Full-scale field measurements under actual weather conditions are considered a realistic approach for the measurement of energy consumption and the assessment of building envelope performance. In this paper, a description of a simply constructed outdoor test chamber is presented; and the requirements for temperature, solar radiation, wind speed, and wind direction measurements are outlined. A simple experimental procedure for evaluating window energy consumption is described. Other aspects such as instrumentation, equipment, data measurements and recording are also addressed. Some of the field measurements obtained were compared with results from a transient three-dimensional heat transfer model and a good agreement was found.