Sunday, March 6, 2011

Green Roofing - It's American

As one of the first beautiful days of spring in the mid-Atlantic settled in, a group of 40+ volunteers from the Urban Land Institute, U.S Green Building Council, and DC Greenworks gathered to assist American University with retrofitting one of four green roof projects on their campus in the District of Columbia. The day began with a talk on crane and roof safety, a tour of an existing green roof at the University, and a speech by the Director of Sustainability describing American University's aggressive goal of going carbon neutral by 2020. With that accomplished, the volunteers were separated into working groups and organized for the day of construction.
Mature Green Roof at American University

The first order of business with retrofitting a green roof to an existing roof is a general inspection of the existing conditions. An engineered structural analysis needs to be performed to ensure the roof can handle the extra weight load, and a design for the roofing system needs to be decided on. Thankfully these tasks were already done by the time we arrived on site to begin the work.

Before placing the "green" on the roof, the existing ballast (large gravel) needs to be removed and stored for later use. A root barrier then needs to be installed on all sections of the roof that will receive plantings. After this, a track will be placed to keep the plantings firmly in the desired section of roof. Finally, custom plastic trays will be placed inside the track to provide growing medium for the plants. These plastic trays are a relatively new technology, and allow for easy installation and maintenance on the roof. After all the trays are placed, a gravel track will be placed around the edge of the roof to provide access, as well as easy discovery of roof leakage around the perimeter (which is where most roof leaks occur). Once the trays are installed, they will be connected to an irrigation system and plantings will be placed in the desired locations to finish off the green roof.
Site Safety Meeting
Green Roofing Supplies

Vegetation Trays

Removing Ballast with Vacuum
Inspecting Existing Conditions

Installing Root Barrier
Installing Track and Tray System on the Roof
 Utilizing volunteer labor through groups like the USGBC and ULI is a great way to lower the cost of green retrofits while increasing awareness and community involvement in sustainability. Working on this project with American University was education and rewarding, and I hope to involve myself in many more projects like this in the region.


  1. Wow! Installing a green roof sure looks fun! It's a great idea to convert into green roofing since it doesn't just gives us a natural cooling system for our home, but it also provides us clean and fresh air! People who don't have an open lawn will also be given a chance to do some gardening, thanks to Green roofing.

    -Adam Waterford

  2. These are great eco-friendly roofs and they look great when mature sometimes better than a real lawn :)

    Nina Jones