Thermal roof inspection

Wet insulation holds heat longer than dry insulation. After a sunny day, as the roof cools in the evening, the wet areas stay warm and show up clearly on an infrared camera. Those areas are marked on the roof and on a plan, and the readings can be confirmed with a moisture probe or a small core where they need to be.

• Before a coating or recoat. Coating over wet insulation seals the water in. The scan tells you what has to be cut out first. See roof coatings.
• After a leak. The drip in the ceiling is rarely where the water got in. A scan maps how far it has spread.
• Repair or replace. If a small part of the roof is wet, it is a repair. If most of it is, the scan is the evidence that replacement is the honest answer.
• Commercial buildings and HOAs. A dated record of the roof's condition for a maintenance program or a capital plan.

Infrared works best on flat and low-slope roofs with insulation under the membrane: foam, built-up, modified bitumen and single-ply. It needs the right conditions, a dry surface after a sunny day, so the scan is scheduled around the weather. It is not much use on tile or shingle, where the standard inspection is the right tool.