There is a trend that is growing in more ways than one: Green – as in living — roofs.
Green roofs refer to more than using solar panels or a certain type of equipment. It really means green: Erik Vickstrom, the lead consultant for Acceleration Advisors and author of “Energy Retrofits for Commercial and Public Buildings: Global Markets,” found that the use of the roof to host plant life is a growing trend worldwide. This is more than few potted plants: It includes inches of soil in which to grow the plant life and in some cases – particularly in Scandanavia –grazing animals. The report was published this month by BCC Research.
The energy efficiency benefits of the roofs are straight forward. “It’s a very energy-efficient technology that provides multiple layers of insulation that helps [to keep the] structure cool in the summer and warm in the winter,” Vickstrom said. “It provides a natural base of insulation to the structure.”
The trend is growing, especially in North America. Vickstrom, whose 262-page report looked at HVAC, Energy efficient lighting and design and electricity submetering trends, found that in 2015 the value of the North American green roof market was $130.1 million. It was $946.4 million in Asia Pacific (covering Japan, India, China, South Korea and Australia) and $3.6 billion in the U.K, Germany – the world leader in green roofs — and France.
The growth will be significant. A compound annual growth rate (CAGR) through 2020 of 34.9 percent will bring the value of the North American market to $582.1 million. The CAGR in Asia Pacific will be 25.4 percent to bring the market value of $2.9 billion. The three European nations will have a CAGR of 16 percent to reach $7.5 billion. The United States is growing faster than Canada.
It is difficult to compare costs of green to traditional roofs for a couple of reasons. The first, simply, is that there are so many variations of each. Not only are capital expenditures different, but they also age differently and must be upgraded or replaced at different points. Vickstrom said that a reasonable average of costs for a representative green roof in the United States is $15 to $25 per square foot. It is $6 to $10 per square foot in the three European countries and $5 to $12 per square foot in the Asia-Pacific nations.
The roofs consist of a water resistant membrane, soil and the vegetation that is being grown. A number of factors determine whether the green roof upkeep is “extensive” (requiring, for instance, only annual weeding and fertilizing), intensive (requiring irrigation and other regular types of upkeep) or somewhere in between, or semi-intensive. The soil depth will vary depending on the demands of what is planted and the amount of maintenance the building managers want to provide. Unlike a traditional roof, an appropriately maintained green roof has an almost limitless lifespan.
Vickstrom said that many of the green roof initiatives in the United States are done by facility managers or owners who are aiming for LEED certification, which awards the second most points for sustainable site-related issues. “Nearly all LEED [certified] buildings I contacted had some form of green roof, whether they are commercial high rises, universities, businesses or others,” Vickstrom said. He added that while there generally is some green roof component, it does not necessary cover the entire available area.
It seems that the commitment to a green roof is unlikely to be made in isolation. The roofs are far more likely to be seen as one element of sustainable entity. “Often, the green roof works in concert with other green elements of a building. For instance, rainwater hitting a traditional roof flows into gutters and eventually into storm drains. In a green roof environment, water that irrigates the plants, flowers or other living matter on the roof can be captured in a cistern. It is saved and used to water the roof during dry periods.
The ways in which green roofs can be implemented seem to be as varied as the ways in which fields and gardens can be configured on the ground. For instance, Vickstrom said that green elements need not involve the entire roof and can be a mix of flowers, plants, herbs, vegetation and even small trees. There also are modular systems that can be moved. The bottom line is that green roofs are far more than the placement of a few potted plants.
Evidence of the acceleration noted in Vickstrom’s research and the close tie between green roofs and the wider universe of energy efficiency and renewables is a new in France. Care2 reports that a new law requires that the at least half the roof of new commercial buildings be at least half green or half covered by solar panels. The business can choose either. The story notes that Greenroofs.org claims that a green roof can reduce air conditioning requirements by as much as 75 percent.