Infrared thermography is an important and powerful technique for diagnostics and evaluation of building envelope, in terms of locating thermal bridges, damaged thermal insulation, air leakage, moisture damage, and cracks, all of which contribute to an increase in the energy consumption of the buildings. This is because typically the thermal gains or losses in practice are greater than those estimated during the design stage. Accurate and detailed information of where a problem occurs can reveal the source of the problem thus avoiding extensive renovation work and hence decreasing the cost of repair work and potential energy savings can be achieved. The present study is aimed at assessing the effective R-value of building envelope, using high definition thermal imaging technique.