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Components of an Energy-Efficient Window

What's an energy-efficient window? Most will have at a minimum:

  • Double-pane insulated glass
  • Heat-resistant (Low-E) glass coating
  • Airtight frames
  • ENERGY STAR® rating

Three Dimensions of Energy Efficient Window Design—An energy-efficient window is a synergy of its components. At Milgard®, we call this the "three dimensions of energy efficient window design." Here's what you should look for in each of the three dimensions: glass, spacer and frame.

Frame, glass and spacer illustration



Frame – One of the important considerations you need to make is frame material. Two of the more energy efficient frame materials are vinyl and fiberglass. They do a particularly good job of reducing heat transfer and contributing to insulation value. Your ultimate decision on which of these to use may be based on aesthetics and cost. In making your selection, be sure to look for vinyl or fiberglass frames that have been specifically engineered for performance. For instance, both can be designed with chambers within the frame that enhance strength, noise reduction and insulation value.

Glass – Dual-pane designs use an air- or gas-filled space between two panes of glass. This insulates much better than a single pane. Special Low-E coating on the glass blocks infrared light to keep heat inside in the winter and outside in the summer. It also filters damaging ultraviolet light (UV) to help protect interior furnishings from fading.

Spacer – A spacer keeps a window's dual glass panes the correct distance apart for optimal airflow between panes. Too much or too little airflow can affect the insulating glass efficiency. The design and material of the spacer also can make a big difference in the ability to handle expansion and contraction and thus reducing condensation.