Is a Green Roof Right for You?

A lot of homeowners, especially in urban areas, are discovering the benefits of green roofs. Green roofs are simply flat sections of rooftop covered with a few inches of soil and plants. In addition to adding an attractive natural look to your rooftop, green roofs also reduce your heating and cooling costs. When properly installed, the soil layer extends the life of the roof by protecting it from the elements. Such roofs help to cool and clean the air, especially in urban environments, and they filter storm water, helping to prevent flooding.

If you’re planning a green roof, first check with your building inspector to see if the local code allows them in your neighborhood. You should also be aware that if you are planning to use an existing roof, you might need some structural reinforcement to support the added weight of the soil (about 20 pounds per square foot). A contractor can help you determine if this is the case. Your roof pitch would also need to be less than 30 degrees, or the soil will wash away in the rain. If you are building a new home from the ground up, ask the architect or builder if they are familiar with green roofs. If they are, they will be able to offer tips and suggestions as the work progresses.

Starting from the bottom, a green roof begins with a waterproof membrane of some sort. These membranes are usually some type of asphalt/rubber combination designed to keep moisture and plant roots from damaging the roof underneath. Next comes a layer of pebble or crushed gravel that acts as a drainage system to keep water from puddling up at the roots, leading to root rot. A layer of filter cloth goes on top of the drainage layer. Finally, a layer of 3 to 6 inches of topsoil is added. The plants that work best on a green roof are those typically used for ground cover. Since climbing up onto the roof on a regular basis could be a problem, it is best to choose plants that don’t need a lot of maintenance.

With the proper plant selection, green roofs should do fine with only rainwater, especially if you use local ground cover plants that are adjusted to the climate. You should only have to water your green roof in extended droughts. About the only routine maintenance you’ll need for your roof garden once it’s established is a weeding once or twice a year, usually in early summer and late autumn.

In addition to helping save on heating and air conditioning costs, your green roof can help reduce noise, double the life of your roof, and add an attractive conversation piece to your home. Green roofs also actually help cool the roof by water evaporation, and help reduce the amount of carbon dioxide in the air. Since green roofs absorb up to 90% of the rainwater that falls on them, they also filter this water before it enters the storm drains, effectively removing most airborne toxins trapped in the rainwater. Green roofs are a novel and attractive way to help the environment while adding value to your home.

If you would like to learn more about green roofs, visit: http://www.greenroofs.org.

Chuck Hall is a Sustainability Consultant and author. His latest book, Green Circles: A Sustainable Journey from the Cradle to the Grave, is now available at the Culture Artist website at www.cultureartist.org. You may contact Chuck by email at: chuck@cultureartist.org.