Thermal survey opportunities

Each day has two candidate slots: the three hours ending at sunrise, and three hours starting three hours after sunset, when solar heating has dissipated. A slot is good when the inside–outside difference is at least 10 °C (using the indoor temperature you choose), the mean wind is 7 mph or less with gusts under 22 mph, and under 0.5 mm of rain fell in the preceding 24 hours with none during the slot. It is usable when the difference is 7–10 °C, wind is up to 12 mph, up to 2 mm fell the day before, or fog or frost is likely. Anything else is unsuitable. These follow the conditions set out in BS EN 13187 for building thermography and our own BINDT Level 2 practice; the drone wind limit is for the thermal payload, which is heavier and more sensitive to vibration than a standard camera.

Test	Good	Usable
Inside–outside difference	10 °C or more	7–10 °C
Wind in the slot	Mean ≤ 7 mph, gusts < 22 mph	Mean ≤ 12 mph, gusts < 22 mph
Rain	Under 0.5 mm in prior 24 h, none in slot	Up to 2 mm in prior 24 h, none in slot
Fog or frost	Neither likely	Either likely (contrast reduced)

Sunlight warms masonry and roof coverings unevenly, and that stored heat masks the pattern of heat escaping from inside. Flying in the last hours before sunrise, after a full night of cooling, gives the cleanest picture. Late evening works once the fabric has shed the day's warmth, usually three hours after sunset.

Heat loss through a wall or roof scales with the temperature difference across it. Below about 7 °C the thermal camera sees noise; at 10 °C and above, missing insulation, thermal bridges and wet insulation stand out clearly. Keep the heating on overnight before the flight, and tell us the set-point so the images can be interpreted correctly.

Wet surfaces cool by evaporation and look cold whether or not heat is escaping behind them, so a wet roof produces false positives. Wind strips heat from exposed surfaces and flattens the contrast between good and bad areas. Light wind also matters for the drone: thermal payloads need a stable platform.

Postcodes are placed with the Office for National Statistics postcode directory via postcodes.io. The forecast is the Met Office Global Spot site-specific forecast for the postcode, in three-hour steps for the next seven days and refreshed hourly. Each window is scored on the three-hour step that best matches the pre-dawn or late-evening slot. Forecasts beyond three days are indicative; we re-check every window the day before we fly. Powered by Met Office data.

Radiometric thermal imagery of every elevation and roof slope alongside matching visual images, interpreted by a BINDT PCN Level 2 thermographer, with heat-loss hotspots, suspected wet insulation and thermal bridges marked up and delivered through your secure portal. Thermal surveys start from £700 + VAT as a fixed fee agreed before we fly. See the pricing page.