They both conduct heat and lose heat fast. They are prone to condensation. Through anodizing, or coating, the corrosion and electro-galvanic deterioration of aluminum frames can be avoided. The placement of plastic strips between the interior and the exterior of the frame can improve the thermal resistance of aluminum frames. Wood frames have higher R-values, are not affected by temperature extremes, and do not generally promote condensation.
Wood frames do require maintenance in the form of periodic staining or painting.
They also warp, shrink, swell and rot. They are available in a wide range of styles and shapes, have moderate to high R- values, are easily customized, are competitively priced, and require very low maintenance. Fiberglass frames are relatively new. They have a high R-value, are excellent for insulating, and will not warp, shrink, swell, rot, or corrode. Fiberglass is always painted because it does not hold up well to the weather.