Obviously as designers of green roofs, we are very happy about the Green Roof Initiative being passed this week. But more so, the environmental and energy efficiency benefits of green roofs make for a no-brainer. For those who do not know, the Green Roof Initiative (Ordinance 300) mandates, “every building, building addition, and any roof replacement of a building, with a gross floor area of 25,000 square feet or greater, constructed after January 1, 2018 shall include a green roof or combination of green roof and solar energy collection.” Specifically, the total coverage of rooftop requirements increases 10 percent every 50,000 square feet, eventually capping at buildings of 200,000 square feet or more with 60 percent of the roof requiring coverage by gardens or solar panels.
So let’s discuss the benefits of green roofs, first, from an environmental perspective. Green roofs provide air quality benefits to the city by filtering particulates from the air in the same manner all green space does. They help to mitigate the effects of urbanization on water quality, often dramatically, by filtering, absorbing and retaining rainfall. And ultimately, from a non-human centric mindset, the green roofs restore biodiversity to the urban environment by returning green space habitats to the local ecosystem.
So now let’s discuss the benefits from an economic perspective. Denver’s status as of a 2014 study by Climate Central, found the city has the third-greatest urban heat island effect of any American city. An effect partially produced by the radiating of heat off rooftops and pavements. The only American cities that ranked higher are Las Vegas, Nevada and Albuquerque, New Mexico. (This is the raising of the temperature in the urban environment in comparison to the surrounding areas). In the summers, by implementing green roofs on the macro level, we can significantly reduce the overall heat index and our energy consumption used to cool buildings. (Urban heat islands are also affected by the reflection of the sun’s rays off the sides of buildings, particularly glass building. The effect can be so intense that it can actually scorch trees and grass. A problem ultimately, solvable with more use of green walls, but we’ll leave that initiative for another day, as we wait for green wall innovation to catch up and make more economic sense.)
On the micro, per building level, green roofs also work to insulate structures by reducing the amount of heat entering a structure in the summers and holding on to artificial heat from the inside in the winters. In addition, the green roof protects the top of the structure from hail damage and wear from the intensity of the sun, ultimately reducing repair and maintenance costs of the roof when compared to a standard roof. From and energy perspective alone, green roof have been found to provide a return on investment within five or six years in many cases.
And finally, from a social and psychological level, green roofs and green spaces in general, provide a mental health benefit called Biophillia. Those who get to enjoy the new view of nature instead of the concrete jungle have been shown to experience therapeutic benefits.
A green roof has a vast range of functional opportunity as well though. Green roofs can be made into community gardens, social spaces, recreational areas, and even meeting spaces in an outdoor setting. The initiative doesn’t have to be looked at solely as a dysfunctional space at higher cost but rather an opportunity, with the required addition of the structural integrity, to turn the roof into a usable space.
Unlike many environmental initiatives, this benefit doesn’t come from taxes at all, because the cost is up to the building owner who in the end is saved money by energy savings. The only people who don’t benefit from this proposal are large scale developers who simply want to build as much, as quickly, and as cheaply as possible to sell. That’s a mindset that hardly represents the best interest of the people of Denver, the ultimate consumer.