Some themal bridges will always exist, where parts of the building envelopes have reduced insulation thickness. A thermal bridge will cause a local area with lower inside surface temperature, where the condensation of indoor moisture risk to cause local high relative humidity, and further mould growth. In practice it is significant that the cold bridge is detected in the design phase, before the building is build, so the design can be changed, and the damage avoided. In order to find out where a thermal bridge will risk causing damage an evaluation method for Danish weather conditions will be introduced in the paper. The method is based on ISO EN 13788:2001 developed to evaluate critical temperature on the inside surface of buildings. Criteria for acceptable minimum surface temperatures for different indoor climates are introduced. Further the paper gives an example on the evaluation of a thermal bridge calculated by means of numerical simulation.