Green, or vegetative, roofs are becoming more popular as sustainable design components. These roofs have several advantages over more traditional options. They minimize heat islands, reduce runoff into storm-water drains, provide excellent insulating values, and provide a green space for vegetation in large cities with limited green spaces.
They also can have disadvantages. Maintenance crews require training to inspect and repair them. Reflective walkways need cleaning.
Also, vegetation requires watering and care. In some cases, a landscape contractor — who now must be trained in fall protection to work on the roof — can be a better option for this task.
To make inspections easier, managers should consider specifying a tray system. Consider the Boston Children's Museum, which has more than 6,400 square feet of green roof made up of trays that workers can remove easily when inspecting and maintaining the roof.
If a green roof is an appropriate choice for a project, it might be best to buy an extended warranty from the company that installs it to ensure vegetation grows properly. This tactic also will provide more incentive for providing a quality installation.
Paving might not seem like a construction item that would cause problems. Concrete and asphalt are proven materials and require little maintenance for many years until they need replacing. But these surfaces are impervious, and runoff is an environmental issue. Large areas of asphalt are also heat islands, and sustainable projects need to minimize them.
To address issues with paved areas, more facilities are installing pervious concrete systems and interlocked paver systems. Once again, both of these systems can be effective at reducing runoff and heat islands if designed and installed correctly. But they also can become safety hazards and maintenance problems.
In my experience, the base is the most important variable with both systems. Pervious paving systems require adequate drainage underneath to divert excess water away from the paved area. Even fabrics can become clogged and prevent proper drainage. If interlocked pavers are not installed on a properly compacted base, they can become uneven and create fall hazards.
While the Occupational Safety and Health Administration (OSHA) does not call out a particular height, ASTM F1637-10 Standard Practice for Safe Walking Surfaces can be interpreted as setting 7/16 inch or less as the maximum elevation difference between two adjacent pavers. If the base was not properly compacted or the evenness not verified before acceptance, this situation could be a liability for owners and a nightmare for maintenance staff.
Another function of paved areas is to carry wheel loads of vehicles. From my experience, managers should be concerned about areas that require access for large emergency equipment and delivery trucks. At one location, we had to install signage in the parking lot limiting the weight of vehicles to 4,000 pounds.
In addition, the aggregate came loose and created a safety issue during mowing. At any rate, managers need to be aware of these potential issues and determine if alternate paving systems are more appropriate for the project.
Christopher R. Williamson, P.E., CMRP, CEM, LEED AP — cwilliamsonpe@gmail.com — works for Jacobs Engineering as a maintenance director for a large federal installation in Southeastern Virginia with more than 270 buildings. He has more than 20 years experience as an electrician, electrical design engineer and maintenance manager.
Achieving Sustainability and Maintainability in Facilities
Green Roofs, Paved Areas Emerge as Sustainable Design Components
