12.3 Tools of the Trade: Infrared Camera

Imagine having X-ray vision for heat. That’s essentially what an infrared (IR) camera gives energy auditors. These specialized cameras detect infrared radiation—the heat energy emitted by all surfaces—and translate it into a visible image called a thermogram.

  • Cooler areas appear blue/purple/black
  • Warmer areas appear yellow/orange/red/white

Critical fact:

IR cameras do not see air—they only measure surface temperatures. When cold air leaks in, you see the wall surface getting cold, not the air itself. 

This works best when there is a large temperature difference between inside and outside temps (at least 20oF). This allows the camera to show bigger contrasts.

Carpeted stair leading to a white door with a thermal image overlay showing cold air flowing under a door.
Optical and thermal Image showing cold air entering below the door.
Text description of the optical and thermal image.

The image shows a carpeted indoor stairway leading to a white-painted wooden door. The stair has dark brown carpet, and the adjoining walls and door are painted white. There is a significant contrast in temperature depicted through a thermal view inlay within a circular border, occupying the right side of the image. This thermal section shows the stair and door area in vibrant colors ranging from deep blue and purple to orange and yellow, indicating cooler and warmer areas respectively. The temperature readout in the thermal view shows 45.3°F.

Credit: Adapted from n.a. “How to Look at a House like a Building Scientist (Part 2: Heat)” Building Science Corporation, December 2019.

What Thermography Reveals (With Real Examples)

  1. Missing or Settled Insulation
    • What you see: Large cool patches on interior walls/ceilings in winter (warm patches in summer)
    • Why it matters: Heat flows through the path of least resistance—uninsulated cavities become thermal highways 
  2. Thermal Bridging (When conductive materials bypass insulation)
    • Classic example: Steel studs in walls (steel conducts heat 300x better than wood!)
      • In winter IR images: Vertical blue lines tracing every stud
      • Real-world consequence: In one infamous Las Vegas case, cool steel studs caused smoke particles to plate out along every stud line, making the entire wall look like a barcode! 
    • Other bridges: Uninsulated concrete slabs, metal window frames, structural beams penetrating insulation layers

3. Air Leaks (Best seen with blower door testing)

  • Without depressurization: Subtle temperature differences at leak sites
  • With blower door: Dramatic black streaks appear where cold air is being sucked through gaps (windows, outlets, rim joists)
  • Pro technique: Auditors first scan the building normally, then depressurize it with a blower door fan and scan again—comparing "before/after" reveals hidden leaks

Go Deeper