(W/art: Courtesy of LiveRoof and J&J Nursery: Native plants, including Blue Fescue and perennials for Jackson, Wyo., project; Four-week old trays for Gibson Science Center at Southern Utah University in Cedar City)
The concept of propagating plants on a roof has ancient and pioneer origins, dating from the Hanging Gardens of Babylon to sod-covered dugouts of American expansion into the Great Plains and Great Basin. Vernacular architecture throughout history provides examples of planted roofs for aesthetic and functional purposes.
Ian McHarg's Design with Nature and landscape architects PeteWalker, Lawrence Halprin, Charles Moore and Richard Whitaker taught a unique perspective and helped design a landmark eco-sensitive new community and modular housing. Cultural Geographer at Harvard's Graduate School of Design J.B. Jackson (author of American Space) provided further insight into multi-disciplinary, energy-efficient design at the onset of the green revolution.
As the first wave of energy efficient housing came during the Carter Administration (recall Jimmy's use of solar panels on the White House), Utah figured prominently in design interpretations of energy efficiency as solar heat sinks, trombe walls, earth sheltering, passive gain and other innovations were initiated by Terracor, Redford's Institute for Resource Management and numerous local architects.
In 1972, the use of sod roofs at Snowbird Ski and Summer Resort gained national attention. The design for a planted roof at Garden Terrace Apartment in the Avenues and the irrigation system for Gallivan Canter enabled the practical translation of landscape amenities to the roof and accomplished for aesthetic value and enhancement.
Phases of Evolution
Phase I: The traditional sod-covered shelter and planted roofs at Archibald Gardner's first house in West Jordan, Snowbird, the Gallivan Center and the LDS Conference Center are examples of an intensive system. Some were water resilient, in the case of the sod house, and eventually water-tight.
Innovations in soil technology enabled the use of light-weight mediums, including Utelite from Wanship, employed to enable cost-effective construction. Integration of storm drainage technologies such a Inka-Drain and MiraDrain have generated acceptance throughout the region in the successful implementation of planted roof gardens. Subsequent innovations include moisture reservoirs (sponges) and pre-planted carpets.
Requiring the patience of a dry farmer, extended and indeterminate seasonal time frames for propagation and establishment of ornamental plants and ground covers is a deterrent to universal acceptance of intensive systems. Other challenges include the invasion of noxious weeds, degeneration of organic soil, drainage system deterioration, root rot and the cost associated with removal of plants and the growing medium to successfully resolve leaks, a procedure that entails a considerable amount of time to re-establish plants.
Phase II: An instant turn-key look and desire to plant on sloped roofs inspired the modular or tray system that provides stability and efficient installation along with the advantages associated with pre-planting in a climate controlled nursery throughout the year. Inherent problems with conventional trays include poor drainage and associated root rot even though high-tech soils are generally employed. An advantage of conventional trays is less costly repair of leaks and long-term stability. A disadvantage: a negative image of exposed edges between plants persists.
As conventional trays are essentially nursery flats, an iteration by Rana Creek was a biodegradable tray composed of coconut husks installed at the California Academy of Sciences in Golden Gate Park. While the coconut trays decomposed as intended, inadvertent failure of stability caused plants to slide down the slopes.
Phase III: German innovations in soils physics, horticulture and agronomy of planted roofs have enabled more sustainable growing mediums and a wide range of adaptive plants. The developers of LiveRoof emulated German technology and virtually cloned the natural process, creating one of the most rational systems that provided LEED Platinum points. Described as an invisible modular system, LiveRoof systems function as nature by allowing free flowing drainage. This eliminates root rot, a problem associated with conventional trays.
The feasible propagation of an even more extensive palate of plant species, including drought tolerant natives, has been demonstrated by High Mountain Nursery at the former Lone Peak facility in Bluffdale. In the sedums planted from cuttings four weeks ago, the removal of the plastic "elevators" used for shipping revealed a continuum of soil across the roof, making the trays disappear. Life-cycle cost is minimal due to the biological balanced culture of propagation and density of plant establishment.
Benefits of a Living Roof
Other benefits of a living roof include protection from UV deterioration, immediate and fully-matured appearance, oxygen regeneration, cost effective leak resolution (especially coupled with electronic leak detection), support of local industry and certified installers and minimal maintenance just 20 minutes per month is required to maintain plants and irrigation for the living roof at the Unified Testing Laboratory in Taylorsville.
James Webster is a registered landscape architect in Utah and Montana. He established James Webster Associates in 1973, practicing traditional landscape design, planning and mined lands reclamation. He is the Utah representative for LiveRoof and J&J Nursery. He can be reached at 801.949.7291.