Sometimes, green roofs don't work at the level they were designed to. Possible failures include leaks, loss of plants, inadequate drainage, soil erosion, and slope instability. There are very few drawbacks, but the cost of installation is the main one. It will be more expensive to install a green roof than a traditional flat roof, as the underlying structure may need to be reinforced to cope with the additional load. Last May I was able to attend the conference of the International Green Roof Association in Hamburg, Germany.
As part of the conference program, we visited the small community of Wohldorf-Ohlstedt. This roof and other similar ones were built in 1943 in one of the three Norwegian settlements. The neighborhood was intended to be a social housing option for those in need, including former concentration camp prisoners. It later became a middle class suburb, and houses with green roofs became in demand, but rarely available.
The watering needs of a green roof are specific not only based on plant selection, but also on the local climate. I recently spoke with Casey Boyter of Casey Boyter Gardens in Austin, Texas, about designing green roofs for the long, hot Texas summers, where temperatures sometimes exceed 100 degrees Fahrenheit all summer long. The lifespan of residential green roofs is still largely undocumented, but some professionals say they can be twice as long as lifespan of a traditional roof. The green roofs of Rockefeller Center in New York City, for example, have the same waterproofing membranes that were installed in the 1930s.
Many semi-intensive green roofs house a variety of plant species, including native grasses and flowers. To offset the costs, irrigation water can be collected as rainwater, as is the case with the green roof in this photo. According to MacIvor research, green roofs provide the greatest benefit when planted with a diverse group of species that are adapted to local conditions. To help you decide if a green roof is right for your home or business, let's look at the advantages and disadvantages of green roofs.
The vegetation barrier helps protect the waterproof membrane underneath and ensures that the roof's lifespan lasts for decades. You should treat your green roof like a garden and, as such, you will need to water, feed and weed it. To withstand these harsh environments, most green roofs are planted with sedum, a non-native species that can survive wind and long periods periods without rain. An “extensive green roof”, on the other hand, is a thinner and lighter version that looks more like a standard roof.
A green roof installation will protect your roof from UV rays and acid rain, thus extending its natural life. People want aesthetically pleasing architecture and green roofs often play an important role in the overall design. There is no question about it, green roofs are heavier and, as such, require more structural support for their implementation. As you can see, with a green roof, implementing one has a lot more benefits, and as such, you should seriously consider the matter.
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