Dustin Brackney of Apex Green Roofs shows sedum cuttings that are being planted on the new green roof on the new Sloan building, E62. Sedum, also known as stonecrop, is a large genus of popular garden plants.The 7,000 square feet of green roof being installed by Apex Green Roofs will contribute points to the building’s LEED certification. In addition to the certification, the roof provides long-term cost savings to MIT by extending the life of the waterproof membrane covering the roof from an average of 20 years to 60–70 years. Many cities are encouraging the use of vegetation-covered roofs because they also reduce stormwater runoff by 65 percent and act as a buffer to delay stormwater from reaching drains.“Green” roofs are so called because they are covered with vegetation. On E62, the roof is covered with 3.5 inches of a light-weight soil media planted with sedum cuttings.The work on the roof began last Thursday and will continue through this weekend. The cuttings will put down roots in about a week and a half, and the roof will not be fully grown for another year.Green roofs do require some maintenance, and workers from Apex Green Roofs will revisit MIT approximately three times per year to check for leaks and ensure that the plants continue to grow.