It’s a novel idea — plants, shrubs and flowers, grown on the roof of urban buildings. The plants help cool surrounding air and provide insulation during both hot and cool temperatures.
But there’s a catch.
According to Dr. Astrid Volder, a Texas A&M AgriLife Research horticulturist, the problem is the rough Texas climate:
The problem with Texas is finding plant species that can survive in such a harsh environment. A plant growing on a roof is going to receive a lot of solar radiation, very high light conditions and not a lot of rain. And the plant is growing in maybe 4 inches of soil on the extensive-type green roof.
Volder has discovered that native Texas plants don’t do very well on the roof because they need deep soil beds. The plants are able to withstand drought because their roots dive deep through the ground.
But a green roof project in Houston that was started six years ago has learned that some flowering shrubs, herbs and ornamental grasses can do well in roof beds, and provide big savings, according to Jeff Mickler. His company, Jacob White Construction, built the roofs:
“We’re able to cut the energy usage with our roof down by about 50 percent,” Mickler said. “Our electric bill in September for our headquarters building was $700. It’s 11,000 square feet, and we run 18 hours a day, seven days a week. And so it uses a small amount of energy.”
He said the building’s management system, which measures conditions “thousands of times per second,” in the hot, dry summer this year recorded a high of 138 degrees on top of the soil while the bottom of the soil never got above 85 degrees. The company also collects water from parking lot and building runoff into large cisterns and uses it to sprinkle the roof garden at noon and 2 p.m.
Read the full story at Agrilife Today.