1. Fiberglass. Relatively new in the window industry, fiberglass may not be widely available. With some of the highest R-values, fiberglass frames are excellent for insulating and will not warp, shrink, swell, rot or corrode. Unprotected fiberglass does not hold up to the weather and should always be painted. Some fiberglass frames are hollow; others are filled with fiberglass insulation.
2. Clad-wood. Clad-wood frames have a regular wood frame that is protected by exterior layers of water resistant material (vinyl, fiberglass or aluminum). Clad-wood is low maintenance, has very low thermal conductivity and comes in a variety of colors. Wood-clad frames are fairly expensive.
3. Wood. Wood-framed windows are popular with log homeowners as wood stay true to the design and materials. Their fibrous makeup means they don’t conduct heat or cold, making them an energy-efficient choice. Unfortunately, wood frames have issues with swelling, shrinking, warping and water damage.
4. Aluminum. Aluminum frames have several advantages over wood: they’re more durable, weigh less, are thinner and easier to work with, and are easy to transport. But while they’re also inexpensive and durable, they also tend to transfer heat out of your home at a high rate (unless you get a high-quality aluminum frame with an incorporated thermal break). They are available in a variety of color choices and can be coated to resist corrosion and can be painted to match your color scheme.
5. Vinyl. Vinyl frames are popular due to low cost and high insulation factors. They don’t conduct heat or cold in the same way that aluminum frames do, and they don’t have the maintenance problems of wood. Color choices are limited and painting may not be recommended (warping may occur from the sun if vinyl is painted a dark color), and the quality can vary greatly. Look for good welded corners and thick frames.