R30/30 Roofing Systems

The roof of a typical commercial building has an average service life of 12 years and a thermal resistance (R-value) of 12h.ft2.oF/Btu. The goal of this program is to demonstrate the marketability of new roof systems that have an average service life of 30 years and a thermal resistance (R-value) of 30h.ft2.oF/Btu.

Issues
Compared with other portions of the building envelope, the roof is much less durable and less energy-efficient. Over the lifetime of the building, the average roof needs to be replaced four times. Over 75 percent of all roofing work in the United States, is re-roofing, and the second largest contributor to solid waste generation in the United States is roofing.

The two major factors that improve the energy efficiency and durability of low-slope roofing systems are moisture tolerance and wind resistance. Moisture leads to the premature failure of roofing systems by degrading the mechanical integrity of the insulation system, corroding metal components such as fasteners and metal decks, and adding excessive weight to the roofing system. An assessment performed by ORNL has shown that if low-slope roofing systems could be kept dry, over three-fourths of a quadrillion Btus of energy could be saved each year in the United States.

The second-largest contributor to premature roofing failure is wind. The insurance industry spends about ten billion dollars each year to compensate for natural disaster losses, most of which are caused by wind. Of this amount, approximately 50 percent of the money goes to replace roofs that have been damaged or lost because of wind.

Objectives

  • Develop an Internet moisture control design tool that will allow roofing professionals to design more moisture-tolerant roofing systems
  • Propose more energy-efficient and environmentally sound alternatives for current re-roofing practices
  • Investigate the reasons roofing systems fail during hurricanes and other major wind events

Research
At ORNL, we have been working on new techniques for incorporating into roof systems components that enhance drying potential. We have compared these new techniques with standard industry practices and have completed the design guide entitled Moisture Control In Low-Slope Roofing: A New Design Requirement. We have also collaborated with private industry on roof re-covering projects. This allows us to study and monitor the effectiveness of re-covering as a re-roofing strategy.

Several advanced concepts that could significantly enhance the thermal performance of roofs, such as highly efficient skylights, green roofs (vegetative cover), and the "electric roof" (photovoltaic cells as part of the roof surface), continue to be explored. We are currently seeking a partnership that will enable us to demonstrate the performance benefits and sustainability potential of a green roof for U.S. buildings.