Roofs are like nose hairs, practically everyone has them and they’re not exactly attractive. Fortunately, a new generation of builders, landscape architects, government officials and property owners are discovering the many benefits of rooftop gardens, as well as other features of a green roof. These secret islands of bucolic beauty that are rarely seen and never heard, on the ground – are quietly moving in, blanketing buildings across the country in verdant shades of living foliage. They’re taking over the tops of structures big and small, from the narrow green terraces of the Empire State Building to the country’s most massive green roof installation, which sits atop a sprawling Ford truck plant in Michigan.
What exactly is a green roof?
The Environmental Protection Agency defines green roofs as any “vegetative layer grown on a rooftop.” The area is covered with foliage and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. While pitching a layer of protective sod on top of buildings and homes is nothing new (the Vikings did this, too), what’s happening now is a bit more over our heads… High-tech, some may say. A green roof comes in two varieties: intensive and extensive. Intensive includes a thick layer of soil that can support large vegetation such as small trees. An extensive green roof is characterized by a thinner layer of soil and smaller plants.
Modern green roofs definitely find their “roots” in ancient times.
The original inspiration came from rugged Iceland, where sod roofs and walls have been used for hundreds of years, becoming popular throughout Scandinavia. In the early 1970’s, Germany was the epicenter of a revitalization of roof top gardening. Technologies and techniques were created to waterproof large flat roofs and shield them from root penetration. Intricate irrigation systems were devised to support large woody perennials. Roof gardens became a status symbol of wealth and prosperity during an age of rapid urbanization. The next evolution began in the 1980’s when light-weight extensive roofs were developed. Popularized by their low maintenance costs and huge environmental benefits, the bird’s eye view of many German cities quickly changed in the subsequent decades. And today, it is estimated that about 10% of all German roofs have been “greened”.
What’s the big deal?
Planting the rooftops of urbanized areas brings many beneficial elements to public, private, economic and social sectors, as well as to the local and global environments. While all green roofs have similar functions, each installation is unique, so technical performance will vary by region, climate, building and green roof type and design. But no matter the set up, the benefits are numerous:
- Unlike traditional black tar roofs, green roofs reduce energy costs by absorbing heat instead of attracting it and providing natural insulation. Just as humans sweat to stay cool, green roofs use a process called ‘evapotranspiration’ to keep their structures cooler, by using heat from the air to evaporate the water in the rooftop plants, fibers and beds. By lowering air conditioning demand, green roofs decrease the production of associated air pollution and greenhouse gas emissions. In the winter, buildings also stay warmer, as the green roof works like an insulating blanket by driving heating costs down. We’re talking big time savings!
- A green roof’s plants remove air particulates, produce oxygen and provide shade. Additionally, this natural protection against extreme heat enables green roofs to last twice as long as traditional rooftops. Most roofs, exposed as they are to sun, wind, snow and rain, go through rather large variations in temperature. These extremes cause the roof membrane to shrink in cooler weather and expand in hot weather. And just like with our waistlines, all those changes can take their toll on the poor roofs, shortening their lifespans. Don’t mourn just yet, though, because there is help available; research shows that after installing a green roof temperature fluctuation dropped from nearly 80 degrees to just 22 degrees F, adding 20 to 60 years to its life.
- Another important benefit of green roofs is their ability to reduce and slow storm-water runoff in urban environments. Because rooftops and streets in cities are hard surfaces, the volume and velocity of storm-water runoff increases tremendously and is a major source of flooding and pollution worldwide. Due to the abundance of nonporous areas, a typical city block generates more than five times the runoff than a woodland area of the same size. The ability a green roof has to absorb (and filter) water significantly lowers the risk of flash flooding and sewer overflows. For wastewater systems that routinely discharge raw sewage after a rainstorm, this finding could turn a seriously unsanitary problem into something a little less disgusting.
- Besides the environmental and financial benefits of green roofs, there’s another perk that’s more difficult to quantify: the age-old pleasure of gardening itself. If you are one of the lucky ones, with the ability to safely and easily access your rooftop space, you may be adding another room to your home, where you can reconnect with the flora around you. Especially in urban areas — where farmland is rare if not nonexistent — rooftop gardens hold the irresistible promise of fresh fruits and vegetables, as well as quiet, green spaces for relaxation and recreation. And… AND… As potentially undisturbed habitats for ground nesting species that may struggle for survival in the ever-changing chaos that isthe large, progressive cities below.
So, given all the benefits, why isn’t every roof green? Although they are on the rise in the United States, green roofs are not nearly as common as in many other parts of the world, like Europe. Despite a list of positives a mile long, there is one expensive drawback… the initial cost. Green roofs will typically run two to three times more than a non-green one. That’s a lot of money to spend, even on something we know is SO good for us… Enter the green roof container garden, giving you all the pleasures and rewards of a green roof but at a fraction of the cost, much to the delight of urban gardeners everywhere.
Different municipalities have different degrees of permitting and other requirements before a roof garden or green roof can be installed. Many of these government officials, however, are coming to realize that all the positive attributes greatly outweigh the risks. It won’t be long before the city skyline is green as far as the eye can see… Fingers crossed.
At Plant Escape, we begin the Green Roof Container Garden installation with a consultation, determining your design and plant preferences; and how you’d like to personal your space with art, pathways, water features, living walls, etc. Then we design your Roof Top Garden within your budget and present it to you for approval. Our installation team is scheduled for a 1-2-day installation process and are available to maintain it thought out the year.
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Plant Escape is a professional plant design company specializing in a variety of plantscaping and landscaping services. As one of the few green roof garden designers in Denver, we are the best company to design and install a green roof garden for your location. You can count on us for quality service and design every time. Contact us today for a free consultation and estimate at 303.584.0496.