This study deals with the measurement of thermal bridges properties in building walls. The methodology is tested on an experimental wall built in laboratory. The setup thermal bridges transmission coefficients ψ and χ are measured in steady-state by infrared thermography. To do so, the thermal bridges impact factor I tb is calculated. In the proposed method, the value of the surface emissivity is not required: only apparent temperatures are used. Experiments proved good reproducibility. Calculations of the uncertainties enabled to identify infrared measurements as the main sources of error.