General Articles
Up On the Roof / by Jane Hodges Young / February, 2010

NorthBay biz takes a look at a growing architecture trend that’s taking root here in the North Bay—living walls and roofs.

There’s an old saying pack rats often employ to justify their obsession with saving everything: “If you wait long enough, it will come back in style.”
The same could be said for one of the latest trends in green architecture—living roofs. While many promote them as a modern day antidote to reducing our carbon footprint, the fact of the matter is they’ve been around for thousands of years. A primary example is the Hanging Gardens of Babylon, which was one of the original ancient wonders of the world.

Put simply, a living roof or wall is one that’s covered with soil or another growing medium that allows for vegetation. There are two basic types: intensive, which are thicker, support more vegetation and are heavier and require more maintenance; and extensive, which have shallow growing mediums, smaller plantings and are much lighter.
One of the most famous green roofs in the Bay Area sits atop the newly redesigned California Academy of Sciences in Golden Gate Park. Others that might not immediately come to mind include Union Square (built over a parking garage) and Yerba Buena Gardens (which covers the original Moscone Center) in San Francisco and Gallo of Sonoma’s soccer field off Dry Creek Road in Healdsburg (which serves as the roof of the mega-winery’s underground barrel cellar).

Throughout the Bay Area, living roofs—as well as living walls—are (literally) sprouting up all over, as municipalities continue to hammer out environmentally thoughtful requirements for sustainable construction practices in new building projects. It’s also driven by consumer demand as more people actively seek businesses and products that embrace environmental and sustainable practices.

John Loomis, a principal with the SWA Group in Sausalito, the landscape architecture firm that designed the living roof on the award-winning California Academy of Sciences (the project recently received a Global Award for Excellence from the Urban Land Institute), also believes living roofs are becoming more common because they make it much easier to attain the coveted Leadership in Energy and Environmental Design (LEED) certified standards set forth by the U.S. Green Building Council. Loomis says many of SWA’s clients set specific LEED certification level goals (platinum is the highest) when they begin projects, because they want to be able to advertise them as such.

“Developers can command higher rents with buildings that are LEED-certified,” he explains. “Some cities are even mandating that new projects reach certain LEED levels, and one of the easier ways to get points is with effective storm water management and noise reduction. Living roofs are the perfect answer.”

Living roofs have been near and dear to the hearts of environmentalists in Europe for nearly four decades now. Germany is credited with reviving the trend in the 1960s and, according to a study on living roofs conducted by Penn State University, more than 10 percent of all roofs in Germany are now green. The concept has been slower to take root in the United States, but interest is growing steadily.

Careful planning

It takes a good team to design and install an effective and efficient living roof. It’s not like you can put down a plastic tarp, load it up with soil, scatter it with seed and hope for the best.

The SWA Group project at the California Academy of Sciences is a perfect example. The living roof became a part of the project after the architect, Renzo Piano of Renzo Piano Building Workshop (RPBW), fell in love with the treetop view from the roof of the former museum building and decided it was something people should experience. It was a natural fit for a science museum as well.

“The architect specifically didn’t want a shaggy, unkempt appearance for the living roof,” Loomis says. “Instead, there was a specific request for a more refined and consistent look to best represent the unique physical form of the structure.” So SWA Group planted it with all native material indigenous to the Bay Area. A small observation deck sits in the middle of the roof, and SWA worked to make a special exhibit with nearly 50 different types of native plants around its perimeter. As the roof expands out from the center, fewer different types of native plants are used.

“You have to make sure the roof is regenerative and adaptive. You have to have enough going on so you don’t constantly have to replant things,” he explains.

Their biggest challenge was that the roof sloped. “Planting a green roof is fairly simple if it’s flat, but if it’s sloped, you have to make sure you build it to avoid landslides—you have to make sure everything stays in place,” Loomis says. This becomes less of an issue as the roof planting matures and the plant root systems begin to form mats.

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.

Bardessono’s green wall

The growing popularity of living roofs has also generated interest in interior décor, pushing living walls into the spotlight. You can find a striking and highly acclaimed example of this unique architectural touch at Bardessono in Yountville—which is awaiting accreditation to become the only luxury hotel in the United States that’s a platinum-level LEED-certified property.

Cristina Salas-Porras, director of guest experience, says the hotel design team was inspired by the many living walls they’d seen in Asia and Europe and wanted to do something similar at Bardessono. The idea worked well with the hotel management’s core values, which looks upon cut flowers for massive floral displays, traditionally found in hotel lobbies, as “a big no-no,” Salas-Porras says.

“We wanted something that was green and alive, something inviting,” she says. So the hotel turned to San Francisco garden designer Flora Grubb, who created four 3-by-12-foot living panels that grace the contemporary hotel lobby.

“The first challenge we had was there was no irrigation system available for the wall,” Salas-Porras says. There also was no drainage. So Grubb conceived the idea of a tillandsia wall. Tillandsia, often called “air plants,” are part of the Bromeliad family. Their roots grow in the air, not the soil, and they’re maintained by twice-weekly mistings. Each plant is on a clip so it can be removed and watered or replaced if necessary.

Grubb also arranged the plants with plenty of space between them, giving each one its own starring role in the composition. The result is a beautiful display of plants that some say resembles fireworks or sea urchins.

“The plant material is so interesting that our guests often ask us if it’s real,” Salas-Porras says. “It’s become our signature piece. It’s just beautiful and the colors change all the time. The walls have become a wonderful conversation piece for our guests, and the financial savings of not having cut flower arrangements is substantial.”

Bardessono is the creation of Phil Sherburne of Seattle, who also owns two other hotels—Willows Lodge outside Seattle and the Inn at Spanish Garden in Santa Barbara. The 62-room hotel opened last February to rave reviews. In building his environmental temple, Sherburne only used salvaged California woods (bought within a 100-mile radius) and rusted steel. He installed a large garden and planted edible landscaping. Amenities were carefully selected and the hotel has no carpeting or drapery. Exterior shades keep each guest room cool or warm. The hotel uses organic linens and upholstery, and surfaces are either wood or polished concrete.

“Phil is an environmentalist,” Salas-Porras says, “and this hotel is his model to show people that this is possible.”

Interestingly enough, when it came to building the living walls, the biggest obstacle was convincing the hotel management it was a good idea. “To be sure, it was a departure from the norm,” Salas-Porras says, “but now they love it and it’s been a huge source of pleasure for our guests.”

And there’s been another side benefit: “The media coverage has been fantastic,” says Salas-Porras. “There’s a huge blog trail online when you search for ‘Bardessono green wall,’ plus we’ve been featured in the New York Times and Sunset magazine, among others [see “Hometown Luxury,” March 2009].”

Getting there

If you’re interested in a living wall or roof for your home or business, there are certain things those we interviewed for this story highly recommend.

• Consider the structure. If you’re using an existing building, make sure an engineer evaluates the building and determines whether or not it can sustain the load.

• Check city requirements for code compliance and building permits.

• When hiring a contractor or engineer, check with green-building associations first. Their members are more likely to have the qualifications and expertise needed to undertake the job.

• Be sure to consider the environment, particularly in the case of living walls. “Work with someone who’s confident and who takes heating and cooling into consideration [when designing the wall],” says Salas-Porras.

• Find someone who understands what vegetation is the most effective, requires the least amount of maintenance and lasts the longest.

As living roofs and walls grow in popularity, it’s likely we’ll see more spring to life in the North Bay. And if maintenance is as easy as some experts profess, many more of us will be singing along to that old song recorded years ago by The Drifters—“Up On the Roof”—especially the part that says, “Right smack dab in the middle of town/I’ve found a paradise that’s trouble-proof/Up on the roof.”