What Are High Performance Windows?

Windows account for 10 to 25% of the exterior wall area of a home and can account for up to 50 percent of the cooling load in Phoenix.  High performance windows can help offset energy costs by providing an improved thermal performance by minimizing the heat gain in a home.
 
When older homes were originally built, home builders installed single pane, metal framed windows.  Efficiency and energy savings were not a consideration. 
 
As home buyers demanded greater efficiency, the materials and construction of windows have improved considerably.
 
High performance windows can be characterized as windows with a low U-Factor (how much heat gain the window has), the SHGC, solar heat gain coefficient, (measures how well the window blocks the heat from the sunlight), and how much air leaks through the window.  High performance windows should have a U-factor of 0.33 or less, a SHGC of 0.55 or less, and does not allow air leakage of no more than 0.15 cfm/ft (cubic feet per minute of air leakage per linear foot of window edge).
 
The material and design of the windows influence the performance of a window.  Materials and designs that do not allow the window to conduct heat into a room is critical.  Wood, vinyl and insulated fiberglass perform better than high conductive materials such as aluminum. 
 
The benefits to high performance windows are numerous:
 

• Improved comfort - high performance windows reduce the heat gain in a room.  In a home, 40 percent of our physical comfort is due to the radiant heat exchange between our bodies and the surrounding environment.  High performance windows reduce this heat exchange.  Furthermore, high performance windows reduce air drafts and provide for more consistent temperatures in the home.
• Quieter home - Multiple paned windows reduce unwanted noises from the outside
• Increased quality - High performance windows are often constructed with better quality materials that result in longer lasting windows.
• Improved indoor air quality - With a tighter air seal, high performance windows reduce air drafts and limit the amount of dust and pollution that enter a home.
• Lower utility bills - Better performance results into increased efficiency and results in lower energy bills. 
• Reduced obsolescence - High performance windows are become the standard for new homes these days and reduced the need for future owners to replace the windows.
• Reduced wear and tear on home furnishings - Low E windows block the harmful UV light that fades fabrics and carpets in a home.
• Improved resale of the home - As home buyers are increasingly looking for more and more green options in their homes, the benefits to high performance windows are resulting into higher resale values and shorter marketing times for a home.