by Adam Robins
Whether you’re upgrading the roof of your shed, or working on a large scale commercial project- Can you have your garden roof and your warranty protection, too?
For years the standard critiques of eco-roof systems have been centered on a few issues:
- How do they perform?
- What about maintenance?
- What about leaks?
Most architects have heard all or some of these if they’ve spent any time talking about eco-roofs with potential clients or the general public. If you’re a homeowner who’s been curious about eco-roofs, these questions may have crossed your mind as well.
On a trip to Los Angeles, I saw the L.A. Metro Division 13 Bus Operations and Maintenance facilities green roof system. I asked out loud, “I wonder what they used for the membrane.” I just happened to be standing next to a colleague of ours from Stantec, who was Project Architect for Division 13. “Oh, it’s a Hydrotech system.” He went on to explain that Hydrotech was able to warrant the system, providing LA Metro transit enough assurances that it would perform. He explained that Hydrotech warranted the assembly provided you met their requirements and used their components, all the way up through the growing media and the plants. If you’re working on a residential project, you might find that hiring a professional to build your eco-roof will offer you the same level of component capability and a warranty.
What should you consider when deciding whether or not to install an eco-roof? Every project, whether big or small, has its list of pros and cons. Here are some points to alleviate eco-roof concerns:
- Aesthetics: The benefit of being surrounded by garden-like settings.
- Longevity: Properly installed green roofs can double the life expectancy of a membrane as they tend to protect the membrane from UV and from temperature extremes.
- Cost: The installation costs are increased because of the added components. The long-term maintenance costs are reduced because of the protection from UV and temperature extremes. Energy savings result from the insulating effect of a green roof. The GSA puts the “payback” for a green roof at approximately 6.2 years for a 40 year green roof, vs a 17 year conventional roof (GSA Green Roof Benefits and Challenges, p. ii).
- Storm-water Management: For building owners with storm-water management concerns, green roofs are a way to help mitigate the effects of storm-water. From Multnomah County, eco-roofs offer “Mitigation of storm water runoff which causes flooding, increased erosion, and which may result in raw sewage that is discharged directly into our rivers. Eco-roofs can absorb storm-water and release it slowly over a period of several hours. Green roof systems have been shown to retain 60-100% of the storm-water they receive”
Fun fact: According to the fall 2019 Living Architecture Monitor, in 2015 Portland had a population of 570,000 and a total area of Green Roofs of 157,989 square meters. This put us above Copenhagen, Singapore, Toronto and Chicago for our area of eco-roofs per inhabitant.
For More Green Roof Information, visit:
https://www.hydrotechusa.com/assemblies/garden-roof-assembly (technical information, more often for a commercial application)
https://www.portlandoregon.gov/bes/44422 (general eco-roof information from the City of Portland)
https://www.portlandoregon.gov/bes/article/492807 (A DIY guide for those wanting to create an eco-roof on their own)