How Green Roofs Can Achieve LEED Credits
Green Roof Systems can help achieve LEED credits under five categories with a potential of 41 points total! Please note there are different versions of the rating system, each with different point totals. e.g., LEED 2009, 4.0, 4.1. Green roofs are ideal because they provide many environmental benefits and benefits for building occupants. To learn more about green roofs, check out our 3-part introduction to green roof series, where we cover the basics of a green roof, its benefits for building owners and occupants, and the different types and layers of green roofs.
What is LEED?
In the early ’90s, an entire movement around sustainable architecture started, which ultimately birthed the U.S. Green Building Council (USGBC). This leading organization promotes sustainability in building design, construction, and operation. The USGBC established Leadership in Energy and Environmental Design (LEED), the internationally known rating system and symbol for sustainable and environmentally sound buildings.
The LEED certification process involves detailed standards and guidelines, using a point system to score green building design and construction categorized into five areas:
Sustainable sites
Water efficiency
Energy and atmosphere
Materials and resources
Indoor environmental quality
There is also a bonus category called Innovation and Design Process. The point system awards buildings with four levels of LEED achievement: Certified, Silver, Gold, and Platinum.
Green Roofs as Sustainable Sites
Under LEED’s Sustainable Sites category, implementing a green roof can lead to six points. In this category, points are awarded to protect habitat and maximize open space, stormwater design, and heat island effect. Green roofs that include native or adapted plants provide wildlife habitats and promote biodiversity. The use of native or adapted plants requires minimal water use and is low maintenance. Green roofs reduce stormwater runoff by more than 60%. Green roofs also reduce surface temperatures, especially in cities affected by urban heat island. The USGBC suggests that a green roof must cover 50% of the roof’s surface to impact stormwater and heat island mitigation.
Water Efficiency of Green Roofs
The sustainable sites category touches on green roofs for stormwater design. However, the water efficiency category takes water reuse a step further. Implementing a green roof can lead to a potential credit of four points. In this category, LEED is looking for water-efficient landscaping reduced by 50% and no use of potable water or irrigation. It is essential to consider more drought-tolerant plants to ensure a green roof requires low water consumption.
Further, the same square foot of rooftop space can be with multiple systems stacked on top of each other. This can include but is not limited to green roofing on top of stormwater retention cells, a solution commonly used in ‘blue roofing’ systems. Managing stormwater in these retention cells can reduce or eliminate the need for costly cisterns. Much of the water held in these rooftop cells evaporate into the atmosphere. The rest is either slowly drained off or used for on-site irrigation.
How Green Roofs can use Sustainable Materials and Resources
The materials and resources category has the potential to award six points for a green roof. This category looks at recycled content and proximity to the manufacturer. Improve your building’s lifecycle impact by reusing building materials as resources for your green roof. To earn credits in this sub-category, 10%-20% of your components (pavers, edge treatments, compost, etc.) must be recycled from pre-and post-consumer materials to earn LEED credits. Cradle-to-cradle materials are available for green roof installations, including trays made from 100% post-consumer recycled materials taken directly from waste streams. Most commonly made from recycled plastic bottles.
Energy and Atmosphere Improvements with Green Roofs
The most influential category is Energy and Atmosphere, where green roofs can land up to 19 points by demonstrating how a green roof can improve a building’s energy efficiency. Green roofs help with building energy efficiency in two primary ways. Firstly, green roofs act as a natural insulator to reduce heat transfer, creating fewer temperature swings when heating and cooling the upper floors. This happens because plant leaves intercept the sun’s photons and use them for photosynthesis. As a result, this solar radiation is kept off the roof, reducing the energy consumption from cooling. The Vikings used to overturn their boats and cover them with sod to create impromptu insulated shelters.
Second, through evapotranspiration, plants naturally cool the air around them. The multiple plants on a green roof create a layer of cool air that, when taken in by rooftop air handling units (RTU), reduces the energy required to cool the air during summer. This reduced load even extends the lifespan of the RTU. For new construction, buildings with a planned green roof can even spec a smaller RTU, further reducing costs.
How Green Roofs Lead to Innovation and Design
Green roofs may qualify for innovation and design credits by improving the workplace environment and creating an educational laboratory or recreational space.
Urbanstrong will work with you to create the ideal green roof space for your unique needs. We will also ensure you secure all the incentives, tax credits, and financing available to improve your investment. Our team is LEED-certified and stays up to date with the latest from the USGBC.
