Buildings to sport plants on roofs to improve sustainability

By Rachel Carlson     8/21/08 7:00pm

Students and faculty are accustomed to seeing flora and fauna around campus, but green roofing on four Rice buildings will give landscaping an entirely new dimension. Rooftop gardens, designed to improve buildings' sustainability and expand roof lifespan, will be installed on Duncan College, the Collaborative Research Center, the Oshman Engineering Design Kitchen and the South Utility Plant.Rice Sustainability Director Richard Johnson (Will Rice '92) said green roofing provides a variety of sustainable and economic advantages.

"As well as providing a natural habitat, it helps reduce temperatures in the surrounding area, helps reduce storm water runoff and keeps the roof cool, which lowers the buildings' energy usage," Johnson said.

Gardens also extend the lifespan of the roof. Roofs in Houston tend to be degraded by high UV radiation and battered by hail, elements that are absorbed by a garden layer. Johnson said the green rooftop system also regulates the temperature fluctuations that damage conventional roof materials. At the surface of the soil, temperatures vary between 80 and 160 degrees Fahrenheit in the summertime, but the base of the soil only experiences a range of 80- to 100-degree heat. This natural buffer offsets extreme temperature shocks on the roof, which prevents wear.

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"You might have to pay a 10- to 15-percent premium on the roof, but its life expectancy will double," Johnson said. "You pay a little more up front, but it pays back over time."

The idea for green roofing was inspired by several models. The University of Texas School of Public Health in the Texas Medical Center has been operating with a garden rooftop for more than five years without any notable difficulties, Johnson said. Green roofs are even required in some areas of Germany, he said.

The stage of roof installation varies for each building. For the Oshman Engineering Design Kitchen, the selection of plant species was recently finalized with input from the Ladybird Johnson Wildflower Center and various experts in Houston. The species are indigenous, drought tolerant and pest resistant. They include Mexican feather grass, Mexican oregano and bicolor sage.

"We wanted to have a lot of blooming things and color at Oshman so that you could look up and see purples and reds," Johnson said.

The plants are currently growing off-campus and will be introduced within a few weeks.

Johnson said facilities personnel are still experimenting with the appropriate species to use on the roof of the South Campus Plant, but it will probably be dominated by a resilient, native species called gulf muhly grass since the roof is not visible from the ground. Plants on all four roofs are expected to be self-sustaining -- able to grow without extensive care and watering -- by next summer, though Johnson predicts some will reach that stage much sooner.

Johnson credits the progress of this environmental initiative to the efforts of Rice students.

"A lot of Rice's commitments to green building and to the environment in general has been due to the partnerships established between students and the administration," Johnson said. "As students see new buildings, they should take pride in the fact that they, whether they knew it or not, made them how they are.

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