Thermography evaluation of defect characteristics of building envelopes in urban villages in Guangzhou, China

In many cities, the building envelope is deteriorating and aging. Understanding the defect characteristics of the envelope is essential to increasing the safety of the house and reducing the loss of energy. A 3-day infrared thermography (IRT) experiment was conducted on 5 buildings (11 rooms) in an urban village in Guangzhou, China. The analysis includes qualitative analysis and quantitative analysis. In qualitative analysis, three types of building defects were found, namely, conduction thermal defects, ventilation defects and moisture. In terms of quantitative analysis, (1) an improved temperature factor framework (ITF) is proposed to evaluate conduction thermal defects, (2) the influence of different influencing factors on the thermal performance of the building envelope is analyzed. Qualitative analysis results showed that conduction thermal de-fects were the most common thermal defects in Nanting Village and occurred 28 times in five residential buildings. It is mainly distributed in the joints of different walls and the joints of walls and other structures. Ventilation defects and moisture were the other two causes of envelope defects. Quantitative analysis showed that orientation has an important effect on thermal defects. The temperature distribution of walls at different heights is different to some extent. Thermal bridges are more likely to occur on extended floors built on the original building.