It’s Green at the Top: A Small Ecoroof Makes a Big Impact

Written by Michelle Blair
Edited by Lauren Saxton

I stood in the pouring rain as it turned to snow remembering what a co-worker told me when I first moved to Portland fifteen years ago, “You’re not a real Oregonian until you don’t carry an umbrella.” Arianne Newton and I inspected the green sedum and dormant grasses that covered the garden shed roof. “Forty children worked on making this roof a reality,” she told me, brushing the accumulating snow from her hair and jacket. The ecoroof tops a circular shed made by students at Trillium Charter School on Portland’s east side. The shed is used for storing supplies for the school’s vigorous gardening program and is a tool in itself; a permanent example of alternative and sustainable building practices.

Newton, a longtime teacher at Trillium, led the charge for the planning and building of the structure. “The shed on the school’s garden plot is constructed nearly entirely of natural, organic and reclaimed materials,” Newton explained. The structure is cob–an ancient building technique using a combination of earth, straw, sand and water–built from materials Newton scavenged from construction sites around town. The roof edge and frame are reclaimed sawed timber. The only new materials are the waterproof membrane and metal edging.

What started as an educational endeavor, soon turned into a community project and a neighborhood asset. To Newton the structure is, first and foremost, a teaching opportunity for the students, “The lessons are so encompassing because there’s so much to talk about. We use the shed to talk about sustainable choices and sustainable models.” The children learn about culture and history, seed propagation and soil chemistry, space planning, wildlife, stormwater runoff, streams and sewage systems. Those who participated in building the shed experienced first-hand what it means to be part of a community when local Marylhurst University architecture students helped plan the structure, neighborhood businesses donated time and materials, and friends, family, and neighbors stopped by to help see the project to fruition. This tiny garden shed teaches a much bigger lesson to both students and adults and sends a clear message to the community that small projects can have substantial impact.

As Portlanders, we are accustomed to looking up and seeing gray, but green? According to the Bureau of Environmental Services, rooftops account for about 20 percent of the surface area in the City of Portland. An ecoroof replaces a traditional roof with two to five inches of special soil planted with hardy, drought-tolerant plants and is not generally intended to be accessed for public use. Both the Hawthorne Hostel and People’s Food Co-op in the southeast neighborhoods are sheltered under partially green rooftops that are visible from the street. Other ecoroofs are positioned on office buildings, government buildings, apartments and academic buildings around town, but are hidden from pedestrian view. Currently six acres of Portland rooftops are ecoroofs, making it the leading city in the North American pack in green roof initiatives. From a regulatory perspective, the city makes it easy and attractive for builders to consider ecoroofs as an environmentally friendly alternative to traditional roofs (which reflect heat and produce storm-water runoff). Portland even provides grant money for individual residential homeowners to help offset the cost of a new ecoroof.

The positive environmental impact of ecoroofs means that the current buzz around the alternative structures is more than just a passing fancy. An ecoroof can retain 10 to 35 percent of rainfall during the wet season and 65 to 100 percent during the dry season, significantly reducing stormwater runoff. Additionally, ecoroofs filter air, insulate buildings, reduce the impact of urban heat islands, replace green space lost to building footprint, provide habitat for insects and birds, buffer noise, eliminate glare, and last up to two times longer than traditional roof systems. Even small areas dedicated to vegetation are important. “I have seen green roof mailboxes, it can be done,” says Laura Bauer of the Peggy Notebaert Nature Museum in Chicago whose building won a Green Roof Award for Excellence back in 2003. “It’s those little spots of manmade surfaces, you cover them with green, you add them all together, cumulatively that can make a difference.”

If you don’t have a roof to support vegetation, or you can’t summon the time and energy to make it happen, you can still make a positive environmental impact by starting small. Here are a few ideas to get you started:
1. Green-up your patio or balcony by creating a container garden. Herbs, grasses and succulents can be grown on any surface or in pots on a small balcony. Your potted garden can still catch rain, filter the air and even help reduce the surface temperature.
2. Replace manmade surfaces around your home. Consider dirt paths or use materials that allow rain to filter through while not reflecting heat back into the environment.
3. Create a rainwater collection system to harness the runoff from your roof. Use that water to irrigate your yard, garden and container plants.
4. Replace your downspouts with rain chains. These allow rain to drip down the chain and percolate into the soil, rather than rushing out into the storm drain pipe in the street.
5. Grow a garden. Start with a small plot of vegetables and grow outward. While you are at it, start a compost pile from the food you consume daily and use it to fertilize your plants.
6. Make it a party. Invite some of your best buds over and get a little dirty greening up your yard or outdoor spaces.

As for that little structure in the garden at Trillium Charter School, it certainly is the little shed that could. While I stood in their garden, sans umbrella, peering out from underneath my dripping hood and pondering the impact a small roof might make, I noticed the steel and concrete building next door. Rain water poured through a downspout, onto the parking lot, streaming past my muddy boots and onto the street. The little garden shed roof didn’t leak a drop.

Layer by Layer
As the children at Trillium Charter School proved, an ecoroof can be an achievable do-it-yourself project. First, be sure your structure can safely handle the extra weight (20-30 lbs/sf) by having it evaluated by a professional engineer, architect or roofing specialist. With proven structural integrity and a building permit from Portland’s office of Planning and Development Review in hand, you’re ready to begin. Here is a breakdown by layer:
Layer 1: Waterproof membrane. Many material options are available, even a pond liner will suffice.
Layer 2: Is actually an edging. Sloped roofs especially require a border to keep the soil in place. 1”x6” cut lumber works for this purpose, or metal edging as used by the Trillium School.
Layer 3: Depending on your choice of material for the waterproof layer, a drainage layer may be necessary (though not usually required for sloped roofs or small flat roofs). This can be manufactured, such as Amerdrain filter material, or even a layer of gravel.
Layer 4: The next layer is growth medium–an engineered blend of soil, pumice and nutrients, depending on the plants being used.
Layer 5: The soil is topped with vegetation, usually drought tolerant succulents such as sedum, herbs and grasses. Note that some weeding may be necessary in the first year or two until the plants are established and completely cover the surface.
Cost: Ecoroof costs can vary widely depending on the structural integrity of the roof, the slope of the roof, the types of plants and materials used. Generally, to replace an existing roof with an ecoroof system, the price can range from six to forty dollars per square foot. According to the City of Portland Bureau of Environmental Services the saving are noticeable on a long term scale. “Although ecoroofs initially cost more than conventional roofs, they are competitive on a life-cycle basis because of reduced maintenance and replacement costs.”

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Michelle Blair is a freelance writer and graduate student in Portland State University’s Writing/Book Publishing program. She and her eight-year-old son enjoyed tromping through the snow and mud, without umbrellas, to examine Trillium’s grass-roots green roof project and are already planning ways to green-up their brick patio come springtime.