Green Roofs are totally green and totally cool! It has become pretty commonplace to see vegetation growing on the rooftops of commercial buildings throughout the Southwestern United States. Advances in technology have discovered ways to use the medium of soil and vegetation as a buffer between the hot sun and cool building as a means of reducing energy consumption for large commercial spaces. Green roofs can reduce energy consumption in these hotter regions by as much as 80%!* Obviously, the benefit is great in keeping buildings cool in hot climates.
But what about green roofs in cold climates? According to the same study, Liu and Baskran found a properly designed green roof can save as much as 20% in energy consumption by insulating the building against heat loss. Similar studies performed in Ontario by the National Research Council of Canada have found savings anywhere between 10% and 24% throughout the winter months. On an annual basis, this could reduce energy costs for commercial buildings as much as .09 cents per square meter.
Emphasis on “design.” One interesting nuance of this study showed that the green roofs that relied upon perennial vegetation (heat resistant grasses, perennial flowers, deciduous ground covers) did not perform as well, as compared to green roofs planted with evergreen plant material. The reason being that after the perennial dies back to the ground, the only insulating factor throughout the winter is the soil medium.
Is a green roof worth it? Any commercial building owner must look at the cost/benefit analysis of installing a green roof in New England. Are there tax advantages? What is the long-term payoff? It must fit into the company’s overall business strategy – financially and otherwise. Perhaps there are public relation benefits to being an industry leader in providing green solutions by making improvements to their building envelope – such as installing a green roof – that inspires others to do the same.
If you are a commercial property owner in New Hampshire, Massachusetts, Maine, or Vermont, who has considered sustainable solutions to your building envelope, call Terrain Planning and Design today for a free initial consultation.
*Thermal Performance of Extensive Green Roofs in Cold Climates,
Liu, Karen K.Y.
September 01, 2005