Lee Lumber Blog

Understanding Energy Efficient Windows

Posted by Lee Lumber on Jan 16, 2017 10:00:00 PM


If you’re looking for energy efficient replacement windows, consider these factors for maximum energy efficiency.  Replacing single pane windows with double or triple pane windows, along with the proper glazing choice will provide cost savings, comfort, and long lasting value to your home.   Consulting with window experts on the following factors will ensure that your new purchase pays you back in energy savings in a very short time.

Considerations for Window Replacement with Energy Efficiency in Mind

There are several factors to consider for window replacements in addition to double or triple panes, and the proper coating or glazing choice.  Other important considerations are the Low E rating, U-Factor, and SHGC rating, all of which are important specifications that the typical homeowner may not be familiar with.  These specifications are especially important in climates with variable seasons like the windy city of Chicago, where brutally cold winters are replaced with mild spring and hot summer weather.  

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As homeowners, we are focused on visual appeal, and price. We just want our windows to look amazing, and protect our home and family from inclement weather.   Luckily, you can rely on the experts at Lee Lumber to explain these options in detail so that you have a full understanding on which type of window replacement is right for you.

Low-E Rating and U-Factor Explained

 With either double or triple panes, different degrees of glazing are available providing various Low E ratings and U-Factors.   The Low E rating refers to the amount of Ultraviolet and Infrared light that passes through the glass while allowing the highest degree of visible light to be transmitted.  Single, double, or triple coating options produce either Low E1, E2, or E3 energy efficient windows.  A Low E1 rating has more heat gain from solar radiation than a Low E3, which has the least amount of heat gain.  Heat gain refers to the amount of solar energy reflected into the room without escaping through the windows. 

The U-factor represents the rate of heat loss, or rather the insulative value of the glass.  With a low U-factor, the window will resist heat flow and provide better insulation than with a high U-factor. 


Let’s review the most ideal combination for your climate:

  • Low E1 windows
    • Feature one single layer of metallic glazing, blocking heat loss and reflecting heat back into the room
    • Ideal in Northern cool climates
    • Have a low U-Factor (highly insulating)
    • High heat gain from solar radiation, reflects heat back into the room


  • Low E2 Windows
    • Double layer of silver coating
    • High performance year-round
    • Better protection from heat transfer than single layer
    • Ideal in Northern, North-Central and South-Central climates
    • Have a low U-Factor
    • Medium heat gain from solar radiation


  • Low E3 Windows
    • Features triple layers of coating
    • Ideal in Southern and South-Central hot climates with high costs for cooling
    • Have the lowest U-Factor
    • Provide the lowest solar heat gain


What is the Solar Heat Gain Coefficient (SHGC)

Quality windows today will display their Solar Heat Gain Coefficient (SHGC), which refers to the amount of solar radiation that is admitted through the window’s glass providing heat inside the home.

  • Windows with a low SHGC block more heat gain from the sun, thus less solar heat is transmitted providing reducing cooling costs in the summer.
  • While a higher SHGC rating would retain more heat inside the home, ideal for cooler climates.

Expert Assistance from Lee Lumber and Marvin Windows

Lee Lumber is an established distributor for Marvin™ Windows, maintaining a high reputation for durability and superior quality windows, skylights and doors.  Marvin windows offers many options with either double or triple panes and a wide range of glazing choices to meet the demands of any climate.   Marvin standard windows are Low E2 with an argon gas fill, although all products can be customized for specific energy efficient requirements in either new construction or replacement windows. 

Marvin’s Tripane glazing is available with either argon or krypton gas for insulation and provides optimum energy efficient performance.  The Tripane glass option has two coated glass panes with a third pane in between, and is offered with various degrees of Low E options on either interior or exterior panes. 

Specialty glass is available in standard, decorative or custom designs, in Low E1, E2 or E3, and either Tempered or Obscure.  For additional information from the experts at Marvin Windows, please review their  detailed brochure on energy efficient windows.

Call Lee Lumber today, an experienced dealer of Marvin Windows, to provide you with the most innovative solutions for your window and glass projects.  Let the experts ensure that your new purchase is customized to your climate and energy requirements, giving you maximum return on your investment. 

Topics: Windows

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