WHAT IS A GREEN ROOF?
The vast majority of urban areas consist of asphalt, black tar and gravel-ballasted rooftops. Yet, there is a new trend that is quickly beginning to pick up, green roofs. A green roof is the roof of a building that is partially or completely covered with vegetation and a growing medium which is planted over a waterproofing membrane.
It may also include additional layers such as a root barrier and drainage and irrigation systems. This roofing system has been long used in Europe and has now begun to appeal to many homeowners, businesses and even cities everywhere as an attractive way to promote environmentalism while solving the problems of conventional roofs. It is a way of taking a neglected space and making it useful. Green roofs are also referred to as Eco-roofs, living roofs as well as vegetated roofs.
Green roofs last longer than conventional roofs, they absorb rainwater, reduce energy costs with natural insulation, create peaceful retreats for people and animals, and help to lower urban air temperatures and combat the heat island effect.
There are many environmental as well as financial benefits to having a green roof.
Green roofs reduce heating by adding mass and thermal resistance to the building as well as reduce cooling by evaporative cooling by fifty to ninety percent.
Green roofs also reduce storm water run off, create natural habitats for wildlife.
Green roofs filter out the pollutants and carbon dioxide out of the air which helps lower health issues such as asthma.
Filter out pollutants and heavy metals out of rain water.
Green roofs help insulate a building for sound; the soil layer aides in blocking out lower frequencies while the plants block out the higher frequencies.
Green roofs also provide agricultural space in urban areas.
Green roofs increase the life span of a roof immensely.
Because of the increased popularity and the benefits of having a green roof, the real estate property value increases.
There are two main types of green roofs; intensive and extensive.
Intensive Green Roofs are essentially elevated parks. They can sustain shrubs, trees, walkways and benches with their complex structural support, irrigation, drainage and root protection layers. The approximate weight for an intensive green roof is 80-150 pounds per square foot.
Extensive Green Roofs are much lighter compared to the intensive green roof weighing approximately 15-50 pounds per square foot.. Extensive green roofs support hearty native ground cover that requires little maintenance. They usually exist solely for their environmental benefits and don't function as accessible rooftop gardens as do intensive green roofs do.
One primary disadvantage of green roofs that tends turn away prospective clients is the higher initial cost. Some types of houses/buildings do not have the structural standards required to support green roofs and that is where the higher costs come in. Green roofs require professional design, careful structural analysis and multiple layers and systems. The fact is that installing adequate waterproofing systems and root barriers do increase the initial cost of the green roof, but seeing that a green roof protects the waterproofing membrane from the elements, primarily UV light, the life expectancy of the membranes doubles and sometimes even triples, making up for the initial higher costs. As the green roof industry begins to grow, one can expect the prices to drop.
Feel free to contact one of our knowledgeable green roof specialists with any questions you may have about green roofs.
Below is a diagram of the different layers within a green roof.