Applying Infrared Thermography for the Purpose of Identifying Concealed Wood Framing Member Type and Subsurface Anomalies with Intended Application Towards Historic Structures (2008-06)

Infrared thermography (IRT) has been in use for decades as a means of nondestructive testing. However limited research has been conducted on applying this technology towards historic preservation, particularly wood framed structures. Furthermore, hardware and information relating to this technology and its preservation applications can be difficult to obtain and interpret resulting in limited use by preservationists. Research conducted at the University of Kentucky through a grant from the National Center for Preservation Technology and Training (NCPTT) begins to address some of these issues.

Research primarily focused on wood and to what extent infrared thermography could assist in interpreting this material within historic structures for conservation, restoration and rehabilitation purposes. Because of woods anisotropic characteristics this proved to be a difficult task. Therefore, primary research was conducted to determine whether woods thermal characteristics varied enough among species that type could be distinguished within a wall system. Coinciding with this was a brief look at subsurface deterioration within wood samples and potential for identification within wall systems. This information is useful during work on historic structures as load capacities vary among wood type and deterioration levels. Determination of such characteristics can also prevent unnecessary destructive investigations resulting in more accurate and preservation friendly cost estimates.

Due to the nature of such testing, mainly the need to obtain results in the field from in-situ samples, traditional ASTM standards for laboratory testing of clear wood samples were not applicable. ASTM standards for IRT testing using passive methods were likewise not applicable as active thermography was employed. Therefore, new procedures and protocols were developed relying primarily on previous studies as well as successes achieved throughout the research process. The resulting protocols as well as results are therefore in need of further refinement, however they have provided the proof of concept necessary to continue and expand research into field testing and various wall configurations. Aiding in the interpretation of results and methods used during research are sections outlining basic concepts associated with infrared thermography, heat transfer and the thermal characteristics of wood.