute to energy conservation primarily because they contain insulation. SOil and plant matter do add some, but not much. Finally, the cost to add a waterproofing membrane to an existing structure could range between $6 and $15 per square foot. The last vegetated roofing system re-roof I was involved with was over $38 per square foot, not including engineering and design fees.
What about using that $30,000 to install solar panels which can shade the roof & also provide electricity or hot water? Plants have a way of working into cracks and breaking apart the house. If I installed a green wall, it would be on a trellis at foot away from the house to provide shade. I like the green roof idea, but for that kind of money you might as well make electricity too.
If you are building a new building check earth sheltered. I just built a new home. It has 40″ of soil and we plant flowers. The home stays 68 degrees in the summer and costs about $40 per month to heat during the two coldest months in the winter. There are a few web sites that can help with ideas. R.J., Idaho
Green roofs do not require watering or maintenance. The plants are drought tollerant. So they do not need watering outside what they receive from precipitation and as the soil soaks up all the precipitation there is no runoff storm water. The benefits are a much cooler habitat inside during the summer. The plants process the carbon dioxide (a greenhouse gas and one cause of global warming) in the air to produce oxygen. In a sense the air around the house is more habital for mankind. I have read and seen where in urban settings, just the use of green roofs on large commericial and municipal buildings , has lowered temperatures on the street 10 to 15 degrees and reduced the need for costly storm sewage.
You idiot. Dry potting soil weighs a minimum of 60 pcf. A best the design snow load on a roof is 30 psf. Therefore 6″ of wet soil exceeds the roof capacity. You better pay yoiur insurance premium for when this comes crashing thru pour roof. Structural Engineer
There is absolytely no way that I would even consider this. the city we live in has building inspectors, they would never allow it. It would be great for 1. a fire hazard for one with change of seasons. 2. be way too heavy for my 100+ year old house. 3. Destroy the structure due to weight, water, mud, roots. 4. With snow it would probably collapse the structure. 5 Tornado season would be such a liability. When we expect high winds, you see people scrambling around picking up plants to protect them (and not make them bullets for high windis). Ivy cuts into brick and destroys the goo that holds it together. Keep the plants on the ground. or in a pot. I had an edible front lawn for years. I still do pots of tomatoes and beans up my satallite dish in the back.
I agree ith the structural engineer, the weight on the roof is a major problem. Also, you would have to water the roof when it does not rain, it has got to get the water from somewhere, it can not create it.MB San Antonio
Just about every building in Europe (that I have seen) has plants or grass growing on it. Its not that big of a deal, people. Some of the posters here are being so closed-minded and negative. I guess it will be up to the leaders in the community to show that it can easily be done. You obviously don’t have to do the entire roof for $30k, just do a small area, maybe in the back of your house and see how you like it.
I am still trying to figure out how this helps the sewer system?
to the 11:34AM poster: you DON’T need to water these roofs. they are planted with plants that are typical for the climate the building is in. look around, nature finds a way to go without water when it doesn’t rain. to the 12:22PM poster: green roofs help the sewer system by reducing peak load during storms. Sewer systems can only handle so much water runoff (pipes are only so big), and lots of paving and impervious surfaces (houses, roads, sidewalks, parking lots, etc) create runoff water where in wilderness the water would soak into the ground. A green roof will soak up most of the water that would runoff a normal roof into the sewers, thus reducing the load on the sewers at their critical times. in urban areas this is a large and increasing problem due to the amount of impervious surfaces.
Anonymous on December 21, 2008 at 12:22 pm: I am still trying to figure out how this helps the sewer system?
It helps with the run off into storm drains that overflow into the sewer system.
The Writer of this article does not know the difference between diesel or gas. Air head journalism example.
It was -12 degrees here yesterday morning. How well do sedem like the cold? Also when the 2 feet of snow slides off the roof is the dirt going to stay on?Be thankfull were expereincing global warming and NOT another ice age. Where will we get the fuel to make this planet habitable if the avereage temp drops by even 5 degrees? Fn hippies
I didn’t bother 2 read the whole thing! she says it pays off in 2or3 years!?! w-w-what? 30grand for utilities in 3years? what a crackpot!!! this is crap journalism
Sounds like a great idea, but with the structural and cost issues, it doesn’t sound practicable for most homeowners. If commecial bldgs were designed and built from scratch, they sound like the ideal customer. They generally are all in one area and take a lot of green space away. Homeowners should plant as many trees as possible on their property and put solar panels on their roofs.
There are people who have homes built into sides of hills and there utilities bill are a whole lot cheaper than mine are. In the summer there house is a constant 70 degree year round. This also uses a natural resource that is abundant and is natural.
Grow pot on your roof and reap all kinds of profits !!
Green roofs are truly positive. They conserve energy for the building owner but more importantly they cool the city around them, spreading their cooling across their neighbors. Is it better to send our money to people that dislike us to buy energy, or conserve it at home first.They protect our waters from pollution, provide beauty and green space, provide wildlife habitat, improve air quality in several ways, reduce roof replacement costs. Green roof systems can weigh as little as seven pounds per square foot. All green roof systems require care and water, more or less. Europeans are very advanced with this technology, and with wide use have lowered costs to as low as four of five dollars per foot. This is good stuff, and as a society we should encourage it.Commercial Green Roof Specialist.
all in all, i don’t think it would be a bad idea to plant something no matter where you live. it doesn’t have to be on your roof, or even at your home! (community gardens?) the point is that we need plants to live and thrive, so doing some gardening wouldn’t hurt anyone.
mY god lighten up its just an article sound like the government needs to bailout your attitudes
Your article about green roofs started out with a comment about cars in Europe running on diesel fuel and getting 40 to 50 miles per gallon on gas. I don’t object too much to calling gasoline gas, but diesel is diesel. I am also uncomfortable with Pickens proposal to use natural gas to run our semi-trucks. Natural gas should be used for home heating, and to provide feed stock for the Haber Process.
I hope this lady reads these comments, because she seriously needs to go back to school. I really like the idea about green roofs and I can see it being used on new industrial construction. However, there are damn few buildings in the US that could support the weight load of green roof. Which means that 30k would quickly because 100k+. You absolutely would have to water the roof, because drought resistant just means that it doesn’t have to watered everyday. These green roofs do have merit and I would love to see a better spokesperson for them.