Benefits of Native Roofs
In our experience, a Native Roof pays for itself in energy and roof replacement savings alone within 15 years. But there are many other valuable benefits of adding a native roof to your building. Additionally, we design our Native Roofs to:
require less maintenance and irrigation. When properly established, they can require no irrigation outside of drought events.
maintain their original design. Highly manicured green roofs are expensive to establish and maintain and can lose their original design as more dominant species take over and as native species are introduced through the wind.
provide habitat for native plants, insects and birds and support the native prairie ecosystem.
raise public awareness and understanding of our natural ecosystem.
Cities benefit significantly from green roofs (see examples of benefits below). It is estimated that over a 50 year period, green roofs deliver an average of over $38 per square foot in public benefits.
Native Roofs bring a wealth of benefits to building owners, the City, the community and the environment.
Conventional roofs act as heat conductors in warm weather; roof surfaces can reach temperatures of 70°C and higher. This heat transfers into the building (increasing air conditioning demand) and heats up the air above the roofs (increasing strain on HVAC units). Green roofs are able to maintain a more constant surface temperature throughout the day, close to ambient air temperature. Throughout the year, green roofs offer improved insulation which reduces heat transfer. The combined improved insulation and lower surface temperatures have been shown to reduce daily heat flow by 70-90% in the summer (vs a conventional roof) and 10-30% in the winter.
We recently completed a review of the energy savings resulting from our own green roof on our two-story Sun Alta building. We found that the green roof contributed to energy savings, reducing our natural gas and electricity bills by about $3,650 per year.
Increased Lifespan of Roof Membrane
Green roofs protect the roof's waterproof membrane from micro-tearing from extreme temperature fluctuations and weather related damage, such as hail damage and ultra violet exposure. Because of this, green roofs have been show to extend the lifespan of roof membranes from 15-17 years to upwards of 40 years. To put this in perspective, today's average waterproof membrane replacement cost is about $6.00 per square foot. On a 6,000 square foot roof, a green roof would save about $36,000 every 16 years.
Green roofs can contribute to the following LEED points:
Sustainable Sites: 4 possible points for new buildings 3 possible points for retrofits
Water Efficiency: 6 possible points for new buildings; 5 possible points for retrofits
Energy and Atmosphere: 21 possible points for new buildings; 18 possible points for retrofits
Increased Property Value
Studies have shown that properties with accessible green roofs are subject to an 11% property value premium. Neighbours with views onto a green roof could gain up to 4.5% of property value.
The added insulation from the soil and vegetative layer of a green roof can reduce overhead noise experienced in buildings near flight paths, bridges and other elevated transit systems. For example, a green roof with a 12 cm substrate layer can reduce sound by 40dB. At 20 cm it can be reduced by 46-50dB.
Tenant Enjoyment, Building Marketability and Goodwill
With increased public interest in environmentally friendly projects, green roofs can improve public opinion of a company or new construction and can increases a development’s exposure and enhances demand for its units. Green buildings can realize as much as 5.7% more rent than conventional buildings and may capture as much as a 2.5% rental premium. With improved aesthetics over conventional roofs that may add as much as 4.5% in property value to neighbouring buildings, Native Roofs are a good option for new developments as they can improve community acceptance of a project.
Making buildings more environmentally friendly may also contribute to talent attraction and worker productivity. Green buildings have been shown to have a benefit of $12 per square foot in terms of greater productivity and lower absenteeism. Additional research has found that office workers are 2.9% more productive when the view out of their office windows includes vegetation.