By using a thermal IR camera we can literally see heat transfer through the building. It’s like x-ray vision for heat. You’ll be able to see wall studs and places where insulation is missing.

Built-out wall above fireplace. Innocent looking...

IR image of built-out wall showing either missing insulation or that behind the sheetrock is a stone chimney.

When used during the blower door test we are able to see where cold air is coming into the house:

Images of air infiltration causing cold areas (blues & purples). The top two are of the same window. Bottom left is an attic hatch. Bottom right is a door.