Green roofs grow on you !

We have been fascinated with green roofs since we first learned about them the mid 1990s. Terra Nova received Sunset Magazine’s WESTERN LIVING AWARD for a garden with a green roof we presented at the 2004 San Francisco Flower and Garden Show.

Here we are building that green roof using succulents and native grasses

Below are pictures of that finished garden

A green roof that blends into the landscape

The following excerpt describes a green roof that Terra Nova and Rana Creek Native Plant Nursery co-created in Carmel Valley:

Built as an embodiment of nature’s gifts, the Ocho House by Feldman Architects, in the Santa Lucia Preserve (a 20,000-acre private preserve in Carmel, California), was designed as an example of sustainable Mediterranean Modernism. The house was designed to integrate itself back into the land through sensitive design including low water use, solar power and habitat enhancement. There are actually three small structures that are built into the hillside where the land seamlessly continues onto the green roofs of each one. Rana Creek ensured that an ecological design approach enhanced the project with a sustainable landscape and green roofs that consist mostly of locally adapted, indigenous plant materials already found thriving onsite prior to building. Their oversight of design and implementation focused on stabilizing all disturbed soils by planting grasses and forb mixes approved for the Santa Lucia Preserve, controlling non-native species, and simply allowing natural regeneration of the local plant assemblages. Adaptive management techniques proved to be the most valuable strategy, as the roof that was being taken care of by weeding, pruning and irrigation was less successful than the roofs left unattended, due to lack of access.

There are 4,250 square feet of green roof installed at a cost of $21 per square foot. The 6” depth of growing medium is composed primarily of sand, lava rock and amendments, which allow for both moisture retention and drainage. The growing media included mycelial inoculants and supporting mushrooms that appear in the cool wet winters. The roofs were installed with irrigation to support the establishment of the plants and for minimal summer maintenance. The waterproofing membrane is American Hydrotech MM6125 followed by a Hydroflex30 Protection Course and Root Stop WSF40. The drainage system is Floradrain FD40 underneath the growing medium layer and gravel with perforated pipe and surface drains at the roofs’ edges. The perennial plant species selected for the roof such as Sand Sedge, Pt. Joe Fescue, Yarrow and Wild Strawberry are typical of the oak woodland understory and representative of the Monterey Peninsula region flora. A host of annual wildflowers were over-seeded in the fall and by springtime tidy tips, lupine, poppies, and goldfields surprised the owners with a colorful bloom. These annuals continue to sprout and flower each spring.

There are 4250 square feet of green roof installed at a cost of $21 per square foot. The 6 depth of growing medium is composed primarily of sand, lava rock and amendments which allow for both moisture retention and drainage. The growing media included mycelial inoculants and supporting mushrooms that appear in the cool wet winters. The roofs were installed with irrigation to support the initial establishment of the plants and for minimal summer maintenance. The waterproofing membrane is American Hydrotech MM6125 followed by a Hydroflex30 Protection Course and Root Stop WSF40. The Drainage system is Floradrain FD40 underneath the growing medium layer and to gravel with perforated pipe and surface drains at the roofs edges. The perennial plant species selected for the roof like Sand Sedge, Pt. Joe Fescue, Yarrow and Wild Strawberry are typical of the Oak Woodland understory and representative of the Monterey Peninsula region flora. A host of annual wildflowers were over seeded in the fall and by springtime tidy tips, lupine, poppies, and goldfields surprised the owners with a colorful spring bloom. These annuals continue to sprout and flower each spring.

The green roofs are designed to provide usable landscape, filter and store rainwater, attenuate sound, increase thermal insulation and provide site sensitive beauty for the home. The occupants benefit by reducing their energy consumption up to 30% during the summer months from the insulation of the roofs. With a growing media depth of 6” the sound is reduced by approximately 43 decibels. The sounds from the humans and their activities within the buildings are also being buffered to protect the wildlife, given the sensitive nature of the habitat in the Preserve.

The Ocho House is a superlative example of a green roof’s potential to limit environmental disturbance and integrate architecture with ecology—the 33 species of native plants used have made for a successful recovery after the disturbance caused by building on the site. The ecology of the site will continue to become more complex and resemble the natural analogs that were emulated in the design!

Article contributed by Rana Creek

Resource: Green Roofs Directory