In part one of this series, we documented the amazing concept of growing grass, shrubs, trees, and even food on top of houses and buildings that can help clean up our environment and provide natural beauty. In this blog, we'll cover the benefits and drawbacks of green roofs, and a few resources if you wanted to learn more or consider a green roof for your home.
Benefits of green and living roofs:
Living roofs are extremely effective sound barriers, helping to drown out the noise of traffic or commerce in busy urban areas. The Chicago City Hall uses a living roof for this reason, and some homes under the flight path of San Francisco International airport have installed living roofs to help reduce the sound of the airplanes. Studies show that these living roofs can reduce noise levels by up to 50 decibels, and even a thin and basic grass roof will drop the outside noise by 5 decibels.
Water runoff control:
A living roof does a great job naturally regulating runoff from heavy rains and storms. Since vegetation and organic materials absorb rain, up to 42% of runoff, or about an inch of rainwater, is captured that would otherwise be wasted. That helps control flooding, overwhelming irrigation and sewer systems, and protects the natural balance of water.
Living roofs naturally cool down the outside air by acting as a heat barrier and also keep warm air inside the house in wintertime. Since heat rises, most of your energy loss is through the roof when you turn the heat on in the cold season. But living roofs can help keep you cool or warm, regulating the outside temperature by approximately 10 – 25 degrees Fahrenheit. The great thing is that the hotter the climate and outside temperature, the better an insulator a living roofs is, saving a lot of money on energy bills in warm climates.
Trees, plants, and grasses help to alleviate the harmful effects of manmade pollution by converting carbon dioxide and other toxic gases into breathable oxygen. Installing livable roofs on big commercial buildings and office spaces in urban areas will not only slow the capture of gases, or greenhouse effect, and help filter airborne particles and pollutants that wash off into the soil. In fact, studies have shown that green roofs can trap up and filter out up to 95% of heavy metals that are caught in the water cycle.
The renewed focus on producing organic, locally grown healthy food has vast potential when it comes to rooftops. Already, schools and many urban centers and office buildings are starting to grow fruits and vegetables on rooftops. Green roofs can also become hosts to edible growth and food production, especially on flat surfaces.
While it may seem like organic grasses and growth on rooftops may be more susceptible to fire, like we see with forest fires, in reality the soil and organic matter is actually fire resistant. Green roofs also hold a good deal of moisture that will thwart fires and burn slow, if at all. In fact, a “bare” roof of just shingles over wood is far more likely to a fire starting, especially over time as the surfaces are weathered and dry out.
Green roofs on large surfaces can also act as natural water filtering mediums. In Australia, they are already using green roofs and walls as a natural filter to treat domestic grey water and wastewater, removing organic matter and pollutants.
Green roofs serve as a natural micro ecosystem and that includes becoming home to a variety of birds, butterflies, and bees. Some people may not be comfortable at first with the idea of a lot of critters living on and in their roof, but as human beings overtake the landscape with pavement and pollution, the loss of native fauna is alarming. Already the huge extinction of bee populations is affecting our food systems and health. Green roofs can help reverse that trend, as we see with a large U.S. auto manufacturer who has built a giant bee farm on the roof of one of their factories.
Of course green roofs take some planning, work, and cost to install and maintain, but once you learn more, you’ll realize it’s well worth it.
Weight of the roof:
Green roofs are heavier than normal roofs, varying widely based on the depth of soil and the type of vegetation grown. Most green roofs weight only a little more than slate roofs, but weight can be a concern that should be carefully planned before any installation starts. It’s relatively simple to retrofit beams and columns of the existing roof to reinforce it for the weight.
Cutting and maintenance:
You probably only get near your roof when you clean out your gutters once or twice a year, but green roofs do take some maintenance. But don’t worry – when you’re mowing the lawn, simply take the weed whacker or hedge trimmers up onto your roof and cut everything back once or twice a year. Other than that, just check on the irrigation system and that’s all the maintenance you’ll need.
In most climates, rainwater will be sufficient to keep your living roof green and thriving most of the year, but in the summer or arid climates homeowners can augment that with irrigation systems that are installed when it’s first built.
Likewise, green roofs have built in drainage systems similar to gutter and downspout systems on any roof.
Where can I get more information?
A green roof can help the environment, lower your energy costs, provide scenic beauty for your family, and also increase your home’s value. So where can you find out more about installing a living roof on top of your house?