TowneBank’s newest “Green Roof” adds beauty and a host of sustainable benefits.  A recent drive through canopy addition, along with interior improvements at 4501 Cox Rd in the Innsbrook development of Glen Allen, VA presented the Bank with an opportunity to take the aesthetic advantage of a green roof.  A “green roof” or “vegetative roof” involves growing plants on top of the roofing membrane, thus replacing the impervious non-vegetated footprint with planted materials.  TowneBank utilized the installation of a green roof as an opportunity to reduce the impact of development, while providing abundant environmental, economic, and aesthetic benefits.  Green roofs can improve stormwater management by reducing runoff and improving water quality, mitigate the urban heat island, increase longevity of roofing membranes, reduce noise and air pollution, sequester carbon, increase urban biodiversity by providing habitat for wildlife, and provide a more aesthetically pleasing and healthy environment to work and live.

The interior and exterior improvements to the facility designed by HBA Architecture and Interior Design Inc. and built by Sussex Development improve and increase customer service with a new drive through canopy providing two additional drive through lanes, one providing twenty-four hour banking and ATM access under approximately a thousand square foot of green roof.  The green roof system utilizes a two foot by one foot modular planting arrangement, which employs a four inch thick tray, growing medium, and protective fabric, which sits on top of a traditional single ply membrane roof system.  The product is designed to exploit stormwater retention using an intelligent reservoir method; the reservoirs hold expanded aggregates that permit the release of stowed stormwater to the plants roots.  Planting for Green roofs are typically broken into two categories, Intensive and Extensive, depending on the plant material and planned usage for the roof area.  Intensive green roofs utilize a wide variety of plant species that may include trees and shrubs, require deeper substrate layers, require ‘intense’ maintenance, and are often park-like accessible areas.

In contrast, extensive roofs are limited to herbs, grasses, mosses, and drought tolerant succulents such as Sedum, can be sustained in a shallow substrate layer, require minimal maintenance, and are generally not accessible to the public.  The drive through canopy planting utilizes various varieties of Sedums that arrive pre-grown.  These hearty drought tolerant plants have been developed and cultivated for local climatic environments, they survive long dry spells, and they perform well in absorbing heavy rainfalls, with little maintenance after establishment.

While function and aesthetics were the driving factor around the canopy roof design, the mitigation of stormwater runoff is considered by many to be the principal advantage, because of the frequency of impervious surfaces in urban areas.  Rapid runoff from roof surfaces can exacerbate flooding, increase erosion, the larger amount of runoff also results in a greater quantity of water.  A major benefit of green roofs is their ability to absorb stormwater and release it slowly over a period of several hours.  In addition, green roofs have a longer life-span than standard roofs because they are protected from ultraviolet radiation and the extreme fluctuations in temperature that cause roof membranes to deteriorate.  The largest benefit to the TowneBank facility is the visually attractive landscape and improved views from the second and third floor offices and conference rooms that look upon the canopy.  The green roof provides a view and sensory connection to the unique ecology growing outside the windows throughout the seasons.  Since roofs represent a significant portion of urban areas, they provide a distinctive opportunity to employ these typically unused spaces to reclaim habitat that was lost due to construction while also aiding in the protecting of the environment through more sustainable practices.

~Michael J. Winner, AIA, LEED AP BD+C