Thermography uses an infrared camera. Cold portions of a depicted surface are seen dark on an oscilloscope screen or on photographic paper. When this method is used in Sweden for building inspection, cameras sensitive to radiation in the wavelength range of 2–5.6 μm are utilized for determining the temperature distribution over wall and floor surfaces. By taking pictures (thermograms) in a building which has to be inspected, and by comparing them with pictures from a correctly constructed building of the same design, it is possible to assess insulation defects (poor insulation work, air leakage, moisture damage). Rules for interpretation of thermograms are drawn up at our institute. The climatic and other conditions necessary for getting reliable results are investigated. This method is now used as a routine instrument for building inspection. A proposal for an international standard in the field of thermography has been submitted to ISO.