An electrochromic device based on a five layer coating deposited on a glass sheet was produced. The layers were all obtained by physical vapour deposition in the same vacuum environment, using a commercial apparatus capable of producing thin films on large area substrates. Small (50 x 50 mm(2)) and medium (300 x 300 mm(2)) size specimens were prepared for preliminary study, to establish the electrochemical and optical performances of the device. Electrochemical measurements were performed on each active material, as well as on the whole specimens, in order to relate electrochemical properties to process conditions. Also, luminous and solar parameters were obtained from (near) normal incidence spectrophotometry in both the bleached and coloured states, to confirm the values used in the design phase of the electrochromic device. One of the specimens was also submitted to variable angle photometric and radiometric measurements, using an integrating sphere. This data was then used to evaluate the room luminance distribution and energy loads using a building simulation code.