Finding Heat Loss & Missing Insulation

Heat loss only photographs well when heat is actually flowing. You want the biggest indoor/outdoor temperature difference you can get — 15°F minimum, 20°F+ ideal. Scan from the inside: in winter, problems appear as cold patterns on interior surfaces; in a hot summer afternoon with the AC on, the same defects appear warm instead. Same shapes, reversed colors.

An hour before scanning, close everything and let the HVAC settle the house. If the sun has been on a wall, discount what you see there or come back before dawn — solar loading swamps the subtle patterns you’re hunting.

Missing or badly installed insulation shows up as sharp-edged cold rectangles between framing — a whole stud bay that was never filled, or a batt that slumped years ago and now insulates only the bottom half of the cavity. The tell is geometry: insulation defects are bounded by studs and joists, so they photograph as crisp rectangles, not blobs.

Sweep every exterior wall, but spend extra time on the classics: the top corners of exterior walls, ceilings under attics, cantilevered floors, bonus rooms over garages, and any wall where an addition meets the original structure. Settled insulation reads as a gradient — warm at the top of the wall fading to cold at the bottom, like a half-empty thermos.

Air leaks look different from insulation gaps: instead of a bounded shape, you’ll see a streak or plume of cold trailing away from a joint — window and door frames, outlets and switches on exterior walls, baseboards, ceiling fixtures, and the attic hatch. That’s outside air physically moving into the room and washing across the surface.

Air sealing is the highest-return energy fix in existence — a tube of caulk and a roll of weatherstripping, no contractor required. Which is why it’s worth amplifying the signal: turn on every bathroom and kitchen exhaust fan for ten minutes before scanning. Depressurizing the house pulls outside air in through every gap, and leaks that were faint smears become vivid streamers.

Pull-down stairs and attic hatches are, in many houses, a square meter of nearly nothing separating living space from a freezing attic. On the thermal they’re unmistakable: a cold panel with a glowing cold halo where air sneaks past the edges.

The fix costs less than this rental — adhesive weatherstrip around the lip and an insulated cover box above. If your hatch lights up, that’s the first weekend project on the list.

On a cold day you’ll see faint, evenly spaced vertical stripes on every exterior wall — one every 16 inches. Those are the studs. Wood insulates worse than the fluffy stuff between it, so each stud conducts a little more heat and reads slightly cooler inside. This is called thermal bridging and every framed house has it.

Far from a defect, it’s a sign your camera and conditions are dialed in — if you can see the studs, you have more than enough contrast to catch real problems. (Bonus: you now own the world’s most satisfying stud finder.)

Rank what you found by area and severity: a whole uninsulated bonus-room floor outranks a drafty outlet. Air-sealing fixes are DIY-weekend material. Insulation voids are worth a contractor quote — bring your images and you’ll get a tighter, more honest estimate because there’s no exploratory guesswork in the bid.