Here’s what the U.S. Department of Energy’s office of EREC has to say about two of the many window frame materials available.

• Vinyl

  “Vinyl frames are also available in many styles and are generally considered low maintenance since they never need painting. However, the sun’s ultraviolet (UV) light can fade colors other than white and cause yellowing and "crazing" in the plastic’s surface. Vinyl frames are also not very rigid. Vinyl windows with large openings usually require an internal metal extrusion to make the frame stiffer. This can lower the frame’s R-value significantly. Vinyl window frames can also soften, warp, and twist if heat builds up within the frame. In very hot, sunny climates direct exposure to sunlight is not recommended."
  
   

• Wood-Plastic Composites

  “Some companies make frames out of a mixture of wood, vinyl, and an epoxy adhesive. Such frames are very strong, insulate well, and resist rot even when exposed to water frequently. The insulation value is also about the same as an ordinary wood frame.”

Visit the Energy Efficiency and Renewable Energy Clearinghouse website for more information.