MSP VISIONS

GREEN ROOFS: BEAUTY AND FUNCTIONALITY	September/October 2008

What is a green roof? In a nutshell, green roofs are vegetated roof covers which include plants, growing media, a waterproofing layer, and drainage. There are two types of green roofs: intensive and extensive. With a soil depth of a foot or more, intensive green roofs can sustain a wide range of plant species, but require substantial structural elements to support the weight, and require more maintenance. An extensive green roof has a much shallower soil depth (usually only 2 to 4 inches deep) and is planted with hardy, drought-resistant plants.
 
The benefits of green roofs are often underestimated. Their aesthetic appeal is only one of the numerous advantages they provide. Other benefits include:

Stormwater Detention
Using a green roof substantially reduces the rate and amount of stormwater runoff. The absorption of water by plants and soil minimize the scale of storm sewer systems. A green roof also acts as a filter, decreasing the amount of pollutants entering local water courses and streams.

Protection of Roof Membrane
A green roof can come close to doubling the life of the roof membrane beneath it.

Heat Island Affect
The plants on a green roof offer solar reflectance, controlling heat gain so that the roof’s surface temperature is typically nearly the same as the ground level.

Reduction of Dust and Smog
Filtering pollutants such as aerosol, dust and smog particles, plants enhance the quality of the air.

Reduced noise levels
A green roof can reduce the level of noise traveling from the exterior to the interior of the building through the roof by 10 decibels.

Insulation
The soil acts as a layer of insulation, in some cases reducing the amount of energy required to heat or cool the building’s upper story by 25-50%.

When the College of Mount St. Joseph installed a green roof on the Archbishop Alter Library in August 2008, it became the first green roof on a college building in Southwest Ohio. MSP provided architectural design services for the school’s new green roof, which contains approximately 8,880 plants.

“One of the best things we can do for our students and this community is to set an example by preserving the earth’s resources. Learning these lessons at the campus library is a great place to begin,” said Tony Aretz, Ph.D., President of the College of Mount St. Joseph.

Due to the weight restrictions of the existing roof, the Library’s green roof was designed to utilize a GreenGrid® modular system, which consists of light-weight trays made of 100% recycled plastic. The GreenGrid® system is also more cost effective, and has the added benefit of making it easier to address potential future issues such as roof leaks.

”We quickly realized that the weight restriction was going to be the driving force in determining the system to use,” recalls Dan Montgomery, AIA, LEED AP, Project Architect with MSP. “The ability to pick up and move the trays in case a repair was necessary was a huge added benefit.”

The completed green roof consists of 4,440 square feet of modules, each of which contain 8 locally-grown plants. The yellow flowers and blue foliage echo the College’s school colors of blue and gold. The center of the roof contains 177 modules filled with white marble chips spelling the schools initials of MSJ. This provides the potential to communicate the College of Mount St. Joseph’s presence to persons on flights arriving or leaving the Greater Cincinnati Airport.

The library roof at the College of Mount St. Joseph is a wonderful example of how a green roof can add value to a building by increasing its aesthetic appeal, while allowing the owners and occupants to enjoy the benefits of sustainable design.

For more information, visit the following links:

Green Roofs for Healthy Cities
http://www.greenroofs.org

International Green Roof Association
http://www.igra-world.com

Green Roofs: An Introduction with Pretty Pictures
http://www.ecogeek.org/content/view/902

The U.S. Environmental Protection Agency
http://www.epa.gov/hiri/strategies/greenroofs.html

Questions about green roofs or other sustainable design features? Call Randy Merrill, AIA, LEED® AP, MSP's Vice President of Architecture, at 513.759.0004.