Green roofs can act as a layer of insulation, meaning they keep the surface temperature of the roof cooler in the summer and they can keep the interior of a structure warmer in the winter, thereby decreasing utility costs. The city of Chicago compared the surface of City Hall (which has been a green roof since 2004) and county hall- which is not a green roof there is sometimes up to a 70 degree difference in surface temperature on a hot summer day. See the results Measureable value?There is no easy calculation to figure out exactly how much the utility savings are with a green roof because it varies with the size and type of structure and regional utility costs. It is not as easy an equation as laying out an array of solar panels and watching your utility meter go backwards. However Lisa Goode of Goode Green who helped design the farm CBS News visited points out that there are several less obvious benefits that make the investment worthwhile. There is a priceless level of community involvement, there are opportunities to educate children about how vegetables are grown, where their food comes from, and perhaps start them on a healthier nutritional path. The social benefits over time, she says, are maybe the most bountiful fruits of such endeavors.
The soil on the ground in Greenpoint, Brooklyn leaves much to be desired for a farmer. The neighborhood has had a long history of oil spills flowing down Newtown Creek and even recently homeowners had concerns about toxic vapors rising up through the ground. As Annie Novak, one of the co-farmers on the nation's first commercial rooftop farm says "elevating" the plants was practical. While the roof farm we visited is an exceptional example, most green roofs don't fall into the same category.
There are "intensive green roofs," which means high maintenance and "extensive"- meaning far less maintenance. From fire stations to hospitals to homes, most of the major green roof projects are not intensive farms but more like passive gardens. If you'd like to search for projects across states and countries, by size and type, check out a great database at greenroofs.com.
What to do
Find a certified professional to help you out.
Green Roofs provides a database of vendors near you. You'll likely have to work with a structural engineer first to figure out if the roof you have can take the load. Next, depending on the level of your green thumb, decide whether you want something which you can visit every so often or something you want to actively tend.
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