An important detail is that aluminum-clad wood windows are constructed with a heavy-duty vinyl liner which has the purpose of preventing water accumulation diverting it from the wood to the exterior; also frames and sashes of these windows have drip edges. Aluminum and wood surfaces have a seal barrier between them. Operating windows such as casements and awnings are sealed with a heavy-duty compression foam which provides a higher level of energy efficiency. http://www.joyfidentchina.com/aluminum-clad-wood-sun-room/