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Guide

How to Use a Thermal Camera to Find Insulation Gaps

Missing, slumped or wet insulation leaves a cold pattern on the inside surface when heat is flowing out. A thermal camera makes the pattern visible in one pass around the house. This guide gives the conditions, the settings, the scan route and how to tell insulation gaps from the things that look like them.

By the Akermin Editorial Team · 3 min read

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Survey on a cold morning after the heating has run overnight, with at least a 10 °C inside-outside difference and no sun on the walls. Set the camera to a locked span of about 10 °C around room temperature, ironbow or grayscale, emissivity 0.95. Walk every room and image each exterior wall and ceiling square-on from 2 to 3 m. Missing or slumped insulation shows as cool areas larger than a stud bay and irregular in shape; thermal bridges as cool lines at floors, lintels and corners; air leaks as cool feathering at joints and openings. Photograph each finding in thermal and visible light and note its location for the contractor.

Conditions

  • Inside-outside difference of 10 °C or more, for at least 4 to 6 hours.
  • Heating on and stable; do not open windows for an hour before.
  • No sun on the surfaces being imaged in the previous few hours; pre-dawn or overcast.
  • Low wind; dry weather for a day.

Without these, defects fade into the noise. See why thermal images change with weather.

Camera settings

  • Manual span: roughly 5 °C below to 5 °C above room temperature; adjust once and keep it.
  • Palette: ironbow for the survey; grayscale for subtle patterns.
  • Emissivity 0.95; reflected temperature = room temperature.
  • Visible overlay on, for location.
  • Shutter (flat-field correction) before each room.

Scan route

  1. Start at the top of the house; ceilings under the loft show slumped or missing loft insulation as cold patches.
  2. In each room, image every exterior wall square-on from 2 to 3 m, then corners, then the junctions with floor and ceiling.
  3. Image around every window and door.
  4. Image behind radiators and inside built-in cupboards on exterior walls where reachable.
  5. Ground floor: image the floor near exterior walls for suspended-floor draughts.
  6. Loft hatch, service penetrations, recessed lights and extractor ducts.
  7. Outside, if conditions allow, image the facade for a second view.

What you will see

Pattern Likely cause
Wide cool bay between regular warm stripes Missing or absent insulation in that bay; the stripes are studs
Irregular cool patch on a ceiling Loft insulation moved, compressed or missing
Cool band along the top of a wall Slumped cavity or frame insulation; or an uninsulated wall plate
Cool horizontal line at floor level Thermal bridge at the floor slab or joist; suspended floor draughts
Cool line above a window Uninsulated lintel
Cool corner, vertically Geometric thermal bridge; normal but worse with poor insulation
Feathered or streaky cool areas at joints and outlets Air leakage; strongest with extract fans running
Cool patch with a defined wet edge, often below a window Wet insulation; confirm with a moisture meter
Warm lines Heating pipes and hot water runs, not defects

Confirming

Missing loft insulation can be confirmed by looking in the loft. Wall bays need a borescope through a small hole or a moisture meter if wet is suspected; see can thermal imaging find water leaks and thermal camera vs borescope. Air leaks can be confirmed with a smoke pencil or by running extract fans to depressurize the house and re-imaging.

Documenting

Save each finding with a thermal and visible image, room and wall identified, the span used and the indoor and outdoor temperatures. A contractor can act on “north wall of bedroom 2, bay between second and third stud from the window, appears uninsulated” and not on a dramatic orange picture alone. See what makes a good thermal image. Suitable cameras are in best thermal cameras for home inspection.

Flir C5 Compact Thermal Imaging Camera, WiFi, 160x120 MSX, Ignite

Flir C5 Compact Thermal Imaging Camera, WiFi, 160x120 MSX, Ignite

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Flir One Pro - Thermal Imaging Camera for iOS Smartphones (iPhone 15 and Newer w/USB-C), 480x360 Super Resolution (160x120 Native IR)

Flir One Pro - Thermal Imaging Camera for iOS Smartphones

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TOPDON TC004 Mini Thermal Imaging Camera, 240 x 240 TISR Resolution

TOPDON TC004 Mini Thermal Imaging Camera, 240 x 240 TISR

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Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.

Frequently Asked Questions

What temperature difference do I need to find insulation gaps?

At least 10 °C between inside and outside, sustained for several hours, with no sun on the walls. A cold early morning with the heating on overnight is ideal.

What does missing insulation look like?

From inside in winter, a cooler area in the shape of the gap: a whole bay between studs, an irregular patch where loft insulation has been pushed aside, or a cold band at the top of a wall where it has slumped.

How do I tell a stud from missing insulation?

Studs are regular, narrow vertical stripes at 400 to 600 mm spacing. Missing insulation is a wide bay between them, irregular in shape, and colder than the stud lines.

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