How Does an Infrared Inspection Work on a Commercial Roof?

Infrared (thermal) scanning is one of the most valuable diagnostic tools for commercial roofing. Here's how it works and why it matters.

The Physics Behind It

Water has a much higher heat capacity than dry insulation. During the day, the entire roof absorbs solar heat. After sunset, dry insulation cools quickly while areas containing moisture retain heat longer. An infrared camera detects these temperature differences — wet areas appear as warm spots on the thermal image while surrounding dry areas appear cooler.

When to Perform the Scan

Infrared scans must be performed at dusk (1–2 hours after sunset) on a clear day following several hours of sunshine. The contrast between wet and dry areas is greatest in this window. Cloudy days, recent rain, or wind can reduce the temperature differential and compromise scan accuracy.

What the Scan Reveals

The infrared scan maps wet insulation locations across the entire roof — not just where leaks are visible inside. This gives a complete picture of moisture infiltration that core samples alone might miss, particularly on large roofs where comprehensive core sampling isn't practical.

Limitations

Infrared scanning identifies wet insulation by temperature differential — but it doesn't distinguish between slightly damp and fully saturated insulation. Core samples are still needed to confirm moisture extent and severity in areas identified by the scan. The combination of infrared mapping plus targeted core samples provides the most complete picture of roof condition.