Windows 101: Lesson 2 – Window Materials

Lesson 2: Window Materials

Windows and doors are the biggest source of energy loss in your home. Accounting for up to half of your lost heating and cooling, new windows can save you up to 7%-15% on your monthly heating and cooling bills. When replacing your windows, the exterior material you choose will directly effect the energy efficiency of your home.

Several materials are used in windows construction. The most common materials include wood, clad wood, aluminum, fiberglass, and vinyl.

Vinyl windows are much improved from past offerings.  They are usually made of polyvinyl chloride (PVC) which has good insulating values.  Initially energy efficient, depending upon outside temperature extremes, the PVC will separate from the glass due to their different properties of expansion and contraction. They can also fade and crack over time, degrading significantly in as little as five years.

Aluminum windows are more durable, but rank lower on the energy efficiency scale than wood or clad wood. Metal is a poor insulator and conducts heat rapidly.  Cheaper aluminum windows often don’t have a long lasting exterior finishes.

Fiberglass windows have thermal efficiency greater than vinyl or aluminum. They are very durable and available in a wide variety of styles and sizes.  And their finish resists fading, chalking, and cracking.




Wood windows are long-lasting and energy efficient. You can paint or stain them any way you like.  Although beautiful and a natural insulator, the exterior of wood windows require regular, consistent maintenance.

Clad Wood windows offer the energy efficiency of wood with a low maintenance exterior. The frame is natural wood with an aluminum or vinyl cover, or cladding, that is snugly wrapped around the exterior of the wood. If you consider clad wood windows, the thickness of the aluminum cladding is important. Marvin Windows and Doors builds their windows with extruded aluminum that is the thickness of a quarter. Most manufacturers use roll form aluminum that is the thickness of a soda can.

Coming Soon: Lesson 3 – Window Replacement Options