As the primary barriers between indoor and out, the openings of the building envelope, high performance windows, doors, and skylights (fenestration) are essential to an energy efficient building. Choosing such products involves several considerations, including appearance, energy performance, human factor issues, technical performance, and cost. Other factors like building orientation, natural and artificial shading, and climate will influence the properties selected for windows, doors, and skylights installed throughout the building.



The first residential building energy codes adopted by many states were the 1992, 1993 and 1995 versions of the Model Energy Code (MEC), the predecessor of the International Energy Conservation Code (IECC). Today, many energy codes contain prescriptive requirements include the fenestration product minimum performance criteria (U-factor, Solar Heat Gain) based on climate zones.

Dramatic improvements in fenestration technologies in recent years have revolutionized performance. A good example of this change is the adoption of Low-E window technology in the 1990s, a period when almost all windows installed in homes were clear glass. By 1995, the first national standard for measuring solar heat gain co-efficient (SHGC) for windows was developed. When minimum SHGC ratings were first incorporated into energy codes in the year 2000, most manufacturers were no longer making clear glass windows. Technology had transformed the market faster than national codes could incorporate the new standards.

Today, high performance windows, doors, and skylights provide myriad benefits, including:

  • Lower energy bills
  • Better views and ambiance
  • Increased comfort
  • Less condensation
  • Less fading
  • Lower maintenance expenses
  • Positive energy tradeoffs