High above the United States Department of Agriculture building in Washington, D.C. lays 3700 square feet of plants, soil and gutters, which trickle into an internal cistern. The Whitten Building is located in the combined sewer system zone in Washington D.C., so the use of green roofs not only adds aesthetic value to the facility, but also helps address a serious environmental problem of combined sewer overflows in the Washington D.C. waterways.
The green roof system used by the USDA is composed of Green Roof Blocks and Green Paks. The 2×2 block units allow great versatility in design. They may be placed to accent a rooftop courtyard or fully cover a flat roof. Three different depth options allow accommodation for various plant life and climates. They are an ideal organic solution for flattop tar roofs.
Green Paks are green roof modules made of high density polyethylene knit fabric. These flexible modules easily conform to irregular and radius areas. The module fabric is available in two colors; standard black and green. Each module contains four inches of our custom blended growth media. The growth media remains sealed within the fabric module until ready to plant. This feature simplifies getting materials to the rooftop. Each 20 inch x 32 inch module covers approximately 4 ? square feet. Green Paks can be used to retain growth media for non-modular green roof projects allowing the green roof area to be easily defined without elaborate retaining construction.