Greenroofs are coming of age. Ironically, our ancestors have long used greenroofs. Most of popular of which are the hanging gardens of Babylon. Original inspiration came from Iceland as sod roofs and walls were used traditionally for years and used in all Scandinavian countries.
People usually say, “The grass is greener on the other side.” But the advent of greenroofs, it’s more like “the grass is greener on the neighbor’s roof.”
The first time I saw a house with a greenroof, I was enthralled. I used to see this sight only in pictures in history books. But to actually see one in Europe was wonderful. Today, in cities like Chicago and Toronto, greenroofs are sprouting on building tops. Riding on a plane, it is a pleasant surprise to look down and spot a thatch of green amongst the cement jungle.
Greenroofs are coming of age. Ironically, our ancestors have long used greenroofs. Most of popular of which are the hanging gardens of Babylon. Original inspiration came from Iceland as sod roofs and walls were used traditionally for years and used in all Scandinavian countries. Sod was not used just for its aesthetic benefit but rather through necessity, people didn’t have anything else to use except sod and stone to build their houses. If driftwood were available, these would be used as timbers as seen in church architectures, oldest of which is the church at Vidimyri, Iceland built in 1834.
Technically, greenroofs find their modern origins in Germany- some 30 years ago. Today they are very popular in Europe because of their environmental benefits. Due to government legislative and financial support, greenroof technology has been well established creating a multi-million dollar market for countries like Germany, France, Austria and Switzerland. Germany boasts of an average population growth of 15-20% since 1982 and a total of 10 million sq. meters of greenroof construction since 1996. In the US and Canada, the greenroof technology is in its infant stages as the technology is poorly understood and underrated. Green roof technologies benefit the owners of buildings with a proven return on investment. The green roof also provides social, economic and environmental benefits for city dwellers as well.
Greenroofs provide many practical benefits such as cooling the air within and without a house or building. Consider the temperature of an ordinary apartment rooftop, which can go up as high as 140 Fahrenheit, “hot enough to fry an egg.” Suzanne Elstone writes, “This heat creates tremendous updrafts, circulating tiny particles that can clog lungs. The additional heat increases the need for electricity production, which further adds to air pollution.” Inside a house with a greenroof, temperatures are at least 3 to 4 degrees C cooler than the air outside even as outdoor temperatures range between 25-30 degrees C. On a summer day, the temperature of a gravel roof can go up as high as 25 degrees C, to between 60-80 degrees C. Covered with grass, temperatures within the house would not rise above 25 degrees C, thus resulting in energy cost savings on air conditioning.
The greenroof itself is guaranteed to heat up only to 77degrees Fahrenheit thus abating city smog and reducing energy consumption. “A 3- to 7-degree temperature drop translates to a 10 percent reduction in air conditioning requirements. For a one-story structure with a green rooftop, cooling costs can be cut by 20 percent to 30 percent.”
Greenroofs don’t just filter the heat and smog; it insulates you from sound as in traffic, machinery and airplane sounds as well. A 12 cm substrate layer greenroof can reduce sound by 40 decibels while having a 20 cm substrate layer can reduce sound by 46-50 decibels.
Western Design Consultants report that if Chicago greens all its rooftops, a $100 million savings in energy consumption is achieved. “Peak demand would be cut by 720 megawatts – the equivalent energy consumption of several coal-fired generating stations or one small nuclear power plant.”
Greenroofs would likewise retain storm water by 50-70% and act as natural air filter as well. “In summer, greenroofs retain 70-100% of the precipitation that falls on them; in winter they retain between 40-50%.”
Social benefits range from the aesthetic to providing health and horticultural therapy, improving safety, providing recreation and community building. Studies on patients in the same hospital, recovering from the same operation, showed that when they were exposed to views onto a landscaped courtyard versus a brick wall, “the patients with the green view had shorter post-operative stays, took fewer strong painkillers and had fewer negative evaluation comments from the nurses.”
Economic benefits include creating jobs for so many people, providing significant, long-term savings for the home or building owner as well as for the community. “Green rooftops last twice as long as standard roofs, reducing maintenance and replacement costs.”
Green rooftops are easy to construct. Flat roofs are replaced with carefully engineered layers. One would need first a reinforced roof structure. A water and root -repellant membrane is then installed on top of that. A drainage layer separates the plant or grass from the underlying membrane. To keep the drainage layer from being congested by the plant, a filter cloth is installed. Greenroof technologists advise to choose the plant to be as light as possible and yet able to support growth.
On the whole, greenroofs are a blessing to the inhabitants of the cement jungle. My family would regularly go off in the weekends to drive into the countryside to get a whiff of fresh air and relax our eyes, ears, body and mind as we feast on the colorful vista of the countryside. Now we wouldn’t even have to do that with greenroofs installed in our house, condo or building. We would have the countryside right at our fingertips or should I say, right above our heads.
On the whole, greenroofs are a blessing to the inhabitants of the cement jungle.