County Office Building Roof Goes Green

Allegheny County Executive Dan Onorato unveiled the County’s latest green building effort today, a green roof covering half of the County Office Building.

The $620,000 project covers 8,400 square feet of the roof with a multilayered system that cools the building and absorbs storm water runoff.

Onorato says he hopes the stimulus-funded development sets an example for other downtown buildings.

“If we can get every flat roof downtown to do this, you’re talking millions of dollars saved on utility costs and you’re talking millions of gallons of water not going into the river and into the combined sewer overflow, which doesn’t have to go there, and increases capacity in our sewer systems and our treatment plants,” says Onorato.

Onorato says the county is projecting about $6,500 in cost savings for the month of July because of the green roof’s cooling effect on the building. The green half of the County Office Building’s roof was shown to be about 45 degrees cooler than the control half.

The green roof on the Office Building is composed of six layers. The bottommost layer is a waterproofing membrane that captures moisture. Above that is protective fabric and a root barrier, which prevents the plants from damaging the roof itself. Next comes a drainage mat to collect water. On top of the drainage mat there is a layer of polystyrene that helps contour the shapes of the landscape. Finally, on top are plants growing inside a pebbly “growth medium.”

“From the business perspective, to energy savings, to the cost of how we’re going to deal with combined sewer overflows, so natural systems are just really using mother nature and what mother nature has given us to solve environmental problems,” says Janie French, Director of Green Infrastructure at the Pennsylvania Environmental Council.