MythBusters
MythBusters: Debunking Green Roof Myths
The folks at Roofscapes, Inc. have logged many hours on green roofs over the years – both in Germany and in the United States, and we have researched all types of green roof materials. We have seen – both in the lab and in the field – what works and what doesn’t. So, we thought we’d reserve this corner of our website to debunk what we consider to be myths in the marketplace. At the very least, we hope that these observations give you some food for thought.
- MYTH 1: Irrigation is essential
for green roof success
Well, no and yes. The requirement for irrigation will depend on the climate and the type of vegetation that must be supported.
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- MYTH 2: The most common reason
for green roof failures is inadequate moisture
Without doubt, when green roofs fail to thrive, the most common culprit is too much moisture.
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- MYTH 3: Fabrics can make good
moisture storage layers
Fabrics offer an effective method for intercepting and distributing water, but distributing water and storing water are two very different things. By their very nature, fabrics can never be very effective as water storage components.
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- MYTH 4: Modules are the lowest
cost, ‘tried and true’ method for green roof installations
Always keeping an eye on the young and dynamic U.S. green roof market, we’ve asked ourselves lately, “What’s with the modular-green-roof craze?” How do modules compare to the traditional German-style green roofs planted ‘in situ?’ (In situ installation involves assembling the green roof, layer-by layer, directly on the roof.)
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- MYTH 5: All green roofs are effective
replacements for open space
All green roofs can replicate open space (meadow) conditions for some storm events. Shallow green roofs will be effective in controlling small rainfall events, while deep assemblies may be required to control large storms.
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- MYTH 6: Green roofs are good insulators
By and large, green roofs are poor insulators. Most of the time, green roofs are heat capacitors; that is, they can absorb and release energy. The effectiveness of green roofs in managing energy is related primarily to two phenomena: 1) heat capacitance, and 2) latent heat of evaporation and freezing.
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