This paper presents research results for better window materials for energy saving purposes. Three alternatives of glazing treatments were developed in this project: Cu2O, CuS + Cu2O, and Cu + Cu2O. The second and third alternatives present an adequate control in the infrared irradiance, achieving a significant reduction of the heat transfer through them. These windows allow the transmission of about half of the heat under hot weather condition, thus reducing the thermal load inside the building. The same windows also reduce the outwards flow of heat at half of the rate of windows without coating, improving comfort and reducing heat loss under cold weather conditions. The thin layers were produced using a sputtering technique with planar magnetrons. A high purity copper target (99.99%) was evaporated through plasma of argon-oxygen (70-30% respectively) in order to obtain Cu2O. Soda-lime glass substrates of 600 x 400 mm were used. About 50% of the infrared is blocked by the Cu2O window, when it is applied for thermal comfort. Thus, it was necessary to add another layer (CuS), which allowed a reduction of up to 20% in the NIR. The spectral behavior of the Cu + Cu2O window showed a transmittance of about 50% in VIS range, while in the NIR, the transmittance decreased from 40% to 20%. The composite windows, which contained CuS, Cu, and Cu2O are suitable solutions for solar control. Simulations of annual energy savings were carried out with the Energy-10 software for the Cu2O + CuS window for two cities, Mexico City and Mexicali, the latter representing extreme weather conditions (over 35 degreesC in summer and below 6 degreesC in winter). The total energy saving was approximately 20% of the total energy demand for Mexicali. Thermal transmission measurements were also carried out at the center of these windows, giving values of about 4 W/m(2) K. (C) 2003 Elsevier Ltd. All rights reserved.