As more of our facility benchmarking clients trend toward environmentally sensitive building practices, we see green roofs growing more prevalent on public buildings.
Green roofs are said to be energy efficient but how does that claim stand up to benchmarking energy consumption comparisons?
In a recent survey, electrical consumption of thirty-three similar facilities was measured. Median consumption of the benchmarked facilities was 34.56 kilowatt hours per GSF. The client with a green roof (See Chart) disclosed energy usage at 28 which put them substantially below the median and within the first quartile of participants. We attributed their high ranking to be helped in part by their green roof.
How do green roofs save energy? There are multiple factors that contribute to the sustainability and efficiency of green roofs. First, the multi-layered roofing systems insulate the building against heat and reduce costs of cooling the building.
Secondly, the plants that make up the outside layer of the system protect the inner roof layers from UV rays. According to Intrinsic Landscaping, Inc, a leader in the green industry, UV protection can extend the life of your roof by 40 — 60%.
Another money-savings benefit is that a green roof significantly reduces storm water by absorbing and retaining rain water. Expert Dusty Gedge, co-author of The DIY Guide to Green & Living Roofs, maintains that green roofs can store more than half the rain water—and on some buildings, retention can go as high as 70 per cent. He cites the example of the green roof on Berlin’s Pottsdamer Platz development, which retains 50 per cent of the water and the remainder is harvested for the toilets and other uses in the mixed office and shopping center.
Green roofs are eco-friendly; they attract wildlife to urban areas by providing habitat and reconnecting wildlife corridors. Further, the easy-to-install systems absorb carbon dioxide and reduce radiant heat released from the roof into the local ozone layer.
There are many types of green roof systems, from as shallow as a 2″ growing medium to implementations with soil depths of 8″ or more that can support scrubs, bushes and trees.
Plant materials are available in:
- pre-planted trays that provide instant green roofs, (arrange trays of different colors of plants into interesting and changing patterns)
- pre-vegetated mats that look like rolls of sod and are delivered on pallets
- hydro-seeding that will produce mature plants in 12 — 36 months depending on environmental zone and climate
Any of these options are easy to implement. Have a pitched roof? No problem: green roof systems are available that hold soil on inclined roofs.
Adding a green roof is a great way to earn compounding LEED credits such as:
- Storm water Management Rate, Quantity, and Treatment
- Design to Reduce Heat Islands
- Water-Efficient Landscaping
- Energy and Atmosphere – Optimizing Energy Performance
- Recycled Content (roof system components)
- Local/Regional Materials (roof components and plants)
- Innovative Wastewater Technologies (Secondary Credit Impacts)
- Water Use Reduction (Secondary Credit Impacts)
Another client, Kevin Streiter, Manager of Facilities & Logistics of the High Museum of Art in Atlanta recently appeared in a CNN news feature on the museum’s green roof system.
“It will protect the roof both in the summer and winter, save money on energy consumption, and use storm water which otherwise would run off into the city’s sewer,” said Streiter describing the seedam tray roofing system. View the informative news article by going to http://www.cnn.com/video/#/video/tech/2008/06/20/barral.green.roof.cnn?iref=videosearch.
Not only are green roofs a sustainable solution for energy savings, but they are easy to install and maintain and offer an abundance of LEED credits. At Facility Issues, we expect to see more benchmarking around green roofs and their ability to lower energy consumption.