Fiberglass replacement windows, compared with wood

Wood and fiberglass are two of the most common materials for replacement windows. Each has its appeal. The differences show most clearly in insulation, strength, resistance to moisture and the care each needs over the years.

The best place to start is with the basics: how each material performs once it is in the wall, and what it asks of you afterward.

Insulation

Fiberglass insulates well against both heat and cold and has strong overall energy performance. For the household, that means lower monthly energy bills. For the environment, it means a smaller footprint. The two benefits come from the same property of the material, so you do not have to choose between them.

Strength

Fiberglass frames resist dents, scratches, splintering and rot. That suits households with children or pets and houses exposed to strong wind. The same strength makes fiberglass windows more secure than wood.

Moisture and heat

Fiberglass frames are molded without breaks or seams in their outer surface, which makes them highly resistant to moisture and leaks.

Wood is sensitive to moisture. Exposed to damp or to strong heat, such as a hot California summer, it can swell, peel, bow and lose its shape. Once that happens, repair is rarely simple.

Maintenance

Every window needs some care to keep working and looking its best. The difference is in degree.

• Wood needs regular cleaning, sanding, sealing and repainting.
• Fiberglass needs only an occasional cleaning.

Over the life of a window, that difference in upkeep adds up to a great deal of time, cost and disruption.

The long view

Weighing cost, design flexibility and long-term performance together, fiberglass makes a sound long-term investment compared with wood, particularly where windows face extremes of temperature.

Replacement windows are also one of the better ways to add to a home’s resale value. The curb appeal of new windows and the low upkeep of fiberglass both contribute to that return.