Roofing industry experts predict that some 450 million square feet of ballasted roof installed from 1976 and 1996 will be in need of replacing within the next decade. On one such project, Bill O'Neill, president of Building Envelope Management Inc. of Boston, was hired by a building owner to look at a 225,000-square-foot combined warehouse and office building in Peabody, Mass.
O'Neill eventually recommended reroofing the building. This sustainable ballasted EPDM reroofing application was one of the largest projects of its kind in the United States, and it's an excellent model for the anticipated trend toward replacing potentially thousands more ballasted roofs in the future.
Consultant's Recommendations
A survey of the existing 225,000 square foot ballasted EPDM roofing system determined that it had been initially installed with 2.25 inches of fiberglass rigid boards, which had an R-Value of about 7.8.The sheets of EPDM were covered with 10 to 12 pounds of ballast consisting of round river stone. The roof has an effective low slope of 1/8 to 1/4 inch per foot to an internal drainage system.
The building owner reported that heat was radiating through the 112,500 square feet of roof into the warehouse portion of the building. The remaining 112,500 square feet of roof covered two stories of offices, for a total of 225,000 square feet of office space. To address the heat radiation, the building owner had installed a $150,000 sprinkler system on the roof to cool down the roof surface during the hottest portion of the day in summer.
"Instead of curing the disease, they were treating the symptoms," O'Neill said. Unfortunately, the treatment was not very effective because the PVC plumbing on the sprinkler system froze by the second or third year after it was installed. For the few years it did function, the building owner paid the additional charge on his water bill as the water for the sprinkler system went into the storm drainage.
The roof was 22 years old and three high wind events had passed through the Boston region since the roof had been installed without any reported wind damage to the existing EPDM roof. Some scouring of the ballast in the corners of the roof was observed,these problems were treated during the reroofing.
The roof was not in bad condition, and the membrane could have been repaired for 20 percent of the original cost of installation, about $56,000, and the owner could have gained another potential 10 years of service from the roof system, but he still would have been absorbing the cost of higher utility bills.
"That's what drove replacing the roof, not necessarily that the roof was in bad condition," O'Neill.
He recommended replacement of the membrane and the addition of 2.8 inches of 25 psi minimum polyiso roofing insulation in 4-foot by 8-foot panels with the joints staggered over the existing fiberglass boards.
The original roofing cost $1.25 per square foot to install at a total cost of $280,000. To replace the roof with additional insulation, new membrane and flashing, and reuse of existing insulation and ballast cost about $487,000.
Efficiency at the Site
The roofers with Capeway Roofing Systems of Westport, Mass., arrived in two crew cabs to avoid the dozen or so workers driving their individual pickups to the job site. The carpooling effort saved gasoline and reduced the impact that the job had on the environment.Work proceeded by first lowering 5,000 square feet of the ballast aggregate to the ground. The contractor did not want to risk damage to the roofing system from the weight of shifting the ballast to another portion of the roof. Once each 5,000 square foot sheet of EPDM was installed, the ballast was returned to the new section of membrane and the last sheet received the aggregate that had been piled on the ground.
An inspection of the existing fiberglass insulation after the membrane had been removed showed only minor facer damage, no gaps between the boards and no indication of moisture within the fiberglass.
The contractor saved approximately $125,000 on dumpsters and labor at the work site because the existing fiberglass was left in place. Only the plastic wrap on the polyiso and the original membrane needed to be taken away to the landfill, saving even more on refuse hauling costs. And because the existing insulation was reused, landfill space was conserved.
Additionally, the aggregate was reused in order to save further on the costs of reroofing and eliminate the environmental impact of quarrying the stone. If the aggregate had been quarried, 1.23 million tons of aggregate would have had to be transported 60 miles to the jobsite. The labor-intensive process of mining, transporting and hoisting the materials were also unnecessary because of reuse.
"For the next 100 years they will be able to use this ballast - now that's sustainable," O'Neill said.
Sustainability of the Roof System
The potential for longevity of a ballasted roofing system is just one way in which its sustainability can be calculated. The ballasted EPDM roofing system has only just recently been tested against cool roof membranes for its thermal performance.Dick Gillenwater, Carlisle SynTec Inc.'s manager of advanced projects, was part of a team of researchers who recently released a study comparing and contrasting the two types of systems.
It was expected that white roofs would provided substantially better energy efficiency for the building envelope because of its high reflectivity. However, the team found that a 10-pound ballast was within 30 percent of the thermal performance of the new white membrane, while the 24 pound ballast was within 5 percent, according to the company's study.
"What we've been finding is the mass of the ballast is working as a shield to the heat gain of the building," Gillenwater explained. He indicated that over time, the heavier the ballast, the more closely it performed like a white membrane in part because the white membrane losses some reflectivity from exposure to pollutants.
In addition, the heavier the ballast, the longer the aggregate prevented heat from radiating into the building envelope, and therefore a reduce in HVAC usage during peak times could be achieved. In areas where building owners pay a premium for peak energy usage, a ballasted roof can potentially provide owners with additional cost savings, Gillenwater noted.
Because this new research indicates that emmisivity as well as reflectivity need to be calculated, building owners and contractors working with existing ballast EPDM roofing systems now have more options.
Additional Incentives
Both recycled ballast and the additional layer of insulation are among the strategies for gaining potential credits toward LEED certification of an existing building or new construction.The added layer of polyiso insulation also will reduce the overall long-term energy consumption of the building.
An energy analysis using the independently developed energy and life-cycle software predicted a potential $1 million savings in energy costs with the new roof compared to the costs incurred with the new previous roofing system. The analysis assumed a 22-year period between roofs and an energy inflation factor of 5 percent.
The electric company in Peabody is municipally owned and therefore exempt from federal requirements that utilities provide incentives for owners who upgrade their buildings for reduced energy consumption.
However, the building owner was able to recoup some of the cost of installing energy-efficient polyiso roofing insulation through a cash incentive from the natural gas provider, Keyspan of Boston. The utility provides an incentive of 75 cents per therm in savings for building owners.
Energy consumption was further reduced when the building's HVAC units were replaced with units with reduced tonnage prior to replacing the membrane.
Because of liability issues, roof consultants often advise building owners and contractors to tear off a ballast roof system down to the deck. As the Peabody project shows, this can be avoided in most cases.
A roofing consultant will be better able to advise clients on the sustainable options available to them when consultants are able and willing and given access to gather more data about each individual roof before making any assumptions.
For example, tools such as thermograpy need to be utilized to determine whether moisture has entered the existing insulation. In other cases, a building history must be available and provided to the consultant. The ballast, for example, may contain broken glass bottles discarded by loiterers or sea shells dropped by aquatic birds to break open the shells as part of their feeding patterns. Ballast that contains glass or shells is not reusable, nor is insulation in a building with a history of a leaky roof.
The point is that site-specific conditions need to be examined and proper testing completed by a qualified roofing consultant in all cases before an investment in a reproofing project is made.
O'Neil, who was a founding member of the Cool Roofing Rating Council, believes educating others on sustainable roofing projects with an EPDM roofing system will help everyone in the roofing industry make an informed choice about roofing.
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