Uncertainty and method limitations in a short-time measurement of the effective thermal transmittance on a building envelope using an infrared camera

Buildings' thermal insulation has received a lot of attention these past years, in an effort to reduce the sector's high energy consumptions. A number of non-destructive methods have been used in order to evaluate in situ the building envelope's effective thermal transmittance, characterised, however, by long-lasting measurement periods. This paper examines the uncertainty and method limitations to use short-time measurements using an infrared camera for this purpose, but also within real environmental conditions that are inevitably unsteady during the measurement series. Experimental measurements were realised with three different infrared cameras, and the results show that a value of effective thermal transmittance could be estimated in situ by a relative uncertainty that does not exceed 20% (coverage factor = 2), a reliable estimation as long as all systematic errors are identified and diminished through calculations.