A Garden (& More) in the Sky

Planters, green roofs, and walled plantings, oh my! These things are part of what we call over-structure amenity design, and they are incorporated into a lot of buildings you enter daily. Whether they’re part of a multifamily residential building, a building on a university campus, or an office building, these green spaces create a sense of peacefulness and community while simultaneously contributing to a more sustainable environment.

Green roofs offer multiple benefits, both for the owner and building developer and for the community and building users. From the perspective of the building owner, the benefits include:

  • Extends the life of the roof

The materials that comprise the green roof protect the roofing system from direct ultraviolet radiation and extreme temperature swings, resulting in an increased life expectancy. The green roof can also require less maintenance, thus saving the owner money that otherwise would be allocated to maintenance costs.

  • Reduces heating and cooling costs

Plants and the green roof profile provide a thermal barrier, reducing loads placed on conditioning systems. Green Roofs for Healthy Cities – North America provides an online calculator that can determine the energy performance of a building with and without a vegetative green roof.

  • Reduces stormwater run-off

The plants and their soil mixture can capture a significant amount of rainwater, which lowers the run-off of substantial amounts of water during a rain event. An example of this is the Star Metals office building project we recently designed. The solution we created captured such a significant amount of stormwater that it offset the need for a planned cistern, saving the owner hundreds of thousands of dollars in construction costs. The total system storage for the 28,676 square foot green roof of the Star Metals building is 26,279 gallons retained and 56,491 gallons detained.

  • Provide development incentives

Incentives vary by city or jurisdiction, but many encourage “green” stormwater strategies, including green roofs. Some cities, such as Portland, Oregon, offer financial, technical, and educational incentives as part of their green roof initiatives. Other cities offer tax incentives or grant monies, and some even waive some fees when green roofs are incorporate into projects. Be sure to investigate and verify the specific programs offered by local municipalities and state agencies.

  • Offers commissioning credits

Green roofs are a strategic part of project design that can help garner many points when pursuing sustainable building certifications, such as a LEED certification. Under the LEED rating system specifically, a green roof can contribute points under several categories: Sustainable Sites, Water Efficiency, Materials and Resources, Energy and Atmosphere, and Innovation and Design Process.

  • Creates a usable and attractive amenity

It’s no secret that accessible green roofs are an attractive amenity. They’re located on a variety of buildings – office, healthcare, educational, residential, and more – and transform what was previously unusable rooftop space into spaces that are marketed as social gathering and special event spaces.

While occupants that inhabit buildings with green roofs also see some of the same benefits as the building owner or developer – such as reduced stormwater run-off and attractive amenity spaces – they also recognize some additional benefits:

  • Improved water quality

While we know that green roofs are a smart approach to manage stormwater run-off, they can also help to improve water quality. This can be done in a variety of ways, including the selection of plant species, fertilization, and growth media. Particularly in urban environments, a green roof reduces water run-off, simultaneously reducing the potential for combined overflow with sewage into local waterways. Furthermore, the rooftop vegetation filters pollutants from the run-off before reaching the local water treatment facility, resulting in cleaner water.

  • Reduces heat island effect

Because green roofs are covered in vegetation, they cover a dark roof. The plants absorb less heat than a dark roof and use solar radiation to evaporate water. The plants use heat to release moisture, which lowers the roof’s temperature. Green roofs can also reduce air pollution and greenhouse gas emissions. They cool the outside air down and help cool off the interior of buildings. As a result, the building’s air conditioning isn’t necessary, decreasing the amount of pollution that would have been produced, thus improving the microclimate.

  • Provides habitat and ecological benefits

Green roofs and vegetated walls are fast becoming tools to protect biodiversity and provide ecological benefits in urban environments. Years ago, green roofs began as engineering challenges, but they’ve evolved into lush urban landscapes that are home to butterflies, beetles, spiders, grasshoppers, and more. They also attract various birds, and some roofs serve as home to honeybee hives showcasing a solid commitment to sustainability and the environment.

  • Improves air quality

Improved air quality is closely related to reducing the urban heat island, as discussed above. Additionally, some studies have found that the air quality brought into a building through outdoor intake vents on buildings with green roofs is improved. For more detailed information on this study, The Science Times offers a detailed summary of a study in Portland, Oregon. Study Proves that Green Roofs Help Rid Indoor Air of Pollutants | Science Times

If you are interested in learning more about what an over-structure design can do for your development, contact Jennifer Ilkin to schedule a lunch and learn presentation!