Many of the main buildings at the three Department of Energy facilities on the Oak Ridge Reservation have been in place for 40 to 50 years and are showing signs of age deterioration in many structural components resulting in:

• Water leaks to the interior of the buildings
• Loss of structural integrity due to rust and deterioration of metal decking
• Reduced energy conservation (wet insulation loses its insulating ability)

To address effectively the repair or replacement of the roofs, a logical program of roof assessment and prioritization is required. This project assessed the utility of remotely sensed thermal data sets as a roof screening tool to direct on-site inspectors to suspect roofs and roof trouble spots to minimize cost and maximize efficiency of on-site engineering assessments.  Since the completion of the project all three Oak Ridge facilities have utilized this technique to assess roof integrity and to assist contractors in determining the location of leaks.

Airborne thermal imagery, acquired with a Daedalus multispectral scanner during both daytime and predawn hours, were subset for each building and rectified to a standard geographic coordinate system.  Each image was then visually inspected for indications of moisture, taking into consideration factors such as type and amount of roof insulation,  roof surface color and texture, and heat generating object inside the buildings and on the roof tops.  In gray-scale thermal imagery, temperature differences in roof surfaces are distinguished by brightness differences.  During nighttime dry building roofs cool more rapidly than free-standing water or saturated roofing materials.  As the image on the left illustrates, moist areas appear brighter (or warmer) than dry surfaces.   During the daytime dry roofing materials warm more quickly than wet areas.  Moist areas appear darker (or cooler) than dry area.  For each building moist areas were digitized as ArcInfo vector polygons for overlay on the thermal images, ortho-photographs, or geo-rectified engineering drawings.
 

In some cases graduated color scales were used to depict different thermal IR values.  With predawn imagery these scales show the lower values (cooler) in shades of blue, intermediate levels as shades of green, and high levels (warmer) as shades of yellow and red.