Green roofs help keep buildings cool and absorb storm water.
They serve two main purposes, either keeping the building cool or absorbing storm water.
Montgomery County is building a new equipment and maintenance operations center near the Shady Grove Metro station, which will be equipped with a green roof.
The Furbish Company of Baltimore will build it, and president Michael Furbish says the goal for this particular roof is absorbing storm water. He says that means they must grow certain plants for the roof.
"We'll probably have somewhere between 7 to 10 kinds of sedums, that will be pre-grown into a mat," says Furbish. "What we're trying to create is a very robust, random meadow of sedums so that you have resiliency in that."
Sedums are known for their water-storing leaves, and Furbish says the plants can absorb up to 70 percent of water that falls in a storm.