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Thermal imaging heat loss survey UK

Updated: 22 October 2026

You want to know whether the loft hatch or the window reveals are worth money before you commission works. A thermal imaging heat loss survey UK homeowners can do themselves is a walk-round in the right weather, read as a surface pattern, and then checked another way. It does not pass or fail Approved Document L. How to set emissivity and how to read the colour bar live on [how to use a thermal camera](/hub/measuring-equipment/flir-thermal-camera/sub/flir-thermal-camera-how-to-use). Which listing matches a house, a phone, or a boat is the [FLIR thermal camera comparison](/hub/measuring-equipment/flir-thermal-camera). The order of what to pay for is the [buying guide](/hub/measuring-equipment/flir-thermal-camera/sub/flir-thermal-camera-buying-guide). A qualifying purchase can earn a commission at no extra cost to you.

You want to know whether the loft hatch or the window reveals are worth money before you commission works.

Our top picks

Thermal Master Thermal Master Thor 002

Best overall

Thermal Master Thermal Master Thor 002
7.2/10about £359
View offer
GOYOJO GOYOJO GW192A

Best value

GOYOJO GOYOJO GW192A
6.4/10about £129
View offer
FLIR FLIR C5 with MR40

Alternative

FLIR FLIR C5 with MR40
6.0/10about £658.80
View offer
On this page
  1. 1.You need a gap, not a gadget
  2. 2.A cold, dry spell, and no sun on the wall
  3. 3.Inside as well as outside
  4. 4.A cold patch, a moisture meter, and Part L

You need a gap, not a gadget

Infrared shows a difference. If the inside and the outside are almost the same temperature, a well-insulated wall and a bare wall can look much alike. Which? uses a gap of about 10°C, with the home heated to around 19–20°C. RICS also looks for about 10°C and describes an internal target of about 20–22°C held beforehand. Those guides sit a degree or two apart. Use them as a reason to wait for a cooler day rather than as a pass mark. On a day that does qualify, walk the loft hatch, the window frame, the edge of a ceiling, and a radiator that is hot at one end and cool at the other. Write down the indoor temperature, the outdoor temperature, and the time.

A cold, dry spell, and no sun on the wall

UKTA describes UK fabric work as a cold, dry spell, typically from about September to May, with scans inside as well as outside, and a preference for the morning before the sun has loaded the walls. RICS often puts external work in the late October to March or April window, and prefers night so solar heat can leave. Wind above about 5 m/s is enough, in that RICS account, to spoil an external pass. NHBC wants you clear of sun, rain, and high wind. A south-facing brick wall at 4 pm can look warm because it has been in the sun, which the BBC has also noted. If you can only go out in the late afternoon, stay on the shaded elevation, or come back after dark.
Thermal Master Thermal Master Thor 002

Testsieger

Thermal Master Thermal Master Thor 002
7.2/10about £359
View offer

Inside as well as outside

UKTA cautions that an external hot spot and an internal cold spot are not automatically the same defect seen from two sides. Do both when you can. Inside, you control the heating and you avoid the solar load. Outside, you see the whole elevation in one go, which a phone camera with a wide field, such as the GOYOJO’s stated 50° view, covers in fewer frames. A loft hatch that glows cold against the ceiling, a mullion colder than the glass, a radiator tail that stays dark: those are patterns you can point at when you talk to a fitter. The FLIR M232 and the AX8 are the wrong chapter for this job. One is a marine pan/tilt, the other a fixed plant camera.

A cold patch, a moisture meter, and Part L

A cold patch is a colder surface. It can be insulation, a thermal bridge, or moisture cooling the face as it evaporates. The camera does not say which. NHBC is explicit that imaging cannot see through the fabric or measure the air, and that the pictures in its guide are not for judging compliance. Which? says the camera is not an X-ray. Confirm with a moisture meter before you pay for works. The MR40 pen that shares one C5 bundle is a contact meter. The thermal frame beside it is still a picture. Approved Document L is guidance on limiting heat loss in dwellings. Buying a camera does not complete that guidance, and a saved JPEG is not a new-build sign-off. Who should skip a row is best thermal imaging camera UK.

Common questions

What temperature gap do I need before I bother?
About 10°C between inside and outside is the figure both Which? and RICS publish. Which? talks about a home around 19–20°C. RICS describes about 20–22°C held beforehand. Those guides sit a degree or two apart. Use them as a reason to pick a cold day. A mild day with a 3°C gap will teach you very little about the hatch.
Should I stand outside, inside, or both?
Both, when the weather allows. Inside you see hatches, reveals, and radiators without solar load. Outside you see the whole wall, and UKTA warns that the outside pattern may not match the inside one. If you can only do one, do the inside with the heating steady. An external pass wants shade or darkness, dry surfaces, and lighter wind.
Why does a sunny wall look as if it is losing heat?
The bricks are warm because the sun has been on them, and the camera reports that warmth. Glass and foil add reflections of the sky and of you. Move to a shaded wall, or wait until the sun has left and the masonry has cooled, before you decide the elevation is a problem. A warm outside face in the late afternoon is stored sunshine.
Does a cold patch mean damp?
It means the surface is colder than the one beside it. Damp can cause that, and so can a gap in insulation or a concrete lintel. The camera does not see moisture through the wall. Use a moisture meter on the same spot, and ask a surveyor if the two disagree and the repair is expensive. The picture is the reason to look.
Does this image satisfy Part L or a new-build sign-off?
It does not. Approved Document L is guidance on conserving fuel and power, and NHBC says its thermal pictures are not a compliance judgement. Photographic evidence for a new dwelling is a set of ordinary build photos. Keep your frame for your own notes. Hand a dispute or a completion argument to someone whose report is written for that purpose.
When do I stop and pay a thermographer?
Stop when you are about to pay for insulation or damp works on the pictures alone, when a dispute needs a document, or when the question is live electrics. A consumer camera here is a walk-round. It sits outside UKTA’s electrical kit, and opening a consumer unit is live work. The boat camera and the plant camera are a different job.

Related pages

Thermal camera vs infrared thermometer

FLIR thermal camera

Best thermal imaging camera UK: who each listing fits

Thermal imaging camera buying guide: job, then pixels

How to use a thermal camera: emissivity, scale, focus

Sources

Public UK sources are listed below. Shelf prices and star lines are the amazon.co.uk figures captured with these eleven listings. The price bands are this set, not a market average.

  1. FLIR C5 (UK) (retrieved 20 October 2026)
  2. Which?: using a thermal camera (retrieved 20 October 2026)
  3. UKTA: building thermography (retrieved 20 October 2026)
  4. UKTA: electrical thermography for practitioners (retrieved 20 October 2026)
  5. Historic England: thermal imaging (retrieved 20 October 2026)
  6. Approved Document L, Volume 1, dwellings (retrieved 20 October 2026)
  7. NHBC: thermal imaging (retrieved 20 October 2026)
  8. BBC News: sun and reflections (retrieved 20 October 2026)