In class when were brainstorming ideas for our symposium project green house roofs were a possible topic. I decided to further research the idea and find out why they are beneficial.
I found and article that talked about how experiments were conducted. The National Research Council of Canada (NRC) and the University of Central Florida conducted two separate studies. The NRC designed a 800 square foot roof that was divided into two parts. One of the parts had a bare waterproofing membrane and the other part of the roof made out of the same waterproofing membrane was covered by a green roof made of six inches of lightweight soil and wildflowers. The University of Central Florida divided a roof into two sections also and but they covered half of their roof with plant vegetation native to Florida and six to eight inches of lightweight soil.
Theoretically green roofs are suppose to lower roof temperatures, better absorb rain water, and protect roof tops. The two experiments proved these theories to be correct. On one hot summer day in Ottawa the temperature was recorded to be 95 degrees F. The regular part of the roof reached 115 degrees f while the green roof only reached 77 degrees F. Similar results were found in Florida. The maximum average everyday temperature for the rooftop in Florida was 130 degrees F where the average temperature for the green roof section of the roof was only 91 degrees F which was about 22 degrees F lower.
This is a green roof that was planted on top of Tarkinton Elementary School in Chicago.
The green roofs also proved to lower the amount of energy demanded for the buildings of the roofs. The experiment in Canada proved to reduce the energy usage by 75%. The roofs also proved to delay the runoff time after a large storm.
Well, you may be asking if green roofs are this beneficial then why aren’t there more of them. The answer is quite simple….they are very expensive at first. According to Seattle’s King County Government, “The cost of green roofs is about $14 to $25/ft² ($150 to $270/m²), including waterproof membranes.” After about 40 years the cost of a green roof compared to a regular roof is only about 10% higher. And if you consider how much money you could save on heating and cooling then I’m sure that it would probably cost less. The long term benefits far exceed the financial burden of building a green roof.
I also discovered that there is a green roof conference. The Fifth Annual International Greening Rooftops for Sustainable Communities, Conference, Awards & Trade Show is being help in Minneapolis, Minnesota on April 29, 30 and May 1. This conference according to its website has three main focuses for the conference. They are “1. Policies and Programs to Support Green Roofs
2. Green Roof Design and Implementation
3. Research and Technical Papers on Green Roof Performance.” This conference is dedicated to advancing the technology of green house building as well as rewarding people who have helped advance the cause. For more information about this conference visit the website http://greenroofs.org/minneapolis/
Sources: http://greenroofs.org/minneapolis/
http://www.wonderquest.com/green-roofs.htm
image; (AP Photo/Nam Y. Huh) http://accuweather.ap.org/cgi-bin/apl.pl
This is really interesting and I’m glad you blogged about it because I didn’t really know what it was either. This sounds like another great solution to reduce the amount of energy that we use in our world. It’s too bad that it’s expensive at first though because I bet that discourages people from trying it out. However, if more people find out about how beneficial it is in the long run then hopefully they will be incouraged to invest in a green roof.