Looking for ways to combat the urban heat island effect, the Chicago Department of General Services decided to install green roofs on four of its fire stations around the city. The city was looking for a green roof system that was quick and easy to install, cost effective, and lightweight. The green roof system they selected that best met these requirements was the GreenGrid? modular green roof system from Weston Solutions, Inc. With the GreenGrid system, plant and soil media are preplanted in modules made of 60 percent recycled plastic at nurseries, not on the rooftop setting. This allows for quicker installations and reduced labor costs.

Weight was also a concern for the green roof installation especially at Engine Company #98. More than a hundred years old, this famous station is listed on the National Register of Historic Places and located on Chicago Avenue, just off the city?s famed ?Miracle Mile.? In December, 2003 GreenGrid installed a 1,056-square-foot modular green roof using a mixture of hearty, sedum species but just three plants per square foot.
The modular systems are already lightweight, weighing ten to twelve pounds per square foot for two-and-a-half-inch modules; fifteen to eighteen pounds per square foot for four-inch modules; and thirty-plus pounds for eight-inch modules when wet. And using fewer plants made these modules even lighter?considerably lighter than a comparable, built-in-place green roof.