When choosing window frames, we ask many times: what material to use? The fundamental to take into account when choosing the window frames is undoubtly the acoustic ans thermal insulation capacity. This is determining if we want to make an option based on the quality of the solution to use. The materials that are addressed here are wood, aluminum and fiberglass, although there are other alternatives. Nowadays there are some solution on the market that conjugate some of the most commun materials, such as wood frame lined with aluminum on the exterior. Opting for each of these materials has often to do with the aesthetic or economic aspect, given that each one of these materials have a similar thermal and acoustic performance. There should be always considered the use of double glazzing, with glasses of 6 and 4 mm and an air gap of 12mm. As such we’ll make a breif analysis of the material considering acoustic and thermal insulation: behaviour in relation to thermal and acoustic insulation: both a wood and aluminum with thermal cut and the window frame has similar behaviour; In the case of external window frames exposed to big climatic variations, follows that a better performance is achieved with the innovation of fiberglass window frames.