Each frame material has its advantages and disadvantages. Though ideal for strength and customized window design, aluminum frames conduct heat and therefore lose heat faster and are prone to condensation. Through anodizing or coating, the corrosion and electro-galvanic deterioration of aluminum frames can be avoided. Additionally, the thermal resistance of aluminum frames can be significantly improved by placing continuous insulating plastic strips between the interior and exterior of the frame. Wood frames have higher R-values, are not affected by temperature extremes, and do not generally promote condensation.
Wood frames do require considerable maintenance in the form of periodic painting or staining.
If not properly protected, wood frames can swell, which leads to rot, warping, and sticking. Available in a wide range of styles and shapes, vinyl frames have moderate to high R-values, are easily customized, are competitively priced, and require very low maintenance. While vinyl frames do not possess the inherent strength of metal or wood, larger-sized windows are often strengthened with aluminum or steel reinforcing bars. Fiberglass frames are relatively new and are not yet widely available. With some of the highest R-values, fiberglass frames are excellent for insulating and will not warp, shrink, swell, rot, or corrode.