Yes, a thermal camera can help you locate a draft. It usually shows the surfaces cooled or warmed by moving air. It doesn't show the air itself, and a dark patch alone won't tell you whether the cause is a gap, missing insulation, a thermal bridge or moisture.
What a draft can look like
On a cold day, air entering around a window can cool the nearby trim or wall. Look for a streak or a patch that starts near a joint and spreads away from it. On a warm day in a cooled room, the same kind of leak can leave a warmer pattern instead. Start at the frame-to-wall joint, where the sash closes, and near the door threshold. Scan the surrounding wall as well, so you can see where the pattern begins.
| What you see | What to check next |
|---|---|
| A streak starting at a joint | Air leakage is plausible. Look for a gap or a change in the pattern as the wind changes. |
| Regular lines across a wall | Compare with the framing layout. Repeated lines can be thermal bridges, even in a wall that doesn't leak air at those points. |
| A broad patch or a cold corner | Compare with a similar section of wall. Insulation, building geometry and moisture are all possible explanations. |
A simple way to check a draft at home
- Start indoors with a steady temperature difference. Pick a time when the house has been warmer or cooler than outside for a while. Don't compare a sunlit wall with a shaded one. See when to scan a house for the right conditions.
- Scan the whole opening, then get closer. Compare the frame, trim and nearby wall with another opening of similar construction. Look at the frame and surrounding surfaces first: reflections can dominate the image on glass.
- Record the location and check a second clue. Take a normal photo as well. At an accessible joint, a light strip of tissue held near the suspected gap may reveal movement. Compare with a nearby joint and note any breeze from a vent. No movement on one pass does not rule out a leak.
- Repeat under comparable conditions. If you adjust a window seal and repeat the scan, use the same angle and temperature scale. Automatic color scaling can make similar temperatures look different.
When the camera isn't enough
A draft might be intermittent, or the air might not be changing the temperature of a surface you can see. A thermal camera cannot tell you how much air the house leaks. An energy auditor can use a blower door to measure whole-building air leakage and use thermography alongside it to help locate suspect areas. A cold patch near a pipe calls for a different check: see what thermal imaging can tell you about water leaks.
Do you need a specialist camera?
For a first look around accessible windows, start with a camera that can focus at your working distance and show the trim and nearby wall together. A phone attachment can be enough for this task. For a professional report, check that the camera can save the original thermal file and a visible-light reference. Open the selector for home inspections or read the home inspection buying guide.
Sources
- Fluke: energy auditing with thermal imagers — surface patterns, temperature contrast and blower-door-assisted inspections.
- Pacific Northwest National Laboratory: enclosure leakage test — what a blower door measures.
This guide is based on the documentation above. The cover illustration is not a field measurement. The Thermogram did not conduct a hands-on test for this article.