A Green Roof?
This a self-sustaining living rooftop. Photo courtesy of lotuslive.org
We've seen green colored asphalt shingles and we've seen roofs that are so in need of replacement that they are green with moss and algae. Perhaps we've even seen a roof or two with saplings on them, maybe they're 8 inches tall in the crevice of the lining between a dormer and the main sprawl of the roof. That's not the green we would like to see. However, writing for the crowd, we would like to believe that something a little more natural is possible for any component of our homes.
The history of green roofs is lengthy and in depth. Some research will tell us that green roof technology stems as far back as Babylon when King Nebuchudnezzar II, during the 7th century, offered the Hanging Gardens of Babylon to his homesick wife. But, more so on a regular basis, Scandinavians have been using green roofs for centuries. Using birch bark as an underlayment for protection against water, sod was stripped from meadows and laid on top of the bark for insulation.
As is usually the case, modern technology is derived from primitive forms of survival. Today's green roofs are no different, with the exception of extensiveness.
There are typically six layers after the structural support. These layers, in order from bottom to top, include:
- a water proofing layer that could be asphalt,
- a moisture retention layer that retains a portion of precipitation and retards major root growth,
- a drainage layer that allows excess water to properly drain,
- a filter layer that prevents soil particles from entering the drainage layer,
- a soil medium layer consisting usually of shale, pumice, sand and peat to reduce weight and then
- the plants, which are subject to the region.
Two types of modern green roofs exist and they are based on their medium depth.
- Intensive mediums are more than 6 inches in depth and can support trees and other large plants but expect much care.
- Extensive mediums are 6 inches or less and are more self-sustaining.
Great! Got through the fundamentals. But are they viable, affordable, doable, worthwhile her in WNY? Well, it just so happens that my family's home needs a new roof so I took it upon myself to get some information and a quote. FYI, there are no "green roof" installers in the Western New York area to my knowledge, and from the research I have done there are only a few in the northeastern United States.
Greensulate LLC, a company based out of New York City was my choice for an estimate. They have installed green roofs on Long Island, New York City, Los Angeles and San Francisco. Quite a resume. They were kind enough to send me a quote, the pros were included and the cons were between the lines.
The green roof Greensulate LLC proposed would improve insulation. Everything is relative so relatively thinking, the "improvement" would have to be comparative, hence the R-value. The R-value is the measure of the resistance to heat flow. The higher the R-value the better, as far as insulation is concerned. Furthermore, roofhelp.com claims that
- a concrete roof has an R-value of .3,
- wood an R-value of .91,
- perlite and R-value of 2.78 and
- asphalt (the most common in WNY) an R-value of .44.
Other benefits include
- the roof lasting three times as long as a normal roof,
- the cleaning and retainment of storm water runoff, and
- reduction of CO2 in the biosphere.
- They are beautiful to look at, by the way.
The drawbacks are less pronounced at first but speak loudly, if I may, in the forum for deliberation. The hindrances are numerous and need to be considered. For starters,
- the typical green roof with 6 inches of medium retains about 1.5 gallons of water per square foot. That is equivalent to about 12 lbs. per square foot of extra weight. Added expenses for permits and maintenance can add up. Oh yeah, and
- did I mention that my family's 2,000 square foot green roof , through Greensulate LLC, is going to cost us about $40,000? That's right, compared to an asphalt roof which would run me about $10,000. It's too bad that one needs so much green to be green.
Here is some good news for New York state, however. On Tuesday, June 24th 2008, the state passed a tax incentive program that will offer a $4.50 per square foot tax credit, up to $100,000, to anyone who installs a green roof. Wow, now that kind of makes it affordable considering that that's about 25% of the cost. Yeah, under the new legislation, owners of buildings residing in New York state cities with a population of at least one million people... oh... wait... isn't New York City the only city with over one million people in our state? Alas, good old New York state leaving us little folk in the dust!
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