This paper deals with the development of a diagnostic testing and calibration system for infrared imaging equipment used in building analysis. The purpose of the research, conducted between 1982 and 1985, was to investigate, measure and document thermographic equipment performance under conditions in which building science investigations are carried out. The research focused on obtaining calibration data collected under a wide range of repeatable, laboratory controlled and simulated climatic conditions. Three hundred tests on twelve government owned thermal imaging systems were conducted. It was found that while object surface temperature played a more significant role than environment in the accuracy of temperature measurement, scanner drift increases as environmental temperatures increase. Of significance was the finding that the calibration curves used prior to this research did not accurately predict measurements in Canadian winter climate, particularly on surfaces below OoC. Of additional importance, was the discovery of other curve fitting formula for predicting instrument performance which is more accurate than the previous used. Although tested equipment was owned by one entity which may have biased results due to use, care and high level of preventative maintenance, significant variance was found in comparison of similar thermographic systems. The findings of this research will also benefit the private sector, provincial, and foreign governments their agencies and standards organizations.