An environmentally friendly “green roof”—containing grass, native plants and approximately 110,000 pounds of soil—opened on the new South 40 House residence hall. The roof shelters the South 40 House's southern lower level.

The 10,150-square-foot green roof connects seamlessly with the lawn to the east, creating a large grassy area that also features paths and benches.

Atop the northern half of the South 40 House—and overlooking the building's green roof—are four stories containing student dining areas and residences.

Installing a green roof rather than a typical black rubber roof benefits the environment in numerous ways, said Matt Malten, assistant vice chancellor for sustainability.

The green roof will help the University improve its water management. Ninety percent of rainwater that falls on a green roof is absorbed by the soil and vegetation, reducing the amount of runoff that flows to sewers and increasing the amount of rainfall naturally recycled through the atmosphere. The vegetation on the roof is either native or has adapted to the region, and the programmable irrigation system determines how much water is needed to keep the plants alive, minimizing unnecessary watering.

The green roof also acts as insulation, keeping the building underneath cooler in the summer and warmer in the winter, which reduces energy usage. The grass also reflects heat back into the atmosphere rather than absorbing it, creating a cooler exterior environment.

Herbs also will be planted on the roof, reducing the amount of ingredients the South 40 House kitchen will need to have transported in.

There are other practical and aesthetic benefits to using a green roof rather than rubber, concrete or shingles. A green roof creates lawn space for students to play, study or picnic. It also adds to the residential feel of the South 40.

“With our redevelopment of our student housing, we have been thoughtful about both the indoor as well as outdoor spaces,” said Justin X. Carroll, associate vice chancellor for students and dean of students. “The South 40 House provided us with a unique opportunity to create something special for the residents of the South 40. Developing a strong sense of community at Washington University is key to the success of our undergraduates. Additional green space on the South 40 not only adds to the beauty of campus, but it also provides a versatile venue that will become a main gathering place for students,” said Dean Carroll.