Understanding Infrared Thermography Reading 3

Figures 5.8 and 5.9 illustrate these distinct pattern differences. Figure 5.8
shows the distinct patterns caused by insulation deficiencies on the
thermogram of an exterior wall of a structure heated rom within, whereas
Figure 5.9. taken of a diffe rent structure under similar conditions. illustrates
the effects of air exfiltration. It should be noted that most structural
applications of thermography focus on qualitative features, such as thermal
patterns and thermal anomalies. rather than quantitative temperature
measurements. The only refe rence to temperature measurements was the
stipulation in ANSUASHRAE 101- 1981 that. forthe inspection to be valid,
"there shou ld be a minimum (difference) of 10 °C ( 18 °F) between the inside
and outside surface tempera tures of the building for at least three hours prior
to the survey." This stipulation was made presumably to establish quasisteady
state heat now thereby avoiding any misleading patterns because of
struclUral differences in heat capacity and rendering images. which more rel
iably represent only resistance di fferences. This standard has been
superseded by ASTM C-106O and ASTM C-1155.
Charlie Chong/ Fion Zhang