by Sarah Holland
When thinking of green roof technology and its advantages, one thinks of reducing storm water runoff, mitigating the heat island effect in the inner city, seeing a small green-growing paradise in the middle of an urban jungle, doing one’s part contributing oxygen and eating up CO2 at the top of a high-rise. Living and landscaping in a mostly rural area, urban being described in terms of villages and small towns, I did not expect to have the opportunity to plan and install a green roof.
The opportunity came my way in 2007 when a client of mine wanted to build a new residence overlooking a gorge beside the Mad River. He had always been interested in ecological and sustainable building techniques and materials, so the challenge of channeling storm water runoff away from the river as well as trialing one of the few residential green roofs in northern Vermont appealed to him. So I was privileged to be able to work with the owners and architects from the planning stage on. The building stage came in 2008 after a winter of reading, searching the internet, and talking with many professionals of many disciplines all over the country (green roof plant nurseries, manufacturers of green roof layers, manufacturers of engineered soil components, to name only a few). The experience was truly awesome. These people were very generous with their time and knowledge – all for the purpose of furthering the success of green roof technology.
We used plugs that were grown for us at a nursery that specializes in green roof plants.
The northern New England location presented challenges. Plant survival was a concern not because of the likelihood of hard winters but actually because of the in-between seasons of fall and spring, with uncertain snow cover, freezing and thawing, resulting in uncertain drainage.
The roof I was given as a site had wonderful drainage. River stone (the roof was engineered to carry this amount of weight) was installed per plan in the areas of drainage along the roof’s edge on the way to the down spouts, and it was also placed around the center monitors, both to catch that runoff as well as to provide a place for maintenance activity and equipment. In the summer months, the system worked flawlessly. The above photo (fall 2008) shows a copper downspout.
In the winter, the river stone heated up in the sun and the resulting snow melt was catastrophic — the client’s worst fear: a leaking roof. The spring of 2009 saw the installation of pipe to drain water away from the monitors and heating wire that keeps downspouts on the north side free of ice. The installed drainage pipe can be seen in the photo above.
The purpose of the roof was not for the client’s use, for relaxing or planting; it was for its technology and the view from the ground and road. It has become a popular place, however. The stepping stones that were solely for ease of maintenance have turned out to be a very useful – especially for the now frequent formal and informal tours of the roof.
The steppingstone are not really stones; they are actually a feature in themselves – cut-outs of rubber horse stall mats. The weight contribution of everything that goes on the roof must be considered.
This green roof installation experience has been of tremendous value professionally. It was a huge multi-year project that helped my business grow in new directions. The recognized areas of growth: learning how to work in a sub-contracting situation; co-operating with many skilled tradespeople on a project together; hiring and employing more than two people; incorporating SAFETY into my every work day; building confidence to take on other large and challenging landscaping opportunities, design as well as installation.
The roof continues to be a very exciting project, and I continue to learn. This year gave us a bumper crop of snails, and rising to this challenge gave me pause. This past week is the only time that I have brought a case of cheap beer to a work site…the snails aren’t picky. And I never knew that diatomaceous earth came in 50# bags!
Sarah Holland is owner of River’s Bend Garden Design in Moretown, Vermont.