Planting Down Roofs

  
In the course of your day how often do you look up at the skyline? Food, water, and shelter are the three elements of basic survival, and yet we do not spend much time thinking about shelter. Unless we are without it, it’s broken, or we are on an architecture tour, we tend to ignore the rooftops that populate our lives. With a few notable exceptions, like the movement from thatch to tiles to prevent fire hazards in 1212, based on an edict by King John of England, the evolution of roof technology isn’t that exciting. Things are changing however, and it’s time to start looking up, and thinking green.

A green roof (i.e., vegetated roof or roof garden) is a roof with vegetation planted over a waterproofing membrane. In Europe, green roofs are already abundant, yet their popularity is just beginning to grow  in the United States — particularly in crowded urban settings and cities. In Washington D.C., universities, advocacy groups, Federal Agencies, and condominiums are installing green roofs. Chicago has built one for its city hall, Philadelphia has installed them on schools, and Los Angeles on restaurants. They offer many substantial environmental and economic benefits, including:

• Reduction in a building’s energy, heating and cooling costs
• Minimization of storm water runoff,  city sewer fees, and the urban heat island effect
• Filtration of pollutants and heavy metals from rain water and from ambient air, including CO₂
• Extension of the life of a building’s roof
• LEED credits

What do green roofs mean in relationship to Deloitte?  Recommending that our clients consider installing green roofs on buildings is one example of the many ways we can help our clients achieve their sustainability objectives.  Helping our clients reach their greening goals is one objective I keep in mind while developing and defining the Energy & Natural Resource Management service offerings, as part of the Sustainability & Climate Change IMO. I’m not suggesting that we literally get our hands dirty and plant gardens on top of our client’s roofs, but we should be talking to our clients about how to take advantage of the benefits. And while it may seem backwards, starting at the top, by greening their roof, may be a great foundation for the rest of their sustainability efforts.

 
Greg Aliff
U.S. Energy & Resources Leader
Deloitte LLP

Comments

[Suzy Tonini]

Thanks for this post-great points on the topic of how one doesn't really think about roofs much these days, but your points are well taken and should definitely be included when talking to clients about greening their goals.

A few other benefits of green roofs are (and this is courtesy of HydroTech USA http://www.hydrotechusa.com/benefits.htm):

Besides being aesthetically pleasing, a green roof can provide numerous environmental, technical and owner benefits.

Ecological Benefits...

Mitigates Urban Heat Island:
Green roofs cool and humidify the surrounding air creating a microclimate which has beneficial effects within the immediate area.

Natural Habitat for Animals and Plants:
Green roofs create biodiversity, encouraging wildlife, such as birds, butterflies and insects, to remain within urban areas.

Reduction of Dust and Smog Levels:
Green roof vegetation helps to fi lter out dust and smog particles. Nitrates and other aerosol contaminants are absorbed out of the air and rainfall and bound within the soil.

Technical Benefits...

Storm Water Retention:
Depending on the design, a green roof can typically reduce storm water run-off by 50 to 90%. Additionally, the peak flow volume is greatly reduced and the peak flow period is delayed by as much as 4 hours, minimizing the impact on existing sewer systems.

Additional Thermal Resistance:
Green roofs can improve the thermal resistance of the roof
assembly throughout the year, especially in summer months by helping to reduce cooling costs.

Reduced noise levels: Typical extensive green roofs (3” - 4” growing media) reduce reflective sound by up to 3 dB and improve sound insulation by up to 8 dB. This is most effective with buildings near airports, factories or busy freeways.

Owner Benefits...

Increased Life Expectancy of the Roof:
A green roof, much like a PMR (Protected Membrane Roof ) Assembly, protects the roof membrane from climatic extremes and physical abuse, thereby greatly increasing the life expectancy of the roof.

Additional Usable Space:
Converting or designing normally unused roof areas into green roofs, simply makes sense. Increase your property value by reclaiming the fifth elevation of a building and make it an amenity to be used by the buildings occupants.

Building Incentives:
More and more municipalities and other government agencies are providing incentives that can help off-set the cost of a green roof.