Thermographic surveys of buildings are typically carried out in the winter months when building's heating system is operating and there is a suitable internal-to-external temperature difference. To limit the effects of solar gain, building surveys are carried out at night or the early hours of the morning to ensure any radiation from the sun has suitably dissipated avoiding unreliable results from the survey.
To achieve a reliable result from the survey, preparations need to be made to ensure the building fabric has been sufficiently heated and that there is a minimum internal–to-external air temperature difference of 10°C both prior to and during the survey. To achieve this, the heating should be in operation a few days preceding the survey to heat through the building fabric.
On the day/night prior to the survey, the heating should be set to run constantly throughout the night at a temperature that will achieve a minimum internal–to-external air temperature difference of 10°C. To assist in maintaining the temperature difference throughout the building, all windows/doors should be kept closed as far as is practical prior to the survey.