Special material allows grass and other plants to grow on top of standard roof.
Chris Rossi/The Gazette
Fred Nichols, of Nichols Contracting, shows a green roof on top of the Bentley building in Sandy Spring on Monday.
From the ground, the shrubs and grasses perched on the roof of the Bentley building in Sandy Spring are barely noticeable.
But when it comes time to tally the building’s heating and cooling bills, Fred Nichols says their presence — and benefits — are obvious.
“We get about an 18 percent savings on our heating and cooling bills,” Nichols, owner of Nichols Contracting Inc., said. Part of the company’s operations are in the Bentley building.
In April workers from Freedom Garden Products installed about 2,000 square feet of AQUALOK foam on the flat roof then planted blue holly, liriope grass, heather, old gold juniper, blue star juniper and golden euonymus directly in the foam. The plants cover about two-thirds of the roof, but Nichols said he is thinking about covering the whole thing.
The work took less than a day.
Wendy Bell, a spokeswoman for Premier Plantscapes, the Burtonsville company that installed the roof, said the roof system is the first of its kind in Maryland. The company installed a similar roof in Arlington. But the benefits of the roof are so great, she expects to see them sprouting up all over the area in the next few years.
“We’ve got the interest, it’s just a matter of getting them out there,” she said. “It’s really the perfect environment for plants to grow in. Two inches of this foam is the equivalent of two feet of soil, and two inches of foam holds an inch and a half of water.”
The system, which is installed directly on top of the existing roof, is significantly lighter than if soil was used. It requires no modifications to the roof before the foam and plants are installed. The new roof weighs 10 pounds per square foot, where a traditional green roof with soil or stone base can weigh anywhere from 25 to 250 pounds per square foot, Bell said.
Making a roof green with traditional materials often requires it to be reinforced to prevent collapse, but that is almost never needed with this lighter design, Bell said.
The system can even be installed on a sloping roof, so long as it is not too steep, Nichols said.
The foam was originally developed to be placed in the fuel tanks of space shuttles to prevent the fuel from sloshing, Nichols said. But its hyper-absorbent properties make it a good fit for using as a planting material.
As a plant grows, the roots integrate into the foam, Nichols said.
He wants to use the green roof on Ashton Meeting Place, a shopping center planned for the intersection of Ashton-Sandy Spring Road and New Hampshire Avenue.
He hopes Park and Planning commissioners will inspect the roof on the Bentley building to see that it is suitable for the Ashton Meeting Place.
“I was skeptical myself when I first heard about it,” he said. “But it’s hard to find a downside.”
The installation on the Bentley building cost $50,000, which is approximately $25 per square foot.
But with the cost-savings on heating and cooling bills in addition to lessened storm water management costs and tax breaks for the environmentally friendly improvement, the roof will pay for itself in four or five year, Nichols said.
And it works, to boot.