Aluminum Frames
Light, strong, durable, noncorrosive, and easily extruded into the complex shapes required for window parts, aluminum can be fabricated to extremely close tolerances to create special forms for the insertion of glazing, weatherstripping, and thermal breaks. Aluminum frames are available in anodized and factory-applied high-performance painted finishes that are extremely durable and low-maintenance (Figure 3-35).

The biggest disadvantage of aluminum as a window frame material is its high thermal conductance, which raises the overall U-factor of a window unit. Because of this, the thermal resistance of an aluminum frame is determined more by the surface area of the frame than by the thickness or projected area, as with other frame materials. Thus, an aluminum frame profile with a simple, compact shape will perform better than a profile with many fins and undulations.