The green roof and terrace areas on the 6th floor podium of the ABN AMRO Plaza at 540 West Madison Avenue in Chicago, were built primarily for the enjoyment of employees. This is the first major green roof installation by the noted developer, Gerald Hines Interests, Houston, TX, on one of their high-end commercial properties.

Designed for maximum accessibility, the roof has 50% green roof and 50% pavers and plantings which are a mix of trees, perennial plants, and annual flowers in planters of mixed heights.  Tree shaded areas are complimented by an open lawn planted with sod. The trees were planted fairly large and have grown quickly, so the green roof looks mature and gives a true garden feel.  All employees can benefit from this green roof which also contributes to the overall greening of Chicago.

The growing media is PM35 - General Purpose Amended Top Soil Blend, provided by Midwest Trading, with growing media depths of 18 to 24 inches in the sod area and perennial planters, and 36 inches around the other planters. The project covers 74,700 square feet at a cost of over $100 per square foot. The plant list includes trees, shrubs, perennials and groundcovers. Various annuals and seasonal plantings have also been installed including summer annuals, spring bulbs and fall mums.

The “Greenroof-Roofscape®” waterproofing assembly, supplied by the Barrett Company, consisted of 215 mils thick Barrett “Ram Tough 250” rubberized asphalt membrane made with recycled tire crumbs, polyester reinforcement, SBS protection course, 60 psi extruded polystyrene insulation, and a root barrier.

The green roof will preserve the integrity of the roof membrane by eliminating damage from the sun’s ultraviolet light, eliminating thermal shock and all mechanical damage.  The monolithic rubberized asphalt waterproofing membrane can withstand constant water immersed conditions and hydrostatic pressures while providing long term physical and chemical stability in an environment subjected to water, fertilizers, root growth and chlorides.

The irrigation system is a combination of two styles of emitters.  The pop up sprinklers irrigate the perennial and annual display area and turf areas with a spray.  The remaining tree, shrub and groundcover beds are irrigated using a drip hose that weeps water.

Three seasons of maintenance are required; spring consists of an initial clean up after the winter months followed by summer weekly service which begins in April and ends at the end of September, lastly, fall clean up starts in September and lasts until the end of November.

A solid addition to Chicago’s green roof success story, with Mayor Daley’s stated objective of making Chicago America’s greenest city, the 6th floor podium on the ABN AMRO plaza contributes towards making Chicago a cleaner, healthier, more energy-efficient environment for its’ citizens and demonstrates the potential of green roofs to provide a  pleasing, tree lined refuge in the center of the bustling city.