Issues Associated with the Use of Infrared Thermography for Experimental Testing of Insulated Systems

Infrared scanning radiometers are used to generate temperature maps of building envelope components, including windows and insulation. These temperature maps may assist in evaluating components thermal performance. Although infrared imaging has long been used for field evaluations, controlled laboratory conditions allow improvements in quantitative measurements of surface temperature using reference emitter techniques.

This paper discusses issues associated with the accuracy of using infrared scanning radiometers to generate temperature maps of building envelope components under steady-state, controlled laboratory conditions. Preliminary experimental data are presented for the accuracy and uniformity of response of one commercial infrared scanner. The specified accuracy of this scanner for temperature measurements is 2 °C or 2% of the total range of values (span) being measured. A technique is described for improving this accuracy using a temperature-controlled external reference emitter. Minimum temperature measurement accuracy with a reference emitter is estimated at ±0.5 °C for ambient air and background radiation at 21.1 °C and surface temperatures from 0 °C to 21 °C.

Infrared imaging, with a reference emitter technique, is being used to create a database of temperature maps for a range of window systems, varying in physical complexity, material properties, and thermal performance. The database is to be distributed to developers of fenestration heat transfer simulation programs to help validate their models. Representative data are included for two insulated glazing units with different spacer systems.