Up On The Roof
Jane Hodges Young
North Bay Biz
The biggest plus to the Academy of Sciences’ living roof is its storm water management, Loomis says.
“San Francisco has a shared sanitary and storm drain system, and storm water runoff from roofs going into the drains puts undue stress on a very old piping system,” Loomis explains. “The soil on a living roof holds moisture. When we looked at the rainfall data, we noticed we only had two months out of the year that were an issue as far as what the soil could hold. Six inches of soil will hold about four inches of water. The runoff from the roof is zero except for those two months. We determined we were holding more than 3.5 million gallons of water out of the storm drain. And what small amount does manage to run off goes into an underground chamber to recharge groundwater within the park.”
Another benefit to the museum’s living roof is insulation. While some say living roofs help with both heating and cooling, Loomis says their impact is more to keep things cool. “There’s no insulation value in wet soil,” he explains.
Loomis believes that without the living roof, the California Academy of Sciences would never have reached LEED platinum certification, noting the structure has a heavy energy load as home to Steinhart Aquarium and the new Rainforest Biodome.
Other benefits
Green roofs have many ecological benefits in addition to reducing energy requirements for heating and cooling and helping to control storm water runoff. For one thing, they filter pollutants. According to the United States Environmental Protection Agency, living roofs retain up to 75 percent of rainwater, gradually releasing it into the atmosphere through condensation and transpiration, but keep air pollutants in the soil.
According to Loomis, living roofs are also popular because they combat what’s called the “urban heat island effect.”
“Roofs heat up,” he explains. “Most of the demand for green roofs in cities is to reduce the ambient air temperature.” Traditional roofs soak up the sun and re-emit it as heat. By some estimates, cities are at least 7 degrees hotter than their nonurban neighbors. With large numbers of living roofs, temperatures can be lowered naturally. One perfect example is Chicago, which installed a living roof on its City Hall. On hot summer days, the temperature on Chicago’s City Hall roof is between 25 and 80 degrees cooler than regular roof structures nearby.
Green roofs are also popular as habitats for animals, plants and insects that frequently encounter limited space in urban settings. According to London-based sustainability consultants Hilson Moran, living roofs have the biggest impact on biodiversity in cities because larger areas of roof space often mimic grasslands or other environments that can create their own ecosystems. Insects drawn to the rooftops entice birds and other animals. The roofs act as “stepping stones,” connecting urban areas with the countryside as birds and insects traverse.
Some use living roofs as a source of human food, planting fruits and vegetables for consumption. It’s also believed that living roofs have an impact on both physical and mental health as people have more contact with nature.
Another benefit is sound insulation. Soil, plants and trapped layers of air absorb, reflect or deflect sound waves—making green roofs popular alternatives for those near airport flight paths. Finally, green roofs supposedly increase the lifetime of a roof, extending it as much as three times.
Since modern living roofs are relatively new, “the jury is still out on that,” Loomis says. “Because the roof is protected from ultraviolet rays and doesn’t experience thermal swings of expanding and contracting like a regular roof does, it’s said a 20-year roof will last 40 to 60 years. One thing you have to consider is that at some point, the waterproofing under the living roof will need to be replaced, which means you’ll have to remove the plants and growing medium—and that can be expensive. Currently, living roofs cost three to four times more than a traditional composite roof, $18 to $24 per square foot versus $6 to $8.”
Of course, the larger the roof, the bigger the investment. That’s why Loomis says living roofs have more appeal when the building projects are smaller. And while you might think traditional roofing companies aren’t overly enthusiastic when it comes to green roofs, think again. “The larger roofing companies have joined the movement and are providing pretty much everything you need for a living roof—except the plants.”
Going gold in Healdsburg
While no one has tried planting vineyards on green roofs (yet!), Loomis reports that several wineries in Napa and Sonoma are taking a serious look at investing in living roofs. His firm is currently working on projects for Staglin Family Vineyard in Rutherford, Paradise Vineyards on Highway 37 in Sonoma and Kenzo Winery in Napa Valley, Angwin Ecovillage and the St. Regis Hotel in Napa.
Two North Bay hotel projects also have embraced both living roofs and living walls as part of their design.
Currently under construction in Healdsburg, the new h2hotel on Healdsburg Avenue, south of Healdsburg Plaza, is a sister inn to the popular Hotel Healdsburg. Designed by David Baker + Partners Architects of San Francisco, the structure will feature an undulating green roof that Circe Sher, the property’s marketing and public relations director, describes as “a fabulous design that will give added value to the overall experience [of our guests].”
According to Sher, part of the impetus for the living roof was Hotel Healdsburg’s ongoing effort to restore Foss Creek (the hotel is located on its banks). “We’ve been intimately involved with restoring the creek and have gained heightened awareness of all our waterways. Since the new hotel will be close to the creek, we felt a living roof would be helpful.”
The h2hotel is striving for gold-level LEED certification, Sher says. “Our decision to go with a green roof is really a combination of both aesthetic and environmental factors. It’s an exciting signature design statement and offers a number of positive environmental attributes,” she says.
“A living roof filters rainwater—water doesn’t flow off the roof and cause erosion. Instead, it slowly percolates down, which lessens the impact on the local sewer system and creek,” she says. “It also provides a natural habitat for insects and birds, which adds value to the guest experience. And it adds some green space to the entire project and provides thermal and sound insulation. We’ll also be lessening our carbon footprint in Healdsburg by having a roof that’s highly reflective, so it doesn’t contribute to heat gain in the urban environment.”
One third of the roof will be occupied by solar collectors for the hot water system and photovoltaic panels to supplement power use, Sher says. In fact, the overall project is a study in sustainability. The hotel will have an innovative heating and cooling system that follows the path of the sun, much like a sundial. Building materials include reclaimed wood and other recycled items from local sources (cutting down on the need for shipping, which uses too much energy), water bars on each floor with refillable glass carafes (no plastic bottled water), a bicycle program offering loaner bikes to guests to encourage less automobile use, drought-resistant native plants, recycling containers in each guest room, organic linens and eliminating bottled amenities (shampoo, conditioner, lotion and so forth) in favor of larger, refillable containers that are permanently adhered to the bathroom walls.
While many of these actions are part of the point system to get LEED certified, the hotel is going beyond LEED requirements, actively working on Foss Creek’s restoration. “Foss Creek is a steelhead trout habitat,” Sher says. As part of h2hotel’s commitment to the community, it has partnered with two organizations—Russian Riverkeeper and Trout Unlimited—to undertake ongoing projects beneficial to the creek.
