Low E Glass

Low E is a coating that is applied to glass that helps with heat transfer through the glass keeping your house cooler in the summer and warmer in the winter.   There are multiple types of Low E glass on the market each with different characteristics that can be tailored to your specific need.   When choosing a Low E coating you want to consider the following things.

  • U-Value — The lower the U-Value the better performing the Low E coating is.   U-Values are the inverse of a R-Value.    To convert a U-Value of 0.25 into and R-Value divide 1 by the 0.25 to get an R-Value of 4.
  • SHGC  —  The Solar Heat Gain Coefficient refers to how much solar heat is allowed to pass through the glass and is given a value between 0 and 1.  In warming climates and passive solar homes homeowners typically want a higher solar heat gain coefficient.  In cooling climates homeowners want a lower number to help reduce their air conditioning bills.
  • Visible Light Transmittance  —  Visible light transmittance is measured on a scale of 100 – 0 with 100 being no blockage of light at all.   Clear double pane glass has a visible light transmittance of 79% while Low E coatings will have a visible light transmittance of between 72%-66%.
  • Reflectivity  —  All Low E glass has reflective qualities.  After all it is designed to reflect the radiated head either back into the room or keep it outside.   As the performance increases in the coatings often the reflectivity does also.    This has proven to be objectionable to some homeowners.

Low E glass is GREEN.   According to the European Association of Flat Glass Manufactures the manufacture of one square meter of Low E glass produces 25kg of CO2 and replacing one square meter of single pane clear glass saves 90kg of CO2 emissions per year.    To learn more about using Low E glass on your next project contact us a