Tuesday, October 13, 2009

October 12 - More on the Green Roof

Over the Thanksgiving weekend - as the turkey was digesting - we were talking a lot about the green roof - and we answered many questions from friends and family about it. So, here, in no particular order are a few fun facts:

There are many benefits of a green roof, including:

  • Reduced energy costs. A traditional shingle roof can reach temperatures of 65 - 80 degrees C in the middle of the day, when the sun is hottest. The same roof covered with plants maintains a steady 15-20 degrees C . This is one of the biggest reasons green roofs drastically reduce air conditioning costs.
  • Green roofs last longer. Plant cover increases a roof's lifespan 30-40 years compred with a shingle roof which typically lasts 15-20 years. That's double. The soil used in a green roof acts as a screen against UV rays which account for 5% of a roof's aging. It also protects against thermal shocks (like when cold rain falls on hot shingles - and acts as a buffer against heat which disintegrates the oils in a typical shingle roof, making them brittle.
  • Better sound proofing: Studies show that a 15 cm layer of soil is enough to reduce sound polution by more than 45 decibles.
  • Improved air quality - the roof will help purify the air by neutralizing carbon dioxide and other gaseous pollutants converting them into oxygen - photosynthesis, like we learned in school! It also absorbs dirt, dust, pollen and other airborne particles.
  • Reduced water treatment costs. Not as much water rolls off a green roof, so there's less going down the drains. The water that does end up draining off the roof is filtered and much cleaner after draining from the plants.
  • Our installer said we might have the largest residential green roof in Ottawa (1450 square feet). There are many much larger commercial ones. The City of Toronto has mandated green roofs on all newly built city properties.
  • One more tidbit - an Environment Canada study showed that the presence of green roofs on just 6% or Canadian buildings would lower temperatures by 1.5 degrees, saving 5 to 6 % of energy costs (mainly through the need for less air conditioning).
  • Ok, the costs. We estimated that the green roof costs slightly less than double a typical shingle roof. There are also costs associated with yearly maintainence, if you choose to do it that way (we did, the husband isn't a massive fan of heights. Sorry, I stand corrected -he is ok with heights, it's falling he doesn't like.) Even so, the extra cost is worth it given the longevity and benefits.

If you want to find out more, give the topic a Google or check on Environment Canada's site. When the husband looked into it, he said there was a ton out there.

Oh, and as you can see from the photos in the previous post, we also have some solar panels. These will only heat our hot water for now, but we can expand the capacity in later days and plan to do so.

And that's the end of the educational side of our program ...


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