GREENING OUR ROOFTOPS
Photo: Ken McMurry
IF YOU SHOULD FLY OVER RANCHO MARGOT (ABOVE) NEAR THE ARENAL VOLCANO IN LA FORTUNA, COSTA RICA, YOU PROBABLY WONT EVEN SEE THE SPRAWLING COLLECTION OF BUNGALOWS, BARNS, AND BAR, NO MATTER HOW LOW YOUR PLANE OR CLEAR THE SKY. THATS AN ASPECT THAT OWNER JUAN SOSTHEIM LIKES ABOUT THE GREEN ROOFTOPS ON THE BUILDINGS THAT MAKE UP THE RANCH. NOT ONLY DO THEY PROVIDE SOME OBSCURITY AND PRIVACY AMID THE MOUNTAINOUS JUNGLE, THE TOP LAYER OF SOIL, ROOTS, AND PLANTS HELP INSULATE THE BUILDINGS SO THEY USE LESS ENERGY FOR HEATING AND COOLING.
Photo: Edmund C. Snodgrass
Its just one of the innovative win/wins that Sostheim has implemented at his sustainable ranch hotel in the heart of one of the worlds most environmentally committed countries. We are totally off the grid here, Sostheim said as he gave me a tour of the nearly 200-hectare estate. Its about time to start making a change for the better. Were trying to teach people how to change their lifestyles and how to live in a healthier way.
FROM THE HANGING GARDENS OF BABYLON TO CITY HALL IN CHICAGO
Green roofs go a long way toward helping to create a more sustainable world. While it may seem an unusual building technique, green roofs go back as far as 600 B.C. to the hanging gardens of Babylon in Iraq, built by King Nebuchadnezzar for his wife, Queen Amyitis, who longed for the tropical gardens of her Persian homeland. The gardens were terraced from the top of their palace to the ground, providing all the fruits and flora she missed. According to legend, the palace and their gardens were destroyed by earthquakes.
In past decades, green roofs have become popular in Europe. Today, building regulations in Germany and Canada support green roof development because of its improved sustainability, longevity, and thermal and water-filtering qualities.
Now green roofs are gaining ground in the United States, too. Chicago Mayor Richard Daley vowed that Chicago would be the city with the most turf on its concrete skyline, greening City Hall in 2001. Currently, the city has achieved his goal of more than 300 buildings – 7,000,000 square feet – of green roofs completed or under way. Washington, D.C.; Minneapolis; and Baltimore also stand out as leaders in the green roof revolution, according to www.greenroofs.org, the website of Green Roofs for Healthy Cities. This organization provides resources and education to help guide the way to rooftop sustainability.
The U.S. Green Building Council® (USGBC®) announced a new award in September 2010, titled the Mayor Richard M. Daley Legacy Award for Global Leadership in Creating Sustainable Cities. Mayor Daley was its first recipient, at the USGBC Greenbuild conference (November 17-19, 2010) in Chicago. USGBC said Chicagos Sustainable Development Policy mandates that projects receiving financial or zoning assistance from the city include sustainable elements such as green roofs, LEED® certification, or designs that allow structures to absorb large amounts of stormwater. Chicagos Green Permit Program allows contractors to shave off as much as $25,000 from the building permit process by choosing to incorporate some of 12 sustainable design elements.
AT WHAT COST?
Despite the up-front cost – from $5 to $35 per square foot – green roofs provide multiple benefits that offset their expense within a few years. The U.S. Environmental Protection Agency estimates a five-year average to recoup costs.
Covering building tops with soil, sod, and gardens provides a pleasant place to spend time, particularly in urban environments; processes CO2 in the atmosphere; and produces oxygen, provides food, and helps insulate buildings so they dont use as much energy to heat or cool. The plants also help filter the air as the breeze moves through them, pulling out particulates that can cause respiratory illness.
Green roofs intercept the solar radiation that would strike dark roof surfaces and be converted into heat, thereby improving energy conservation, said Hitesh Mehta, a landscape architect who has designed many sustainable resorts around the world. He recently released a guide to the worlds most eco-friendly lodges, Authentic Ecolodges (Collins Design, 2010). Because green roofs reduce the surface temperature of a roof by minimizing heat-absorbing surfaces, a green roof helps to reduce energy costs inside the building as well. Like urban forests and reflective roofing surfaces, they absorb and/or deflect solar radiation so that it does not produce heat. The urban heat island effect increases the use of more electricity for air conditioners, and it increases the rate at which chemical processes generate pollutants such as ground-level ozone. It also exacerbates heat-related illnesses.
EXTENSIVE OR INTENSIVE
Building a green rooftop involves installing a waterproof barrier over the roof, then overlaying one to six inches of soil. There are two systems of green roof design: extensive and intensive. Both systems include rainwater catchments that send the filtered runoff into barrels for landscape irrigation, either feeding back to the roof garden during droughts or to surrounding yards and preventing runoff that typically pollutes waterways and groundwater.
Extensive roof design is the most lightweight with the least amount of soil. It supports water-retentive plants such as succulents, which need little maintenance once established.
Intensive design uses a deeper soil level to support vegetables and even trees for a productive garden.
Photo: Edmund C. Snodgrass
Intensive green roofs have deep soil that can support trees, shrubs, and lots of visitors.
An intensive green roof is usually specified when the green roof goals are aesthetic, versus simply economic, in nature whilst an extensive green roof is primarily implemented for environmental and economic purposes, said Mehta.
The layer of soil helps moderate the temperature within the buildings underneath the rooftop garden, and the landscape maintains a lower temperature than a typical roof – as much as 25 to 80 degrees lower. A study conducted by Environment Canada found that a typical one-story building with a grass roof and 3.9 inches of growing medium reduces summer cooling needs by 25 percent. A six-inch extensive green roof can reduce heat gains by 95 percent and heat losses by 26 percent. Chicago City Hall has recorded roof temperatures 100 degrees cooler than a neighboring building with traditional roofing.
A HEALTHIER PLANET
Intensive roof gardens can add to the local economy by producing food that provides greater nutritional value to the community because its accessible immediately from the garden, without travel time. In addition, the visual benefit of adding greenery, particularly to the urban landscape, has been shown to reduce stress and to have therapeutic health benefits, which accelerates recovery from illness. Rooftop gardens also increase habitat opportunities for birds, bees, and other insects.
Green roofs are a great example of how creating more sustainable ways of doing things can benefit the planet, its people, and even their pocketbooks.
Photo: Courtesy of Green Roofs for Healthy Cities (www.greenroofs.org) and Rana Creek Living Architecture.
The steep slopes of the roof at the California Academy of Sciences act as a natural ventilation and cooling system.
Trish Riley is the author of The Complete Idiots Guide to Greening Your Business and The Complete Idiots Guide to Green Living, publisher of www.gogreennation.org, and director of Cinema Verde (www.verdefest.org), an environmental film festival.
WEB RESOURCES FOR GREENING YOUR ROOF
Rancho Margot boasts nearly 200 hectares of rolling hills nestled against one of Costa Ricas marvels, the Arenal Volcano, which constantly rumbles, smokes, and, occasionally, tosses fire. Juan Sostheim and his family have created a fully sustainable ranch here. The staff of 43 and about 15 volunteers welcome up to 100 guests at a time.
The ranch is powered by hydropower from streams running across the property as well as waste from the chickens, pigs, and cattle raised on the organic produce grown from the farm. We throw away about what a family of four discards in the U.S. Every bit of the trash we produce is sorted through twice. We recycle everything we can here, said Sostheim. One ton of compost produces 23 million BTUs, and that equals 5,000 kilowatts of power for us.
Sostheim uses excess power to heat the hot pool, a cave-like, stone-lined pool where guests can relax in the evenings. An open-air massage bungalow and morning yoga add to the ambience.
The ranch farm provides organic food for the hotel and produces its own soaps for guests. Horses are available for rides to mountainside waterfalls or the nearby volcano. Sostheim even has established a wildlife sanctuary to care for local squirrel and howler monkeys that have been rescued from civilian life and are released back to the wild when theyre ready.
For information on visiting or volunteering at the ranch, go to www.ranchomargot.org.
From Hitesh Mehta, landscape architect and author of Authentic Ecolodges
Considering the relative high temperatures in Florida throughout the year, it is important that the state embrace this form of roofing because of its many benefits. Five years ago, when I was interviewed by a radio station in Miami, I had spoken about the how all the concrete roofs in South Florida are creating an urban island heat effect, which was draining the energy usage of the state. Some of the most important benefits of green roofs are:
- Green roofs intercept the solar radiation that would strike dark roof surfaces and be converted into heat, thereby improving energy conservation. Because green roofs reduce the surface temperature of a roof by minimizing heat-absorbing surfaces, a green roof helps to reduce energy costs inside the building as well. Like urban forests and reflective roofing surfaces they absorb and/or deflect solar radiation so that it does not produce heat. The urban heat island effect increases the use of more electricity for air conditioners and it increases the rate at which chemical processes generate pollutants such as ground level ozone. It also exacerbates heat-related illnesses.
- A green roof can double the life span of a conventional roof. A green roof helps to protect roof membranes from extreme temperature fluctuations and the negative impact of ultraviolet radiation.
- Green roofs can work to reduce urban heat islands, minimize heat-absorbing surfaces, provide improved air quality, as well as help with stormwater retention and filtration.
- Green roofs provide visual appeal and create a functional and aesthetic environment. Trees and shrubs can be included as well as other larger plants in a wider variety. This green space is often an inviting and well-utilized area providing a green respite in an urban setting.
- If green roofs conform to the rigorous Green Building Rating System standards created by the U.S. Green Building Council, there are inherent savings including Leadership in Energy and Environmental Design (LEED) certification for tax benefits.
– Hitesh Mehta, FASLA, RIBA
Green roof resources from Damon van der Linde, communication and research coordinator for Green Roofs for Healthy Cities
Every year we compile a list of the cities with the largest areas of green roofs in North America and issue the findings in a press release. The most recent is from 2009, and Chicago is still the leader.
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Bell Book & Candle
A new restaurant in Greenwich Village, Manhattan, Bell Book & Candle takes a different twist on the green roof idea. The restaurant is supported by a rooftop of state-of-the-art hydroponics. Chef John Mooney grows a substantial amount of the herbs, greens, and vegetables served to his patrons in self-supported towers of greenery atop the restaurant. Its one of the first restaurants in the United States to grow its own food on its roof.
Space-saving vertical towers flood plants with nutrients, water, and sun. The towers provide a nutrient-rich solution, using no soil, Mooney told CNN audiences. Theyll never see a refrigerator. Theyre not going to be gassed, and theyre not going to be treated in any way for transport. I just pluck them straight from the vine. It makes a difference. This is the wave of the future for home and commercial use. Roots are attached, so they stay with the plant until its prepared in the kitchen. I call it living lettuce.
Check it out at:
141 West 10th Street
New York, NY