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Johnson Space Center Takes Green to a New Level: the Roof
jsc2012e018599 -- Green Roof at Building 12

Building 12 is the first at JSC to have a green roof, also known as a garden or vegetative roof. Photo credit: NASA

jsc2012e018607 -- A sky view of the new Building 12 rooftop

A sky view of the new Building 12 rooftop. Photo credit: NASA

Johnson Space Center team members have been observing the renovation of Building 12, one of the most visible of the ongoing construction projects at the center. But it’s not just any construction. Building 12, which will house personnel from several mission support directorates, will be the first at JSC to have a green roof, also known as a garden or vegetative roof.

The revamped structure will have an open-office concept to improve workflow and day lighting. The building was designed to meet or exceed Leadership in Energy and Environmental Design (LEED) gold certification criteria set by the U.S. Green Building Council and will do that and more with the innovative green roofing system. Also, alternative energy sources will be relied on with the installation of photovoltaics and four vertical helix wind turbines.

What’s all the buzz about green roofs?

Jeff White, NASA project manager, said there are quite a few benefits to having a green roof. For one, it is very environmentally friendly because it reduces what they call the urban heat island effect.

“If you have a roof that absorbs the solar radiation, then it creates heat,” said Brian Dark, Gilbane Construction manager. “Then you have the concrete out here that’s doing the same thing and the black top street and the store parking lots, throughout the city; there are all these heat islands. So, it actually raises the temperature somewhere between 10-15 degrees, in some cases. LEED really focuses on reducing that by using a high reflectivity roof surface like a white PVC-coated roof. Or, you go to a green roof and completely eliminate it. So, that’s what it does.”

There’s also less storm water run-off on this type of roof system. Instead of just running off the roof and in the drain, “It actually soaks into the soil and is used to water the plants,” White explained. “Overall it makes the building envelope more energy efficient. It takes less energy to heat and cool the building. The green roof is a great insulator and helps reduce noise level, as well. If you have a noise, it will bounce off a regular roof and reflect, but in this type of roof, it will actually absorb it. So there’s quite a few benefits to it.”

What does the maintenance of such a roof entail?

Dark said since it’s a natural habitat, there will be less maintenance. The JSC grounds keeping staff will oversee the roof maintenance as they do with the rest of the center.

“It’s landscaping, as in weeding it and keeping it clean,” Dark said. “They’re going to look to make sure no drains are clogged, look for wind erosion and check the irrigation system to make sure it’s functioning. And really just keeping an eye on the plants themselves, making sure that they look good, and keeping any foreign plants out.”

The roof is not one that can entertain spectators because of the need and cost of structural upgrades.

Facts and figures

Building 12’s new roof will have:

Quantity Scientific Name Common Name
11,661 Glandularia Bipinnatifida Dakota Mock Vervain
11,661 Ruellia Brittoniana ‘Pink’ Dwark Pink Ruellia
11,661 Sedum Moranense Red Stonecrop
10,810 Malephora Lutea Rocky Point Ice Plant
10,810 Sedum Mexicanum Mexican Sedum
10,810 Sedum Rupestre ‘Angelina’ Angelina Stonecrop

The total plant count is approximately 67,413. They are planted in an 8-inch triangular pattern with an even mix. Plant coverage is about 50 percent of the roof after one year and 80 percent after two years. There are 1.2 million pounds of growing media (soil). The growing media is developed specifically for garden roofs and consist of blends of lightweight aggregate, lightweight aggregate fines, low clay sandy loam, medium coarse sand, compost, peat moss and perlite.

This project is expected to be finished in June 2012.
Neesha Hosein
Johnson Space Center, Houston