FAQs – Green Roofs and Walls


What is Green Infrastructure?

A 2013 American Planning Association defines green infrastructure this way. “At the city and regional scales, it has been defined as a multifunctional open space network. At the local and site scales, it has been defined as a stormwater management approach that mimics natural hydrologic processes.” The Green Roof and Wall Systems installed by Greensulate are integral to the overall site landscape that works to blend natural and human ecosystem processes to provide multiple benefits for people and their environments.

What is a Green Roof?

Green roofing is a natural, supremely efficient, history-tested insulation method. Green roofs are essentially a living extension of the roof construction. Green roof systems are made up of layers designed to mimic the many vast benefits of nature while providing additional benefits to buildings’ envelopes.

The first layer consists of a protective membrane that goes directly on the pre-existing roof followed by a drainage element, a filter sheet, a level of substrate, and then a layer of vegetation. There are three main types of green roofs: extensive, intensive, and hybrid (a combination of the two). Each green roof system, depending on the type, is full of possibilities. At Greensulate we are not a product-based company, but rather we stay up to date with all of the most recent and innovative products offered in the industry.

Will a green roof make my roof leak?

No. If your waterproof membrane/layer is in good shape (and compatible to a green roof installation), it will continue to be free from leaks once the green roof overburden is covering it. In fact, the protective layer the green roof provides, will extend the life of your roof,  and will not harm the waterproofing.

If I live in a dry climate, can I still have a green roof without irrigation?

The amount of water required can be controlled by the type of green roof installed. And, green roof plantings should be selected based on the climate, rainfall and other conditions of the area. In many places, irrigation is not required for extensive and some hybrid roofs. For example, many New York City green roofs do not need irrigation because it rains at least once a month. In San Francisco, it is possible to have extensive roofs that are irrigated by fog during the dry months (and perhaps supplemented by an occasional hosing.) But, for very arid climates, like Los Angeles and Phoenix, irrigation is required for months when there is no rainfall.  Ideally, the irrigation water can be provided through gray-water (non-potable) and often using rainwater harvesting strategies.

What is a Green Wall?

A wall that is partially or completely covered with vegetation. A green wall can be inside or outside. Green walls are also known as living walls. The soil and irrigation of the living wall can be either contained in the wall itself – in panel green walls – or in containers at the bottom or the top of the green wall.

What are the benefits of Green Walls?

Green walls in urban environments can reduce the overall temperatures of the building, reducing energy used for cooling. The plants absorb solar radiation from roads and surrounding buildings, and plant transpiration cool the building surface. Living walls also clean local air, provide a serene, green environment at the pedestrian level and can be used for urban agriculture and gardening. They are popular in Europe and Asia, and increasingly popular in U.S. cities as an amenity for urban residents, workers and visitors.

Are LEED credits available for Green Walls?

Green walls can contribute to several LEED credits when used in combination with other sustainable building elements:

  • Sustainable Sites Credit 7.1: Landscape Design That Reduces Urban Heat Islands, Non-Roof (1 point)
  • Exterior green walls reduce the solar reflectance of a structure, thus reducing the urban heat island effect.
  • Water Efficiency Credits 1.1, 1.2: Water Efficient Landscaping (1 to 2 points)
  • Buildings can incorporate a stormwater collection system for irrigation of the green walls and other landscape features. Using only captured, recycled, or nonpotable water may enable the project to achieve this credit.
  • Water Efficiency Credit 2: Innovative Wastewater Technologies (1 point)
  • Green walls can be utilized as wastewater treatment media. Other features, such as the incorporation of compost tea from a composting toilet, is another way for green walls to aid in the reduction of wastewater.
  • Energy and Atmosphere Credit 1: Optimize Energy Performance (1 to 10 points)
  • Green walls can provide additional insulation and natural cooling, which reduces a building’s reliance on mechanical systems.
  • Innovation in Design Credits 1-4: Innovation in Design (1 to 4 points)
  • Green walls may contribute to innovative wastewater or ventilation systems. ( Source http://www.bdcnetwork.com/6-things-you-need-know-about-green-walls)

How heavy is a green roof? Will my roof support the load?

A green roof’s weight is measured by “dead load” and this weight is determined prior to a green roof being designed. The dead load capacity of any roof can (and should) be analyzed using existing building plans or through an engineer’s inspection. The range of green roof loads starts at 10 lbs square foot (for a very light weight system) and goes up to as high as 250 lbs a square foot for a park-like green roof structrure such as NYC’s highline park. All weight estimates for green roofs are created using the fully-saturated projections of the green roof.

What are some of the benefits of Green Roofs?

Green roofs mitigate the negative consequences of highly urbanized environments. They absorb pollution, cool the air, absorb stormwater and act as a natural noise insulator. Furthermore, conventional roofs degrade over time due to membrane erosion from temperature fluctuations, UV radiation and damage from stormwater. Green roofs protect against all of this, extending a roof’s average life by approximately three to four times that of a traditional roof. They also provide thermal insulation, conserving significant amounts of energy usage. The benefits extend through a year’s cycle, as heat is retained naturally in the winter while also allowing a building to breathe and maintain a cooler environment in the summer.

There are many additional benefits; of particular importance is the reduction of carbon emissions. And by pairing a green roof with solar panels, the efficiency rate of the panels will increase as the green roof provides a cooling effect to the roof’s surface and will absorb pollutants in the air. Plants not only reduce toxins and improve air quality, but studies have shown that the presence of green spaces increases worker productivity and individual happiness and reduces stress. Many important players have stepped up to support the growth of this industry by providing incentives such as credits towards Leadership in Energy and Environmental Design (LEED) certification and tax abatements up to $5.23/square foot in New York City. In addition, the mere presence of green roofs or green walls can raise property values by up to 20%.