The eco roof, also called the “green roof,” is not just an environmentalist’s dream. It’s a reality that is literally planting roots in city-scapes and countrysides all over the world.
The Environmental Protection Agency (EPA) estimates that nearly 8.5 million square feet of green roofing will have been installed in the United States by 2008.
What is an eco roof?
There are a variety of different styles of eco roof, ranging from what looks like a lawn on top of your house to a complete park crowning a city office building. However, the basic structure of a green roof looks like the photo below.
The top layer is a shallow-rooted vegetation, typically sedums, which are drought resistant and low growing- so you won’t have to mow or water your roof! There are many varieties of sedum, allowing for a varied or more uniform look depending on your preference.
The second layer down is a growing medium, a specially engineered mix that will provide an optimum growing environment for the sedum without being too heavy on the building’s structure.
The next layer is a filter layer, followed by a drainage material. These prevent heavy rains from causing a landslide off the side of your house.
Then you have a protection, or root-blocking layer. This stops any local fauna that may have planted itself on your roof from wheedling its longer root systems through the roof.
Finally, the whole thing sits on the waterproof membrane, which lays directly onto your roof deck.
The final product can look like a gnome home, nestled cozily into its natural surroundings, like this little abode on the Feroe Islands.
Or it can look like this well-groomed park on the top of Chicago’s city hall.
At the Maple Cafe (below), the green roof is more like a patchwork of color and variety. Their eco roof is three years old in this picture, and nicely filled in with many different types of sedum.
Why the green roof?
With the initial cost of an eco roof ranging from $10 per square foot for the more common extensive eco-roof, to $25 per square foot for the deeper-rooted intensive system, why would anyone want to switch?
Here are five good reasons to switch to an eco roof:
1. Increased roof life: The green roof is more insulated from weather damage.
2. Decreased stormwater drainage: The roof uses the rainwater, so it doesn’t run off. This is less taxing on your drainage system and on the marine ecosystems in your area.
3. Reduced energy use: Since the rooftop ecosystem absorbs heat and insulates the home, you will not have to run your a/c or furnace as much, impacting your pocketbook and your carbon footprint.
4. Reduction in urban heat island effect: Urban heat islands (a condition where the city is hotter than surrounding rural areas) are caused by heat-absorbing rooftops and concrete. This can damage ecosystems, human health, climate, storm patterns, and increase greenhouse gas emissions.
5. Enhance ecosystems: Rooftop vegetation can provide habitats for many types of indigenous plants, insects, birds, and animals.
Can I put an eco roof on my house?
It’s possible to put an eco-roof on an existing home, but it will take some structural reinforcement due to the heavier burden of soil and sedum… not to mention the water it will hold, adding to the weight.
Higher-pitched roofs are more difficult, whereas a flat or low-grade roof lends much better to the eco-roof transition. However, with the evaluation of an architect and a knowledgeable contractor, you can enjoy the benefits of a green roof on nearly every type of home.