Project 4: Green Roof
Next came their most ambitious project yet: a green roof, a cover of vegetation over a water-impervious layer, laid on a building’s existing roof. A green roof absorbs water and helps to heat and cool a building more efficiently, but can be expensive to install. Rush told de la Fleur, “If you can find the money, let’s do it.” So the landscape architect applied for and received a grant from a local conservation organization, and they were off and running.
They chose to plant the front porch roof of the house, which was approximately 250 square feet with a pitch of about 15 degrees. De la Fleur’s wife, Catherine Haibach, and friend Ann Tranter installed a 1-inch lightweight aggregate drainage layer. Over that went 3 inches of growing medium, and into it were planted drought-tolerant plants. The system weighs about 25 pounds per square foot when wet. The total cost came to about $15 a square foot.
An established green roof requires little care, needing to be checked and weeded a few times each year. The growing medium and plants extend the roof’s life by protecting it from sunlight and temperature fluctuations. Before installing a green roof, however, a structural engineer should check that the roof can support the weight of wet growing medium and plants.
Projects 5 and 6: Cistern and Bioswale
At this point, Rush was so hooked on saving water that he wanted to aim for 100 percent retention of the water runoff on the property. An old underground masonry cistern, typical of homes built before the 1920s, sat unused on the north side of the house. Early residents of the house probably used the stored water for cleaning and laundry. The pair cleaned and repaired the old cistern to use the water for irrigation.
Next to the cistern on the north side of the house ran a strip of scraggly, seldom-used lawn. The men decided to replace it with a bioswale. Just like a rain garden—except for its shape, which is longer and narrower—a bioswale would capture any overflow from the cistern and allow it to percolate into the ground rather than flow into the street. Because this area was in the shade of the house, they used plants that prefer those conditions. The result turned an awkward, narrow space into another infiltration tool, one that bursts with color and texture from interesting native savanna and woodland plants such as perennial geraniums, ferns, asters, grasses, and sedges.