Look to the skies

Garden centers looking to attract customers, expand their market and conserve energy might want to look up — about as high as the roof. The green roof market has warmed up during recent years and is expected to get even hotter.

The green roof industry grew 115 percent in 2011, after an increase of 28.5 percent in 2010, according to Green Roofs for Healthy Cities’ annual industry survey. Proof the growth is still trending upward, Lux Research, a strategic intelligence firm that provides data on emerging technologies, predicts the green roof and green wall market will reach $7.7 billion worldwide by 2017.

Garden centers have the opportunity to sell the plant materials and even install a green roof to reap the benefits of the technology and physically show customers how it works.

“Green roofs are the best, most effective, all-around technology that exists in the marketplace,” says Steven Peck, president and founder of the North American association Green Roofs for Healthy Cities. “There is no other type of building technology that provides the same scale and scope of benefits both public and private as does a green roof system.”

What is a green roof?
A green roof system is simply a garden built on top of a roof. It incorporates a waterproofing, root-repellant layer, a drainage layer, a filter membrane, growing medium, vegetation and, sometimes, an irrigation system.

Green roofs can be either extensive or intensive, the main difference being the amount of growing medium used and irrigation installed. Intensive roofs, which have more than 6 inches of growing medium, are often seen on corporate buildings and accommodate space for people to walk and relax. Larger plants, irrigation systems and hardscapes are usually incorporated. Extensive roofs, which have less than 6 inches of growing medium, are often found on homes and residential buildings.

“Extensive roofs are the largest portion of installations,” says Marianne C. Duckworth, a consultant at Green Gate Farms, which is the exclusive grower and regional distributor for the green roof system designer and installer LifeRoof. “However it does depend on the load-bearing capacity of their structure and what the ultimate goal is for the roof.”

What are the benefits?
Garden centers considering a green roof need to think about the benefits the investment can offer and how it will be used.

Green roofs can be installed to conserve energy, mitigate stormwater runoff, improve air quality by decreasing CO₂ and prolong the life of a roof’s waterproofing membrane.

Green Roofs for Healthy Cities’ research has found that, depending on the depth of a system’s growing medium, in the summer, 70 to 90 percent of precipitation can be retained; in the winter, 25 to 40 percent. Not only does this decrease the amount of stormwater hitting sewer systems, but the water can then be stored and taken up by the plants.

Another benefit is saving on a building’s heating and cooling bills. “Green roofs can cool the space beneath them by 8 to 12 degrees, which is of great benefit in the summertime,” Duckworth says. “In the winter, they can reduce heat loss by approximately 25 percent. Plants are not as full in the winter, so maximum benefit of energy savings is enjoyed in the summer months.”

Besides environmental reasons, think about whether the garden center can find benefit in expanding its useful space, perhaps adding a second showroom on the roof.

“Most importantly, the facility must be inspected by an engineer for load-bearing capacity,” Duckworth says. “You also need to be aware that, while minimal, there is maintenance. And of course, what goal you are trying to achieve. Do the research. Know the different types of systems and how well they have or have not performed on the projects [where] they’ve been installed.”

How much do green roofs cost?
While a green roof is essentially a garden on top of a building, the creation of a habitat is more involved.

An extensive green roof with a root-repellant, waterproof membrane can cost between $10 and $24 per square foot to install, according to Green Roofs for Healthy Cities. Costs obviously increase based on the system’s complexity and the height of the roof. Garden centers can have a green roof designed and installed from scratch, or they can look into the many pre-vegetated modular systems on the market that snap into place like a puzzle once on the roof.

Whatever the cost, more cities and even rural counties have noticed the benefits of green roofs and are passing public policy to support installation.

“We’re certainly seeing more market activity where there are public policies that support green roof implementation,” Peck says. “Cities like Chicago, Portland, Washington, which provide a variety of incentives.”

In some cities there are tax incentives and grants available to building owners installing green roofs. “There are density bonuses where developers are able to add floor space to a project in exchange for a green roof,” Peck says. “There are stormwater fee reductions where the owner of the building can pay less money on their stormwater chargers. If they have what’s called lot-level stormwater, they pay an amount of money that relates to how much water is flowing on their property.”

Garden centers considering a green roof should research local incentives and building codes to maximize their investment.

How can green roofs improve business?
Green roofs are visible and easily identifiable. A second showcase on the roof not only provides great curb appeal, it’s also a good marketing tool to attract customers and shows a garden center’s commitment to the green industry and green movement.

Once the customer is in the garden center, the green roof can also be used to increase the sale of sedums and accent plants that are used in the installation, Duckworth says.

Plant selection varies based on the composition and depth of the growing medium, the roof’s loading capacity and irrigation systems. Green roof plants also need to be hardy and resilient to windy conditions. Garden centers may be able to sell a new line of products based on these specifications.

“The most commonly used plants to date are sedums and perennials,” Duckworth says. “Mostly, they have to be drought tolerant, have shallow root systems and, preferred, easy care. More and more trials are going on. Depending upon the climate, ornamental grasses, cactus, shrubs and many more species are being used.”

Statistics on the green roof market’s growth in 2012 haven’t been released. The consensus is the industry will continue to see upward movement. Garden centers, with their vast plant knowledge, stand to benefit by taking a chunk of the market.

“Why not become a certified installer and increase the scope of your business?” Duckworth says. “At the very least, increase your offerings of plants to flourish in green roofs.”

The layers of a green roof
Green roofs are multifaceted, to say the least. Here is a breakdown of the basic components, based on a study by the National Research Council Canada.
 

Carolyn LaWell is a freelance writer based in Lakewood, Ohio.

Photo courtesy of PWL Partnership Landscape Architects and DA Architects and Planners; Green Roofs for Healthy Cities