Building the EVERGREEN, The Finishing Touches
Originally Published in the Winter Park Home Magazine: Issue 2, 2009
The EVERGREEN has earned LEED Gold certification (Leadership in Energy and Environmental Design) from the US Green Building Council, an independent nationwide organization devoted to fostering sustainable building practices. This certification and the home itself clearly demonstrate that GREEN homes can be economically designed and built to blend into existing Winter Park neighborhoods. For any green building project to succeed, the architect and contractor must be open to new ideas and willing to adopt new technologies and approaches to the overall construction process. With that caveat in mind, I thought it would be appropriate to wrap up the series of columns that focused on the EVERGREEN by reviewing a few of the finishing touches that we made to the home, including the green roof and water storage systems.
Recent advances in technology have made green roofs reliable roofing systems that can offer significant environmental benefits. These benefits include increasing the energy efficiency of a building, filtering rainwater, reducing storm water runoff, and improving the appearance of the structure. Although, adding soil and plants to a roof adds significant weight to a roofing system, so it is harder to retrofit existing buildings with green roof systems than it is to design a new building with a green roof in mind.
The first step in planning for a green roof is to determine the structural capability of your building. In other words, how much weight can the roof carry? There are many different green roofing systems available that can accommodate different weight limitations. In most instances, the minimum depth of soil media must be at least four inches, if you plan to use any type of green roof plants. Roofs tend to be harsh environments for plants and the range of available plants that can succeed on a roof increases as the soil media gets deeper. In planning the EVERGREEN, we designed several sections of the roof to carry additional loads of 30 to 40 pounds per square foot in order to accommodate soil media, plants, and water.
The next step is to ensure that the roof is protected against water intrusion beneath the green roof system. For the Evergreen, we installed a heat-welded TPO membrane on the roof. This roofing material is approved for use with green roof systems. We also installed a drainage mat under the soil media to create a root barrier and drainage pathway for the roof system.
Proper plant selection is a critical part of ensuring a green roof system’s ultimate success. The plant palette for use on our green roof was created by Denise Smith (my wife), who is a Landscape Architect and LEED AP. In our climate, there are a limited range of plants that have been successfully used in roof applications, so she carefully researched a lot of data to arrive at an appropriate selection of plants. We opted to plant a proven variety of sedums and also try some bulbines, society garlic and sea pursulane. Finally, we installed a drip irrigation system to provide regular watering of the plants. Without an irrigation system, green roof systems in our climate often fail.
It seems counter-intuitive to use precious water resources on the roof plantings, but the environmental benefits of the green roof outweigh the water use. Furthermore, we are able to offset that water consumption through the use of rain barrels and water cisterns. These simple devices are fed by gutters around the house and allow us to significantly reduce water use for irrigation and save money. We will ultimately have between 300 and 400 gallons of rainwater capacity for use in irrigating plants around the house or on the roof. A rain barrel is a very low cost and easy addition for any homeowner that wants to reduce their water use. Typical 55-gallon rain barrels sell for around $100 and can be installed at gutter downspout locations.
We made small changes at each phase of construction to create The EVERGREEN Home. All of the topics discussed in the Evergreen series helped the home achieve the LEED GOLD certification – the first home in central Florida to earn this high level of green building. When remodeling or building in Winter Park, always ask your architect and contractor to incorporate green building techniques in your home.