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What is the most energy efficient replacement window?

Krypton vs. Argon

One of the most sought after qualities in a replacement window is energy efficiency. Most people however wouldn’t know how energy efficiency can be achieved with different window options and configurations. For instance, did you know that some windows are made with certain types of gas between the panes of glass, and that the type of gas can greatly affect how energy-efficient your windows are?  The two common types of gas used in replacement windows are Argon and Krypton.

Argon and Krypton are known to make a measurable difference in replacement windows energy-efficient ratings. The most common measurements of energy efficiency in a replacement window are the U Value,  and Solar Heat Gain Coefficient (SHGC).

  • U Value is the rate of heat flow through a window; the lower the value, the better the insulating quality.  Most commonly the U Value is used to measure a windows total insulating value.
  • SHGC is an energy performance rating that measures the fraction of incident solar radiation admitted through the total window unit. The lower the windows SHGC, the less solar heat transmits through it.
  • R-Value (which we will talk about when we get to krypton)  is the resistance of a material to heat flow; the higher this number is the better the insulating value.

So what’s the difference?


Argon is a common gas with approximately 9,300 PPM which is actually more abundant in the atmosphere than Carbon Dioxide.  Argon is an inert gas, which means it does not react with many other elements. This is what makes Argon a  great solution for energy-efficient replacement windows.  Argon is also about 25% more dense than air (which is what is normally between the panes of glass in your windows).  Argon’s higher density adds more insulation than air.  The addition of Argon gives certain applications like Lang Exterior’s Energy Efficient Enhanced Glass Package  a U Value of .30 and an SGHC Value of .30,  commonly referred to in the industry as 30/30 windows, which are very energy-efficient.


Krypton occurs only in trace amounts in the atmosphere. In fact the name “krypton” comes from the greek word meaning “the hidden one.”  Krypton is a denser gas, making it a greater insulator than Argon. Krypton is also chemically un-reactive. This gas is known for being energy-efficient in many different industries.  At Lang Exterior we use krypton to make the most energy-efficient window in the industry. Our R5 Super Series windows are triple paned windows, with Krypton Gas between the panes. With this gas we are able to achieve an R Value of 5, and a U Value of .20!  Please take a look at additional information on these energy-efficient R5 Windows.


This entry was posted on April 3, 2012 by in Energy Efficient and tagged , , , , , , .