By Duane St. Clair

As more ambitious energy conservation methods evolve and become more common, rooftop gardens are likely to be among them. Dublin already includes some examples, one on a new home and several at Dublin Methodist Hospital.

Architect Kevin Knight designed and installed one as a terrace outside the carriage house in a home built by his business, Kevin Knight & Company. The home was featured in last summer’s BIA Parade of Homes at Tartan Ridge on the city’s quickly developing northwest side.

Knight, who has a strong interest in “green” building practices, says, “We did it for all the good (green) reasons.” It is expected to be an energy and water saver. It keeps the sun off a dark roof while it also helps keep warm and cool air inside the “Garden Room,” the name Knight uses for the family room. The garden also absorbs rainwater that would otherwise run off.

The plant materials Knight used – various types of sedums – require little water because they’re “like the cactus of Ohio,” he says. Sedums store water and are drought resistant.

They’re planted in a special lightweight soil developed by LiveRoof LLC, headquartered in Spring Lake, Mich. Knight, who has been trained and certified by LiveRoof to use its products, says regular soil would be too heavy for a rooftop without expensive underpinning.

The company provides large flats with maturing plants in the soil. They’re grown in Sandusky, so they readily adapt to the Central Ohio climate. The flats are placed on a membrane to control water and create a seamless garden that requires little care after the plants mature, Knight says.

The garden is laid out with a walkway and seating area made of Pennsylvania blue stone. From inside the house, the garden has a pleasant view throughout the year. Some of the sedums are evergreens. In the winter, some turn an attractive rust or brown shade and look pretty when covered with snow, Knight adds. And in the spring, readying for another growing season is as simple as cutting them down.

“There could be a 40- to 50-percent reduction in energy use because of the insulation value of the roof,” Knight says, adding he’ll be interested in seeing the figures after several months of varied weather. The garden’s his first and he’s discussing adding one to an existing home as well as including one on a home to be built in New Albany.

At Dublin Methodist, a half dozen outdoor gardens were installed during construction in 2008 and seven more are being completed as money is contributed for them, usually by families to commemorate a loved one. Their purpose goes beyond energy savings. They have therapeutic value for patients, family and relatives and even the staff, says chief nursing officer Lamont Yoder, who refers to them as “healing gardens.”

The hospital is one of 60 members of the Centers for Health Care Design, a consortium of hospitals and health care organizations studying how the environment, including outdoor space and gardens, helps with health care. Yoder explains that patients experiencing depression or pain may be helped by “just viewing” a garden or by sitting in one of the several within the hospital.

“Research shows (they help) patients with stress and recovery whether they go out or just see it,” Yoder says. The gardens can also be appreciated by visitors, who can enjoy a relaxing outdoor environment without leaving the building.

Plant content varies – one near the emergency room is a zen garden with bamboo. Others have small trees and low-lying shrubs, but all are very low maintenance, according to Yoder.

John Loos, project manager for GreenScapes Landscape Co. of Columbus, supervised the installation of six gardens, including one on a rooftop on the third floor between patient towers. It’s only for viewing and is not accessible to pedestrians, which is typical of rooftop gardens in large buildings. While the company is a certified LiveRoof installer, the company used the “farming method” in the hospital gardens.

This method entails specially-prepared lightweight soil named Halite that has no heavy clay and contains fertilized planting mix. Plants are then added. It provides about 25 percent plant coverage until the plants mature compared to about 90 percent when flats are used.

The hospital irrigates the gardens with its regular water supply. Tanks to store runoff and recycle the water would have been a costly alternative, Loos says. In flats, an underlying material is designed to hold some water that plants consume if nature or a watering system do not.

In the third floor garden, sedums and some ornamental grass – both drought and heat tolerant perennials – were planted. Low growing plants or trees, including Japanese maples, English yews and boxwoods are used variously in other gardens that are accessible. While they require some maintenance, such as trimming, the object was to create gardens requiring the least amount of maintenance as possible because access for gardening equipment and materials is a problem, according to Loos. Although all the gardens are not on roofs, they are outside and planting and care methods are similar.

Loos adds that rooftop gardens have been used for decades in Europe. In Chicago, Mayor Richard M. Daley has been pushing for them to replace masses of black, heat absorbing roofs. They’re not used so much in the Central Ohio area, but Loos says Franklin County’s new courthouse in Downtown Columbus will have a rooftop garden, and predicts they will “take off” in five years.

Duane St. Clair is a contributing editor for Dublin Life.