The Installation
The project targeted retrofitting an 11,900-square-foot metal roof on a 10,000-square-foot Security Forces building at Goodfellow Air Force Base.
Prior to the installation of the roof system, DOE’s Oak Ridge National Laboratory, Oak Ridge, Tenn., installed a data acquisition system to monitor various temperatures and heat information on the building. In addition to measuring energy data, the building’s utility billing information was collected. When the baseline of energy usage was established, installation of the retrofit metal roof system began in April 2012 and was completed in June 2012.
The integrated technologies were installed in the following manner:
- Structural purlins were installed over the existing metal roof.
- Additional insulation, using rigid insulation board, was placed over the existing roof to meet the current
code requirements. - A waterproof roof underlayment was then applied over the insulation.
- A radiant barrier was installed over the underlayment.
- An integrated solar thermal system using a closed-loop tubing array with a water/glycol mix heat-exchange medium was installed over the radiant barrier to optimize the heat transfer.
- The thermal purlin used to position the solar thermal system tubing is configured to allow for above-sheathing ventilation (convective cooling) to take place from the eave to the ridge.
- Panels of 24-gauge standing-seam metal roofing, prepainted with a polyvinylidene fluoride cool coating, were laminated with a thin-film PV system and then installed directly over the solar thermal system.